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ANODIZING INSTRUCTION MANUAL

SECOND EDITION Revised 4-19-2010

Copyright ©2009 SIFCO Industries Inc. All Rights Reserved

Table of Contents

SECTION 1 GENERAL INFORMATION................................................................................1 GENERAL INFORMATION ON THE SIFCO PROCESS .....................................................1 INTRODUCTION...................................................................................................................1 OVERVIEW OF THE FIVE TYPES OF ANODIZING ..........................................................4 CHROMIC (TYPE I) ..........................................................................................................4 SULFURIC (TYPE II) ........................................................................................................4 HARD COAT (TYPE III) ...................................................................................................4 BORIC-SULFURIC ............................................................................................................4 PHOSPHORIC....................................................................................................................4 LIMITATIONS.......................................................................................................................5 SECTION 2 EQUIPMENT AND MATERIALS.......................................................................6 POWER PACKS .....................................................................................................................6 PROCESSING CAPABILITIES OF MODEL SP 15-50......................................................7 FLOW SYSTEMS...................................................................................................................7 SOLUTION FLOW SYSTEM MODEL 75 .........................................................................7 ANODIZING WATER HEATING SYSTEM .....................................................................7 HARD COAT SOLUTION COOLER .................................................................................7 SOLUTION FLOW SYSTEM MODEL 15 .........................................................................7 THERMOCOUPLE THERMOMETER ..............................................................................7 ANODIZING TOOLS & EQUIPMENT..................................................................................8 ANODIZING TOOLS FOR THE CHROMIC AND BORIC-SULFURIC ACID ANODIZING GELS............................................................................................................8 ANODIZING TOOLS FOR PHOSPHORIC ACID GEL.....................................................8 PUMPS .............................................................................................................................10 SOLUTIONS ........................................................................................................................10 PRE-TREATMENT SOLUTIONS....................................................................................10 ANODIZING SOLUTIONS AND GELS ..........................................................................10 POST TREATMENT SOLUTIONS..................................................................................10 SECTION 3 THE ANODIZING PROCESS............................................................................11 ALLOY BEING ANODIZED ...............................................................................................11 EFFECTS OF ALUMINUM ALLOY ON ANODIZING.......................................................12 SIZE OF AREA BEING ANODIZED...................................................................................13 ANODIZING TOOL-TO-PART CONTACT AREA.............................................................13 CURRENT DENSITY ..........................................................................................................13 VOLTAGE............................................................................................................................14 TEMPERATURE..................................................................................................................15 ANODIZING PROCESS TIME ............................................................................................15 SECTION 4 CARRYING OUT AN ANODIZING OPERATION...........................................16 PRE-CLEANING THE PART ..............................................................................................16 MASKING............................................................................................................................16 Masking with Tapes and Paints ..........................................................................................16 Masking with Fixtures........................................................................................................17

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MAKING ELECTRICAL CONTACT WITH PART.............................................................18 SOLVENT CLEAN SURFACE PRIOR TO ANODIZING ...................................................19 STRIPPING OF EXISTING ANODIC COATINGS .............................................................19 METHODS OF ANODIZING...............................................................................................19 ANODIZING ........................................................................................................................20 ANODIZING WITH A STANDARD POWER PACK ......................................................21 ANODIZING WITH A MODEL SP 15-50 POWER PACK ..............................................21 SECTION 5 PLANNING AN ANODIZING OPERATION ....................................................22 PROCEDURE FOR PLANNING AN ANODIZING OPERATION ......................................22 EXAMPLE OF PLANNING FOR AN ANODIZING OPERATION .....................................24 SECTION 6 ANODIZING SOLUTION INSTRUCTIONS AND TECHNICAL DATA SHEETS ...................................................................................................................................26 COMMON USES OF SIFCO ANODIZING SOLUTIONS ...................................................26 Chromic (Type I) ...............................................................................................................26 Sulfuric (Type II)...............................................................................................................26 Hard Coat (Type III) .........................................................................................................27 Boric-Sulfuric ....................................................................................................................27 Phosphoric.........................................................................................................................28 SECTION 6.1 CHROMIC ACID (TYPE I)..............................................................................29 IMPORTANT CHROMIC ACID ANODIZING OPERATING CONDITIONS ....................30 EFFECTS OF ALUMINUM ALLOY ON CHROMIC ACID ANODIZING......................30 TEMPERATURE..............................................................................................................31 VOLTAGE........................................................................................................................32 ANODIZING TIME..........................................................................................................32 CURRENT DENSITY ......................................................................................................32 OBTAINING THE DESIRED FINAL RESULTS.................................................................33 ACHIEVING THE BEST COLOR OR APPEARANCE MATCH ....................................35 ANODIZING TOOLS...........................................................................................................36 TECHNICAL DATA SHEET SIFCO PROCESS CHROMIC TYPE I CODE 5010..............37 TECHNICAL DATA SHEET SIFCO PROCESS CHROMIC TYPE I GEL CODE 5027 .....38 SECTION 6.2 SULFURIC ACID (TYPE II)...........................................................................39 IMPORTANT SULFURIC ACID ANODIZING OPERATING CONDITIONS....................40 EFFECTS OF ALUMINUM ALLOY ON SULFURIC ACID ANODIZING.....................40 SIZE OF AREA BEING ANODIZED...............................................................................41 CURRENT DENSITY ......................................................................................................41 VOLTAGE........................................................................................................................42 TEMPERATURE..............................................................................................................42 ANODIZING PROCESS TIME ........................................................................................43 OBTAINING THE DESIRED FINAL RESULTS.................................................................43 CONTROLLING THE THICKNESS OF THE ANODIZED COATING ..........................43 MAINTAINING SOLUTION TEMPERATURE IN THE PROPER RANGE ...................44 TECHNICAL DATA SHEET SIFCO PROCESS SULFURIC TYPE II CODE 5011............46 SECTION 6.3 HARD COAT (TYPE III) ................................................................................48 SELECTIVE HARD COATING APPLICATIONS IN GENERAL.......................................49 REPAIRING A WORN OR OVERMACHINED ALUMINUM SURFACE ......................49

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REPLACING TANK HARD COAT AS A STANDARD MANUFACTURING PROCESS ..........................................................................................................................................49 REPAIRING A DAMAGED OR WORN HARD COAT ...................................................49 IMPORTANT HARD COATING OPERATING CONDITIONS ..........................................51 EFFECTS OF ALUMINUM ALLOY ON HARD COATING ...........................................51 SIZE OF AREA BEING HARD COATED .......................................................................53 CURRENT DENSITY ......................................................................................................53 VOLTAGE........................................................................................................................54 TEMPERATURE..............................................................................................................54 HARD COATING PROCESSING TIME..........................................................................54 OBTAINING THE DESIRED FINAL RESULTS.................................................................55 CONTROLLING THE THICKNESS OF THE HARD COAT ..........................................55 CONTROLLING TEMPERATURE WHILE HARD COATING ......................................55 TECHNICAL DATA SHEET SIFCO PROCESS HARDCOAT TYPE III CODE 5025........58 SECTION 6.4 BORIC-SULFURIC ACID ANODIZING ........................................................60 REPLACEMENT OF CHROMIC ACID ANODIZING IN OEM APPLICATIONS .............60 SPOT REPAIRS ...................................................................................................................60 IMPORTANT BORIC-SULFURIC ACID ANODIZING OPERATING CONDITIONS.......61 EFFECTS OF ALUMINUM ALLOY ON BORIC-SULFURIC ACID ANODIZING........61 TEMPERATURE..............................................................................................................61 VOLTAGE........................................................................................................................61 CURRENT DENSITY ......................................................................................................61 ANODIZING TIME..........................................................................................................62 OBTAINING THE DESIRED FINAL RESULTS.................................................................62 ACHIEVING DESIRED COATING WEIGHT.................................................................62 MAINTAINING TEMPERATURE IN THE PROPER RANGE .......................................65 TECHNICAL DATA SHEET SIFCO PROCESS BORIC-SULFURIC CODE 5031 .............66 TECHNICAL DATA SHEET SIFCO PROCESS BORIC-SULFURIC GEL CODE 5032.....67 SECTION 6.5 PHOSPHORIC ACID ANODIZING................................................................68 ANODIZING TOOLS...........................................................................................................69 PREPARATION OF SURFACE FOR ANODIZING ............................................................69 INSPECTION OF COATING ...............................................................................................70 TECHNICAL DATA SHEET SIFCO PROCESS PHOSPHORIC CODE 5023.....................71 TECHNICAL DATA SHEET ...............................................................................................72 SECTION 6.6 PRE-TREATMENT.........................................................................................73 ANODIZE AND HARD COAT STRIPPING SOLUTION CODE 1046 ..............................73 No. 10 ACTIVATING SOLUTION CODE 1031/4450 .........................................................75 SECTION 7 DYEING AND SEALING..................................................................................76 BLACK ANODIZING DYE CODE 5101 .............................................................................77 TRIVALENT CHROMIUM POST-TREATMENT ANODIZE SEAL CODE5020... ......79 ANODIZING SEAL No. 1 CODE 5021...............................................................................80 ANODIZING SEAL No. 2 CODE 5022...............................................................................81 DICHROMATE SEAL CODE 3003 .....................................................................................82 ................................................................................................................................................ SECTION 8 INSPECTING ANODIZED COATINGS............................................................84

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VISUAL................................................................................................................................84 ADHESION ..........................................................................................................................84 THICKNESS ........................................................................................................................84 SECTION 9 REFERENCE SECTION ....................................................................................85 DEFINITIONS AND ABBREVIATIONS: ...........................................................................85 SIFCO PROCESS CALCULATION FORMS .......................................................................88 SPECIFICATIONS ...............................................................................................................91

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SECTION 1 GENERAL INFORMATION

GENERAL INFORMATION ON THE SIFCO PROCESS The SIFCO Process® of Selective Anodizing is an advanced, well-engineered and complete method of selectively anodizing localized areas of aluminum components without having to use an immersion tank. Currently, five types of anodic coatings can be applied with good results on virtually all the commonly used aluminum alloys. Quality and performance of the coatings are equivalent or superior to those which may be obtained using good tank anodizing practice. This manual contains instructions for anodizing with SIFCO Process Anodizing Solutions. This manual is not intended to be a free standing manual. It is complemented by the SIFCO Process Instruction Manual which provides for more information on equipment, materials, masking and definitions. The SIFCO Process of selective electroplating has been expanded to provide a portable method of selectively applying these anodized coatings for a variety of localized-area applications. INTRODUCTION Anodizing is a widely used electrochemical surface treatment process for aluminum and its alloys. Depending on the particular type of anodizing process used, the resulting anodic coatings provide improved wear resistance, corrosion protection, and/or improved adhesive properties for subsequent painting or adhesive repair. Selective anodizing is used when limited, selective areas of large, complex aluminum assemblies need anodizing to either restore a previously anodized surface or to fulfill an original specification requirement. The SIFCO Process of selective anodizing is a versatile tool which can be used for many different, demanding OEM and repair applications. This portable process can be used both in the shop and in the field. Anodizing is the formation of an oxide film on aluminum using reverse current (part is anodic) and a suitable electrolyte. The five principal types of anodized coatings are chromic, sulfuric, hard coat, boric-sulfuric and phosphoric. Details on these five types are given in Table 1.

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Table 1. Information on the Five Types of Anodizing Type of Coating Chromic (Type I) Sulfuric (Type II) Hard Coat (Type III) Boric-Sulfuric Phosphoric Specification Applicable Mil-A-8625 (Type I) AMS 2470 Mil-A-8625 (Type II) Undyed AMS 2471 Dyed AMS 2472 Mil-A-8625 (Type III) AMS 2468 AMS 2469 Mil-A-8625 (Type I) BAC 5632 ASTM D 3933-80 BAC 5555 Bae 146 Subject Purpose of Coating Corrosion Protection, Base for Paint and Organic Finishes Corrosion and/or Wear Resistance Primarily Wear Resistance, but also Corrosion Protection Corrosion Protection Base for Adhesive Bonding Typical Thickness (in.) 0.00005 - 0.0003

0.0001 - 0.001

0.0005 - 0.0045

0.00002 - 0.00007 0.00005 - 0.0001

Selective (brush) anodizing utilizes the similar techniques of selective (brush) plating but reverses the current flow. When anodizing, the tool becomes the cathode (negative) and the part becomes the anode (positive). The anodized coating (an oxide film) is formed on a localized area of the aluminum surface in the presence of the electrolyte (anodizing solution). In all anodizing processes, three processes occur simultaneously during anodizing: 1. Electrolytic etching of aluminum. 2. Formation of the aluminum oxide (Al2O3) at the aluminum surface. 3. Dissolution of some aluminum oxide by the anodizing electrolyte. This is shown schematically in Figure 1.

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Figure 1. The three processes that occur when anodizing

Growth

Anodizing Solution

Coating

Base Metal

Start

Processing Time

Dissolution

The anodizing process is, therefore, more complex than the single process occurring in electroplating. To understand much of the following material, it will be important to remember that there are three different processes that occur while anodizing. The first two processes are developing the anodic coating, but the third one hinders its buildup and causes decreased coating hardness. When the anodic coating hardness is a primary requirement, such as in Type III hard coating, the anodizing process is carried out at temperatures ranging from 32°F/0°C to 55°F/13°C, according to the alloy, to minimize the coating dissolution. This requires the use of high-capacity cooling equipment. Depending on the application requirements, some anodized coatings may need to be sealed as a final step while others may also require dyeing. The dyeing step is performed after anodizing and prior to sealing. (Dyed coatings are always sealed.) Often, however, the anodized coating is left as formed and subsequently finished by painting or other similar methods. In military and commercial applications, anodized coatings are usually applied for dimensional reasons (salvage), corrosion protection and/or wear resistance purposes. Selective anodizing meets the performance requirements of Mil-A-8625 for Type I, II and III anodized coatings. In the consumer marketplace, anodizing is often utilized for cosmetic appearance reasons.

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The five types of anodizing differ markedly in the electrolytes used, in the typical thickness of the coating formed, and in the purpose of the coating. Also, the five types of anodized coatings are formed under distinctively different operating conditions. Electrolytes for selective anodizing may be in the form of anodizing solutions or gels. Solutions are available for all five types of anodizing and gels are available for chromic acid, boric-sulfuric and phosphoric acid anodizing. The operating conditions for the gels are the same as for their respective solutions and they apply coatings of the same quality. The gel is used when working near critical components that may be damaged by splashed or running anodizing solutions. The gel stays over the work area and does not stray into inappropriate places such as aircraft instrumentation, equipment and crevices where corrosion would start. With the gel there is also less likelihood of damage to the airframe. OVERVIEW OF THE FIVE TYPES OF ANODIZING CHROMIC (TYPE I) o Providing localized area anodizing on previously uncoated parts for corrosion protection. o Repairing damaged anodized coating to restore corrosion protection. o Used as a base for paint. SULFURIC (TYPE II) o Providing localized area anodizing on previously uncoated parts for corrosion and/or wear resistance. o Repairing an anodized area for dimensional reasons. o Restoring corrosion protection of a damaged anodized coating where final appearance is not a factor. HARD COAT (TYPE III) o Building up worn or mismachined aluminum surfaces to blueprint tolerances. o Replacing tank hard coat in new part manufacture. o Providing wear resistance and/or corrosion protection. BORIC-SULFURIC o Environmentally suitable alternative to chromic acid anodizing. o Providing localized area anodizing on previously uncoated parts for corrosion protection. o Repairing damaged anodized coatings to restore corrosion protection. PHOSPHORIC o Preparing aluminum surfaces for adhesive bonding.

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LIMITATIONS The following are typical problems encountered in repairing a damaged anodic coating: 1. Brush anodized coatings will not give cosmetic improvement or concealment. If the aluminum component is scored or abraded, the brush anodizing will produce an anodic coating over the scratch or abrasion mark, but will not conceal the mark. 2. Color matching is very difficult to achieve since the operating parameters and the surface before anodizing will be different than in the case of the original tank anodizing. The new coating may also appear as a "tire patch". Dyeing a part and trying to match color is also very difficult since over 1200 color dyes are available. SIFCO offers a black dye, with other colors available from chemical companies specializing in these items. 3. Coating Thickness and Build-up Thickness are significantly different terms in anodizing. For a successful application it is very important to understand the difference between them. The Coating Thickness is nearly twice that of the Build-up Thickness. The reason for this is that aluminum must be dissolved to form the aluminum oxide, and each volume of aluminum generates two volumes of anodic coating. When anodizing or hard coating for dimensional restoration, we need to apply a coating that is twice the dimensional buildup requirement. In other words, if a build-up of 0.001 in. is required, the coating thickness will have to be 0.002 in. There will be 0.001 in. penetration and 0.001 in. growth. Please see Figure 1 for an illustration of this.

