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Rapid Infrared Imaging of Corrosion and Structural Defects under Organic Coatings

Rapid Infrared Imaging of Corrosion and Structural Defects under Organic Coatings

John D. Weir, Donald DiMarzio, Steven Chu, Nils J. Fonneland, Dennis J. Leyble, Robert P. Silberstein, and Joanne S. McLaughlin

Northrop Grumman Integrated Systems

John E. Benfer

U.S. Navy, Naval Air Systems Command, Materials Engineering

High-fidelity infrared (IR) reflectance and blackbody radiation images can show corrosion and other structural defects under organic coatings. Such images significantly aid engineers in deciding whether the coating must be removed before repair of corrosion or other structural defects hidden beneath. By adopting a process in which IR measurements are used to determine if and when coating removal is required, it is possible to eliminate unnecessary removal of organic coatings and thus significantly reduce hazardous pollutants. The Northrop Grumman study, based on an aircraft with a surface area of about 6,500 ft2, projected an environmental savings of 220,000 lb of volatile organic compounds and 3,000 lb of chromates for a fleet of 100 aircraft over a four-year period. The study also estimated additional labor and material savings of $135,000 per aircraft, based on current labor and material costs.

Introduction

Surface corrosion on aluminum aircraft skins, near joints and around fasteners, is often an indicator of buried structural corrosion and cracking. Today, aircraft paints are routinely removed to reveal corrosion on metal surfaces, and the aircraft must be repainted following repairs. Both expensive and time-consuming, that process can also generate air pollution and waste resources. A method is therefore needed to detect the early onset of corrosion on metal substrates covered by protective coatings, so that aircraft primers and topcoats need not be stripped. Nondestructive techniques to inspect the aircraft exterior structure without removing coatings would substantially reduce the amount of stripping and reapplication of coatings needed. To address those issues, the Strategic Environmental Research and Development Program (SERDP) funded an investigation by Northrop Grumman Integrated Systems into techniques to detect corrosion under coatings [1]. SERDP was established jointly by the U.S. Department of Defense (DoD), U.S. Environmental Protection Agency, and U.S. Department of Energy to meet the requirements of new environmental regulations. The Environmental Security Technology Certification Program (ESTCP) awarded and funded a followon contract to eliminate or minimize pollution from unnecessary paint removal operations on weapon platforms such as aircraft. SERDP's objective was to develop inspection techniques to locate hidden corrosion on aircraft surfaces without removing the coating. The Northrop Grumman study identified several techniques able to achieve that objective, including the imaging of the surface using spectral nondestructive evaluation and wide-area spectral imaging. The spectral

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imaging work indicated that this technique can be used to detect small quantities of corrosion under most conventional coating systems. Adequate infrared (IR) transmittance is obtained with standard epoxy and polyurethane primers, such as epoxy primer MILPRF-85582, epoxy primer MIL-PRF-23377, and polyurethane primer TT-P-2760. (These and all other military product descriptions introduced below can be found at the DoD's Acquisition Streamlining and Standardization Information System (ASSIST) web site, a database for military specifications and standards [2].) Such coatings are typically applied to a thickness range of 0.6 to 0.9 mils. In addition, this technique can see through up to 10 mils of a standard polyurethane topcoat (MIL-PRF-85285). The SERDP study successfully investigated a number of specific techniques that showed significant promise to reliably detect corrosion under coatings and warranted a recommendation to perform a comprehensive ESTCP demonstration and validation program. Under the SERDP contract, Northrop Grumman Integrated Systems developed processes that included the IR reflectance imaging technology (IRRIT) method and a passive method known as the blackbody radiation method: · IR reflectance imaging technology method. The surface is illuminated with IR energy that passes directly through the coating in the 3- to 5-µm range. The IR reflects off the metallic substrate and passes through the coating to an IR camera, which provides a corrosion image resulting from the lower reflectance of the corroded surface. · Blackbody radiation method. The IR camera detects the radiation passively emitted by the surface and images the corrosion of the metallic surface as a result of its higher emissivity, compared with that of the uncorroded metal. In effect, the warm surface of the substrate itself provides the IR emission, which is filtered in the blackbody method by the coating before being imaged by the camera. The advantage of the blackbody method is that the IR radiation must pass through the coating only once, and special IR illumination-handling equipment is not required, allowing use of the blackbody method in more restricted spaces.

