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

Abstract 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.