Regulating the ablation of nanoparticle-doped MAO coating on Mg alloy by MgF2 passivation layer construction

Abstract

The corrosion of magnesium (Mg) alloys in various environments limits their practical applications in many fields. Incorporating corrosion-resistant nanoparticles in microarc oxidation (MAO) coating can enhance their corrosion resistance, but excess addition leads to high discharge voltage and coating ablation. In order to reduce the high discharge voltage, the structure of MAO passivation layer is regulated by using F- salts to generate low dielectric constant MgF2 phase. The results exhibit that several kinds of nanoparticles (Al2O3, SiO2, TiO2, ZnO, ZrO2) addition with high-content would not result in ablation due to the presence of MgF2. With the addition of high-content corrosion-resistant nanoparticles, the MAO coating demonstrates improved corrosion resistance. Especially the corrosion current density, it exhibits a reduction of approximately 2–3 orders of magnitude. This strategy of regulating the MAO passivation layer provides a novel approach for further enhancing the corrosion resistance of Mg alloy MAO coatings.