Effect of aging treatment on microstructure and corrosion behavior of Al-Zn-Mg aluminum alloy in aqueous solutions with different aggressive ions

The microstructure and corrosion behavior of Al-Zn-Mg alloy (namely 7xxx) after natural aging treatment (NAT) and artificial aging treatment (AAT) in aqueous NaCl solutions containing different aggressive ions have been investigated in current work. Results of microstructure characterization demonstrate that the aging treatment has a great influence on the grain size and precipitates. The grain size is relatively sizeable and no evident precipitates are observed in alloy after NAT comparable with that after AAT. The electrochemical corrosion behavior of alloy was studied by polarization curve and electrochemical impedance spectroscopy (EIS). The corrosion potential (Ecorr) of the aluminum alloy is more negative in 3.5 wt.% NaCl containing 0.052 wt.% NaHSO3 solution than that in 3.5 wt.% NaCl solutions with or without 0.907 wt.% NaHCO3. Charge transfer resistance (Rct) results reveal that alloy after AAT has an enhancement of corrosion resistance compare with that after NAT. With the immersion time increasing, mostly pitting spreads over the surface of the alloy only in NaCl solution, whereas exfoliation corrosion mainly occurs in NaCl solutions containing NaHSO3 or NaHCO3. (C) 2019 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

Automated summary

The microstructure and corrosion behavior of Al-Zn-Mg alloy after natural aging treatment (NAT) and artificial aging treatment (AAT) in aqueous NaCl solutions with different aggressive ions were studied. Results showed that AAT improved corrosion resistance compared to NAT, with noticeable differences in grain size and precipitates.