Influence of water purity on the corrosion behavior of Mg0.5ZnX (X = Ca, Ge) alloys

Influence of water purity on the corrosion behavior of as-cast Mg0.5Zn, Mg0.5Zn0.5Ca and Mg0.5Zn0.2Ge alloys was investigated by preparing 0.9 wt % NaCl solution with deionized and tap water. Mg(OH)(2) layer with limited protection ability was predominately formed on the surfaces in solution prepared with deionized water. In contrast, besides the primary Mg(OH)(2) layer, different crystals of CaCO3 were formed as a secondary corrosion products layer in solution prepared with tap water, which improved the corrosion resistance of alloys by almost one order of magnitude. Moreover, the crystallographic form of CaCO3 was influenced by the content of calcium in the alloy.