镁合金表面微弧氧化—SiO_2复合膜层的微观结构和耐蚀性

Microstructure and Corrosion Resistance of Composite Micro-arc Oxidation and SiO_2 Coatings on Magnesium Alloy

采用有机醇盐水解法制备SiO_2溶胶,用浸渍-提拉制膜技术在AZ31B镁合金微弧氧化陶瓷层表面制备SiO_2膜层,研究了镁合金表面微弧氧化-SiO_2复合膜层的微观结构和耐蚀性。结果表明:SiO_2溶胶进入微弧氧化陶瓷层表面的微孔并形成了SiO_2膜层;由微弧氧化陶瓷层和SiO_2膜层组成的复合膜层的腐蚀电位比单一陶瓷层明显提高,其腐蚀电流密度减少约二个数量级;水/正硅酸乙酯的摩尔比显著影响复合膜层微观结构,进而改变SiO_2膜层阻挡腐蚀介质的能力。

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.