Preparation and characterization of duplex PEO/MoC coatings on Mg–Li alloy

A combined PEO and chemical conversion process was employed to fabricate duplex plasma electrolytic oxidation/molybdate conversion (PEO/MoC) coating on the surface of Mg–Li alloy. The microstructure and composition of the composite coatings were investigated by SEM, EDX, XRD and XPS. The anti-corrosion properties of duplex PEO/MoC coatings were evaluated by potentiodynamic polarization and EIS. The duplex PEO/MoC coating was composed of crystalline NaMgF3, Mg2SiO4, MoO3 and MgO. Spherical-like microparticles accumulated and dispersed uniformly on the surface of the PEO coating. The corrosion resistance for Mg–Li alloy was improved by using a combination of plasma electrolytic oxidation and chemical conversion.