Technical Approach to Infrared Imaging

The Northrop Grumman study discovered that mid-IR energy can be used to detect corrosion under coatings via the directional hemispherical reflectance method--i.e., observing the intensity of the reflected signal from both a corroded and an uncorroded substrate. Figure 1 shows the difference in fractional reflectance between a corroded and an uncorroded aluminum substrate, both of which have been finished with Alodine® in accordance with MIL-DTL-5541, Class 1A, plus an epoxy primer in accordance with MILPRF-23377, Type I, and a topcoat in accordance with MIL-PRF-85285, Type I. The uncorroded surface acts more like a mirror than does the corroded surface, resulting in a higher intensity reflection. That result is demonstrated by Figure 1, which compares the signals from the uncorroded and corroded specimens. In addition, the coating appears to have an IR window between 4 and 5.4 µm. This technique by no means reveals an image of the corrosion under a coating, but it does indicate the presence of corrosion or other surface anomalies by a degraded IR reflected signal. Figure 2 shows that the urethane topcoat in accordance with MIL-PRF-85285, Type I, has a negative effect on IR reflectance as a function of increasing thickness. It also shows that an IR window exists between about 3.5 and 5.5 µm. That window allows the IR radiation to pass through the urethane coating.

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18 16 14 12

Reflectance (%)

10 8 6 4 2 0 2.0 Measured, 3.5 mils: Uncorroded Measured, 3.5 mils: Corroded 2.5 3.0 3.5 4.0 4.5 Wavelength ( m) 5.0 5.5 6.0

Figure 1. Directional hemispherical reflectance compared for corroded and . uncorroded substrates, both having primer and topcoat

60

50

Measured, 1.4 mils: Uncorroded Measured, 2.4 mils: Uncorroded Measured, 3.5 mils: Uncorroded Measured, 9.6 mils: Uncorroded

40

Reflectance (%)

30

20

10

0

2.0

2.5

3.0

4.5 4.0 3.5 Wavelength ( m)

5.0

5.5

6.0

Figure 2. Directional hemispherical reflectance of uncorroded aluminum panels with variations in coating thickness Technology Review Journal · Spring/Summer 2008 47

Rapid Infrared Imaging of Corrosion and Structural Defects under Organic Coatings

Figure 3 illustrates the effect of coating pigments: visible light is blocked, while IR energy passes through coatings with pigmentation. That phenomenon is due to the longer wavelength of the IR radiation and the chemistry of the coatings.

Infrared Methods Used to Produce Images of Corrosion under Coatings

The Northrop Grumman Integrated Systems investigation focused on the IRRIT and blackbody radiation methods. Both can produce an image with an IR camera that uses a germanium optical lens transparent in the mid-IR range. The lens focuses an image on an indium antimonide (InSb) focal plane after passing through the filter, as shown in Figure 4. InSb was chosen for its ability to create sensitive, uniform mid-IR detectors with a high signal-to-noise ratio. The IR reflectance method is preferred in the field because of its ability to increase IR illumination more readily. The blackbody radiation method has advantages where the inspection site is difficult to access because of the geometry of the IR illuminators. However, the blackbody method requires the substrate to be at a higher temperature than the background temperature for good contrast imaging. That specification restricts the blackbody method to more limited situations in the field. Infrared Reflectance Imaging Technology. The first method, IRRIT, involved the use of IR heaters to provide IR energy that penetrates the coating down to the reflective substrate, which is aluminum in the case of many aircraft parts. The IR energy wavelength is long enough to be transmitted through the coatings, but shorter wavelength visible light is absorbed and/or scattered, effectively obscuring the underlying surface in Figure 3. The IR energy then reflects back from the substrate through the coating and into an IR detector. A Merlin® midwave IR camera, manufactured by FLIR Systems, Inc., was used as the detector for much of the program because of its high temperature sensitivity and compressor-cooled focal plane technology. The IR illumination reveals any corroded area under the coating because the corroded area does not reflect the IR energy as well as the uncorroded aluminum. Figure 5 shows the superiority of IR illumination (Figure 5a) in differentiating a corroded area from an uncorroded area under an organic coating. Standard visible-light illumination (Figure 5b) distinguishes the two areas very poorly. The image is a painted Joint Surveillance Target Attack Radar System (Joint STARS) aircraft part coated with commercial epoxy primer Boeing Material Specification (BMS) 10-11, Type I, that was corroded in service. (This product and its descriptive material are available from the Boeing Company, but only to authorized contractors.) In Figure 5b, the corrosion is only partially visible in the visible-light image from standard photography. Figure 5a shows the same part as seen under IR reflectance illumination with an IR camera as the detector. The dark areas indicate the full extent of the corrosion. Figure 5a indicates that the green primer and black line visible in Figure 5b are transparent to the IR radiation. As a result, corrosion can be seen under and to the left of the black line. In addition to corrosion, pitting and other structural defects hidden under organic coatings can be observed. IR reflectance observation of pitting under coatings was studied by generating pits or blind holes of various sizes ranging from 1.3 to 8.4 mils in diameter. Tungsten wires of varying diameter were used to produce the pits by the

