Filiform corrosion studies of analogue automotive model alloys based on super-purity aluminium

The effect of the metal substrate microstructure on FFC susceptibility was investigated for super purity based AA 6111 model alloys. For cold rolled and laboratory simulated continuously annealed materials, the FFC susceptibility of the surface substrate was found to decrease with increasing Cu content, while the iron content, at the levels investigated, did not strongly affect FFC properties. Subsequent paint baking was found to reduce the FFC susceptibility further. Alkaline etching and desmutting before coating resulted in a significant reduction of the FFC susceptibility for all alloys and substrate conditions investigated.