Establishing a correlation between interfacial microstructures and corrosion initiation sites in Al/Cu joints by SEM–EDS and AFM–SKPFM

A lap joint of AA3003 and pure copper was produced by friction stir welding and the induced interfaces were investigated. Interfacial regions were characterized by SEM–EDS, AFM, SKPFM, OM and Vickers micro-hardness. Multimodal Gaussian distribution (for characterization of surface potential patterns) showed the formation of multiple compounds. A quantitative correlation between microstructure constituents and Volta potential distribution was recognized and confirmed by corrosion attacked sites observations. It was observed that the Al-rich regions proximate the dispersed Cu particles and Cu–Al intermetallics were most susceptible to corrosion attack initiation due to a galvanic driving force between these surface constituents.

Intermetallics , AFM , SEM , Interfaces , Pitting corrosion , Welding