Effect of hydrothermal treatment on the corrosion resistance of CO2 gas-assisted MAO coatings

Abstract

1Micro-arc oxidation (MAO) is an effective method for preparing highly corrosion-resistant coatings on metal surfaces, but the presence of a porous structure on the surface tends to limit further improvements in corrosion resistance. In this paper, we report a CO2 gas-assisted MAO method to prepare a ceramic coating on the surface of magnesium alloys and seal the pores using a hydrothermal reaction. By comparing the corrosion resistance of the coatings of the specimens in different electrolytes, the study reveals the mechanism of the influence of CO2 gas and hydrothermal post-treatment method on the initial structure of the coating, as well as the influence law of the corrosion resistance of different coatings. The results show that the coating prepared in NaOH + Na2SiO3 solution has the largest thickness and exhibits the most excellent corrosion resistance, which is at least one order of magnitude higher than that of several other groups of specimens.