Texture-governed electrochemical corrosion behaviour of AA 6082 alloy

Abstract

The variations of through-thickness corrosion behaviour with the β-fibre evolution of hot-rolled AA 6082 alloy at the sub-surface layer (SL), quarter layer and middle layer (ML) in 3.5 wt% NaCl solution were mainly investigated by EIS, potentiodynamic polarization, SEM, XRD and 3D-MLM. Results showed that the strong β-fibre (rolling) and shear orientation formed at ML and SL, respectively. Compared to ML, charge transfer resistance increased, whereas double-layer capacitance was reduced at SL. From ML to SL, corrosion current density decreased and corrosion potential and pitting potential rose successively. Moreover, the deepened pits occurred at ML. Based on the surface energy of Al in the order (111) < (100) < (110)/high-index planes, the worse corrosion resistance at ML with strong β-fibre orientation stemmed from the high surface energy. As a consequence, the available shear textures are beneficial to improving the corrosion resistance. This provides a new design strategy to enhance the corrosion resistance for the commercial Al alloys.