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Coating/ Primer

Substrate

Visible Wavelength

Infrared Radiation Wavelength

Figure 3. Effect of coating pigments: Infrared radiation passes through organic coating, but visible light is blocked

Coated Aircraft Part

Spectral Filter

Focal Plane Imager

Infrared

Corrosion Cracks Figure 4. Infrared energy reflected or emitted from surface of part being surveyed

electrical discharge machining (EDM) process in a 2024-T3 aluminum alloy plate, after which the plate was painted with both primer and topcoat to obtain a total thickness of 3.5 mils (0.0035 in.). Figure 6 shows the results. The pits appear as white round dots. The 1.3- and 2.4-mil-diameter EDM pits are visible but hard to see in Figures 6a and 6b. The metal scribed arrows seen in Figures 6a and 6b were added to point out the simulated pits. Figures 6c and 6d show larger pits of 4.4 and 8.4 mils in diameter, repectively, without the aid of arrows. Surface cracks can also be detected under coatings using the IRRIT method. Figure 7 presents an IR image of a fatigue crack of known length manufactured in the laboratory. As with corrosion, detection of fatigue cracks around fasteners and other critical structural areas, such as fittings, without coating removal can reduce pollution, because fewer

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a. Infrared image

2661

b. Visible-light image Corrosion

2647

Corrosion Removed

Figure 5. Hidden corrosion revealed clearly by infrared reflectance imaging, but not by standard visible-light illumination

a. 1.3-mil diameter, 1.2-mil depth b. 2.4-mil diameter, 2.1-mil depth

c. 4.4-mil diameter, 4.1-mil depth

d. 8.4-mil diameter, 8.2-mil depth

Figure 6. Electrical-discharge-machined pits simulating corrosion pits in 2024-T3 aluminum alloy plate imaged through 3.5 mils of primer and topcoat

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Figure 7. 0.060-in.-length fatigue crack in 2024 aluminum bar imaged through 3.5-mil primer and topcoat

cycles of stripping and replacing will be required when technicians are able to see, without stripping, whether any defects are present. Unnecessary "just in case" stripping and replacing will be avoided. The process has the additional benefit of reducing processing time and cost. Infrared Blackbody Radiation Method The second detection method uses the same Merlin IR camera to detect corrosion under coatings, but uses IR radiation emanating directly from the part itself, eliminating the need for external heaters to provide IR energy. In this case, IR radiation is emitted from the part's surface in the form of blackbody radiation that penetrates out through the coating and is imaged by the IR camera. As indicated earlier, the advantage of the blackbody method is that external illuminators are not needed. Also, in the case of blackbody radiation, the corrosion actually emits more IR radiation than the uncorroded surface, so corrosion shows up as a lighter (hotter) area than the uncorroded area. This appearance is just the opposite from the IR reflectance method, which shows corrosion as a dark area when imaged with the Merlin camera. Structural Integrity of Composite Parts. Both methods, IRRIT and IR blackbody, can also be used to inspect the structural integrity of composite parts. Figure 8 shows the results for the blackbody method. IR illumination (Figure 8a) surpasses standard visible-light illumination (Figure 8b) in revealing the details under the coatings on a graphite epoxy panel with a graphite weave. The lower portion is finished with standard military green epoxy primer in accordance with MIL-PRF-23377, Type I; the top portion is finished with the same epoxy primer, plus a military gloss gray urethane topcoat in accordance with MIL-PRF-85285, Type I. In the blackbody image (Figure 8a), the weave of the graphite is clearly visible under both the epoxy primer coating and the combination of the epoxy primer and a urethane topcoat. The visible-light image (Figure 8b) presents the same graphite epoxy panel configuration, but the weave cannot be seen. The IRRIT and IR blackbody methods are particularly important when a composite structure has been hit accidentally by a tool or other object. The structural integrity of the composite must be checked. The IRRIT and blackbody methods are currently the only means of very rapidly inspecting composites under coatings over wide areas, so they represent a major step forward in reducing both pollution and cost.