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SECTION 2 EQUIPMENT AND MATERIALS

Most of the equipment and accessory items used in traditional SIFCO Process brush plating applications can be used for selective anodizing. Caution should be taken that only new tooling, cover material and masking material are used to avoid contamination. Submersible pumps, used in plating, must be thoroughly cleaned prior to their use in anodizing. Chromic acid and boricsulfuric acid anodizing require heating of the electrolyte. Flow systems which heat and filter solutions must have special fittings to accommodate the corrosive nature of the solutions. Solution coolers are used for hard coat application. POWER PACKS Power packs need to have a voltage output of approximately 50 volts to allow proper anodizing of all alloys in all types of applications. Please see technical data sheets for specific voltage and current. The use of standard selective plating power packs with lower voltage outputs could result in long process times and poor coating properties. SIFCO Applied Surface Concepts has developed a special power pack, Model SP 15-50 particularly suited for anodizing. It is designed particularly to fulfill the voltage, current and current density requirements of chromic acid anodizing, boric-sulfuric acid anodizing, and hard coating. Any SIFCO Power Pack can be used for phosphoric acid and sulfuric acid anodizing, although operation is not as convenient as using the Model SP 15-50 Anodizing Power Pack. The Model SP 15-50 power pack is intended for anodizing areas up to approximately 100 sq in. with chromic, up to 50 sq. in. in corrosion resistance applications and 6 sq. in. in wear resistance applications with sulfuric, and up to 40 sq. in. with hard coat.

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PROCESSING CAPABILITIES OF MODEL SP 15-50:

Anodizing type/ Purpose Chromic (Type I) Sulfuric (Type II)/corrosion protection Hard Coat (Type III)/wear resistance Hard Coat (Type III) Boric-Sulfuric Phosphoric

Max. recommended processing area (sq. in.) N/A ­ No ACD 75 60 15 385 N/A ­ No ACD

The Model SP 15-50 provides up to 15 amperes DC at 0 to 50 volts. The unique feature of this power pack is its ability to operate at either constant current or constant voltage. In the constant current mode the current may be pre-set between 0 and 15 amperes with a voltage limit pre-set at any value between 0 and 50 volts. A voltage between 0 and 50 volts may be pre-set for operating in the constant voltage mode. This flexibility is important in selective anodizing, because some processes, such as selective chromic anodizing, are better carried out at constant voltage. Other processes, such as selective hard coating, are better done at constant current with a voltage limit to prevent burning. FLOW SYSTEMS SOLUTION FLOW SYSTEM MODEL 75 The Model 75 Solution Flow System has been developed for use with anodizing solutions. It includes provisions for heating and pumping of the solution along with special fittings that resist the corrosive nature of the anodizing solution. It operates using 4 to 6 liters of solution. HARD COAT SOLUTION COOLER A Hard Coat Solution Cooler is required to cool and maintain the hard coat solution at a proper refrigerated operating temperature. Recommendations on where to purchase the Hard Coat Solution Coolers can be made by contacting SIFCO ASC. The Hard Coat Solution Cooler consists of a refrigeration cabinet, a stainless steel immersion cooling coil, a stainless steel immersion temperature sensor, and a tank to contain the hard coat solution and the immersion cooling coil.

THERMOCOUPLE THERMOMETER A thermocouple thermometer is available for monitoring anodizing temperature. Included is a Teflon® encased, 0.025 in. diameter, 3 ft. long probe. The probe is flexible and is usually inserted between the cathode (anodizing tool) and the cover. It is particularly useful when anodizing with the gels.

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ANODIZING TOOLS & EQUIPMENT Standard SIFCO plating tools may be used for anodizing. The need for solution-fed tools to maintain proper temperature, however, is greater in anodizing as compared to electroplating; this should be considered in selecting tools. Standard tools are often modified to allow pumping solution through them, particularly when the hardest, most wear resistant coatings with sulfuric acid or hard coat must be obtained. When special tools are made, the anode material may be graphite, aluminum, stainless steel, lead or platinum-clad niobium. Standard or special tools should cover all, or as much as possible, of the area to be anodized. This is particularly important when the hardest, most wear resistant hard coat or sulfuric coating must be applied. The tool covers should be polyester, that is, Polyester Batting, Polyester Sleeving, Polyester Jacket, PermaWrap or White TuffWrap.

ANODIZING TOOLS FOR THE CHROMIC AND BORIC-SULFURIC ACID ANODIZING GELS A special type of tool, internally heated with hot water, is usually used when anodizing with chromic or boric-sulfuric acid gels. This type of tool simplifies the matter of how the work area will be maintained in the proper temperature range. The Model 75 Solution Flow System is used with this type of tool. See Figure 2 for an example. White TuffWrap or Gel Covers are used as the cover material for the above tools. The anodizing gel material is forced into the cover from both sides using a stainless steel spatula. This is continued until it is certain that the gel has saturated the cover. The cover is then tightly secured to the electrode part of the tool. Inspect the covered tool to make sure there is no possibility of the cathode shorting against the workpiece. More gel material is then applied on the cover and squeezed through to insure good electrical contact between the tool and the cover. ANODIZING TOOLS FOR PHOSPHORIC ACID GEL Special, stainless steel, perforated sheet tools are used with the gel. The perforated sheet is 0.030 in. thick and has 3/32 in. holes on 5/32 in. centers. The material is thin enough to be easily bent to match contours such as OD and ID, but thick enough to maintain the bent shape during use. Electrical contact is made to it by means of long No. 8 stainless steel machine screws and nuts and a plating tool lead with a ring terminal. Plastic handles are attached to the perforated sheet using No. 8 stainless machine screws. See Figure 3 for an example. White TuffWrap or Gel Covers are used as the cover material for the above tools. The anodizing gel is forced into the cover from both sides using a stainless steel spatula. This is continued until it is certain that the gel has saturated the cover. The cover is then tightly secured to the electrode part of the tool. Inspect the covered tool to make sure there is no possibility of the cathode shorting against the workpiece. More gel material is then applied on the cover and squeezed through the perforated stainless steel to insure good electrical contact between the stainless steel and the cover. 8

Fig. 2. Example of a hot water tool used with Anodizing Gels

Fig. 3. Display shows the different anode types, including graphite, a perforated stainless steel sheet tool, and a hot water tool

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PUMPS All SIFCO pumps are suitable for use in anodizing, provided they are large enough for the size of the area to be anodized. General recommendations are as follows: Size of Area to be Anodized (sq. in.) Up to 1 1 to 10 10 to 30 Over 30 Solution Supply Method Dip. Pumping not necessary Submersible pump Model S Large Pump Model L Model 75 Solution Flow System

AeroNikl MASKING TAPES AeroNikl tape is the only tape that should be used since it is capable of performing well under elevated temperatures and has better adhesive properties than the vinyl tapes. TuffMask MASKING PAINT "TuffMask" is the most widely used brush-on paint for anodizing since: 1. 2. 3. SOLUTIONS PRE-TREATMENT SOLUTIONS Anodize and Hard Coat Stripping Code 1046 Solution. No. 10 Activating Code 1031/4450 Solution. Code 1011 Cleaner Z Solution ANODIZING SOLUTIONS AND GELS Chromic (Type I) Code 5010 Solution Chromic (Type I) Code 5027 Gel Sulfuric (Type II) Code 5011 Solution Hard Coat (Type III) Code 5025 Solution Boric-Sulfuric Code 5031 Solution Boric-Sulfuric Code 5032 Gel Phosphoric Code 5023 Solution Phosphoric Code 5024 Gel POST TREATMENT SOLUTIONS Black Anodizing Dye Code 5101 Anodizing Seal No. 1 Code 5021 Anodizing Seal No. 2 Code 5022 Dichromate Seal Code 3003 It dries quickly It is a flexible coating resistant to mechanical damage. It withstands rubbing contact with the anodizing tool cover.

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SECTION 3 THE ANODIZING PROCESS

Operating conditions that may affect the anodizing process and the thickness, structure, appearance, and properties of the coating are: 1. Alloy being anodized. 2. Size of area being anodized. 3. Anodizing tool-to-part contact area. 4. Current density. 5. Voltage. 6. Temperature. 7. Anodizing processing time. ALLOY BEING ANODIZED

Table 2. Alloy and Temper Designation Systems for Aluminum Wrought Al & Al Alloy Number System Cast Al & Al Alloy Number System Aluminum-99% minimum ............1xxx Aluminum-99% minimum............1xx.x Alloys by major alloying elements: Alloys by major alloying elements: Copper ...................................2xxx Copper..............................2xx.x Manganese .............................3xxx Silicon+Cu &/or Magnesium...3xx.x Silicon....................................4xxx Silicon..............................4xx.x Magnesium.............................5xxx Magnesium.........................5xx.x Magnesium and silicon...........6xxx Zinc.................................7xx.x Zinc........................................7xxx Tin..................................8xx.x Other elements .......................8xxx Other elements....................9xx.x Unused series .........................9xxx Unused series...........................6xx.x

Basic Temper Designations: F O H W T As fabricated Annealed Strain hardened Solution heat treated Thermally treated to give tempers other than F, O, or H.

The above table is useful since it indicates that 2014, 2024, 2219, etc., are similar, having copper as the major alloying element. Being similar, the alloys anodize in a similar manner.

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EFFECTS OF ALUMINUM ALLOY ON ANODIZING Each aluminum alloy responds differently to the anodizing process. Some difference are: 1. Certain aluminum alloys burn more easily than others; these require lower current densities. 2. The solution's factor varies slightly depending on the alloy. 3. The color of the coating varies depending on the alloy.

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SIZE OF AREA BEING ANODIZED The principal effect of size of area being anodized is its effect on solution temperature. Larger areas (when full contact is made with the tool) result in more current and, therefore, more rapid heating of the solution. To compensate for this when processing larger areas, pump the anodizing solution rather than dip for solution, and then use larger pumps rather than small pumps. Larger areas also require more amp-hr, and this results in more overall heating of the solution. Therefore, the larger the area, the greater the need for a larger starting volume of solution, or for a means of cooling the solution. ANODIZING TOOL-TO-PART CONTACT AREA Anodizing occurs essentially only where the tool meets the part. Dissolution of the coating occurs, on the other hand, wherever the solution contacts the area being anodized. If, for example, the tool covers only 10% of the total area being anodized, 10% of the area is being anodized while the other 90% of the area is being degraded and losing coating. The ideal anodizing tool, therefore, covers the entire area to be anodized. Less than full coverage requires an increase in coating time. For example, if the tool covers only 10% of the total area, only 10% of the total area is being anodized at a given time. This requires a ten-fold increase in coating time. The overall result is a soft and/or low thickness coating. It is strongly desirable, therefore, to select a tool that will cover all, or as much as possible, of the area to be anodized. CURRENT DENSITY Current densities play a key roll in the success of a sulfuric or hard coat application. The current density is a minor issue with chromic and boric-sulfuric and has no role with phosphoric acid anodizing. Please see technical data sheets for specific information on current densities. Sulfuric acid anodizing and hard coating operations should be controlled by current density. The proper current density for a given application is dependent on the purpose of the coating. The higher the current density, the faster the coating is applied. Too high of a current density, however, results in overheating of the work area and soft, thin coatings. At even higher current densities, localized burning may result. Burned areas are very soft, degraded coatings, generally circular in shape, and different in color and texture than the surrounding areas. Too low of a current density results in a long anodizing time and, therefore, ample time for the electrolyte to dissolve the coating. The results are: 1. A soft coating with poor wear resistance. 2. A coating that is thinner than expected. Voltage has a significant effect on current density. The relationship between voltage and current density is not linear, that is, doubling the voltage does not double the current density. The relationship is more complex. See Figure 4 for an example of the relationship in the initial stages of an operation before the first 0.0005 in. of coating is applied. After approximately 0.0005 in. of anodizing has been applied, the effect of coating thickness on current density is usually noticeable, with the current density tending to decrease as the coating

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builds up. An increase in voltage is then required to maintain the current density. The amount of voltage increase needed to maintain the current density depends on the alloy. At the proper current density, hard, wear-resistant, and corrosion-resistant coatings are applied as rapidly as possible and to the desired thickness.

30

25

Volts after 5 sec. contact

20

15

10

5

0 0 0.5 1 1.5 2 2.5 3 3.5

Current density after 5 sec. contact (amp/sq in.). Fig. 4. Sulfuric Anodizing Voltage vs. Current Density Base material: 6061-T6. Area: 9 sq in.

Note 1: It takes approximately 5 seconds for the current density to stabilize after a change in voltage is made. Note 2: At current densities above 3 amp/sq in., burning occurs, and the current density gets out of control, rising to extremely high levels. Note 3: At low voltages, (less than about 15 volts), increasing the voltage has little effect on amperage. Note 4: Above 15 volts, small increases in voltage cause large increases in current density. VOLTAGE Voltage has a significant effect on the properties of the coatings during chromic, of the boricsulfuric and phosphoric anodizing, while having more of an impact on the current density during

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sulfuric acid anodizing or hard coating. Please see technical data sheets for specific voltage requirements. Chromic, boric-sulfuric, and phosphoric acid anodizing should be controlled by constant voltage. Voltage does affect the appearance of the coating on some alloys during chromic or boric-sulfuric acid anodizing. Changes in voltage will have a significant effect on the appearance of chromic acid anodized coatings on 2024-T3 and 7075-T6. Changes in voltage have only a slight effect on the appearance of chromic acid anodized coatings on 6061-T6 and no effect on Clad Aluminum alloys. TEMPERATURE Temperature has the greatest effect on most of the anodizing process. It will have a direct result in the hardness and thickness of sulfuric and hard coat coatings while the appearance of the chromic and boric-sulfuric coatings are affected. Temperature also affects the coating efficiency and coating weight of the chromic anodizing. Please see technical data sheets for specific temperature requirements. Heat is developed by the electricity driving the anodizing process, primarily in the coating being applied. The heat is dissipated by the part being anodized and by the anodizing solution. The higher the coating thickness and the larger the anodized area, the more heat will develop. Excessive overheating of the solution can be prevented by: 1. Starting out with an adequate amount of solution. 2. Cooling the solution when necessary to maintain the proper temperature range. ANODIZING PROCESS TIME Unnecessarily prolonged anodizing times result in severe dissolution and degradation of the coating. Anodizing operations, therefore, should be carried out as rapidly as possible. To accomplish this: 1. Select or make a tool that will, if possible, cover the entire area. 2. Provide for an adequate rate of solution supply. 3. Use a correct power pack with sufficient amperage or voltage output. 4. Manipulate the voltage properly to obtain optimum current density when sulfuric acid anodizing or hard coating. 5. Keep the tool in proper and constant contact with the part.

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SECTION 4 CARRYING OUT AN ANODIZING OPERATION

The sequence of steps in an anodizing operation is listed below. 1. Pre-clean the part. 2. Mask around the area to be anodized. 3. Make electrical contact to the part. 4. Solvent clean the surface to be anodized. 5. Use Solution Code 1011 Cleaner Z to achieve a water break free surface. 6. When applicable, in repairing a damaged coating, strip the existing anodic coating and the resulting protective coating that is formed while stripping. 7. Anodize. PRE-CLEANING THE PART The area to be masked must be cleaned to ensure that masking materials will stick. Use a suitable cleaner to remove oil and grease. This should be done prior to any mechanical cleaning operation such as abrasive blasting or sanding, in order to prevent oil or grease that may be present on the surface from being forced into the pores of the material. Use sand paper or gray abrasive pads to remove any corrosion, oxides, paint, or dirt. MASKING Masking for an anodizing operation is more demanding than masking for plating. Two reasons for this are: 1. The basic difference in how the coatings are formed. Anodized coatings inherently tend to undermine masking, while plating tends to build up over masking and hold it down in place. 2. The high "throwing power" of anodizing operations. In anodizing, the coating is an electrical resistor. Since current takes the easiest path there is a tendency for current to stray several inches away from the anodizing tool. Three consequences of the above are: 1. When masking with tapes and paints, masking must be carried out very carefully. 2. Larger adjacent areas must be masked. 3. Masking fixtures are more commonly used. Masking with Tapes and Paints Do not routinely assume that the part can be successfully masked with tape and paints. Instead, critically consider the masking that has to be done and what materials will be used. Consider the following before making a decision to use tape and/or paint:

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1. Masking tape and paint adhere better on a surface that is anodized as compared to a surface that is not. 2. Tapes do not adhere as well on rougher surfaces, but paints adhere better on rougher surfaces. 3. Tapes work better on an OD, as compared to an ID, but paints work equally well on both. 4. Complex surfaces with all kinds of curvature are difficult to mask with tape, but paints work well. 5. Lifted masking can greatly expand the area being anodized, which in turn causes: a. Operator confusion about the rising current and what to do about it. b. Loss of control over coating thickness. c. Anodizing of areas where it is not wanted or a slight degradation of anodizing on adjacent areas. Masking with tape and/or paint must be carried out very carefully. Solvent clean the area to be anodized and adjacent areas. After the pre-cleaned surface has been thoroughly dried, mask in a careful, deliberate manner. AeroNikl® tape is recommended as a masking tape. Apply AeroNikl tape so that bubbles are not present. Iron the tape down with a plastic tool, particularly next to the area to anodized. When masking with tape, a particularly troublesome area is where one layer of tape rises over another. It is extremely difficult to press the second layer of tape into the internal corner formed by the first layer of tape and the part. This area is, therefore, not usually masked properly and solution and current enter this area. The end result is lines of discoloration after anodizing. One method of overcoming this problem is to paint these corners with masking paint. A second method is to use a large single piece of tape with a cut-out to expose the desired area. This avoids the problem of seepage where a layer of tape rises over another. In this approach: 1. 2. 3. Use a large single piece of tape when making cut-outs. Use devices such as sharp cork bores or punches to make circular cut outs. Press tape down firmly and thoroughly.

