ZK61S镁合金微弧氧化膜层的结构及耐腐蚀性能

Structure and Corrosion Resistance of Micro-Arc Oxidation Coating on ZK61S Magnesium Alloy

为了提高ZK61S镁合金的耐腐蚀性能,采用微弧氧化方法以不同电压(300,380,450 V)在ZK61S镁合金表面制备氧化膜并进行封孔处理。利用金相显微镜、扫描电镜、X射线衍射仪分析膜层的形貌、结构和组成;通过腐蚀电位试验、中性盐雾腐蚀试验及抗剥落腐蚀试验进行耐腐蚀性能考核。结果表明:微弧氧化呈现疏松多孔形态且均匀覆盖于基材表面,主要由Mg、MgO和Al_2Si_2O_5(OH)4相组成;微弧氧化处理后试样的腐蚀电位显著提升,且380 V所得微弧氧化试板的腐蚀电位达到-881.53 m V,经过408 h的中性盐雾腐蚀试验后的腐蚀速率为0.012g/(m^2·h),耐蚀性能比未进行表面处理的基材提高了88倍;经封孔处理的微弧氧化试板经过456 h的中性盐雾腐蚀试验后腐蚀速率降低到0.003 g/(m^2·h);封孔处理使微弧氧化膜的抗剥落腐蚀性能由微弧氧化后的EB级提升到EA级。

In order to improve the corrosion resistance of ZK61S magnesium alloy,the oxidation coatings were prepared by micro-arc oxidation under different voltages （300,380,450 V）,and then the coatings were treated by hole-sealing technique.The metallographic microscope,scanning electron microscope and X-ray diffractometer were used to analyze the morphology,structure and composition of coatings.In addition,the corrosion potential test,neutral salt spray corrosion test and anti-desquamate corrosion test were employed to evaluate the corrosion resistance of coating.Results showed that the micro-arc oxidation coating performed porous structure and uniformly covered the surface of substrate,mainly composed of Mg,MgO and A12Si2O5（OH） 4 Furthermore,the corrosion resistance of sample treated by micro-arc oxidation technique was improved greatly.The corrosion potential of micro-arc oxidation coating obtained under 380 V reached to-881.53 mV,and the corrosion rate after neutral salt spray corrosion test for 408 h was 0.012 g/（m^2 · h）,which presented that the corrosion resistance of the coating was higher 88 times than that of the substrate without surface treatment.The corrosion rate of micro-arc oxidation sample after follow-up sealing treatment decreased to 0.003 g/（m^2 · h） after neutral salt spray corrosion test for 456 h.Besides,the sealing treatment improved the antidesquamate corrosion property of micro-arc coating from EB level to EA level.