Void formation and alloy enrichment during anodizing of aluminium alloys containing cadmium, indium and tin

• Published in: Corrosion science 1998-12, Vol.40 (12), p.2125-2139
• Main Authors: Felhosi, I., Habazaki, H., Shimizu, K., Skeldon, P., Thompson, G.E., Wood, G.C., Zhou, X.
• Format: Article
• Language: English
• Subjects: Applied sciences; Corrosion; Corrosion prevention; Exact sciences and technology; Metals. Metallurgy
• ISSN: 0010-938X; 1879-0496
• DOI: 10.1016/S0010-938X(98)00098-5

The formation of voids at the alloy/anodic film interface and the enrichments of alloying elements in a thin alloy layer immediately beneath the anodic film as a consequence of anodizing have been examined for Al-0.28 at.% In alloy and Al-0.5 at.% Cu alloys containing ∼0.11 at.% Cd, ∼0.07 at.% In or ∼0.27 at.% Sn. Fine voids are formed for the indium- and tin-containing alloys for the selected conditions of anodizing, which is suggested to be associated with the relatively low Pilling–Bedworth ratios of the alloying element oxides incorporated into the anodic films. Thus, the formation of voids is dependent upon oxidation of the alloying element. Consequently, no voids were resolved for the cadmium-containing alloy for which limited or no oxidation of cadmium occurred. The enrichment of the binary alloy was equivalent to 3.5 at.% In, with enrichments of the ternary alloys to the ranges 11–16 at.% Cu and 2–7 at.% Cd, In or Sn respectively, for an assumed 2 nm thick enriched layer.