Masking with Fixtures Masking fixtures are used more often in anodizing as compared to plating because of the high tendency to lift tapes and paints and the high throwing power of the operation. Some of the items used in the fixtures are O-rings, stoppers, neoprene sheet, and polypropylene, PVC and CPVC materials. See Figures 5 for an example.

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Fig. 5. Masking fixture and anode setup used to anodize four parts simultaneously

The design of the fixture should take in account the high throwing power in anodizing. For example: 1. Insure that all sealing surfaces are leak-proof. 2. Insure that solution and current can not get to surfaces that are not to be anodized even though they are several inches away from the area being anodized. MAKING ELECTRICAL CONTACT WITH PART In repairing damaged anodized coatings, a problem that often arises is where to make electrical contact with the part. In many cases, it appears that the entire part has been anodized. Clamping onto a coated surface is not effective since it will not pass current. However, it is important to remember that contact was made with the part when it was originally tank anodized. Therefore, there is an area that is not anodized. Usually, a careful examination of the part will reveal where the uncoated area is located. However, in some cases the area is so small that it cannot be found or it might have been covered by paint or other components. In these cases, determine where it is of least importance to have an anodized coating and remove or penetrate the coating in this area. For example, a screw is often driven into a threaded bore in the part so that the screw penetrates through the coating and into the base material.

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SOLVENT CLEAN SURFACE PRIOR TO ANODIZING Quickly degrease and clean the surface so not to lift the tape, just prior to starting the anodizing process, with acetone, MEK or other suitable solvents. Use Code 1011 Cleaner Z Solution to achieve a water break free surface. STRIPPING OF EXISTING ANODIC COATINGS The stripping is done after solvent cleaning the repair and adjoining areas, and after masking for anodizing. Care should be exercised in masking to assure that the sharply defined edges will be maintained throughout the masking, stripping, and anodizing process. Painting over the existing anodized coating prior to masking with tape can help assure a better protection. Stripping methods of damaged anodized coatings will depend on the type and extent of the damage which can be categorized into three types: 1. A few sharp gouges through the anodic coating into the base metal. 2. A relatively large area of anodic coating removed. The feathered edges of the area gradually change from bare metal to undamaged coating. 3. Numerous, closely-spaced penetrations down to the base metal. Stripping is usually not performed on type I damage since a better appearance match will result after a subsequent brush anodizing repair operation. Stripping is usually performed on types II and III damage since a better appearance match will be subsequently achieved. The purpose of the procedure is to remove the thin, partially damaged coating immediately adjacent to the area where wear or physical damage has penetrated to the base material. If the thin coating is not removed, the thin area will not pass current, and it will remain unchanged while anodizing. The end result would be a full thickness of repair coating in the area where penetration occurred into the base material, and a thin original coating around it. This type of repair is generally not attractive and is suspect as far as corrosion protection and/or wear resistance. After stripping a repair area, a smoother area of undamaged aluminum will surround a rougher damaged area. Using fine stones, fine sandpaper, and/or a buff, smooth the damaged area so that it looks like the surrounding area. The area is then ready for anodizing. Refer to technical data sheets for 1046 and 1031 in Section 6.6. METHODS OF ANODIZING The Chromic Acid Anodizing Code 5010 Solution may be used with either the brush or "cell" method. An example of the cell method is anodizing a blind bore. In this case, the part would be oriented with the open end of the bore up. The bore can then be filled with solution and an electrode can be placed in the middle of the bore. For chromic acid anodizing, this method is as effective as the traditional "brush" method, which is not the case for other types of anodizing. Cell chromic acid anodizing works as well as brush anodizing because of the low current densities that are used.

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The Sulfuric Acid Anodizing Code 5011 and Hard Coat Code 5025 Solutions may be used with either the brush or "flow" method. In the flow method, a chamber is built around the area to be anodized. While anodizing, solution is pumped rapidly through the chamber. Usually the solution is pumped in at the bottom and discharged at the top; this prevents gas pockets from forming in the chamber. The flow method is not as efficient as the brush method in cooling the anodized coating, as it is forming. Lower current densities, therefore, must be used and the time necessary for anodizing increases. As a general rule, use current density at two-thirds of the value given for average current density. The flow approach, however, is considerably less labor-intensive, since the operator does not have to continuously move the tool on the surface. This in many cases makes the flow approach the preferred method. The Boric-Sulfuric Acid Code 5031, Phosphoric Acid Code 5023 Solutions and the Gels are used with the brush method. ANODIZING Various anodized coatings are formed using 10 to 50 volts, current densities of 0.039 to 3.0 amp/sq. in., and anode-to-cathode speeds of approximately 10 to 50 ft/min. when movement is required, depending upon the coating being applied. The anodizing operations are controlled by current density or voltage. The method of controlling voltage or current during the operation is dependent on the type of power pack to be used. If a Model SP 15-50 Power Pack is used, it is done in one manner; if another type of power pack is used, it is done in a different manner. Careful consideration must be taken when choosing a power pack to insure the proper voltage or amperage is available from the power pack. While anodizing, manipulate the tool in a manner that prevents the anodizing solution from overheating the surface. When dipping for solution, dip often or use a squirt bottle. When using cylindrical tools, such as the ID-13 on flat areas, rotate the tool. With solution-fed tools, do not press the tool on the surface so hard that solution flow is restricted. When moving the tool manually, attempt to obtain the recommended anode-to-cathode speed. Anode to cathode movement may be dependent on part configuration. Proper processing may require no anode to cathode movement, which is an acceptable application, providing all other operating parameters are met. Thoroughly rinse all anodizing material from surface as soon as possible after anodizing, using distilled or deionized water. The rinsing method will depend upon the anodizing material used and upon the circumstances of the application. When a Gel is used, it will probably be necessary to first wipe off most of the material. In this case lightly wipe, rather than rub, with a soft, lint free material moistened with distilled or deionized water. Then rinse with water. If a solution is used, only a water rinse may be necessary. After thoroughly water rinsing, dry the surface and remove any masking. The anodizing operation should be conducted without interruptions. There will be cases, however, when an interruption is unavoidable, such as from an electrical power failure. In these 20

cases, rinse and dry the surface and insure that the surface is kept clean. When the anodizing operation can be continued, start anodizing at 0 volts and raise the voltage slowly until the desired current is reached. There is no need to clean the surface; the anodizing operation should proceed as if there had been no interruption. This holds true for interruptions of up to 8 hours long. ANODIZING WITH A BRUSH PLATING POWER PACK Prewet the surface and start anodizing at 0 volts. Raise the voltage in 1 to 2 volts increments to about 13 volts. With each increase in voltage in this range, the current will increase momentarily and then drop back in a few seconds to a lower level. When the current has stabilized, make the next adjustment. Throughout this voltage range not much current will be drawn. Above 13 volts, small changes in voltage cause large changes in amperage. Therefore, after reaching 13 volts, raise the voltage in 1/2 volt increments, until the planned anodizing current or voltage has been reached. Make each 1/2 volt adjustment after the current has stabilized from the last adjustment. Continue anodizing at the planned current or voltage, making any voltage adjustment necessary, until the computed amp-hrs or time have been passed. Do not however, adjust above the maximum volts while hard coating. Usually only minor adjustments have to be made when at the planned anodizing current. Small, gradual decreases in voltage may have to be made due to an increase in solution temperature since the current obtained at a given voltage is very sensitive to temperature. A rapid rise in current and the need to make quick, large decreases in voltage may indicate burning. If this occurs, decrease the current to about two-thirds of the original or planned current and watch the voltmeter. The voltage should drop slightly and then rise again. If it does not, decrease the current another one-third of the original current. Continue anodizing until the calculated amp-hr have been passed. ANODIZING WITH A MODEL SP 15-50 POWER PACK See operating instruction for the specific anodizing solution that has been chosen for the correct voltage and current requirements.

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SECTION 5 PLANNING AN ANODIZING OPERATION

PROCEDURE FOR PLANNING AN ANODIZING OPERATION Step 1. Gather necessary information about the job including: o Number of parts or areas to be done. o Aluminum alloy to be anodized. o Area to be coated, that is, size and shape. o Purpose and requirements of coating, that is, corrosion resistance, wear resistance, appearance, dimensional repair, etc. o General idea of what is adjacent to the area to be coated. o Thickness of coating required. Step 2. Decide on the general approach to the anodizing operation: o Decide on the type of coating that needs to be anodized. o Decide on whether the part will be flow, cell or brush anodized. o If the part is to be brush anodized, decide: o How tool-to-part movement will be maintained. Acceptable methods are rotating the part, moving the tool by a turning accessory, and moving the tool by hand. o Whether the anodizing solution will be supplied by dipping/squirt bottle or pumping. o Decide whether solution or gel will be used. If solution is used decide how it will be supplied to the work area. o Decide on how the proper temperature range will be maintained for the solution or gel. o Decide on how the part will be masked. Step 3. Calculate the area to be coated. When touching up damaged anodized coatings, calculate only the area of bare, exposed aluminum. Do not include adjacent anodized and sealed areas, since no current will pass through these areas. Step 4. Calculate the required amp-hr for the job. amp-hr = F x A x T F = factor obtained from Technical Data Sheet A = area of surface to be coated T = thickness of deposit desired Note: In dimensional restoration applications, the deposit thickness required is twice as much as the build-up required. For example, if a build-up of 0.001 in. is required, the coating thickness should be 0.002 in.

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Step 5. Decide what type of anodizing tool will be used, that is, a standard tool or a special tool. The tool should preferably cover the whole area. There are cases such as on an OD where it is impractical to get more than 50% contact with the part. Fifty percent contact will, except in rare cases, give acceptable results. In less demanding applications, such as the need to only pass an electrical continuity test, an even lower percent contact area will provide acceptable results. Step 6. Determine the contact area if it was not established in Step 5. Step 7. Determine the anodizing amperage that will be used, using the formula: AA AA CA CD = = = = CA x CD anodizing amperage the contact area established in Step 6 current density selected from Technical Data Sheet based on alloy and purpose of coating. = = = = amp-hr x 60 AA anodizing time (min.) from Step 4 from Step 7

Step 8. Determine Anodizing Time. AT AT amp-hr AA

Step 9. Verify that the anodizing solution temperature will stay in the proper range depending upon the application. L L amp-hr PIT = = = = 40 x amp-hr PIT liters of solution required to prevent an excessive increase in temperature. ampere-hours required for the anodizing operation. permissible increase in temperature, in °F, that is, if the starting solution temperature is 45°F and the maximum permissible temperature for hard coating is 55°F, the permissible temperature rise is 10°F.

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EXAMPLE OF PLANNING FOR AN ANODIZING OPERATION Selective anodizing an area that is not anodized for corrosion or wear resistance. Step 1. Information gathered on job: o No. of parts or areas: Continuous job, one area on one part per day. o Base material: 6061 T6. o Area to be coated: 2 in. long x 24 in. OD. o Purpose of coating: Some corrosion protection. Must pass electrical continuity test. o Adjacent areas: Adjacent areas are hardcoated. o Thickness required: 0.0005 in. Step 2. Decide on the general approach to the anodizing operation: o Sulfuric ( Type II ) will be anodized. o Part can and will be rotated at 50 ft/min. or 8 rpm. o Tentatively select a Model 15 Solution Flow System.

Step 3.

Calculate the area to be anodized. A = 3.14 x D x L A = 3.14 x 24 x 2 = 151 sq in.

amp-hr = 70 x 151 x 0.0005 = 5.3

Step 4. Calculate amp-hr. Step 5. A special flow-through anodizing tool is obviously required for the large diameter. It was felt that a maximum of 20 in. of contact going around the circumference would be practical. Step 6. Contact area. CA = L x W CA = 20 x 2 = 40 sq in. Step 7. Anodizing amperage. AA = CA x CD A decision had not been made at this point whether to use the current density recommended for corrosion protection or the "average" current density. Therefore, calculations were made using both. AA = 40 x 0.2 = 8 (using 0.2 amp/sq in., based on current density recommendation for corrosion protection) AA = 40 x 1.5 = 60 (using "average" current density of 1.5 amp/sq in.) Step 8. Anodizing time - min. 24

AT = amp-hr x 60 AA AT = 5.3 x 60 = 40 min. at a current density of 8 0.2 amp/sq in. AT = 5.3 x 60 = 5.3 min. at a current density of 60 1.5 amp/sq in. A decision had to be made at this point whether to anodize at the recommended current density for corrosion protection for 40 minutes (during which a considerable amount of dissolution of coating may occur) or anodize at the average anodizing current density for 5.3 min. Since corrosion resistance requirements were not stringent, the latter course was chosen. Step 9. Determine whether solution temperature will stay in proper range assuming that a Model 15 Solution Flow System will be used with 6 liters of solution at 65°F. L = 40 x amp-hr PIT L = 40 x 5.3 = 10.6 liters 20 More than 6 liters of solution will be required to complete the job so a larger solution flow system was selected for holding and pumping the anodizing solution.

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SECTION 6 ANODIZING SOLUTION INSTRUCTIONS AND TECHNICAL DATA SHEETS

One of the first and most important decisions to be made in carrying out a SIFCO Process anodizing operation is to select the proper anodizing solution. This section provides the information for making proper selections. The uses of SIFCO Process anodized coatings are similar to those of tank coatings, since a given coating will have the same basic properties, whether applied by tank or by the SIFCO Process. This section has been prepared to give the common and unique uses for the various SIFCO solutions based on past experience, as well as the more important special characteristics of the solutions and their coatings which lead to their use in certain applications. In addition, this section gives specific operating instructions for SIFCO Process solutions to help finalize selection of the proper anodizing solution. COMMON USES OF SIFCO ANODIZING SOLUTIONS Chromic (Type I) These coatings can be applied in as little as 15 minutes as a base for organic coatings and finishes, and in one hour to provide coatings for corrosion protection. The use of Chromic Gel is beneficial for on-site applications such as the underside of a part, where pumping solution could present a problem. SIFCO's chromic acid anodized coatings meet the performance requirements of AMS 2470 and MIL-A-8625. Applications: o Localized area anodizing on previously uncoated parts for corrosion protection. o Repair damaged anodized coating to restore corrosion protection. o Use as a base for paint. Examples: o Refueling tubes and slat skin sections of helicopter components required Chromic (Type I) anodizing on areas of damaged coating for corrosion protection. o Repair of wing droop leading edge on aircraft skin where coating often gets damaged during maintenance or in-service-use. Sulfuric (Type II) Coatings are used to provide corrosion protection, wear resistance, and dimensional restoration of worn or mismachined parts. Coating thickness of up to 0.002 in. can be obtained. Selective sulfuric acid anodizing also can be used to repair damaged sulfuric coatings. SIFCO's sulfuric acid anodized coatings meet the performance requirements of AMS 2471, AMS 2472, and MILA-8625.

