Infrared Reflectance Corrosion Inspection Through Organic Coatings

This ESTCP Pollution Prevention project addresses the reduction of hazardous chemical/waste by employing non-destructive techniques to inspect aircraft interior and exterior structures through coatings coatings thus reducing the amount of stripping and repainting that occurs at military rework facilities. Hazardous pollutants will be significantly reduced by eliminating scheduled organic coating removal and moving to a process where IR inspection results will be used to determine when and if coating removal is required.

The technology exploits an optically transparent spectral window in military paint systems within the Mid-IR spectrum and also the difference in infrared (IR) reflection properties between corroded and non-corroded metallic surfaces. The IR energy passes directly through the coating and then reflects off the metallic substrate back through the coating and into an IR camera. Since the corroded areas do not reflect the IR energy as well as the non-corroded areas, a picture or image is generated by the IR camera much the same as observing the corrosion under standard visual techniques.

The demonstration and validation measurements at NAVAIR Jacksonville and Oklahoma City Air Logistics Center on P-3, B-52 and KC-135 aircraft illustrated clearly that the IR imaging is an improved method of corrosion inspection compared to the visual inspection method. IR imaging will give engineering and corrosion control personnel the capability to make sound decisions regarding coating removal based upon improved detection of corrosion through coatings. A level of 70-80% accuracy was achieved with this technique as compared to the 5-25% accuracy of the visual inspection method.