Influence of retrogression and re-aging treatment on corrosion behaviour of an Al–Zn–Mg–Cu alloy

Influence of retrogression and re-aging treatment on the microstructure, strength, exfoliation corrosion, inter-granular corrosion and stress corrosion cracking of an Al–Zn–Mg–Cu alloy has been investigated by means of optical microscope (OM), transmission electron microscope (TEM) and electrochemical impedance spectroscopy (EIS). The results show that retrogression and re-aging treatment can increase the size and the distribution discontinuity of the grain boundary precipitates, and lead to the increase of the corrosion resistance without the loss of strength and ductility. In addition, the analysis of electrochemical impedance spectroscopy shows that retrogression and re-aging treatment can enhance the resistance to exfoliation corrosion.