On the microstructural control of localized corrosion in non-anodized and TSA-anodized AA7475-T761 aluminium alloy

Abstract

The corrosion behaviour of the AA7475-T761 alloy in non-anodized and tartaric–sulfuric acid (TSA) anodized conditions in a chloride environment is investigated. In the non-anodized alloy, localized corrosion initiated at constituent intermetallic particles (IMPs) and grain boundary precipitates, leading to trenching and intergranular attack. In contrast, in the anodized alloy, corrosion initiated at defects located at the film/alloy interface, originating from the dissolution of IMPs during anodizing. These defective regions acted as preferential pathways for electrolyte ingress, promoting underfilm corrosion and pit growth beneath the oxide. While the anodic film delayed the onset of corrosion, the highly localized nature of the attack in the anodized sample increased the severity of the damage once initiated.