Chemistry of corrosion products of Zn and MgZn pure phases under atmospheric conditions

We present a corrosion behaviour study of pure phases of zinc and zinc–magnesium contaminated with NaCl and exposed to humid air for 30 days: Zn, Mg2Zn11 and MgZn2. The composition of corrosion products is analysed using infrared spectroscopy (FTIR), X-ray diffraction (XRD), ion chromatography (IC), and X-ray photoelectron spectroscopy (XPS). The improved corrosion stability of MgZn2 is found to be connected to changes in the surface pH and to the nature of the formed corrosion products. The presence of magnesium modifies the proportion of the OH and CO3 bonds in the corroded products. This explains the improvement in corrosion resistance.

► Atmospheric corrosion with chloride contamination of zinc and zinc–magnesium pure phases were investigated.
► An improvement of corrosion resistance of zinc–magnesium, in comparison to zinc was observed.
► The corrosion products were characterised in depth using X-ray photoelectron spectroscopy.
► Modeling of O(1s) with OH and CO3 contributions was correlated with surface pH.
► The reduction of charge transfer at the interfaces was correlated to the improvement in corrosion resistance.