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a. Infrared image

b. Visible-light image

Topcoat

Primer

Bare

Note: Blackbody method, part at 90°F

Bare

Figure 8. Graphite weave revealed clearly by infrared blackbody imaging, but not by standard visible-light illumination

Infrared Reflectance versus Blackbody Emissions. Some situations prohibit one or both methods from detecting corrosion. For example, IRRIT cannot distinguish corrosion if the illuminator power level produces reflectance off the uncorroded aluminum surface that matches the blackbody emission of the corroded area. Similarly, the IR blackbody method cannot distinguish corrosion if other IR sources produce reflectance equal to the blackbody emission. When both conditions exist, neither method can detect corrosion. Figure 9 compares the different methods and issues associated with a hot substrate. Corrosion on an aluminum panel can be seen under the coating when observed with IR, as demonstrated by Figures 9a and 9b. The two figures show the primary observable difference between the IR reflectance and the blackbody radiation methods. In the reflectance method (Figure 9a), the corrosion is denoted by the dark areas, whereas for the blackbody method (Figure 9b), the corrosion is white. When Figures 9a and 9b are superimposed, the dark and light corrosion patterns match. It is essential to avoid the circumstances that produce no contrast and thus negate the ability to observe corrosion. Therefore, the project conducted a laboratory study using a controlled-temperature bath, in order to determine the actual parameters required to eliminate such a possibility. Controlled-Water-Bath Thermal Analysis. The study project investigated the corrosioncontrast issue with a test configuration combining · A water bath that provided a tightly controlled, uniform surface temperature · Directional IR heaters with precisely controlled wattage and IR light angles · An IR camera to detect radiation flux from the temperature-controlled substrate · A monitor that continuously displayed the corrosion image in real time during the temperature analysis The laboratory setup was focused on the temperatures that are likely to exist during inspections in warm-climate areas (e.g., Jacksonville, Florida).

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a. Infrared reflectance image: Dark areas indicate corrosion

b. Infrared blackbody radiation image: Light areas indicate corrosion

Figure 9. Reflectance image of corrosion compared with blackbody image

Figure 10 shows the test configuration of the setup. The water bath was used to control the surface temperature of the corroded panels, which were epoxy-primed in accordance with MIL-PRF-85582, Type I, and polyurethane-topcoated in accordance with MIL-PRF85285, Type I. The monitor to the left of the IR camera continuously displayed the corrosion image in real time during the temperature analysis. A number of IR photographs were taken to determine the potential effects of temperature on contrast. The study first investigated the effects of substrate temperatures to ensure that the performance of the IRRIT would not be degraded by the temperature conditions likely to be encountered at the depot inspection areas. The water bath had sufficient thermal mass to maintain an even temperature. One painted corroded face also formed one face of the thermal bath. The temperature of that face was monitored with a Raytech Corporation laser-sighted infrared pyrometer. With the water directly against the face, a very closely controlled, uniform temperature was observed. That uniformity allowed for accurate determination of the thermal illumination necessary to observe the corrosion. The first test runs were blackbody observations of corrosion at elevated temperatures. Since the corrosion is more emissive than the surrounding aluminum, it appeared white under the IR camera. As the water temperature dropped, the intensity of the blackbody radiation also dropped. This test confirmed the need for IRRIT, rather than the blackbody method, to effectively detect corrosion in an operational environment with uncontrolled temperature fluctuations. The study performed additional testing on a heavily corroded standard panel produced with the aid of American Society for Testing and Materials (ASTM) 117 salt fog and Clorox® bleach. The set of images in Figure 11 shows the effect of a 95°F substrate temperature on images from a surface that has been primed and painted with a P-3 Orion­ equivalent finish system. Figure 11a shows the corrosion as light in the blackbody method when illuminators are not used, since the corrosion in this method emits more energy than the surrounding uncorroded areas. As Figure 11b demonstrates, the corrosion in this environment cannot be detected when illuminated with IR heaters operating at 4.35 W for this example. Figure 11c shows the corrosion indicated in the dark squares using the IRRIT method. In Figures 11a­c, the camera lens is seen as a small black dot with a larger black circle surrounding the black dot. This is the reflection of the camera lens off the substrate, an effect easily identified by the operator.

