Inhibitive effect of sodium molybdate on corrosion of AZ31 magnesium alloy in chloride solutions

•Corrosion of AZ31 Mg alloy in 0.05 M NaCl solution was examined.•Na2MoO4 inhibitor provides reliable inhibition of AZ31 alloy.•The chemical composition of the molybdate-based protective layer was studied.•Inhibition effect is provided by a surface film of mixed Mo(VI)–Mo(V)–Mo(VI) species. In this work, corrosion inhibition of the AZ31 magnesium alloy was investigated in NaCl solutions containing different amounts of sodium molybdate inhibitor. Electrochemical, hydrogen evolution, microscopic, and spectroscopic experiments were utilized to examine the mechanism of corrosion inhibition by molybdates. The results showed that Na2MoO4 inhibitor provides reliable inhibition at high concentrations (150 mM). Surface examination by Raman and XPS spectroscopy confirmed the formation of a protective surface layer of mixed Mo(VI, V, IV) species. Based on these results, the mechanism of corrosion inhibition of the AZ31 alloy by aqueous molybdates was proposed.