Effect of nano-SnO2 on the microstructure and properties of Micro-arc oxidation coatings on AZ91D magnesium alloy

To solve the defects of magnesium alloy micro-arc oxidation coatings with large holes and cracks, nanoparticles were introduced into the electrolyte to densify the coatings. In this study, MgO/SnO 2 composite coatings were prepared and the effects of SnO 2 concentration on the microstructure, corrosion resistance and photocatalysis of the composite coatings were investigated. The growth process of the coating was elucidated. The results showed that the addition of SnO 2 significantly improved the breakdown and cut-off voltages of the coatings, with increased up to 16 V. The coatings thickness, hardness and densification increased and then decreased with the addition of nano-SnO 2 concentration. When the concentration of SnO 2 reached 6 g/L, the MgO/SnO 2 composite coating had the most corrosion resistance. The corrosion potential decreased to 5.636 × 10 −9  A cm −2 , which was 3 orders of magnitude lower. The MgO/SnO 2 composite coating surface contained nano-SnO 2 particles to effectively enhanced the photocatalytic performance. The degradation efficiency was optimal up to 21.02 % after 3 h of light exposure.