Features in aluminium alloy grains and their effects on anodizing and corrosion

Distinct chemically and mechanically induced features, evident in the grains of the AA5083-O aluminium alloy, and their effects on anodizing and corrosion have been studied. The grain distinct features are orientation dependent and are ridge-like. These features were found after anodizing in Barker's reagent and after micro-trimming with a diamond knife (during the ultramicrotomy process). The grain features were also found to have a relationship with the anodic films formed on the alloy. Distinct striations (associated with the formation of the ridge-like features found after anodizing) were observed on the surface of the alloy after the removal of the anodic layer (using a solution containing 20g Cr₂O₃+30ml HPO₃ in 1l of deionised water at 60°C). Further etched regions, after the removal of the anodic layer, revealed subsurface micro-layers which appear to have significant influence on the corrosion, anodizing and mechanical (at micro-scale) behaviour of the alloy.