Some particularities of the corrosion behaviour of Mg–Zn–Mn–Si–Ca alloys in alkaline chloride solutions

The influence of silicon and calcium on corrosion behaviour of Mg–6Zn–Mn alloys was investigated in alkaline solutions. The corrosion behaviour of the alloys with varied silicon and calcium content mainly depends on volume fractions and morphology of the intermetallics. In Cl-ion-free solutions silicon increased the corrosion resistance of alloys causing the growth of the surface passive film mostly composed of hydroxide products. Calcium had caused trouble to the formation of the stable protective film through the formation of Ca–Mg–Si intermetallics. In Cl-ion containing solutions intermetallic Ca–Mg–Si phase was responsible for extreme initial corrosion of Mg–6Zn–Mn–Si–Ca alloys.