Development of Spray Coating Methods and Materials to Replace Aluminum Cladding of Aging Aircraft for Corrosion Protection

The proposed work will be directed towards developing aluminum-based crystalline and glassy/amorphous coating using thermal spray techniques (plasma and cold spray) for the corrosion protection of high-strength aluminum alloys (2024 and 7075). The coating material should be anodic to the base material for protection against galvanic corrosion. Glassy metal coatings generally exhibit superior corrosion resistance because of their structural and compositional homogeneity. While significant progress has been made recently in developing bulk metallic glasses including aluminum-based alloys, problems of depositing glassy metal coatings remain to be resolved. Plasma spray technique involves rapid cooling rates and can successfully synthesize metallic glassy coatings. Cold spray technique can also deposit amorphous or glassy aluminum coatings using precursor amorphous or glassy powder. The addition of rare earth elements to aluminum will be considered for this purpose. Optimal processing parameters of plasma spray and cold spray methods will be identified. Coatings will be characterized, and their corrosion performance will be evaluated through corrosion-potential measurements and accelerated corrosion tests in the laboratory. On the basis of Phase I results, the most promising materials and spray coating methods will be selected for more extensive trials and evaluations towards exploring their commercial potential in Phase II.