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Corrosion Identification, Removal and Cleaning of Galvanic Couples in Difficult to Access Areas


OBJECTIVE: Provide improved technologies that provide earlier detection and ease of repair for the inspection, detection, and removal of corrosion from aluminum (Al) alloy galvanic couples in difficult to access areas of components and/or end items. DESCRIPTION: Almost all metals used in aerospace are subject to corrosion of various types. One form of corrosion that is of great concern is dissimilar metals corrosion. When two dissimilar metals are in contact and connected by an electrolyte, accelerated corrosion of one of the metals will occur. The more easily oxidized surface becomes the anode and corrodes. The less active member of the couple becomes the cathode of the galvanic cell. The degree of attack depends on the relative activity of the two surfaces; the greater the difference in activity, the more severe the attack. When metals from two different groups are in contact with each other, special protection is required to identify galvanic coupling to detect corrosion, especially hidden corrosion in difficult to access areas. The existing methods of corrosion inspection, detection, removal and repair in the Air Logistics Complex (ALCs) are in need of process improvement and equipment enhancement. Early detection of corrosion is difficult, in some components and regions of the end items (aircraft, missiles, ground support equipment, etc.). Often, aircraft and their components must be partially disassembled in order to accurately detect and access areas in need of repair. Once corrosion has been detected, specialized equipment and materials, including abrasive blast media and hazardous solvents, are required in conjunction with removal. These methods are costly, time consuming, labor-intensive, and result in undesirable environmental conditions including the release of Volatile Organic Compounds (VOCs), particulate matter, and dusting. Moreover, these methods are not precise and cannot be effectively used to remove corrosion damage from hard to reach areas and areas adjacent to critical features. The need for disassembly of the end item contributes to the inefficiency of repairs and decreases the availability of weapons systems to warfighters. Ideally, corrosion would be repaired in-place, with minimal removal of parts to access areas inside the structure. An in-depth assessment of the corrosion repair processes would identify areas that can be improved in efficiency, ease of use, and reduced environmental impact. There have been numerous improvements to equipment and techniques that will contribute to a solution for the issues encountered during the corrosion removal and repair process. Cross utilization existing commercial of the shelf (COTS) manufacturing readiness level (MRL) 8/9 equipment and methods, especially those approved for use in related commercial and general aviation applications, could provide significant efficiency and cost savings across the defense industrial base (DIB). But cross utilization requires research, process engineering, and further development, prior to substitution and implementation into DoD. PHASE I: Develop an innovative technology, methods and approach that will provide earlier detection and improved ease of repair procedures or capability. Provide a concept demonstration and report that includes technology developed, methodologies, and procedures for corrosion detection, removal, cleaning and repair without damaging the underlying substrate or adjacent features. PHASE II: Based on the outcome of Phase 1 concept demonstration, develop the technology for a prototype system that address the collective needs of the described applications. Test the prototype system in a real-world environment and obtain MIL-SPEC approval for use of the process within Air Force Material Command (AFMC). PHASE III: The equipment and methods developed in response to this solicitation can be used in corrosion repair and prevention efforts throughout the DoD, commercial and general aviation industries. Laser technologies are prime candidates to be cross utilized from cleaning to coating removal. REFERENCES: 1. Aerospace Corrosion Protection by John Routledge,
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