Effect of current density on the structure, composition and corrosion resistance of plasma electrolytic oxidation coatings on Mg–Li alloy

Highlights: ► The PEO coatings exhibit tunable characteristics by controlling the current density. ► The coating formed at 5 A/dm2 exhibits the highest corrosion resistance. ► Anti-corrosion properties of PEO coatings are related to coating surface composition. - Abstract: The effect of current density on the oxidation process, morphology, composition and anti-corrosion properties of coatings are elucidated. X-ray photoelectron spectroscopy and X-ray diffraction analysis of coatings show that coatings prepared at different current densities are composed of MgO and γ-Mg2SiO4 and α-Mg2SiO4 phase. The chemical composition of PEO coatings varies from surface to the interior of the oxide coating. The PEO coatings exhibit tunable thickness, composition ratio, and porosity by controlling the current density, which ultimately affects film morphology and anti-corrosion properties. The superior corrosion resistance of coating obtained at 5 A/dm2 is attributed to the compactness of the barrier layer and the highest MgO/Mg2SiO4 ratio.