Localized corrosion in anodized aluminium alloys

Abstract

The influence of defects formed by dissolution of constituent intermetallic particles (IMPs) on the corrosion resistance of anodized aluminium alloys, including AA2024-T3, AA2198-T8, AA2198-T851, and AA7475-T761, is investigated. Localized corrosion initiates cavity defects located at the film/alloy interface, mainly due to the dissolution of high-copper-containing IMPs. In AA2024, Si-containing particle-induced defects also contributed to a reduction in corrosion resistance. Low-copper-containing IMPs in AA7475-T761 alloy, however, do not affect corrosion resistance. The effects of particle density, composition, size, and location on the formation of defects in anodic films and, subsequently, on corrosion resistance of anodized alloys are discussed.