In situ monitoring of the electrochemical reactivity of aluminium alloy AA6060 using the scanning vibrating electrode technique

Localized electrochemical activation of aluminium alloy AA6060 surfaces during immersion in chloride-containing aqueous solution has been characterised using the scanning vibrating electrode technique (SVET). Ionic current flows in the electrolyte phase adjacent to corroding microcells are imaged in situ, allowing their evolution with time to be monitored with spatial resolution. A heterogeneous response due to the presence of intermetallic inclusions in the material is found on AA6060 surfaces. The highly localized anodic activity was thus detected, which has been interpreted as a result of the galvanic coupling between the matrix and the intermetallic particles. Metallic inclusions behave cathodically whereas the aluminium matrix undergoes metal dissolution due to the activation of anodic sites in the proximity of those inclusions. Hydrolysis of aluminium ions leads to local acidification of the electrolyte adjacent to the anodic sites, and it is accompanied by hydrogen evolution.