Corrosion behavior of anodized Al-Cu-Li alloy: The role of intermetallic particle-introduced film defects

The role of intermetallic particle (IMP)-introduced anodic film defects in the initiation and propagation of localized corrosion in an anodized Al-Cu-Li alloy prior to sealing is investigated. Anodizing of IMPs results in cavity defects of micrometer-scale in the anodic film. Corrosion is preferentially initiated in the regions with anodized IMPs at the film/alloy interface. Localized corrosion then propagates in the alloy substrate beneath the anodic film, which ultimately results in cracking of the bulk anodic film. It is suggested that the barrier and porous layers of the anodic film play different roles in different stages of a localized corrosion event.