Aqueous Non-Chromate Conversion Coatings for Aluminum Alloys

Chromate conversion coatings are presently applied to military aircraft to increase the operational life of structural components fabricated from aluminum alloys. Coasts of applying these coatings have increased with increasing concerns about the health and environmental effects of hexavalent chromium. American Research Corporation of Virginia has worked to extend a trivalent chromium conversion coating (tccc) process to approach the corrosion resistance imparted by chromate conversion coatings without the health and environmental effects of hexavalent chromium. Optimal compositions of the tccc were found to be more effective in protecting 7000 series aluminum alloys that 2000 series and performed better when immersion coated that spray coated. To develop coatings more suited to Air Force needs, this proposal suggests the use of solid-solution film-forming compounds to modify tccc solutions to provide large area protection for series 2000 aluminum alloys. This program is innovative in combining film-forming materials known to achieve high levels of aluminum alloy protection with a proven tccc approach. Phase I Technical Objectives include a evaluation of solid-solution film-forming thin films, acquisition of families of test data, and optimization of coating compositions in preparation for the Phase II proof-of-concept system.