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Infrared Heater

Water Bath

Infrared Camera Infrared Heater

Figure 10. Equipment used to analyze effect of different temperature ranges

Heavy corrosion is shown by the light squares and tapering rectangle to the right in Figure 11a. In the blackbody method, corrosion emits more heat than the surrounding uncorroded aluminum structure. The physical transfer of heat is clearly seen where the corrosion appears white, indicating a higher heat flux. Figure 11b shows the effect of near-zero contrast produced when both the corroded surface and the uncorroded surface give off approximately the same heat flux. That condition occurs when the blackbody heat flux from the corroded area is equal to the IR reflected heat flux of the uncorroded area, the competing methods of detection cancel out the contrast, and the corrosion is no longer apparent. Figure 11c shows the effect of the heat flux when the IR reflected heat flux is greater in the uncorroded area of aluminum than in the corroded area, which appears cooler and therefore darker. This result demonstrates that the 95°F blackbody emission from the corroded area is overwhelmed by the 7.7-W illuminator source. In the example shown in Figure 11, the surface of the aircraft is 95°F. To ensure detection of corrosion by the IR illuminator system, the heat source must be at least 7.7 W, as oriented in the test. With that power level, corrosion will always show clearly as dark areas in the resulting image. Conversely, the tests show that wattage from other IR sources must be lower than 4.35 W, and preferably be at 0 W, to observe the corrosion under the coating in the blackbody method. We found that, even at elevated temperatures, the IR illumination lamps were able to override the effects of the blackbody condition and turn the corrosion observed in the IR camera from white to dark, as normally seen in the IRRIT method. The wattage required to change the image from blackbody-dominated to IRRIT- or reflectance-dominated is low-- only about 8 W for our laboratory test. Further, the test showed that contrast will not be an issue during inspection, provided the illumination procedures include the use of controlled, angled IR sources adjusted to optimize the image contrast.

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a. Blackbody emissive method b. Equilibrium (no contrast) c. Infrared reflective method

Corrosion Appears White Surface T = 95.7ºF Infrared source = 0 W Surface T = 95.6ºF Infrared source = 4.35 W

Corrosion Appears Dark Surface T = 95.0ºF Infrared source = 7.70 W

Figure 11. Blackbody-dominated, equilibrium, and IRRIT-dominated controlled-waterbath infrared images of same corroded panel

Our test and analysis also established that IRRIT has an advantage in the field over the blackbody method, since the IR flux can be controlled by the user to optimize the contrast ratios between corroded and uncorroded areas under an organic coating. In addition, IRRIT is more consistent across temperature regimes. The blackbody method is preferred only when the available space in the inspection area is small and does not accommodate IR illuminators. Otherwise, no general rules can be specified, because the equilibrium point of no contrast varies according to different illumination angles, coatings, air temperature, and part/sample temperature. The Northrop Grumman study simulated the field conditions likely to be encountered during the field inspection of a P-3 Orion aircraft. We specified selected parameters, including wattage, that would be appropriate for detection of corrosion under coatings in the field. Although other stray sources of IR exist in the laboratory or aircraft inspection hangar, they were determined not to be a factor in this test. Demonstration and Validation of Infrared Reflectance Imaging Method. The ESTCP Program Office approved an IRRIT inspection demonstration of P-3 Orion aircraft maintained at the Naval Air Depot (NADEP) in Jacksonville, Florida. That inspection is considered a worst-case scenario for external corrosion, and the IR characteristics of the current paint system are compatible with the IRRIT inspection technique. The P-3 Orion aircraft is a good test article because its external paint is stripped every four to five years to inspect for corrosion. Such regular stripping allows a study to determine potential environmental savings, as well as to conduct a comprehensive cost/benefit analysis to ascertain whether the inspection process is acceptable from the engineering and environmental perspectives. Metrics studied include hazardous materials savings in terms of federal Resource Conservation and Recovery Act (RCRA) waste, volatile organic compounds (VOCs), chromate reduction, and associated costs. The aircraft was inspected for corrosion by two independent teams during demonstration and validation of the IRRIT process. The Navy team inspected the aircraft visually for corrosion. The Northrop Grumman team inspected the aircraft using the IRRIT. The general test process was as follows:

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· · ·

First, inspect the aircraft visually and record the corrosion sites. Second, inspect the aircraft by the IRRIT. Third, compare both methods with the visual inspection of a stripped aircraft to validate the findings.

