Effects of Mg on microstructure and corrosion properties of Zn-Mg alloy

Zn-Mg cast alloys with different Mg contents were prepared. Their microstructures, chemical compositions, microhardness and corrosion resistances were investigated in details, and compared with pure Zn. The alloy containing 3 wt.% Mg showed nano-structure and possessed the best corrosion resistance. Electrochemical tests in 3.5 wt.% NaCl solution indicated that the corrosion potential of Zn-3 wt.% Mg alloy is more positive than that of Zn, and the corrosion current density is about 34% the value of pure Zn. The results of EIS tests were simulated to investigate the mechanism of this improvement. The corrosion rate decreased when the Mg content is higher than 3 wt.%, which is likely related to the formation of the hexagonal Mg rich structure. The microhardness of Zn-Mg alloy increased with increasing Mg content, and is likely attributed to the formation of more Zn-Mg intermetallics. (C) 2014 Elsevier B. V. All rights reserved.