In-Situ Detection of Hidden General and Pitting Corrosion of Aircraft Structure

Corrosion is becoming an increasing problem in the Air Forces aging fleet. Corrosion is developing in airframes in inaccessible areas never intended for disassembly. Mitigation efforts are proving to be costly and time consuming. A methodology to locate and evaluate hidden corrosion in-situ is needed. X-rays produced by laser Compton scattering (LCS) have the potential to meet this need. This proposal details a plan to evaluate the effectiveness of LCS x-ray beams at finding and quantifying hidden corrosion in aircraft materials. Samples mimicking hidden corrosion will be made for imaging that simulate corrosion using anodized patterns of different shapes, sizes, and oxide layer thicknesses. Additionally, samples or components exhibiting corrosion mechanisms of interest (e.g., pitting, intergranular, general, etc.) will be tested, if available.  Digital detection techniques will be used, enabling detailed analysis of x-ray absorption information to analyze corrosion features such as defect size and depth.  The data will be used in Phase II to create an inspection framework to be designed that enables degradation rates to be analyzed by recording successive inspections on the same part.  Phase II will also focus on image reconstruction using multiple views so that defects within assembled structures can be characterized. BENEFIT: Benefits to be realized by the Air Force with the successful implementation of LCS x-ray beams begin with improved aircraft safety. Significant reductions in aircraft maintenance cost will be possible through reduced teardowns to inspect for corrosion and the ability to schedule corrective maintenance based on actual condition. Commercial applications exist anywhere hidden corrosion is a problem. Commercial airlines will benefit for the same reasons as the Air Force. Other industries that will immediately benefit include the automotive industry, the petroleum extraction and processing industries, and the nuclear energy industry. Fundamental   materials research will benefit as well, as this technology will allow for corrosion to be examined in-situ.)