不同表面处理工艺压铸镁合金涂层耐蚀性研究

为了研究不同表面处理工艺下压铸镁合金涂层的抗腐蚀性能,通过浸泡腐蚀和电化学腐蚀的方法,比较了微弧氧化和无铬化学氧化等表面处理试样的耐蚀性.结果表明,无铬化学氧化和微弧氧化处理能显著提高镁合金表面耐蚀性,而以微弧氧化处理更优;且两种处理方法覆盖层对孔洞、裂纹不敏感.根据交流阻抗图谱,拟合得到了微弧氧化、无铬化学氧化和未处理三种试样电化学腐蚀时体系的等效电路,拟合结果与实测结果吻合.XRD分析表明这两种处理方法得到的覆盖层中主体相均为Mg3Al2Si3O12等含硅的尖晶石型氧化物和Mg0.36Al2.44O4、MgAl2O4等不含硅的镁、铝复合氧化物,有利于提高镁合金耐蚀性.

Corrosion resistance of die casting magnesium alloy treated by different surface treatment methods

The corrosion resistance of coatings formed by micro-arc oxidation and free-Cr chemical oxidation on the die casting magnesium alloy surface was compared by immersion tests and electrochemical tests.The results showed that micro-arc oxidation and free-Cr chemical oxidation could strongly improve the corrosion resistance of AZ91D Mg alloy and neither of the two coatings was sensitive to holes or cracks.Equivalent circuits were fitted for the electrochemical test systems of micro-arc oxidation samples,free-Cr chemical oxidation samples and untreated samples according to the impedance atlases.The fitted curves agreed with the data of actual measurement very well.XRD analysis shows that the coatings mainly consist of silica oxides such as Mg3Al2Si3O12,and complex oxides without Si,such as Mg0.36Al2.44O4 and MgAl2O4,which can improve the corrosion resistance of AZ91D Mg alloy.