电压对AZ31镁合金微弧氧化涂层微观结构及腐蚀性能的影响

为研究过程参数对镁合金微弧氧化涂层的微观结构及耐腐蚀性能的影响,在AZ31镁合金基体上,采用不同电压,在电解液磷酸三钠(Na3PO4)中制备微弧氧化涂层.采用扫描电子显微镜(SEM)及光学显微镜,分析膜层腐蚀前后的微观组织结构；通过X射线衍射仪(XRD)分析涂层样品腐蚀前后的相组成.采用动电位极化曲线和电化学阻抗谱(EIS)测试对涂层的耐腐蚀性能进行评价.结果表明:AZ31镁合金微弧氧化涂层主要由Mg3(PO4)2,MgO,Mg和少量MgAl2O4组成,腐蚀产物由Mg(OH)2,quintinite和Ca10(PO4)6 (OH)2组成.在电压为325 V,频率3 000 Hz,氧化时间为5 min下制备的微弧氧化涂层具有最致密均匀的微观形貌和最小的腐蚀电流密度,因此表现出最强的耐腐蚀性能.

Effects of Voltage on the Microstructure and Corrosion Performance of Microarc Oxidation Coated AZ31 Magnesium Alloys

To study the effect of process parameters on the microstructure and corrosion resistance of microarc oxidation (MAO) coatings, the MAO coatings were prepared on AZ31 Mg alloys in the electrolyte of sodium phosphate (Na₃PO₄) at various applied voltages. The microstructures of the samples before and after corrosion were observed by scanning electron microscope (SEM) and optical micrograph. The composition of the MAO coatings and corrosion products were determined by Xray diffraction (XRD). The corrosion behaviors were analyzed by the potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The results show that the MAO coatings are primarily composed of Mg₃(PO₄)₂, MgO, Mg and MgAl₂O₄; and the corrosion products are composed of Mg(OH)₂, quintinite and Ca₁₀(PO₄)₆(OH)₂ . The coatings produced at 325 V and 3 000 Hz for 5 min show the best corrosion resistance with the densest morphology and the least corrosion current density.