Anodic film formation on aluminium alloys

Abstract

In the present study, anodic film formation on high-strength aluminium alloys (AA2024-T3, AA2198-T8, AA2198-T851 and AA7475-T761) in tartaric–sulfuric acid (TSA) is investigated, with focus on defects induced by the dissolution of constituent intermetallic particles (IMPs) during anodizing. High-copper-containing IMPs dissolve rapidly, generating micrometer-sized cavities in resultant anodic films. In contrast, Fe–Mn–Si (Cu) IMPs in AA2024-T3 and low-copper-containing IMPs in AA7475-T761 exhibit slower dissolution rate than high-copper-containing ones, resulting in locally modified porous morphology and non-uniform film thickness. Further, it is observed that the morphological and compositional uniformity of resultant anodic films are largely affected by the size, location and composition of IMPs.