Figure 12 presents standard photographs and infrared images of corrosion on a P-3 aircraft in the strip hanger at NADEP Jacksonville, Florida. Figure 12a is a standard photograph of the coated aircraft surface before stripping, with no apparent corrosion visible. Figure 12b is an IRRIT image showing the corrosion on the organic coated substrate before the coating was stripped from the surface. Figure 12c is a standard photograph of the stripped surface, showing the corrosion after the organic coating was stripped. The corrosion by the fasteners that was clearly visible in the IRRIT image can also be seen after stripping, validating the IRRIT process. The IRRIT image with the organic coating in place (Figure 12b) actually shows the corrosion under the coating slightly better than does the IRRIT image after stripping (Figure 12d). Hence, we suspect that some of the original corrosion products could have been removed during the stripping process. We surmise, however, that any corrosion removed during stripping would have been considered superficial.

a. Standard photograph of coated surface before stripping b. Infrared image of corrosion under paint

c. Standard photograph of corrosion on stripped surface

d. Infrared image of corrosion on stripped surface

Figure 12. Standard photographs and infrared images of corrosion on P-3 Orion aircraft before and after paint was stripped 56 Technology Review Journal · Spring/Summer 2008

Rapid Infrared Imaging of Corrosion and Structural Defects under Organic Coatings

Environmental and Cost Considerations. The cost to strip and paint a P-3 aircraft is estimated to be $135,000, based on a general burdened labor rate of $65/hr, including materials and costs associated with hazardous RCRA waste and toxic air pollution. If a P-3 normally is stripped every four years and the strip cycle is extended to every eight years, a savings of $135,000 could be made every other four years for each aircraft in the fleet. Continuing with the example of the P-3, the study showed that 220,000 lb of VOCs and 3,000 lb of chromates for a fleet of 100 P-3s can be saved every four years, if the life of the coating can be extended to an eight-year cycle. Table 1 breaks out the detailed pollution savings. That extension would result in a cost reduction of $13 million for stripping and refinishing the fleet of 100 aircraft every eight years versus every four years. To project similar environmental benefits and cost savings, other aircraft programs would have to review different maintenance scenarios for their specific aircraft.

Conclusions and Recommendations

If implemented by the DoD, the innovative IRRIT inspection technology can pave the way for condition-based maintenance of aircraft structures. Routine removal of organic coatings to inspect for corrosion and other structural defects, such as fatigue cracks and pitting, will no longer be needed. The objective of the Northrop Grumman study has been met: IR imaging of corrosion and structural defects under coatings is practical, reduces hazardous waste and toxic air emissions, and offers the additional benefit of reducing maintenance costs. IRRIT showed an advantage in the field over the blackbody method, since the IR heat flux can be controlled by the user to optimize the contrast ratios between corroded and uncorroded areas under an organic coating. The blackbody method is preferred only when the available space in the inspection area is small and does not accommodate IR illuminators. Each aircraft program can use the engineering data generated from this study and test program to determine how IR imaging can be implemented for its needs. Maintenance procedures can be modified to check specific corrosion-prone structures. Programs can

Table 1. Potential environmental savings from use of IRRIT inspections (based on aircraft with estimated 6500 ft² surface area)

Saved over 4-yr Cycle Product Required over 4-yr Cycle (gal/aircraft) 40 50 330 20 In Product (lb/gal) Per Aircraft (lb) Per 100 Aircraft (lb)

Product Primer: MIL-PRF85582, Type I, Class C1 Topcoat: MIL-PRF85285, Type I Stripper: Turco 6881 Solvent: TT-T-2935

Volatile Organic Compounds 2.8 3.5 5.4 7.5 112 175 1,782 150 11,200 17,500 178,200 15,000 220,000

Total

2,219 Chromates

Chromate: 44-GN-7

40

0.75

30

3,000

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develop condition-based maintenance plans that will extend the service life of coatings that are deemed otherwise in good condition. The technology inventions described by References 3, 4, and 5 can be licensed to insert this technology into the DoD logistics commands.

Acknowledgments

The authors sincerely thank John J. Munyak, Kevin H. Cook, and Allen M. Sinowitz of Northrop Grumman Technical Services and Charles J. Pellerin of the SERDP/ESTCP Program Office for their support on this project. Additionally, the authors thank Major (Ret.) John M. Speers, Major (Ret.) Brian A. Pollack, and Master Sergeant (Ret.) David M. Allen for contractor support through Wright-Patterson Air Force Base. The authors are also grateful to Concurrent Technology Corporation employees Matthew G. Campbell and Scott W. McPherson for their contribution to the cost/benefit analysis.