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Applications: o Localized area anodizing on previously uncoated parts for corrosion and/or wear resistance. o Dimensional restoration of damaged anodized surfaces. o Repairs damaged anodized coating to restore corrosion protection. Example: o The SIFCO Process of Selective Anodizing has been used to repair main gearbox support fittings, forward sponson mounts, and tail cone fuselage support fittings. Mating surfaces of these various helicopter components often are corroded. Repairs are made, in place, with a 0.0005 in. thick Sulfuric (Type II) anodized coating to resize the mounting face bores. Hard Coat (Type III) Selective hard coat deposits are applied for wear resistance, corrosion protection, and dimensional restoration of worn or mismachined parts. The coatings meet the performance requirements of AMS 2468, AMS 2469, and MIL-A-8625. Thicknesses of up to 0.0045 in. can be achieved using SIFCO's Hard Coat Solution. Applications: o Restores worn or mismachined aluminum surfaces to blueprint requirements. o Replaces tank hard coat in new part manufacture. o Provides wear resistance and/or corrosion resistant coatings. o Repairs damaged Hard Coat coatings. Examples: o Tail rotor drive shaft: OEM application. Hard Coat (Type III) Anodized Coating on flange faces for wear resistance. o Repairing the leading edge of heavily corroded vanes with Hard Coat (Type III). The eroded areas were first ground to a smooth finish and were then hard coat anodized with a coating thickness of 0.004 in. to provide maximum corrosion and wear resistance. o Underwater diving motor control and motor control base: Salvage of mounting faces and seal areas using Hard Coat (Type III) Anodized Coating. o Torpedo after-body shell: Salvage application. Hard Coat (Type III) Anodized Coating on O-ring seal area for dimensional restoration and corrosion protection. Boric-Sulfuric Produces a protective film that provides corrosion resistance greater than or equal to chromic acid anodized coatings without the use of chromium in the anodizing solution. Anodic coating weights exceed the minimum values listed in MIL-A-8625 (Type I). Also, boric-sulfuric offers an

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environmentally suitable alternative to chromic acid anodizing. superior to chromate conversion coating repairs. Applications:

In addition, boric-sulfuric is

o Provides localized area anodizing on previously uncoated parts for corrosion protection. o Repairs damaged coatings to restore corrosion protection. Example: o Repair of damaged areas on outside diameter of guide cylinder and accumulator pistons, subsequently sealed for additional corrosion protection. Phosphoric Coatings are used to prepare aluminum surfaces for adhesive bonding and as a preparatory procedure for a subsequent plating operation. Both solution and gel are available for the phosphoric coatings, which can be applied in 10 minutes. Application: o Prepares aluminum surfaces for adhesive bonding. Example: o Punctured aircraft skin was repaired using Phosphoric Anodizing to assist the adhesive bonding process and accomplish a permanent repair.

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SECTION 6.1 CHROMIC ACID (TYPE I)

Chromic acid anodizing is a relatively slow process whether done in a tank or with a hand-held tool. Depending on the objective of the anodizing operation, anywhere from fifteen minutes to one hour of coating time is required. A fifteen minute coating time, for example, should allow passing an electrical continuity test and should be adequate as a preparation for organic coatings. A coating time of one hour, however, is recommended for assuring good corrosion protection. This assumes the anodizing is done properly. If the anodizing is not done properly, either more time will have to be spent on the coating operation, or the desired objective will not be met. The Chromic Acid Anodizing Code 5010 Solution or the Chromic Acid Anodizing Code 5027 Gel is used to perform the actual anodizing operation. The solution is usually used on small parts, since maintaining the anodizing temperature in the proper range is easily accomplished by pumping heated solution through the anodizing tool. The gel, however, is usually used for on-site applications where flowing solution would present a problem. Examples of this are working on the underside of a part and working on surfaces where flowing solution could get into interior areas where damage of components could occur. The solution and the gel are equivalent except for their viscosity; they are used in the same way, the electrochemical data such as factors are the same, and the final results are the same. The Chromic Acid Anodizing Code 5027 Gel is thixotropic, that is, it becomes more fluid when it is disturbed. When the gel has been undisturbed for a day, its viscosity is approximately that of gelatin. When this material is disturbed for a few minutes such as by stirring, the material becomes much more fluid and its viscosity approximates that of a thick oil. The material, however, reverts to its gelatin-like viscosity after it is allowed to remain undisturbed for a day. The Chromic Acid Anodizing Code 5010 Solution may be used with either the brush or "cell" method. An example of the cell method is anodizing a blind bore. In this case, the part would be oriented with the open end of the hole up. The hole can then be filled with solution and an electrode can be placed in the middle of the hole. This method of chromic acid anodizing is as effective as the traditional "brush" method, which is not the case for other types of anodizing. Cell chromic acid anodizing works as well as brush anodizing because of the low current densities that are used. In chromic acid anodizing, as compared to electroplating or other types of anodizing, changes in operating conditions have unusual effects on the operation. For example, increasing the voltage causes a temporary, but not permanent, change in the anodizing current or current density.

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Factors that are applicable to electroplating or other types of anodizing are not necessarily applicable to chromic acid anodizing. The important operating conditions of chromic acid anodize processing should be well understood before chromic acid anodizing. IMPORTANT CHROMIC ACID ANODIZING OPERATING CONDITIONS Operating conditions that affect the chromic acid anodizing process, and the quality, thickness and appearance of the coating are: 1. Alloy being anodized. 2. Temperature. 3. Voltage. 4. Anodizing processing time. 5. Current density. EFFECTS OF ALUMINUM ALLOY ON CHROMIC ACID ANODIZING The particular aluminum alloy to be anodized affects the coating efficiency and the appearance of the deposit. This is illustrated in Table 3. Table 3. Effect of the Alloy on Coating Efficiency and Appearance of the Coating. Operating Conditions: 1 hour, 100°F, and 30 Volts Aluminum Alloy Alclad 2024-T3 6061-T6 7075-T6 Coating Efficiency mg/amp-hr 360 180 220 200 Coating Weight Unsealed mg/sq ft 900 500 700 500 Appearance Very light-gray, metallic Dark-gray, dull Very light-gray, matte Medium-gray, with salt and pepper appearance

The above table shows that two different alloys processed the same way can have widely different appearances and that the coating weight can vary by a ratio of 2 to 1.

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TEMPERATURE Temperature has the greatest effect on the chromic acid anodizing operation. See Table 4 for an example. Table 4. The Effect of Temperature on the Chromic Acid Anodizing Process. Operating Conditions: 1 hour, Base Material 6061-T6, and 30 Volts

Temperature °F 125 100 72

Current Density amp/sq in. 0.044 0.021 0.009

Coating Efficiency mg/amp-hr 119 252 295

Coating Weight mg/sq ft 749 755 378

The table illustrates the following: 1. There is a significant increase in current density progressing from 72 to 100°F, and from 100 to 125°F. 2. There is only a slight decrease in coating efficiency (mg/amp-hr) when progressing from 72 to 100°F and a large decrease when progressing from 100 to 125°F. 3. The final result of 1 and 2 above is a significant increase in coating rate (mg/sq-ft after 1 hr) progressing from 72 to 100°F, and essentially no change progressing from 100 to 125°F. Brush chromic acid anodizing, therefore, should be conducted in an operating range of 95 to 105°F. Temperatures up to 125°F are acceptable with the solution. Do not exceed 115°F with the gel, because the gel may dry up at higher temperatures. Some heat is developed by the chromic acid anodizing process. The amount of heat, however, is small. For example, if one anodizes a 30 sq in. area for 1 hour at 95°F, the amount of heat developed would be sufficient to raise the temperature of 1 liter of solution (or gel) by 23°F. This small amount of heat, however, is easily dissipated into the part, solution, tool, and atmosphere. In most cases the problem will be keeping the temperature up in the 95 to 105°F range, rather than preventing overheating of the solution (or gel). Temperature Maintenance for Code 5027 Gel An effective method of keeping the temperature in the proper range when using the gel is to use a special hot water heated tool. See Fig. 2 for an example. When this type of tool is not available, it becomes more difficult to maintain the temperature in the proper range. Temperature Maintenance for Code 5010 Solution Some methods of keeping the temperature in the proper range when using the Chromic Acid Anodizing Code 5010 Solution are: 1. Using the SIFCO Model 75 Solution Flow System. 2. Using stainless steel, titanium or quartz immersion heater, stainless steel or glass thermometer and the appropriate size SIFCO submersible pump or flow system. 3. Making additions of preheated solution throughout the anodizing job.

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Preheating the work piece to approximately 105°F is useful in maintaining anodizing temperature for both the solution and the gel. VOLTAGE A voltage within the range of 20 to 40 volts is recommended when chromic acid anodizing. Thirty volts is normally recommended if no special cosmetic requirements are to be followed. Increasing the voltage typically increases current density and coating rate in electroplating and other types of anodizing. In chromic acid anodizing, however, increasing the voltage in the 20 to 40 volt range does not increase the current density and coating rate, that is, the current density and coating rate will be the same whether 20, 30, or 40 volts is used. Voltage, however, does affect the appearance of the coating on some alloys. Changes in voltage will have a significant effect on the appearance of chromic acid anodized coatings on 2024-T3 and 7075-T6. Changes in voltage have only a slight effect on the appearance of chromic acid anodized coatings on 6061-T6 and no effect on Clad Aluminum alloys. See Table 11 for more information on this. ANODIZING TIME Increasing the anodizing time up to approximately 1 hour increases the coating weight and thickness. The increase in coating weight is proportional to the increase in time for purer aluminum alloy surfaces such as Clad 2024. For more highly alloyed materials, such as 2024-T3, the increase in coating weight is less than proportional, that is, doubling the coating time results in an increase in weight, but less than twice as much. Dissolution of the coating, even with the tool covering the entire surface to be coated, accounts for this. Unnecessarily prolonged anodizing times result in severe dissolution and degradation of the coating. Anodizing operations, therefore, should be carried out as rapidly as possible. To accomplish this: 1. Select or make a tool that will, if possible, cover the entire area. 2. Provide for sufficient solution supply. 3. Keep the tool in proper and constant contact with the part. CURRENT DENSITY Current density is an operating condition that cannot be changed easily during the course of a chromic acid anodizing operation. Current density is affected mostly by the anodizing temperature which in turn is mostly dictated by the set-up of the anodizing operation. A change in voltage while anodizing causes a temporary, but not permanent, change in current density. A change in the aluminum alloy, also, will not result in a significant change in the anodizing current density.

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OBTAINING THE DESIRED FINAL RESULTS A primary objective in any chromic acid anodizing operation is achieving the desired coating weight or thickness in a reasonable amount of time. A second important objective in some repair applications is achieving the best color or appearance match. ACHIEVING DESIRED COATING WEIGHT OR THICKNESS There will be cases where amp-hr can not be used to control thickness or weight of coating. These cases will be when very small areas, less than approximately one square inch, are to be anodized. Thickness or weight of coating in these cases can be controlled by time. Tables 5, 6, and 7 have been prepared to assist in this. Use Table 5 when anodizing to a particular thickness, Table 6 when anodizing to a particular coating weight before sealing, and Table 7 when anodizing to a particular coating weight after sealing. Table 5. Time (min.) Required to Develop Various Coating Thicknesses on Various Alloys Alloy Time (min.) Thickness (in.) 0.000040 0.000060 0.000080 0.000100 0.000120 0.000140 0.000160 0.000180 0.000200 0.000220 Alclad 11 16 22 27 33 38 44 49 55 60 2024-T3 16 24 32 40 48 56 64 ---6061-T6 16 24 32 40 48 56 64 ---7075-T6 20 30 40 50 60 ------

Note: The above times apply for most power packs. When using the Model SP 15-50 Power Pack, use 70% of the above times.

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Table 6. Time (min.) Required to Develop Various Coating Weights (before Sealing) on Various Alloys Coating Weight mg/sq ft - Unsealed 100 200 300 400 500 600 700 800 900 1000 Alclad 8 16 24 31 39 47 54 62 70 77 2024-T3 12 24 36 48 60 72 84 ---6061-T6 10 19 28 38 47 56 66 75 84 -7075-T6 12 24 36 48 60 72 84 ----

Note: The above times apply for most power packs. When using the Model SP 15-50 Power Pack, use 70% of the above times. Table 7. Time (min.) Required to Develop Various Coating Weights (after Sealing) on Various Alloys Coating Weight mg/sq ft - Unsealed 100 200 300 400 500 600 700 800 900 1000 Alclad 6 11 17 22 28 33 39 44 50 55 2024-T3 9 17 26 34 43 52 60 ---6061-T6 7 14 20 27 34 40 47 54 60 -7075-T6 9 17 26 34 43 52 60 ----

Note: The above times apply for most power packs. When using the Model SP 15-50 Power Pack, use 70% of the above times.

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ACHIEVING THE BEST COLOR OR APPEARANCE MATCH Factors that affect the color and appearance of a chromic anodized coating include: 1. Weight or thickness of coating. 2. Type of power pack used. 3. Texture of surface before anodizing. 4. Alloy being anodized. 5. Voltage used while anodizing. Weight or Thickness of Coating Coatings up to about 300 mg/sq ft are light-gray and iridescent with typically pale-red and palegreen shades. Above 300 mg/sq ft the iridescent colors are not seen. Type of Power Pack Used The appearance will vary depending on the power pack used. Using the same operating conditions, the Model SP 15-50 power pack will produce an appearance that is different than that resulting when most other types of power packs are used. When processing test samples for color match, the test work should be done with the same type of power pack that will be used on the actual job. Some color can be achieved by using different power packs, but under different anodizing conditions. For example, a dark gray, opaque, paint-like anodize repair is required on 2024-T3. This can be achieved by using 40 volts with a Model SP 15-50 and 30 volts with most other power packs. Texture of Surface The texture of the surface before anodizing has a significant effect on the appearance of the coating. For example, dry blasting the surface before anodizing will produce a more matte appearance and a darker color than if the surface had not been blasted. Varying the type of blast media used will also change the texture and color of the anodized coating. Sanding or polishing the surface after stripping will also affect the appearance of the coating. Usually a sanded or polished area will result in a shinier texture and a lighter color after anodizing. Alloy Being Anodized and Anodizing Voltage The effects of the alloy being anodized and anodizing voltage on the color and appearance are shown in Table 8.

35

Table 8. The Effect of Anodizing Voltage on the Color and Appearance of Coating for Different Aluminum Alloys Alloy Alclad 2024-T3 6061-T6 7075-T6 20V Very light-gray, transparent, metallic Medium-gray, dull Off-white, semi-shiny Medium-gray, shiny 30V Same as at 20V Dark-gray, very dull Very light-gray, not shiny Medium-gray, dull, salt and pepper appearance 40V Same as at 20V Light-gray, dull Light gray, dull Medium-gray, dull, uniform

Other Comments on the Appearance of Coating Anodizing temperature does not directly affect appearance for coatings with over a 300 mg/sq-ft coating weight. Low anodizing temperatures, however, result in low current densities and low thickness coatings. Since thickness of coating affects appearance, temperature can have an indirect effect on the appearance of the coating. Dyeing is carried out in some cases to darken a chromic acid coating. See Section 7 for more information.

ANODIZING TOOLS

The Chromic Acid Anodizing Solution and Gel both attack the anodized coating that is being applied. To minimize this attack, the anodizing tools for both materials should cover the entire area and conform to the area to be anodized so that the tool cover always touches all of the surface to be anodized. For specific information on the accepted types of tools, please see Section 2.

36

TECHNICAL DATA SHEET

SIFCO PROCESS CHROMIC TYPE I CODE 5010

ANODIZING SOLUTION ANODIZING DATA Factor Average Current Density Maximum Current Density Voltage Range Optimum Tool-To-Part Speed Operating Temperature Thickness Range Process Time Maximum Recommended Usage FACTOR TABLE (F) Factor for Controlling Coating Thickness (U.S.) (F) Factor for Controlling Coating Thickness (Metric) (Fwu) Factor for Controlling Coating Weight (mg/ft²) Unsealed 0.000025 0.000046 0.000035 0.000035 (Fws) Factor for Controlling Coating Weight (mg/ft²) Sealed 0.000018 0.000033 0.000025 0.000025

See Table Below N/A N/A 20 - 40 10 FPM 95 to 105°F 0.000050" to 0.0003" 15 - 60 min. 40 Amp-hr per liter

3 MPM 35 to 41°C 1.3 to 7.6 microns

Base Material

Alclad 2024-T3 6061-T6 7075-T6

90 150 160 140

0.00055 0.00092 0.00098 0.00085

COVER MATERIAL RECOMMENDATIONS Polyester Batting, Polyester Sleeving, Polyester Jacket, PermaWrap, White Tuff Wrap

GENERAL NOTES:

Chromic Anodizing using Code 5010 Solution is a constant voltage type process. The current density remains constant, regardless of voltage. The current density is affected by the solution temperature. The voltage will affect the appearance of the coating on some alloys. Chromic anodizing is generally sealed after anodizing. Please see Section 7 for more details.

37

TECHNICAL DATA SHEET

SIFCO PROCESS CHROMIC TYPE I GEL CODE 5027

ANODIZING GEL ANODIZING DATA Factor Average Current Density Maximum Current Density Voltage Range Optimum Tool-To-Part Speed Operating Temperature Thickness Range Process Time Maximum Recommended Usage FACTOR TABLE (F) Factor for Controlling Coating Thickness (U.S.) (F) Factor for Controlling Coating Thickness (Metric) (Fwu) Factor for Controlling Coating Weight (mg/ft²) Unsealed 0.000025 0.000046 0.000035 0.000035 (Fws) Factor for Controlling Coating Weight (mg/ft²) Sealed 0.000018 0.000033 0.000025 0.000025

See Table Below N/A N/A 20 - 40 10 FPM 95 to 105°F 0.00005" to 0.0003" 15 - 60 min. 40 Amp-hr per liter

3 MPM 35 to 41°C 1.3 to 7.6 microns

Base Material

Alclad 2024-T3 6061-T6 7075-T6

90 150 160 140

0.00055 0.00092 0.00098 0.00085

COVER MATERIAL RECOMMENDATIONS White Tuff Wrap, Gel Covers

GENERAL NOTES: Chromic Anodizing using Code 5027 Gel is a constant voltage type process. The current density remains constant, regardless of voltage. The current density is affected by the solution temperature. The voltage will affect the appearance of the coating on some alloys. Chromic anodizing is generally sealed after anodizing. Please see Section 7 for more details.

