Effects of Sc and Zr microalloying additions and aging time at 120 °C on the corrosion behaviour of an Al–Zn–Mg alloy

Sc and Zr microalloying additions and increasing aging time at 120 °C both can effectively improve the corrosion resistance of Al–Zn–Mg alloys. The low corrosion susceptibility caused by adding Sc and Zr is from refining grains and restraining the formation of precipitate free zone. The improved corrosion resistance from prolonging aging time at 120 °C is due to the coarsening of matrix and grain boundary precipitates, and the increased spacing of grain boundary precipitates. Aged at 120 °C for 36 h, the Al–Zn–Mg alloy microalloyed with 0.25 wt.% Sc and 0.10 wt.% Zr exhibits high mechanical properties and admirable corrosion resistance.

► Report effect of Sc and Zr additions on corrosion behaviour of an Al–Zn–Mg alloy. ► Investigate effect of aging time at 120 °C on corrosion behaviour of an Al–Zn–Mg alloy. ► Discuss the reason for improved corrosion resistance caused by Sc and Zr and aging. ► Find the relationship between corrosion and microstructures of the studied alloys. ► Develop an Al–Zn–Mg with high mechanical property and admirable corrosion resistance.