References

1. J.D. Weir, D. DiMarzio, and H.S. Isaacs, Non-Destructive Testing of Corrosion under Coatings, U.S. Department of Defense, Strategic Environmental Research and Development Program, SERDP Pollution Prevention Project 1137, Final Report, September 1, 2004, https://dtic-stinet.dtic.mil/stinet/GetDataService?reqType=tr Pdf&docId=A439080&Location=U2&doc=GetTRDoc.pdf. Department of Defense, Acquisition Streamlining and Standardization Information System (ASSIST) web site, http://assist.daps.dla.mil/online/start/?CFID=989597 &CFTOKEN=c04547be90f11b2-E4CC8976-1372-548A-D38F3259169B1E21 &jsessionid=06302e4952ea2c42473d. D. DiMarzio, R.P. Silberstein, and J.D. Weir, System and Method for Imaging of Coated Substrates, U.S. Patent 7,193,215, issued March 20, 2007, http:// patft.uspto.gov/netacgi/nph-Parser?patentnumber=7193215. J. D. Weir, D. DiMarzio, S. Chu, and R.P. Silberstein, System for Detecting Structural Defects and Features Utilizing Blackbody Self-Illumination, U.S. Patent 7,164,146, issued January 16, 2007, http://patft.uspto.gov/netacgi/nph-Parser?patentnumber =7164146. D. DiMarzio, J.D. Weir, S. Chu, N.J. Fonneland, and D.J. Leyble, Spectral Filter System for Infrared Imaging of Substrates through Coatings, U.S. Patent Application 20060289766, filed December 28, 2006, http://appft1.uspto.gov/netacgi/nph-Parser? Sect1=PTO1&Sect2=HITOFF&d=PG01&p=1&u=%2Fnetahtml%2FPTO%2 Fsrchnum.html&r=1&f=G&1=50&s1=%2220060289766%22.PGNR.&OS=DN/ 20060289766&RS=DN/20060289766.

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3.

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Author Profiles

John D. Weir, project manager, led the technical effort for the ESTCP project for Northrop Grumman Integrated Systems, Eastern Region, Technology Development Center, Bethpage, New York. Previously, he managed the award-winning SERDP 2003 Pollution Prevention project. A registered professional engineer in the states of New York and Pennsylvania with 35 years of experience, Mr. Weir supports numerous aircraft and ship programs as a materials engineering subject matter expert. He was the chief materials engineer responsible for the A-10 aircraft program. He has published more than 70 presentations and articles, many of which were given at national and international conferences. He has served as past chairman and executive director for the Metro­New York Chapter of the Society for the Advancement of Material and Process Engineering. He holds 10 U.S. patents in materials and processes. He received a BS in engineering science and an MS in materials science from Stony Brook University, as well as an MBA in finance from Long Island University. [email protected] Donald DiMarzio, an Associate Technical Fellow at Northrop Grumman Integrated Systems, Eastern Region, has worked more than 20 years in research and development program management in the areas of advanced materials fabrication, processing, and nondestructive testing and characterization. He has broad expertise in related electrooptical systems, including the design and development of optical reflectance instrumentation for remote-sensing multi- and hyperspectral materials data acquisition and analysis. Dr. DiMarzio also has extensive experience with nondestructive inspection of aerospace materials and structures. While serving as principle investigator of the original SERDP nondestructive analysis program, he invented multispectral methods for direct imaging of substrate conditions under paints and polymer coatings. An award-winning scientist and engineer with over 50 published papers and reports and 8 U.S. patents, Dr. DiMarzio holds a BS in physics from Stony Brook University and a PhD in physics from Rutgers University. He worked as a postdoctoral associate at Brookhaven National Laboratory before joining the Grumman Aerospace Corporation. [email protected]