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SECTION 6.2 SULFURIC ACID (TYPE II)

Sulfuric acid anodized coatings are used to provide corrosion resistance and/or wear resistance. When only wear resistance is desired, sealing is not done. When corrosion resistance is desired, the coating must be sealed. Sealing significantly increases corrosion resistance, but it decreases wear resistance slightly. The coatings are usually sealed. Sulfuric type coatings are often dyed to obtain colors such as black, green, or red for low optical reflectivity or identification purposes. This is done after anodizing and before sealing. The Sulfuric Acid Anodizing Code 5011 Solution may be used with either the brush or "flow" method. In the flow method, a chamber is built around the area to be anodized. While anodizing, solution is pumped rapidly through the chamber. Usually the solution is pumped in at the bottom and discharged at the top. This prevents gas pockets from forming in the chamber. The flow method is not as efficient as the brush method in cooling the anodized coating as it is forming. Lower current densities, therefore, must be used and the time necessary for anodizing increases. As a general rule, use two-thirds of the value given for average current density in Table 9 (page 41). The flow approach, however, is considerably less labor-intensive, since the operator does not have to continuously move the tool on the surface. This in many cases makes the flow approach the preferred method. The temperature of the anodizing process is critical in achieving good results with the sulfuric acid solution. It is dependent on: 1. The temperature of the part. 2. The temperature of the solution. 3. The current density being used. The coating is an electrical resistor. The anodizing current, therefore, produces a considerable amount of heat in the coating, and the greater the current the more heat is produced. 4. The thickness of the coating. The thicker the coating, the more the electrical resistance, and the more heat is developed. Thicker coatings also decrease heat flow to the part and to the solution which adds to the temperature rise in the coating. The hardest, most wear resistant coatings are developed in the proper temperature range. Excessive temperature causes dissolution and degradation of the coating. This is prevented by:

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1. Starting with a cold part and cold solution. 2. Forming the coating fast enough to minimize the amount of time the solution can attack the coating, but slow enough that the deposit is not overheated by excessive current. Progressively softer, less wear resistant, and thinner coatings result as anodizing operating conditions depart from ideal conditions and dissolution and degradation of the coating increases. Burning can also occur during anodizing. This happens when the operating conditions are not uniform over the entire area and there is a localized overheated area. This results in a higher current density in the area, which leads to more heating. The final result is a localized, burned area where the coating is thin and severely degraded.

IMPORTANT SULFURIC ACID ANODIZING OPERATING CONDITIONS

Operating conditions that affect the anodizing process and the thickness, structure, appearance, and properties of the coating are: 1. Alloy being anodized. 2. Size of area being anodized. 3. Current density. 4. Voltage. 5. Temperature. 6. Anodizing processing time. EFFECTS OF ALUMINUM ALLOY ON SULFURIC ACID ANODIZING Each aluminum alloy responds differently to the anodizing process. Some difference are: 1. Certain aluminum alloys burn more easily than others. These require lower current densities. 2. The factor varies slightly depending on the alloy. 3. The color of the coating varies depending on the alloy. Table 9 shows how the aluminum alloy being anodized affects the anodizing process.

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Table 9. Effect of Aluminum Alloy on Sulfuric Acid Anodizing Current Density (amp/sq. in.) Max. Aluminum Alloy 2024-T3 See Note 1 1.00 Avg. 0.5 For Max. Corrosion Protection 0.2 Factor: (amp-hr for 1 in. on 1 sq. Grams in. at 0.2 asi Per Ampand above) Hr 80 0.49 Appearance at 0.0005 in. thickness Light-gray color with yellow tinge, semishiny, translucent Light-gray, semi-shiny, opaque Colorless, transparent, shiny Light-gray, dull, opaque Light-gray color with yellow tinge, semishiny, translucent Medium-gray, dull, opaque

3003-H14 5052-H32 6061-T6

2.50 5.00 3.00

1.25 2.50 1.50

0.2 0.2 0.2

70 70 70

0.55 0.55 0.55

7075-T6

2.50

1.25

0.2

70

0.55

A-356-T6

2.0

1.0

0.2

80

0.46

Note 1: Coatings will burn above the maximum current density, even with an excellent set-up. Use the average current density when anodizing for corrosion protection. Use a 0.2 amp/sq in. current density when anodizing for wear resistance and apply a 0.0005 in. thick coating. SIZE OF AREA BEING ANODIZED The principal effect of size of area being anodized is its effect on solution temperature. Larger areas (when full contact is made with the tool) result in more current and, therefore, more rapid heating of the solution. To compensate for this when processing larger areas, pump the anodizing solution rather than dip for solution, and then use larger pumps rather than small pumps. Larger areas also require more amp-hr, and this results in more overall heating of the solution. Therefore, the larger the area, the greater the need for a larger starting volume of solution, or a means of cooling the solution.

CURRENT DENSITY The higher the anodizing current density, the faster the anodized coating is applied. Too low of a current density results in a long anodizing time and, therefore, ample time for the electrolyte to dissolve the coating. The results are: 1. A soft coating with poor wear resistance.

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2. A lower than expected coating thickness. Too high of a current density (for the setup being used) results in overheating of the work area and soft, thin coatings. At even higher current densities, localized burning may result. Burned areas are very soft, degraded coatings, generally circular in shape and different in color and texture from surrounding area. At the proper current density hard, wear resistant, corrosion resistant coatings of the desired thickness are developed at the maximum possible rate. Sulfuric acid anodizing operations should be controlled by current density. The proper current density for a given application is dependent on the purpose of the coating. When maximum corrosion protection is desired, a current density of 0.2 amp/sq in. is recommended. When the coating will be dyed, a current density of 0.5 amp/sq in. or less is recommended. When maximum wear resistance or minimum processing time is desired, the "average" current density given in Table 9 is recommended. The "average" current density is also usually used in salvaging mismachined or worn parts. VOLTAGE Voltage has a significant effect on current density. The relationship between voltage and current density is not linear, that is, doubling the voltage does not double the current density. The relationship is more complex. See Figure 4 for an example of the relationship in the initial stages of an operation when the first 0.0005 in. of coating is being applied. After approximately 0.0005 in. of anodizing has been applied, the effect of coating thickness on current density is usually noticeable, with the current density tending to decrease as the coating builds up. An increase in voltage is then required to maintain the current density. The amount of voltage increase needed to maintain the current density depends on the alloy.

TEMPERATURE

The proper temperature range for sulfuric acid anodizing is 65 to 85°F. Temperatures above this range produce soft, low thickness coatings. Temperatures below this range slow down the anodizing rate. The part to be anodized and the solution should be in the recommended temperature range throughout the anodizing operation. In wear resistance applications, 65 to 75°F is preferred. In corrosion protection applications or when the coating is to be dyed, 75 to 85°F is preferred. Heat is developed by the anodizing process, primarily in the coating being applied. The heat is dissipated by the part being anodized and by the anodizing solution. The total amount of heat developed is dictated by the application, that is, the thickness of the anodized coating to be applied and the area to be anodized. The higher the thickness and the larger the area, the more heat will be produced. Excessive overheating of the solution can be prevented by: 1. Starting out with an adequate volume of solution. 2. Cooling the solution.

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The anodizing solution, while in the tool cover, is heated momentarily to a temperature higher than that of the solution in the supply container. The higher the current density, the more the solution will be heated while it is in the tool cover. Overheating of the solution, while it is in the tool cover, is prevented by: 1. Keeping the main supply of solution cool and, 2. By circulating the solution through the tool cover rapidly enough by frequent dipping or rapid pumping of solution. ANODIZING PROCESS TIME Longer anodizing times result in more dissolution and degradation of the coating. Anodizing operations, therefore, should be carried out as rapidly as possible. To accomplish this: 1. Select or make a tool that will, if possible, cover the entire area. 2. Provide for an adequate rate of solution supply. 3. Use a power pack with sufficient amperage output. 4. Manipulate the voltage properly to obtain optimum current density. 5. Keep the tool in proper and constant contact with the part. OBTAINING THE DESIRED FINAL RESULTS CONTROLLING THE THICKNESS OF THE ANODIZED COATING

The thickness of sulfuric acid anodized coatings is controlled by computing the amp-hr necessary for a job and then passing this number of amp-hr while anodizing. The formula for calculating amp-hr follows: amp-hr = F x A x T F = factor obtained from Technical Data Sheet A = area of surface to be coated T = thickness of deposit desired Example: A coating 0.0005 in. thick is desired on a 3 sq in. area of 6061-T6:

F = 70

A = 3 T = 0.0005 Placing these values in the above formula: amp-hr = 70 x 3 x 0.0005 amp-hr = 0.105

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MAINTAINING SOLUTION TEMPERATURE IN THE PROPER RANGE

The proper temperature range for sulfuric acid anodizing is 65 to 85°F. In wear resistance applications, 65 to 75°F is preferred. In corrosion protection applications or when the coating is to be dyed, 75 to 85°F is preferred. Methods of keeping the solution temperature in the proper range during anodizing include: 1. 2. 3. Using cooling coils. Making additions of solution chilled in a refrigerator. Starting with a sufficiently large volume of solution so that the heat developed during the anodizing operation will not get the temperature out of range. For this purpose, the following formula is used to determine how much solution is needed to prevent an excessive temperature rise while anodizing. L = 40 x amp-hr PIT L amp-hr PIT = = = liters of solution required to prevent an excessive increase in temperature. amp-hr required for the anodizing operation. permissible increase in temperature in F. For example, if one expects to start with solution at a temperature of 72°F and the maximum recommended temperature for anodizing is 85°F, the permissible in increase in temperature is 13°F. 13 0.40 40 x 0.40 13 1.23

Example:

PIT amp-hr L L

= = = =

Therefore, 1.23 liters or more of anodizing solution should be used to prevent the solution from rising above 85°F.

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NOTES

45

TECHNICAL DATA SHEET

SIFCO PROCESS SULFURIC TYPE II CODE 5011

ANODIZING SOLUTION ANODIZING DATA Factor Average Current Density Maximum Current Density Voltage Range Optimum Tool-To-Part Speed Operating Temperature Thickness Range Process Time Maximum Recommended Usage

See Table Below See Table Below See Table Below 20 - 40 50 FPM 65 to 85°F 0.0001" to 0.002" 15 - 60 min. 40 Amp-hr per liter

15.2 MPM 18 to 29°C 2.5 - 50 microns

OPERATING PARAMETERS (U.S.) CURRENT DENSITY (amp/in²) For Max. Base Material Factor Corrosion U.S. Avg. Protection A-356-T6 80 1.00 0.2 2024-T3 80 0.50 0.2 3003-H14 70 1.25 0.2 5052-H32 70 2.50 0.2 6061-T6 70 1.50 0.2 7075-T6 70 1.25 0.2 OPERATING PARAMETERS (Metric) CURRENT DENSITY (amp/cm²) For Max. Base Material Factor Corrosion Metric Avg. Protection A-356-T6 0.00049 0.16 0.031 2024-T3 0.00049 0.08 0.031 3003-H14 0.00043 0.19 0.031 5052-H32 0.00043 0.39 0.031 6061-T6 0.00043 0.23 0.031 7075-T6 0.00043 0.19 0.031

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COVER MATERIAL RECOMMENDATIONS Polyester Batting, Polyester Sleeving, Polyester Jacket, PermaWrap, White TuffWrap

GENERAL NOTES: Sulfuric Anodizing using Code 5011 Solution is a constant current process. Too high of a current density results in overheating of the work area and soft thin coatings or even a burned coating. The proper current density for a given application is dependent on the purpose of the coating. When maximum corrosion protection is desired, a current density of 0.2 amp/in² is recommended. When maximum wear resistance or minimum processing time is desired, the "average" current density is recommended. Voltage has a significant effect on the current density. Maintaining the proper solution temperature is essential to a successful application. Sulfuric coatings are usually dyed and most coatings are sealed. Please see Section 7 for more details. While anodizing, the voltmeter should be watched. Normally the voltage increases slightly to maintain the current. A slight drop over the course of the operation may occur if the temperature of the solution has been allowed to increase. A rise in voltage and then a rapid, significant drop in voltage may indicate burning has started. If this occurs, decrease the current to about two-thirds of the original setting and watch the voltmeter. The voltage should drop slightly and then rise again. If it does not, decrease the current another one-third of the original setting. Continue anodizing until the calculated amp-hr has been passed.

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SECTION 6.3 HARD COAT (TYPE III)

It is very important to determine the purpose of the hard coat; that is, what functions the coating is expected to perform. The purpose will dictate the equipment and processing techniques required. One or more of the following may be the purpose of the coating: 1. Provide wear resistance. Corrosion protection may or may not be important. A thickness of approximately 0.002 in. usually provides suitable service life. 2. Provide corrosion protection. A thickness of 0.002 in., combined with the hardness of the coating, helps insure that corrosion protection will be provided even after some abuse during handling or shipment. 3. Build-up the surface, such as on a mismachined part. The hardest, most wear-resistant hard coats are applied only in a tight range of operating conditions. Applications requiring maximum hardness and wear resistance will require: 1. Special equipment such as high voltage power packs and solution cooling equipment. 2. Tight processing controls, including close control of solution temperature and careful manipulation of voltage and current density during the hard coating operation. 3. A highly knowledgeable and well-trained operator. Coatings for corrosion resistance may be applied under a much wider range of processing conditions, and corrosion resistance applications may or may not require special equipment. Some reduction in hardness and wear resistance of the coating will generally result due to the wider processing range. Resizing worn or mismachined parts normally does not require maximum wear resistance or corrosion protection of the base material. As long as it is not burned, any type of coating will provide adequate service. In this type of application: 1. Special equipment such as high voltage power packs and cooling equipment will not be required. 2. There will not be a need for tight process controls. Hence, the purpose of the coating has a considerable bearing on the need for special equipment and the need for tight process controls.

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SELECTIVE HARD COATING APPLICATIONS IN GENERAL Applications for selective hard coating may be divided into three major types: 1. Repairing worn or over-machined aluminum surfaces. 2. Replacing tank hard coating as a standard, new part manufacturing process. 3. Repairing damaged, worn, or mismachined hard coated surfaces. The type of application and the purpose of the coating will determine whether a given application is appropriate for selective hard coating, and how easily the application can be carried out. REPAIRING A WORN OR OVERMACHINED ALUMINUM SURFACE This is a relatively simple application for selective hard coating. Maximum hardness and wear resistance are not usually necessary and, as long as the coating is not burned, the coating will have better properties than the base aluminum. Special equipment such as high voltage power packs and cooling equipment are not ordinarily required. The primary limitation in this application is in the amount of build-up that can be achieved. A build-up of 0.001 in. per surface, which requires a hard coat 0.002 in. thick, is easily accomplished. Build-up of up to approximately 0.002 in. (hard coat thickness of up to 0.004 in.) is possible, but difficult to achieve. REPLACING TANK HARD COAT AS A STANDARD MANUFACTURING PROCESS This is more demanding than the previous application, since it can be assumed that maximum hardness and wear resistance are required. Special high voltage power packs and cooling equipment may be required. Good processing techniques must be used to insure proper thickness, hardness and wear resistance of the coating. Tight dimensional tolerances and good surface finish requirements are usually given for the final coating. The procedure will probably include over-machining the surface approximately 0.001 in., hard coating approximately 0.002 in. thick, and then honing the surface to the proper surface finish and dimension. REPAIRING A DAMAGED OR WORN HARD COAT This could vary from a simple application to an impossible application depending upon the nature of the part, the requirements on the repair area, and the exact nature of the damage. The mechanism of the Hard Coat formation and the limitations on the coating properties will determine our capability in repairing a damaged or worn hard coat. The limitations are a result of the following basic rules of hard coating: 1. Aluminum must be consumed (etched) to form hard coat. 2. The thickness of the hard coat will be twice as much as the thickness of the aluminum consumed when the hard coating operation is carried out properly. 3. Usually, existing hard coat does not pass electrical current and additional hard coat cannot be formed over existing hard coat.

