Effect of Sc and Zr additions on corrosion behaviour of Al–Zn–Mg–Cu alloys

In this paper, the relationship between recrystallization and corrosion behaviour of Al–Zn–Mg–Cu alloys has been investigated. The additions of Sc and Zr inhibited the recrystallization of Al–Zn–Mg–Cu alloys remarkably. Intergranular corrosion, exfoliation corrosion, stress corrosion cracking and electrochemical properties of Al–Zn–Mg–Cu alloy and Al–Zn–Mg–Cu–Sc–Zr alloy under peak-aged treatment have been studied. Results show that the additions of Sc and Zr to Al–Zn–Mg–Cu alloy can improve the corrosion resistance observably due to the inhibition of recrystallization behaviour. The spacing of grain boundary precipitates Al–Zn–Mg–Cu–Sc–Zr alloy was found to be larger than that in recrystallized Al–Zn–Mg–Cu alloy, the discontinuity of precipitates distribution along the grain boundary was enhanced by the introduction of Sc and Zr.