Thermal control property and corrosion resistance of PEO coatings on AZ91 Mg alloy

Abstract

The thermal control property and corrosion resistance of plasma electrolytic oxidation (PEO) coatings on AZ91 Mg alloy were investigated in the present study. Silicate, and phosphate based electrolytes were used to fabricate coatings with different thicknesses. The influence of microstructure, morphology and phase composition on the thermal control property (absorptance and emissivity) of the coating was investigated, and the effect of coating degradation on the evolution of the absorptance and emissivity was studied meanwhile. It was found that the thickness and roughness are more influential on the emissivity of the coating compared to the coating composition. The absorptance of the coating decreases with the increase of the coating thickness, while the emissivity of the coating increases with the coating thickness. In addition, the emissivity of PEO coatings has been remarkably increased after performing corrosion test, while the absorptance of the coatings is not significantly changed. This can be ascribed to the accumulation of corrosion products on the coating surface.