49

4. The selective hard coat must be at least twice as thick as the hard coat being repaired to end up with the repair surface that is level (on the same plane) with the original hard coat surface. 5. The thicker the selective hard coat required, the more difficult it is to form the coating, and the more difficult it is to maintain maximum hardness and wear resistance. The dielectric properties of existing hard coat will affect our ability to repair a worn or damaged hard coated surface in the following ways: o In some applications, wear, damage, or mismachining may penetrate through most, but not all, of the coating thickness. This type of area can not be repaired as is, since even a thin coating will not pass current. o In other applications, wear, damage, or mismachining penetrates to the base material, but a thin coating usually remains next to the bare aluminum. While repairing the area, hard coating will form only where the bare aluminum was exposed; the thin layer of hard coat remains unchanged. This results in an unattractive repair that does not provide wear and corrosion resistance. Stripping of the repair area overcomes the problems arising from "thin" coatings. When the stripped area is subsequently hard coated, a more acceptable repair is accomplished, since the existing and the new hard coats may be uniform in thickness. However, the selective hard coat may not be level with the existing, adjacent hard coat which is unacceptable if the repair is on a bearing or seal surface. For the selective hard coat to be level with the adjacent hard coat, the selective hard coat must be considerably thicker than the existing hard coat. Whether this can be done successfully will depend on the thickness of the adjacent hard coat, how deep the aluminum was penetrated, and how good the repair has to be dimensionally. Some dressing of the repair area will have to be done after hard coating. Some reduction in hardness and wear resistance in the repair area must also be expected because of the much higher thickness of the selective hard coat. Appearance requirements add to the difficulties in making a repair. The color of a hard coat varies widely with the operating conditions and the thickness of the coating, so a considerable amount of experimentation may be required to get a reasonable color match. In summary, repairing hard coat is simple if corrosion protection and/or wear resistance is required. The repair can be accomplished by stripping any thin or damaged coating that is present, and then selectively hard coating approximately 0.002 in. thick. If there are dimensional or appearance requirements the repair becomes more difficult, if not impossible, to accomplish.

50

IMPORTANT HARD COATING OPERATING CONDITIONS The following operating conditions will affect the hard coating process and the thickness, structure, appearance, and properties of the resulting hard coating: 1. Alloy being hard coated. 2. Size of area being hard coated. 3. Current density. 4. Voltage. 5. Temperature. 6. Anodizing processing time. EFFECTS OF ALUMINUM ALLOY ON HARD COATING Each aluminum alloy responds differently to the hard coating process. Some differences are: 1. Certain aluminum alloys burn more easily than others. Such alloys require lower current densities. 2. Certain alloys require higher voltages than others. 3. The factor varies slightly depending on the alloy. 4. The color of the coating varies depending on the alloy. Table 10. Hard Coating Parameters for Various Alloys Alloy Recommended Current Density at Room Temperature (amps/sq in.) See Note 1 2024-T3 3003-H14 6061-T6 7075-T6 A356-T6 0.5 1.0 1.0 1.0 1.0 30 40 43 21 37 75 76 77 71 63 Pale olive-drab to charcoal-gray Light-beige to black Dark-gray to black Tan to darkbrown Charcoal-gray to black Typical Final Voltage at Room Temperature and at Recommended Current Density Factor: (Amp-Hr for 1 in. on 1 sq in.) Color Range for Various Operating Conditions

51

Note 1: Hard coating may be done at room temperature in salvage applications where the hardest, most wear resistant coatings are not required.

52

SIZE OF AREA BEING HARD COATED The size of the area being hard coated has an important effect on solution temperature. Larger areas (when full contact is made with the tool) result in more current and, therefore, more rapid heating of the solution. See Section 2 for pump selection depending on the size of the area being hard coated. Larger areas also require more total amp-hr, and this results in more overall heating of the solution. Therefore, the larger the area, the greater the need for a larger volume of solution, or a means of cooling the solution. CURRENT DENSITY Hard coating operations should be controlled by current density. The higher the hard coating current density, the faster the hard coat is applied. Excessive current density, however, results in overheating of the work area and soft, thin coatings. At even higher current densities, localized burning may result. Burned areas are very soft, degraded coatings, generally circular in shape, and different in color and texture from the surrounding areas. Too low of a current density results in long hard coating time and, therefore, ample time for the electrolyte to attack the coating. This may result in thinner than expected, soft coatings with low wear resistance. At the proper current density, hard, wear-resistant, and corrosion-resistant coatings are applied as rapidly as possible and to the desired thickness. Voltage has a significant effect on current density. The relationship between voltage and current density is not linear, that is, doubling the voltage does not double the current density. The relationship is more complex. See Figure 4 for an example of the relationship in the initial stages of an operation, when the first 0.0005 in. is being applied. After approximately 0.0005 in. of hard coat has been applied, the effect of coating thickness on current density becomes noticeable, with the current density dropping as the coating builds up. An increase in voltage is then required to maintain the current density. The amount of voltage increase needed to maintain the current density depends on the alloy. The voltage increase necessary to maintain the current density also varies from one lot of the base material to the next. For example, when hard coating 6061-T6 to a thickness of 0.002 in., at 0.5 amp/sq in. the voltage required at the end of the operation was 50.3 for one lot and 30.3 for a second lot. The amount of voltage increase necessary also depends on the hard coating solution temperature. For example, when hard coating 7075-T6 to a thickness of 0.002 in. at 0.5 amp/sq in., the voltage required at the end of the operation was l6.5 volts at 70°F, 27.1 volts at 50°F, and 38.5 volts at 30°F.

53

VOLTAGE Voltage adjustments are made during a hard coating operation to maintain the desired current density. In some cases this is done during the entire operation. In many cases, however, there is a maximum recommended voltage. Exceeding this voltage reduces the hardness and wear resistance of the coating. In these cases the voltage is adjusted to maintain the desired current density during the first part of the hard coating operation. When the maximum voltage is reached under load (with the hard coating tool on the part), no further increases or decreases are made. As the hard coating operation continues, the current density decreases and the voltage increases slightly. No adjustments are made during this latter part of the operation, that is, the voltage is allowed to rise slightly above the maximum recommended voltage. The maximum recommended voltage is usually approached only when the solution is refrigerated. TEMPERATURE Hard coating is done in a temperature range of 30 to 70°F. When it is mandatory to achieve maximum hardness and wear resistance of the coating, the process is done at 30 or 50°F, depending upon the alloy to be anodized. A considerable amount of heat is developed by the hard coating process, primarily in the coating itself. This heat is dissipated by the part being hard coated and by the hard coating solution. The size, shape, and temperature of the part determine how much heat will it absorb, and how fast. Nothing can be done about the size and shape of the part; but when applicable, the part should be cooled to a suitable temperature. To insure proper dissipation of the heat by the solution, the following plans and procedures should be used: 1. When necessary, pre-cool the solution to be used. 2. Overheating of the solution can be prevented by using an adequate starting volume of solution or by cooling the solution as it is used. Processing of larger areas result in more heating of the solution during hard coating and, therefore, require larger starting volume of solution or heavier duty cooling equipment. 3. Avoid local overheating of the solution within the tool cover, on small areas by dipping for solution frequently, and on large areas by pumping solution fast enough. HARD COATING PROCESSING TIME Longer hard coating times result in more dissolution and degradation of the coating. Hard coating operations, therefore, should be carried out as rapidly as possible. To accomplish this: 1. Select or make a tool that will, if possible, cover the entire area. 2. Provide for sufficient solution supply. 3. Use a power pack with sufficient amperage output. 4. Manipulate the voltage properly to obtain optimum current density.

54

5. Keep the tool in proper and constant contact with the part. OBTAINING THE DESIRED FINAL RESULTS CONTROLLING THE THICKNESS OF THE HARD COAT The thickness of hard coat is controlled by the total number of amp-hr passed while hard coating. The formula for calculating amp-hr follows: amp-hr = F x A x T F = factor obtained from Technical Data Sheet A = area of surface to be coated T = desired coating thickness Note: The coating thickness required is twice as much as the build-up required. For example, if a build-up of 0.001 in. is required, the deposit thickness should be 0.002 in. This is especially important in dimensional salvage applications. Example: A hard coat 0.0018 in. thick (resulting in a dimensional build-up of 0.0009 in.) is required on a 6 sq in. area of 6061-T6. F = 77 A = 6 T = 0.0018 Placing these values in the above formula: amp-hr = 77 x 6 x 0.0018 amp-hr = 0.8316

CONTROLLING TEMPERATURE WHILE HARD COATING The proper temperature range for hard coating varies with the type of application and/or the aluminum alloy being hard coated. As shown in the Operating Parameters Table, page 65, when maximum wear resistance is desired, the proper range is 25 to 35°F or 45 to 55°F depending on the particular alloy. When maximum wear resistance is not required, such as in repairing mismachined parts, the proper range is 65 to 80°F. In most cases, to assure proper starting temperature, the hard coating solution will have to be precooled. Also, significant amounts of heat are developed while hard coating. The higher the 55

thickness of the hard coat and the larger the area, the more the solution will be heated. The solution may be pre-cooled and its temperature may be kept in the proper range by: 1. Using the Hard Coat Solution Cooler. 2. Pre-cooling the solution in a refrigerator, freezer, or outside on a cold day (the solution will not freeze at a temperature of 10°F or higher) for initial make-up and for later additions of chilled solution. 3. Starting with a sufficient volume of solution so that the heat developed during the hard coating operation will not get the temperature of the solution out of range. The following formula can be used for this purpose. L L = = 40 x amp-hr PIT liters of solution required to prevent an excessive increase in temperature. ampere-hours required for the hard coating operation. permissible increase in temperature, in °F, that is, if the starting solution temperature is 45°F and the maximum permissible temperature for hard coating is 55°F, the permissible temperature rise is 10°F.

amp-hr = PIT =

Example:

A hard coating operation will be carried out on 6061-T6 and maximum wear resistance is required. The technical data sheet indicates the proper temperature range is 45 to 55°F. The amp-hr required is 0.6 and the solution will be chilled to 45°F.

amp-hr = PIT L = =

0.6 10 40 x 0.6 = 2.4 liters 10

Therefore, at least 2.4 liters or more should be used to prevent the solution from rising above 55°F.

56

NOTES

57

TECHNICAL DATA SHEET

SIFCO PROCESS HARDCOAT TYPE III CODE 5025

ANODIZING SOLUTION ANODIZING DATA Factor Average Current Density Maximum Current Density Voltage Range Optimum Anode-To-Cathode Speed Operating Temperature Thickness Range Process Time Maximum Recommended Usage FACTOR TABLE Base Material A356-T6 2024-T3 3003-H14 6061-T6 7075-T6 Factor U.S. 63 75 76 77 71 Factor Metric 0.00038 0.00046 0.00046 0.00047 0.00043

See Table Below See Table Below See Table Below 0 - 45 50 FPM See below 0.0005" to 0.0045" 10 - 45 min. 40 Amp-hr per liter

15.2 MPM 12.7 to 114 microns

OPERATING PARAMETERS TABLE When Maximum Wear A356-T6 2024-T3 Resistance is Necessary Solution Temperature Range 45-55°F 25-32°F °F/°C 7 - 13°C -4 - 2°C Current Density (amps/in²) 0.25 0.25 Current Density (amps/cm²) 0.04 0.04 Maximum Voltage 45 45 When Maximum Wear Resistance is not Necessary Nominal Solution Temperature 65 - 80°F 65 - 80°F °F/°C 18 - 27°C 18 - 27°C Current Density (amps/in²) 1 1.5 Current Density (amps/cm²) 0.16 0.23 Maximum Voltage N/A 45

3003-H14 25-32°F -4 - 2°C 0.25 0.04 45

6061-T6 45-55°F 7 - 13°C 0.25 0.04 45

7075-T6 45-55°F 7 - 13°C 0.25 0.04 25

65 - 80°F 18 - 27°C 1.5 0.23 45

65 - 80°F 65 - 80°F 18 - 27°C 18 - 27°C 1 1.5 0.16 0.23 45 N/A

58

COVER MATERIAL RECOMMENDATIONS

Polyester Batting, Polyester Sleeving, Polyester Jacket, PermaWrap, White TuffWrap

GENERAL NOTES: Hard Coating using Anodizing Code 5025 Solution is a constant current type process. At the proper current density, hard, wear-resistant, and corrosion resistant coatings are applied. Voltage has a significant effect on the current density. Voltage adjustments will need to be made during the operation to maintain the desired current density. Maintaining the proper solution temperature is essential to a successful application. Hard coats are not usually sealed since sealing decreases wear resistance. Sealing, however, may be required by the purchase order, blueprint or drawing to improve corrosion protection. If required, sealing should be performed as soon as possible after hard coating. See Section 7 for more information. While hard coating, the volt meter should be watched. Normally the voltage increases to a greater or lesser extent. A slight drop over the course of the operation may occur if the temperature of the solution has been allowed to increase. A rise in voltage and then a rapid, significant drop in voltage may indicate burning has started. If this occurs, decrease the amperage to about two-thirds of the original setting and watch the voltmeter. The voltage should drop slightly and then rise again. If it does not, decrease the amperage another one-third of the original setting. Continue hard coating until the calculated amp-hr has been passed.

59

SECTION 6.4 BORIC-SULFURIC ACID ANODIZING

Boric-Sulfuric acid anodizing was developed because of the push to get away from the use of hexavalent chromium, which is a major environmental hazard. Boric-Sulfuric has been shown to be a suitable replacement for Chromic Acid anodizing in tank applications by Boeing Aircraft Company, as described by their specification BAC 5632. While using boric-sulfuric acid anodizing, sufficient corrosion protection and coating weights can be obtained for compliance with MIL-A-8625 Type I specification. Driven by the potential industrial applications, the use of boric-sulfuric anodizing can be put into two groups: 1. Replacement of Chromic Acid anodizing in OEM applications 2. Spot Repairs of existing Chromic Acid anodized coatings REPLACEMENT OF CHROMIC ACID ANODIZING IN OEM APPLICATIONS By using boric-sulfuric acid and selective brush anodizing procedures, proper coating weights and corrosion protection can be produced on most aluminum alloys. This will provide the operator with an OEM selective brush anodizing process designed to replace selective brush chromic acid anodizing. SPOT REPAIRS The major use of selective brush boric-sulfuric acid anodizing is repairing damaged chromic acid coatings on aircraft parts. The coatings are often damaged from in-service use, or removed during maintenance. Like selective brush plating, brush anodizing is accomplished on the surface of a given part without the need to immerse the whole part into an anodizing tank. The Boric-Sulfuric Acid Anodizing Code 5031 Solution or the Boric-Sulfuric Acid Anodizing Code 5032 Gel is used to perform the actual anodizing operation. The solution is usually used on small parts, since maintaining the anodizing temperature in the proper range is easily accomplished by pumping heated solution through the anodizing tool. The gel, however, is usually used for onsite applications where flowing solution would present a problem. Examples of this are working on the underside of a part and working on surfaces where flowing solution could get into interior areas where damage of components could occur. Except for their viscosity the solution and the gel are equivalent in their application data and in the final results.

60

The Boric-Sulfuric Acid Anodizing Gel is thixotropic, that is, it becomes more fluid when it is disturbed. When the gel has been undisturbed for a day, its viscosity is approximately that of gelatin. When this material is disturbed for a few minutes such as by stirring, the material becomes much more fluid and its viscosity approximates that of a thick oil. The material, however, reverts to its gelatin-like viscosity after it is allowed to remain undisturbed for a day. IMPORTANT BORIC-SULFURIC ACID ANODIZING OPERATING CONDITIONS o Alloy being anodized o Temperature o Current Density o Anodizing processing time EFFECTS OF ALUMINUM ALLOY ON BORIC-SULFURIC ACID ANODIZING The aluminum alloy to be anodized has the most effect on the factor of the solution (or gel). See the Technical Data Sheets on pages 65 and 66. The factor in this case is a certain number of amphrs/in², for a minimum coating weight of 200 mg/ft². TEMPERATURE Brush boric-sulfuric acid anodizing process should be conducted in an operating range of 76 to 84°F. Do not exceed 90°F with the gel, because it may dry up at higher temperatures. A small amount of heat is developed by the anodizing process. For example, when anodizing a 30 sq in. area for 1 hour at 90°F, the amount of heat developed would be sufficient to raise the temperature of 1 liter of solution by 11°F. This small amount of heat, however, is easily dissipated into the part, solution, tool, and atmosphere. In most cases the problem will be keeping the temperature up in the 76 to 84°F range, rather than preventing overheating of the solution (or gel). CURRENT DENSITY Current density is an operating condition that cannot be changed easily during the course of a boric-sulfuric acid anodizing operation. Current density is affected mostly by the anodizing temperature which in turn is mostly dictated by the set-up of the anodizing operation. A change in voltage while anodizing causes a temporary, but not permanent, change in current density. A change in the aluminum alloy will not result in a significant change in the anodizing current density. Anodizing at constant current density does provide a number of advantages over constant voltage process, such as: o Less variation in coating weights o Anodizing in a shorter period of time o Variations in temperature are not as critical

61

ANODIZING TIME The processing time depends on the weight of the anodic coating when boric-sulfuric acid anodizing and controlling the process by a constant current density. OBTAINING THE DESIRED FINAL RESULTS ACHIEVING DESIRED COATING WEIGHT The coating weight of boric-sulfuric acid anodizing is controlled by the total number of amp-hr passed while anodizing. The formula for calculating amp-hr for 200 mg/ft² follows: amp-hr = F x A x wT F A wT = = = factor obtained from Technical Data Sheet area of surface to be coated (in²) Area weight of target coating (mg/ft²)

See example on the next page.