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Steven Chu is a senior technical specialist for Northrop Grumman Integrated Systems, Eastern Region. He assists in managing the Technology Development Laboratory in the Advanced Concepts and Integrated Solutions group. He has over 17 years of experience in planning, organizing, and executing advanced engineering assignments in the areas of design, development, and analysis. Most recently, he contributed to materials characterization efforts with the Materials Signature Exploitation program, as well as performing on the SERDP and ESTCP IR technology programs. He holds two patents, along with two patents pending, in the fields of IR imagery and composite manufacturing. Mr. Chu holds a BS in physics from the State University of New York, Binghamton, as well as an MBA from Long Island University. [email protected] Nils J. Fonneland is an engineering specialist for Northrop Grumman Integrated Systems, Eastern Region, Advanced Concepts and Integrated Solutions group, Technology Development Laboratory business area. He has 24 years of experience in the design, development, and testing of optical systems, including general optical test systems, optical correlators, holography systems, Fabry-Perot filters, and IR camera systems. He was most recently involved in materials characterization for the Materials Signature Exploitation program, as well as performing on the SERDP and ESTCP IR technology programs. He holds 16 patents in the fields of electrooptics and optical signal processing and has three patents pending in the field of IR imagery. Mr. Fonneland holds a BS in electrical engineering from Stony Brook University. [email protected] Dennis J. Leyble is an engineer in the Northrop Grumman Integrated Systems, Eastern Region, Advanced Concepts and Integrated Solutions group, Technology Development Center business area. He provides engineering support for test hardware installation, instrumentation setup and application, and test operation. He has more than four years of experience in laboratory testing and analysis. Most recently, he conducted image analysis for the Materials Signature Exploitation program. He has conducted extensive testing and evaluation of IR imaging and nondestructive inspection. He also is engaged in the SERDP, ESTCP, and the

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Technology Review Journal · Spring/Summer 2008

Rapid Infrared Imaging of Corrosion and Structural Defects under Organic Coatings

U.S. Navy's advanced destroyer (DD(X)) programs. He has two patents pending, one on coating self-decontamination and one on improved IR filters. Mr. Leyble holds a BE in engineering science from Stony Brook University. [email protected] Robert P. Silberstein is a Technical Fellow at Northrop Grumman Integrated Systems, Eastern Region, as well as the sector area lead for Sensor Integration. He has over 25 years of experience in materials and sensor technology, including optical and RF characterization, electromagnetic properties, laser effects, nondestructive inspection and imaging, and remote sensing. He is responsible for the sensors area of a current Defense Advanced Research Projects Agency program for a structural integrity prognosis system. He led a recent Office of Naval Research program for demonstrating novel nondestructive imaging techniques using thermographic and spectral imaging. He holds a BS in physics, as well as MS and PhD degrees in electrical engineering and computer science from the Massachusetts Institute of Technology. [email protected] Joanne S. McLaughlin is a lead engineer for the development and qualification of materials and processes at Northrop Grumman Integrated Systems, Western Region. She has more than 15 years of research and development experience in materials development and testing, surface finishing, and corrosion control for aircraft manufacturing. Ms. McLaughlin serves as program manager and principal investigator on numerous internal and contract research and development programs. She has supported various programs focused on material qualification and corrosion control. The aircraft programs worked on included F/A-18, B-2, Joint Unmanned Combat Air Systems (J-UCAS), and F-35. She holds a BS in chemical engineering from Pennsylvania State University and an MS in engineering from California State University, Long Beach. Ms. McLaughlin is a registered professional chemical engineer in the state of California. [email protected]

Technology Review Journal · Spring/Summer 2008

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Rapid Infrared Imaging of Corrosion and Structural Defects under Organic Coatings

John E. Benfer is an associate fellow and the senior corrosion engineer and corrosion control program manager for the U.S. Navy, Naval Air Systems Command (NAVAIR), in Jacksonville, Florida, with 17 years of NAVAIR and Naval Sea Systems Command (NAVSEA) engineering experience. Mr. Benfer provides in-service engineering support to the depot and fleet through his duties within NAVAIR and the Aging Aircraft Integrated Program Team. He also supports research, development, test, and engineering programs through ESTCP, NAVAIR's Environmental Program Element Line (Y0817), and collaboration with the Naval Air Warfare Center. He also provides corrosion engineering acquisition support to the P-8A program office. Mr. Benfer is a certified member of the International Association of Corrosion Engineers and is currently published in the American Society of Materials Handbook (Vol. 13), American Society of Materials International, Materials Information Society. Mr. Benfer holds a BS in materials engineering from the Virginia Polytechnic Institute and State University in Blacksburg, Virginia, as well as an MS in materials science and engineering from the University of Florida. [email protected]

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Technology Review Journal · Spring/Summer 2008

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