Corrosion behavior of Zn-Mg alloys in saturated Ca(OH)2 solution

The influence of Mg addition on the corrosion behavior of Zn-x%Mg (x = 0.5, 1.5 and 3) alloys in saturated Ca(OH)2 solution was investigated with pure zinc as a reference. The Zn-Mg alloys were passivated but less resistant to corrosion. Mg alloying caused more negative corrosion potential of the Zn-Mg alloys and inhomogeneity of the passivation layer. Alternately preferential dissolution of the primary Zn-rich dendrites (PZD) and Zn-Mg eutectics (ZME) regions was observed. This was probably linked to the galvanic coupling between the PZD and ZME regions, and/or the Mg-rich passivation layer less resistant to corrosion than the Ca-rich passivation layer.