62

Time and charge density required to build an oxide coating from Boric-Sulfuric on various aluminum alloys at a constant current density of 0.039 amp/in². 2024 6061 7075 Coating Weight Factor Anodizing Factor Anodizing Factor Anodizing Time Time Time 2 2 2 2 Mg/ft A*hr/in Minutes A*hr/in Minutes A*hr/in Minutes Unsealed 200 0.0033 5.1 0.0031 4.8 0.0003 0.5 300 0.0053 8.2 0.0047 7.2 0.0029 4.5 400 0.0073 11.2 0.0063 9.8 0.0055 8.5 500 0.0093 14.4 0.0080 12.3 0.0081 12.5 600 0.0114 17.5 0.0096 14.8 0.0107 16.5 700 0.0134 20.6 0.0112 17.4 0.0133 20.5 Table 11 Example 1: Aluminum = Alloy 2024, Weight = 400 mg/ft², Area = 3 in², Current Density = 0.039 amp/in² Determine Total Amps: Multiply Current Density by Area = 0.039 amp/in² x 3 in² = 0.117 amps Determine AH's: Multiply the area to be anodized by the Factor for 400 mg/ft² in Table 11, 3 in² x 0.0073 AH/in² = 0.0219 AH's Look up in Table 11: For a 400 mg/ft² coating the anodizing time is 11.2 minutes. (or Multiply AH's by 60 to convert to amps per minute. 1.314 amps per minute, divide amps per minute by total amps 0.117 amps to obtain 11.2 minutes)

63

Example 2: Aluminum = Alloy 6061, Weight = 550 mg/ft², Area = 9 in², Current Density = 0.039 amp/in² Determine Total Amps: Multiply Current Density by Area = 0.039 amp/in² x 9 in² = 0.351 amps Determine AH's: Multiply the area to be anodized by the Factor for 550 mg/ft² in Table 11 9 in² x 0.0088 AH/in² = 0.0792 AH's. 0.0088 is halfway between 0.0080 and 0.0096. Look up in Table 11: For a 550 mg/ft² is halfway between 500 (12.3 min.) and 600 (14.8 min.) which is 13.5 minutes of anodizing time. (or Multiply AH's by 60 to convert to amps per minute, 0.0792 x 60 = 4.752 amps per minute by total amps 0.351 amps to obtain 13.5 minutes)

64

MAINTAINING TEMPERATURE IN THE PROPER RANGE The temperature of the anodizing solution or gel in the cover should be above 76°F throughout the anodizing operation to assure that the desired thickness or coating weight is formed in a reasonable amount of time. How to maintain the temperature is one of the more important decisions that must be made in the planning process. When Using the Boric-Sulfuric Acid Anodizing Solution Some methods of keeping the temperature in the proper range when using the Boric-Sulfuric Acid Anodizing Solution are: 1. Use the SIFCO Model 75 Solution Flow System. 2. Use a stainless steel, titanium or quartz immersion heater, a stainless steel or glass thermometer and the appropriate size SIFCO submersible pump or flow system. 3. Make additions of preheated solution throughout the anodizing job. Preheating the part to approximately 85°F is useful in maintaining anodizing temperature for both the solution and the gel. When Using the Boric-Sulfuric Acid Anodizing Gel An effective method of keeping the gel temperature in the proper range is the use of a special hot water heated tool. See Fig. 2 (page 9) for an example. When this type of tool is not available, it becomes more difficult to maintain the temperature in the proper range.

65

TECHNICAL DATA SHEET

SIFCO PROCESS BORIC-SULFURIC CODE 5031

ANODIZING SOLUTION

ANODIZING DATA Factor Average Current Density Maximum Current Density Voltage Range Optimum Anode-To-Cathode Speed Operating Temperature Thickness Range Process Time Maximum Recommended Usage

See Table 11 See Table 11 0.039 amps/in² 0.006 amps/cm² N/A 15 - 25 50 FPM 15.2 MPM 76 to 84°F 25 to 29°C 0.00002" to 0.00007" .50 to 1.80 microns 8 - 12 min. for 400 mg/ft² coating 40 Amp-hr per liter

COVER MATERIAL RECOMMENDATIONS Polyester Batting, Polyester Sleeving, Polyester Jacket, PermaWrap, White TuffWrap

GENERAL NOTES: Anodizing with Boric-Sulfuric Anodizing Code 5031 Solution is a constant current process. The process is best conducted by using a constant current. The resulting coating is generally sealed after anodizing. Please see Section 7 for more details. While anodizing, the voltmeter should be watched. Normally the voltage increases slightly to maintain the current. A slight drop over the course of the operation may occur if the temperature of the solution has been allowed to increase. A rise in voltage and then a rapid, significant drop in voltage may indicate burning has started. If this occurs, decrease the current to about two-thirds of the original setting and watch the voltmeter. The voltage should drop slightly and then rise again. If it does not, decrease the current another one-third of the original setting. Continue anodizing until the calculated amp-hr have been passed.

66

TECHNICAL DATA SHEET

SIFCO PROCESS BORIC-SULFURIC GEL CODE 5032

ANODIZING GEL

ANODIZING DATA Factor Average Current Density Maximum Current Density Voltage Range Optimum Anode-To-Cathode Speed Operating Temperature Thickness Range Process Time Maximum Recommended Usage

See Table 11 See Table 11 0.039 amps/in² 0.006 amps /cm² N/A 15 - 25 50 FPM 15.2 MPM 76 to 84°F 25 to 29°C 0.00002" to 0.00007" .50 to 1.80 microns 8 - 12 min. for 400 mg/ft² coating 40 Amp-hr per liter

COVER MATERIAL RECOMMENDATIONS White TuffWrap, Gel Covers

GENERAL NOTES: Anodizing with the Boric-Sulfuric Anodizing Code 5031 Gel is a constant current process. The process is best conducted by using a constant current. The resulting coating is generally sealed after anodizing. Please see Section 7 for more details. While anodizing, the voltmeter should be watched. Normally the voltage increases slightly to maintain the current. A slight drop over the course of the operation may occur if the temperature of the solution has been allowed to increase. A rise in voltage and then a rapid, significant drop in voltage may indicate burning has started. If this occurs, decrease the current to about two-thirds of the original setting and watch the voltmeter. The voltage should drop slightly and then rise again. If it does not, decrease the current another one-third of the original setting. Continue anodizing until the calculated amp-hr have been passed.

67

SECTION 6.5 PHOSPHORIC ACID ANODIZING

Phosphoric acid anodized coatings are used to prepare aluminum surfaces for adhesive bonding and occasionally as a preparatory procedure for subsequent plating. This section deals only with phosphoric acid anodized coatings for adhesive bonding. On aircraft, applications for the process include the attachment of components to frames and skins and the repair of damaged or punctured skins with replacement plates. Phosphoric acid anodizing is currently the preferred method of preparing an aluminum surface for adhesive bonding. A sulfuric acid-sodium dichromate "FPL" tank etch or chromic acid anodizing has been used in the past for this purpose. Subsequent service experience and laboratory testing, however, showed that these methods resulted in disbands after exposure to low stress levels and a corrosive environment. Phosphoric acid anodizing, when used as a means of preparation, has overcome this problem. Tank (bath) specifications on the process include Boeing BAC 5555 (original issue 1-24-74), Lockheed Georgia STP58-211V01 (original issue 10-15-81) and ASTM D3933-80. British Aerospace's BAel46 Structural Repair Manual specifies the "DALIC Process", to be used for "Phosphoric Acid Swab Anodizing". Phosphoric acid anodizing is generally performed on aircraft or aircraft parts. It is obvious that great care should be taken, from initial planning through post-anodizing care of surfaces, to assure that damage does not occur on any aircraft component. The Phosphoric Acid Anodizing Code 5023 Solution and the Phosphoric Acid Anodizing Code 5024 Gel are available for phosphoric acid anodizing. The only difference in the materials is in their viscosity. There is no difference in the anodizing characteristics or the subsequent quality of the coating. The former is used when solution running from the area being anodized is easily controlled and damage to nearby equipment and structures can be prevented with certainty. The latter is used when working on the underside of a part, or for extra assurance that adjacent areas or equipment will not be damaged by flowing solution. The Phosphoric Acid Anodizing Code 5024 Gel is thixotropic, that is, it becomes more fluid when it is disturbed. When the gel has been undisturbed for a day, its viscosity approximates that of gelatin. When it is disturbed for a few minutes, such as by stirring, the material becomes much more fluid and its viscosity approximates that of a low viscosity grease.

68

The Phosphoric Acid Anodizing Solution and Gel rapidly attack aluminum. Precautions must be taken to insure that the solution or gel will not flow into areas where they can not be removed from, and that they are completely removed after anodizing. The produced coating must be protected in the period after anodizing and before bonding. This is very important, since contamination of the surface will decrease the bond strength of adhesive bonds. The following steps should be taken to protect the coating: 1. Select the method, equipment and materials to be used to "rinse" and dry after anodizing. 2. Prepare signs that forbid touching the anodized area. 3. Clean-up the surrounding area prior to anodizing. 4. Remove from the area any equipment that generates dust, oil, or contaminating vapors. 5. When necessary and as applicable, use clean storage containers or "tents". ANODIZING TOOLS The Phosphoric Acid Anodizing Solution and Gel both attack the anodized coating that is being applied. To minimize this attack, the anodizing tools for both materials should cover the entire area and conform to the area to be anodized so that the tool cover always touches the entire surface to be anodized. For specific information on the accepted types of tools, please see Section 2. PREPARATION OF SURFACE FOR ANODIZING 1. Remove all foreign materials, such as paint, from the area to be anodized. 2. Solvent clean the area to be anodized using a suitable solvent and a lint-free cloth. 3. Abrade area using a Gray Abrasive Pad until a uniform abraded surface is obtained over the entire surface. 4. Use Code 1011 Cleaner Z Solution to obtain a water break free surface. 5. If applicable, perform masking. Conventional masking materials may be used. 6. Anodize. Start at 0 volts, reverse current. Slowly (in about 30 seconds) raise voltage to 10 volts. A current density as high as 0.2 amp/sq in. may be reached but this will drop to approximately 0.02 amp/sq in. after about a minute. Anodize for 10 minutes moving the tool at approximately 10 ft/min. Thoroughly rinse all anodizing material from surface as soon as possible after anodizing, using distilled or deionized water. The rinsing method will depend upon the anodizing material used and upon the circumstances of the application. When the Code 5024 Gel is used, it will probably be necessary to first wipe off most of the material. In this case lightly wipe, rather than rub, with a soft, lint free material moistened with distilled or deionized water. Then rinse with water. If the Code 5023 Solution is used, only a water rinse may be necessary. After thoroughly water rinsing, dry the surface and remove any masking. The phosphoric acid anodized coating that has been applied is approximately 0.000010 in. thick and must not be abraded. 69

Bonding should be performed as soon as possible after anodizing. INSPECTION OF COATING The surface after anodizing should look slightly whiter, more matte, and less metallic than before anodizing. The general appearance and surface texture of the aluminum component will remain unchanged. Verification of the presence of a phosphoric anodized coating is made using a polarizing filter and light from a fluorescent or mercury vapor light (daylight is acceptable). The reflection of light by the anodized surface from these sources is observed through the polarizing filter held close to the eye. A change in color should be noted as the filter is rotated. The colors will be complimentary: examples are yellow and blue, red and green, and purple and yellow-green. What colors are seen is unimportant, as long as a color change is observed. A color change may be seen when the angle of incoming light is at approximately 30° to the surface of the coating. If no color change is seen, reduce the angle of incident light to 5° or less. If a color change is seen at this angle, the presence of a coating is verified. Rejection of a coating can only be made when no color change is seen when the incident light is at 5° or less relative to the anodized surface.

70

TECHNICAL DATA SHEET

SIFCO PROCESS PHOSPHORIC CODE 5023

ANODIZING SOLUTION

ANODIZING DATA Factor Average Current Density Maximum Current Density Voltage Optimum Anode-To-Cathode Speed Operating Temperature Thickness Typical Process Time Maximum Recommended Usage

N/A N/A N/A 10 10 FPM Room Temperature 0.00001" 10 min. 40 Amp-hr per liter

3 MPM 0.25 microns

COVER MATERIAL RECOMMENDATIONS Polyester Batting, Polyester Sleeving, Polyester Jacket, PermaWrap, White TuffWrap

GENERAL NOTES: Phosphoric Anodizing using Code 5023 Solution is a constant voltage process. It is simply carried out by anodizing at 10 volts with reverse current for 10 minutes.

71

TECHNICAL DATA SHEET

SIFCO PROCESS PHOSPHORIC GEL CODE 5024

ANODIZING GEL

ANODIZING DATA Factor Average Current Density Maximum Current Density Voltage Optimum Anode-To-Cathode Speed Operating Temperature Thickness Typical Process Time Maximum Recommended Usage

N/A N/A N/A 10 10 FPM Room Temperature 0.00001" 10 min. 40 Amp-hr per liter

3 MPM 0.25 microns

COVER MATERIAL RECOMMENDATIONS White TuffWrap, Gel Cover

GENERAL NOTES: Phosphoric Anodizing using Code 5024 Gel is a constant voltage process. It is simply carried out by anodizing at 10 volts with reverse current for 10 minutes.

72

SECTION 6.6 PRE-TREATMENT

TECHNICAL DATA SHEET

ANODIZE AND HARD COAT STRIPPING SOLUTION CODE 1046

PRE TREATMENT SOLUTION

The Anodize and Hard Coat Stripping Code 1046 Solution is used to do the stripping of existing anodic coatings. The stripping is done after solvent cleaning the repair and adjoining areas, and after masking for anodizing. Care should be exercised in masking to assure sharply defined edges will be maintained throughout the masking, stripping, and anodizing process. The Anodize and Hard Coat Stripping Code 1046 Solution is applied to the area to be stripped using a Polyester or Red TuffWrap pad. Rubbing the pad over the area is necessary for stripping to take place. No current is used in the operation. Stripping is continued until there is an obvious change in color that indicates stripping has been completed. This should not take more than 15 minutes, depending upon the size of area being stripped. After stripping, the surface must be treated with No. 10 Activating Solution, Code 1031/4450. The operation is completed by water rinsing. The surface should be water break free prior to anodizing.

73

TECHNICAL DATA SHEET

SIFCO PROCESS Code 1011 CLEANER Z

PREPARATORY SOLUTION

OPERATING DATA Factor Voltage Range N/A 10 (smaller tool contact area) to 15 (larger tool contact area) 8 MPM 25 FPM

Minimum Anode-to-Cathode Speed

COVER MATERIAL RECOMMENDATIONS Cotton Batting, Cotton Sleeving, Cotton Jacket, White TuffWrap

APPLICATIONS Used to electroclean aluminum surfaces prior to masking, and then again just prior to anodizing. SPECIAL NOTES The operation is carried out at 10 to 15 volts, forward current and is continued until the following rinse water does not break on the surface.

74

TECHNICAL DATA SHEET SIFCO PROCESS

No. 10 ACTIVATING SOLUTION CODE 1031/4450

PRE TREATMENT SOLUTION

The No. 10 Activating Code 1031/4450 Solution is used to remove a film that has formed on the aluminum while using the Anodize and Hard Coat Stripping Solution. The film protects the aluminum from excessive attack during the stripping operation. The film is removed by applying the Code 1031/4450 Solution on the surface using a Polyester pad and no current. Some gassing occurs on the surface as the film is being removed. The operation is continued until the gassing stops and there is a change in color on the surface. These changes indicate the film has been removed. This should not take more than a minute. The operation is completed by water rinsing. The surface should be water break free prior to anodizing.

75

SECTION 7 DYEING AND SEALING

Anodized coatings applied using the SIFCO Process may be dyed. This is done to get a better color match with adjacent existing anodized coatings. Dyed coatings can be sulfuric, hard coat and occasionally chromic. Sulfuric and hard coat applied at lower current densities, (below 1 amp/sq in.) will accept dyes. Dyeing should be done as soon as possible after anodizing, rinsing, and drying of the surface and before sealing. The dye is applied to the surface by swabbing with a cotton swab. After dyeing, the surface is rinsed with water and then dried and sealed Unsealed coatings applied for 1 hr at 100°F using the Chromic Acid Anodizing Code 5010 Solution or the Code 5027 Gel will pass the corrosion resistance requirements of MIL-A-8625. Sealing, therefore, is not necessary for improving corrosion protection. However, when required, and if the part lends itself to it, the coating may be tank sealed as required without any detrimental effects. Sealing should be done as soon as possible after anodizing and after any dyeing. Sealed coatings can be chromic, sulfuric, boric-sulfuric and possibly hard coat. Sealing of hard coats decreases its wear resistance. Nevertheless, it may be required by the purchase order, blueprint or drawing to improve corrosion protection. Sealing shall be accomplished in a sealing medium, such as a hot aqueous solution of sodium dichromate (see Technical Data Sheet Code 3003), boiling deionized water, or other suitable solutions (see Technical Data Sheet Code 5021 or 5022), per Mil-A-8625. Sealing increases the coating weight of chromic acid coatings by approximately 40%. This should be understood when interpreting data in this manual, and when establishing exactly what the coating weight requirements are for a job. Sealing is performed as soon as possible after anodizing if no dyeing is to be done. If dyeing is to be done, seal as soon as possible after dyeing. Do not seal before dyeing. The solutions can be used by one of three methods: by dipping the part into the solution, by making a dam and then pouring the solution into the dam, or by swabbing. When swabbing, use polyester covers and keep the surface wet with solution.

