A mechanistic study on localized corrosion of sandwich multi-layered aluminium sheet in 3.5 wt.% NaCl solution

Multi-layered aluminium sheets are quickly gaining wide applications in several industries. However, a complete understanding of how the macro- and microstructures of composite influence the corrosion behavior is still far from being achieved. In this work, the electrochemical behavior of a 4343/3003/7072 aluminum alloy (AA) composite in 3.5 wt.% NaCl solution was investigated using electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and scanning electron microscopy (SEM). The evolution of corrosion morphologies was analyzed from cross-sectional and plane directions, and the localized corrosion mechanism was discussed. Due to the galvanic effect existed in the cross-section, the corrosion resistance of the cross-section was higher than that of the plane surface. From the cross-section, the AA3003 was protected as the cathode and the adjacent AA4343 and AA7072 acted as anodes. Localized corrosion mainly initiated around Al-Si-Mn-Fe and Si-rich phases.