Microstructure and Corrosion Resistance of Composite Micro-arc Oxidation and SiO_2 Coatings on Magnesium Alloy
镁合金表面微弧氧化—SiO_2复合膜层的微观结构和耐蚀性

SiO2 sol was prepared by hydrolyzing of organic alkoxide, and the dipping–costing method was employed to prepare the SiO2 layer onto micro–arc oxidation(MAO) coating of AZ31B magnesium alloy. The sol structure, differences in micro–morphology and corrosion resistance between ceramic coating and composite coatings were investigated. The results show that SiO2 sol immersed into the micro pores on the surface of MAO coating and formed an inorganic SiO2 layer. The corrosion potential of composite coatings which composed of ceramic coating and SiO2 layer increased, and the corrosion current density reduced by about 2 orders of magnitude comparing with the ceramic coating. The molar ratio of TEOS to H2O affects the structure of SiO2 layer seriously and the action of suppressing the corrosion medium of SiO2 layer.