76

TECHNICAL DATA SHEET SIFCO PROCESS

BLACK ANODIZING DYE CODE 5101

POST TREATMENT SOLUTION

Anodized aluminum, dyed black, is used in a variety of applications ranging from optical applications (to inhibit the reflection of light inside telescopes, and microscopes) to decorative applications. The SIFCO DALIC Black Anodize Dye Code 5101 Solution may be used to do the dyeing. The actual process for dyeing aluminum is fairly simple; however, there are many factors that can affect the depth of color obtained when dyeing a particular part or area. The factors that influence the depth of color are the thickness of the anodized coating, the anodizing current density, and the time elapsed between anodizing and dyeing. The recommended minimum thickness of the anodized coating is 0.0004 in. (10µm); the depth of color increases as the coating thickness increases. The best results are obtained when the current density is kept at or below 1 amp/sq in. (0.15 amp/sq. cm). After the area has been anodized, it is important to dye the area as soon as possible. Leaving the anodized coating exposed to the atmosphere for some time produces a partial seal that can hinder or prevent dyeing. If appearance repeatability is desired, it is important to monitor these factors closely. The dye is best applied at room temperature with cotton batting. The dyeing temperature should be maintained between 68 and 77ºF (20 and 25ºC) to reduce the rate of evaporation of the dye. Saturate the cotton batting with dye and apply by swabbing over the entire area in a circular motion. Continue swabbing the area for 2 minutes. Re-saturate the cotton if necessary. Allow the area to air dry for 10 minutes before sealing. Seal the dyed area in boiling deionized or distilled water for 30 minutes. Excess dye will probably leach out into the water. However, a good anodized coating retains the majority of the dye in its pores. After sealing, rinse the part with deionized or distilled water and blot dry with cotton batting. To remove any dye residue off the surface, lightly saturate cotton batting with acetone or isopropyl alcohol and swab the surface in the same manner as the dye was applied. To remove any streaks and to make the appearance more uniform, lightly saturate cotton batting with oil and buff the area using small circular motion until uniform appearance is obtained. Using a fresh piece of cotton batting, wipe off the excess oil.

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BLACK ANODIZING DYE CODE 5101

Mixing Instructions For 1 Liter

1. Using a graduated cylinder, measure out 1.0 liter of acetone or isopropyl alcohol; add approximately 500 ml to the powdered dye. 2. Tightly seal the container and shake vigorously for 1 minute. 3. Add the remaining 500 ml of liquid and continue to mix for another minute. Note: If a graduated cylinder is unavailable, fill the can approximately half full. Mix well. Pour in the remaining liquid, leaving the solution level approximately 1/4" from the top of the container. Shake well. Caution: Container should be grounded to avoid electrostatic shock. Consult with your facilities safety coordinator.

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TECHNICAL DATA SHEET SIFCO PROCESS

TRIVALENT CHROMIUM POST-TREATMENT ANODIZE SEAL CODE 5020

POST TREATMENT SOLUTION

The SIFCO Process Anodizing Seal Code 5020 Solution is used to seal anodic coatings and will allow passing the salt spray requirements (336 hrs) of MIL-A-8625. No current is used in the sealing operation. The Code 5020 solution is environmentally friendly (hexavalent chromium free). It operates at ambient temperatures and does not require expensive disposal procedures due to its low concentration. It does not impart any color to the coating. The solution can be used by one of three methods: by dipping the part into the solution, by making a dam and then pouring the solution into the dam, or by swabbing. When swabbing, use polyester covers and keep the surface wet with solution. Sealing conditions are as follows: Seal Solution Code 5020 Temperature 60 to 75°F 15.5 to 24°C Time 2 to 10 min. Comments Increase of treatment time will enhance corrosion resistance.

Samples processed at evaluated temperature do not show performance benefits. The operation is completed by water rinsing and air drying.

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TECHNICAL DATA SHEET SIFCO PROCESS

ANODIZING SEAL No. 1 CODE 5021

POST TREATMENT SOLUTION

The SIFCO Process Anodizing Seal No. 1 Code 5021 Solution is used to seal anodic coatings and will allow passing the salt spray requirements (336 hrs) of MIL-A-8625. No current is used in the sealing operation. The Code 5021 solution provides a greater tolerance for errors in processing as compared to Code 5022. The Code 5021 solution, however, imparts a light yellow color to the coating which might be undesirable for appearance reasons. When the light yellow color cannot be tolerated, use the Code 5022 solution. The solution can be used by one of three methods: by dipping the part into the solution, by making a dam and then pouring the solution into the dam, or by swabbing. When swabbing, use polyester covers and keep the surface wet with solution. Sealing conditions are as follows: Seal Solution Code 5021 Temperature 60 to 75°F 15.5 to 24°C Time 2 min. Comments Do not over-seal since the anodized coating might be stripped off.

Note 1: The solution should not be reused when using a swab or dam technique of application. The operation is completed by water rinsing and air drying.

80

TECHNICAL DATA SHEET SIFCO PROCESS

ANODIZING SEAL No. 2 CODE 5022

POST TREATMENT SOLUTION

The SIFCO Process Anodizing Seal No. 2 Code 5022 Solution is used to seal anodic coatings and will allow passing the salt spray requirements (336 hrs) of MIL-A-8625. No current is used in the operation. The solution can be used by one of three methods: by dipping the part into the solution, by making a dam and then pouring the solution into the dam, or by swabbing. When swabbing, use polyester covers and keep the surface wet with solution. Sealing conditions are as follows: Seal Solution Code 5022 Temperature 85 to 90°F 29.5 to 32°C Time 10 min. Comments Part should be preheated to maintain seal temperature.

Note 1: The solution should not be reused when using a swab or dam technique of application. The operation is completed by water rinsing and air drying.

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TECHNICAL DATA SHEET SIFCO PROCESS

DICHROMATE SEAL CODE 3003

POST TREATMENT SOLUTION

The SIFCO Process Dichromate Seal Code 3003 Solution is used to seal anodic coatings and will allow passing the salt spray requirements (336 hrs) of MIL-A-8625. No current is used in the operation. The Code 3003 solution imparts a iridescent yellow/orange color to the coating which might be undesirable for appearance reasons. When the light yellow color cannot be tolerated, use the Code 5022 solution. The solution can be used by one of two methods: by dipping the part into the solution, or swabbing. When swabbing, use polyester covers and keep the surface wet with solution. Sealing conditions are as follows: Seal Solution Code 3003 Temperature 208 to 212°F 98 to 100°C Time 15 min. Comments Part should be preheated to maintain seal temperature if swabbing

The operation is completed by water rinsing and air drying.

82

TECHNICAL DATA SHEET SIFCO PROCESS

TRIVALENT CHROMIUM POST-TREATMENT ANODIZE SEAL CODE 5020

POST TREATMENT SOLUTION

The SIFCO Process Anodizing Seal Code 5020 Solution is used to seal anodic coatings and will allow passing the salt spray requirements (336 hrs) of MIL-A-8625. No current is used in the sealing operation. The Code 5020 solution is environmentally friendly (hexavalent chromium free). It operates at ambient temperatures and does not require expensive disposal procedures due to its low concentration. It does not impart any color to the coating. The solution can be used by one of three methods: by dipping the part into the solution, by making a dam and then pouring the solution into the dam, or by swabbing. When swabbing, use polyester covers and keep the surface wet with solution. Sealing conditions are as follows: Seal Solution Code 5020 Temperature 60 to 75°F 15.5 to 24°C Time 2 to 10 min. Comments Increase of treatment time will enhance corrosion resistance.

Samples processed at evaluated temperature do not show performance benefits. The operation is completed by water rinsing and air drying.

83

SECTION 8 INSPECTING ANODIZED COATINGS

VISUAL The coating should be examined visually for uniformity of color and texture. Differences in color and texture, particularly when circular in shape, and that are not related to any known differences in the base metal may indicate burning and degradation of the coating or a non-uniform coating thickness. Differences in color or texture, due to a difference in surface texture prior to anodizing, will affect appearance but will not affect corrosion protection or wear resistance. Please see Section 6.5 for specific information on Phosphoric Acid anodized coatings. ADHESION Because the anodic coating is not "applied" or "deposited" on the surface, but is rather made by converting some of the base aluminum into aluminum oxide, it is extremely unlikely, if not impossible, to get a poorly adherent anodic coating. Traces of oil, grease, oxides or dirt will not affect adhesion, since after anodizing they will be on the top surface of the coating. Heavy coatings of oil, grease, dirt, oxides, or paint will prevent anodizing and this can be detected visually. A tape test might be performed for reassurance of adhesion after all processing, including dyeing and sealing has been completed. THICKNESS Thickness of coating can be confirmed using a thickness tester that uses the eddy current method. This method requires careful calibration of the tester before making measurements since some anodized coatings, such as chromic or boric-sulfuric coatings are extremely thin.

84

SECTION 9 REFERENCE SECTION

DEFINITIONS AND ABBREVIATIONS:

amp: Ampere. A measure of the rate at which electrical current flows through a conductor such as wire or a conductive solution. Comparable to rate (liters/gallons per minute) at which water flows through a pipe. amp-hr: Ampere-hour. See AMPERE-HOUR. AMPERE-HOUR: A measure of the quantity of electricity that flows through a conductor. Comparable to the quantity of water, liters or gallons, that flows through a pipe in a given length of time. ANODE: Technically, the positive terminal in a solution. Metal ions in the solution flow away from the positive terminal. When operating in REVERSE, the part is positive and there is a tendency to remove material or "etch" the part. In the FORWARD direction, the part is negative and metal ions flow to the part, i.e. the part is plated. In SIFCO Process Anodizing terminology, the anode is the part being anodized. ANODE-TO-CATHODE SPEED: The rate of movement of the anodizing tool relative to the surface being anodized. The relative movement can be obtained by moving the tool, by moving the workpiece or by moving both. ANODIZED COATING: A non-conductive oxide coating formed on aluminum for corrosion protection, wear resistance and/or dimensional restoration. Thickness varies from 0.5 to 75 µm (0.000010 to 0.003 in.) depending upon the application. ANODIZING AMPERAGE (AA): The amperage being used while anodizing. AREA (A): Surface to be anodized in square centimeters or square inches. Used in SIFCO Process formulas. AVERAGE CURRENT DENSITY (ACD): The current density at which an anodizing solution is used under average conditions. In the average case some conditions are not ideal; i.e., the anodizing tool or solution temperature is not optimum, and/or there is insufficient anode-to-cathode speed. Average current density values are generally used for SIFCO Process calculations and in the design of special tools. With a good set-up this value can be used as a guide as to the minimum current density that one should be able to draw. Bhn: Brinell Hardness Number. Also called Hardness Brinell or HB.

CATHODE: Technically, the negative terminal in a solution. Metal ions in a solution flow to the negative terminal. In the "FORWARD" or plating direction, the workpiece is negative and metal ions flow to it. In SIFCO Process Anodizing terminology the cathode is the anodizing tool.

CONTACT AREA (CA): The area of contact made by an anodizing tool on the part measured in square inches or square centimeters.

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CURRENT DENSITY (CD): The anodizing current being passed per square centimeter or per square inch of contact area. The value may be determined by dividing the anodizing current by the contact area. When 10 amperes are drawn with a tool making 32.5 square centimeters (5 square inches) of contact with a part, the current density is 0.3 amperes per square centimeter (2 amperes per square inch). ESTIMATED ANODIZING AMPERAGE (EAA): Amperage calculated based upon the contact area and the average current density for a given anodizing solution. ESTIMATED ANODIZING TIME (EAT): Time calculated based upon the required amp-hr and the estimated anodizing amperage for a given job. FACTOR (F): The ampere-hours required to form the coating equivalent to one micron thickness on one square centimeter of area or one inch thickness on one square inch of area, or the coating equivalent to a desired coating weight. FORWARD CURRENT: Direction of electrical current flow in which metal ions tend to move away from the tool and toward the part. Selective Plating is done under forward current. FPM: Recommended anode-to-cathode speed for an anodizing solution in feet per minute. HARDNESS: The ability of a material to resist indentation. Brinell and Rockwell C are common hardness tests. MAXIMUM CURRENT DENSITY: The highest current density that can be employed with an anodizing solution when anodizing conditions are ideal. METERS PER MINUTE (MPM): Recommended anode-to-cathode speed in meters per minute. PREWET: Applying solution to the surface before applying current. This is usually done by placing the anodizing tool on the part for a few seconds with the anodizing tool lead disconnected or the power pack shut off. Also called swab. Rc: Rockwell C Hardness Number. REVERSE CURRENT: Direction of electrical current flow in which metal ions flow away from the part and toward the anodizing tool. Selective Anodizing is done under reverse current. THICKNESS (T): Thickness of the coating to be anodized, stated in terms of inches or microns. VOLT: Unit of measure of electrical potential. The higher the electrical resistance in the system, the higher the electrical potential that is required to maintain a given current flow.

86

WATER BREAK: The breaking of a water film into beads such as on a waxed car which indicates that the surface is not clean. Mil-A-8625 requires a water break free surface prior to anodizing.

87

SIFCO PROCESS CALCULATION FORMS It is necessary to go through a series of calculations to effectively plan and carry out anodizing jobs. Many new operators find it difficult to make these calculations since they: o Do not understand the proper sequence of calculations. o Do not make the calculations in a disciplined, orderly fashion. o Scatter and intermix formulas, calculations and answers. o While calculating, forget the answer that they are trying to achieve. o Cannot locate a previously determined answer. The SIFCO Process calculation form for anodizing has been provided to assist operators in making these calculations. Use the formulas located in the section of the coating to be anodized and make calculations in the space provided for each item on the form.

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SIFCO PROCESS ANODIZING CALCULATION FORM DEFINITIONS Area (A) = This calculation is for the total area to be anodized. It will include all exposed areas of aluminum adjacent to the actual area requiring anodizing. Amp-Hr (AH) = This calculation is used to control coating thickness or weight, and requires the factor (F) of the desired solution, the area to be anodized (A), and the desired coating thickness (T) or coating weight (W). The resulting value, a measure of amps x time, can be read on the power pack ampere-hour meter. Contact Area (CA) = This is the actual area on the part that is being touched by the anodizing tool. It can be determined by placing the tool on the part and measuring the contact dimensions (L and W), or it can be determined by estimating the percentage of the total part area being touched by the anodizing tool at any one time. Estimated Anodizing Amps (EAA) = This calculation gives a rough idea of what the anodizing amperage should be under typical conditions. The actual anodizing amperage may be less than estimated due to anodizing conditions. It may be greater than estimated, not to exceed the maximum current density, if anodizing conditions are ideal. Estimated Anodizing Time in Minutes (EAT) = This calculation gives a rough idea of how long the anodizing operation should take. The actual anodizing amperage will affect the anodizing time. Liters of Solution Required to Prevent Temperature Rise = This calculation is used to determine how much solution should be used to prevent an excessive temperature rise while anodizing. Permissible Increase in Temperature (PIT) = The difference between the starting temperature of the solution and the maximum recommended temperature for the solution. RPM = This calculation for revolutions per minute is used when either the part or the tool is being mechanically rotated. The desired anode-to-cathode speed for the particular solution is converted into revolutions per minute

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SIFCO PROCESS ANODIZING CALCULATION FORM Area (A) = ( L x W ) Rectangle, ( 0.785 x D² ) Circle, ( 3.14 x D x L ) OD or ID

Amp - Hr (AH) = ( F x A x T ) or ( F x A x W ) for Chromic only, or ( F x A ) for Boric-Sulfuric only

Contact Area (CA) = ( L x W ) or ( % x A )

Estimated Anodizing Amps (EAA) = ( CA x ACD )

Estimated Anodizing Time in Minutes (EAT) = ( AH EAA ) x 60

Solution Required L = ( 35 x AH ) PIT

RPM = ( FPM x 3.82 ) D

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SPECIFICATIONS An important specification that covers tank anodizing is MIL-A-8625. The SIFCO Process does not meet the processing provisions of the specification due to the technicality that it is a tank (not selective brush) specification. However, SIFCO Process anodized coatings do meet the performance provisions of these specifications along with any other specifications listed in this manual.

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