An electrochemical study of repassivation of aluminium alloys with SEM examination of the pit interiors using resin replicas

The pitting and repassivation behaviour of two aluminium alloys, AA5083 and spray formed Al–Mg–Li were investigated. The alloys did not exhibit classic repassivation on the back scan instead showing a transition to high current, potential independent behaviour. A series of experiments were performed to establish a clearer understanding of the mechanisms occurring in this region. The switch from pit growth to one-dimensional tunnelling is now believed to cause the transition. This is supported by SEM observation of tunnels using a resin replica technique. Tunnels were seen after the transition, but there was no evidence that tunnels were present before the transition.