Chromate-free self-healing coating (SHC) system for repaired and restored aluminum alloy surfaces

ABSTRACT: We propose to demonstrate the benefits of a self-healing coating (SHC) system (comprised of MIL-PRF-85285 compliant self-healing top coat; MIL-PRF-23377 Class N primer; chromate-free pretreatment) on repaired and restored aluminum. Innovations are proposed for a self-healing polyurethane-based top coat that satisfies the functional performance requirements for the present application. The proposed SHC system is expected to be capable of self-healing scratches and cuts (without any external heat or stimulus) when used on repaired aircraft parts, and provide enhanced corrosion protection. The proposed SHC system will be demonstrated on repaired test coupons in Phase I for proof of concept, and on repaired Air Force aircraft parts in the field in Phase II. As part of the Phase I work, damaged aluminum alloy panels will be repaired and restored. Subsequently, the panels will be coated with an in-house developed or a qualified chrome-free pretreatment, a compatible MIL-PRF-23377 Class N primer and the proposed SH top coat. The corrosion resistance and overall coating performance will be compared with state-of-the-art complete chrome and non-chrome coating systems. A successful outcome will be the demonstration that the proposed SHC exhibits better performance than the currently used non-chrome system and approaches that of the chrome based system. BENEFIT: Successful completion of this program will offer a complete package to repair, restore and subsequently protect the damaged aircraft parts with a SHC system. The need for a cost-effective, environmentally-favorable, self-healing coating that heals completely and multiple times has been expressed by both the private sector as well as other branches of the armed services. This proposed program will spur the development of a new coating technology to address the unmet needs of a number of different applications. Once a coating is developed successfully for the Air Force"s needs, it can be transitioned rapidly and effectively into other applications. Commercialization of this novel coating to the Air Force, other branches of the military and commercial sectors will be facilitated due to the broad-based interest in non-chrome, effective, and self-healing corrosion resistant coatings.