电解液组分对镁合金微弧氧化成膜及膜层耐蚀性的影响

Effect of electrolytes on the formability and corrosion resistance of micro-arc oxidation coating of AZ91D magnesium alloy

摘要:

基于单纯形重心设计改变Na₂SiO₃、NaOH、KF和NaAlO₂四种组分的搭配,在AZ91D镁合金上进行微弧氧化处理,研究了电解液配方对膜层成膜及耐蚀性能的影响。结果表明,所得到的回归方程非常显著,预测精度高。帕累托分析显示,四种电解质均对膜层耐蚀性影响显著。通过响应面分析可知,增大主盐Na₂SiO₃或者NaAlO₂的浓度可以显著提高膜层的耐蚀性。但二者复合却不利于耐蚀性的提高。主盐对于提高膜层成膜性及耐蚀性至关重要。当电解液中无主盐时,膜层的成膜性及耐蚀性都很差。当电解液中含有主盐时,适当增加NaOH与KF的浓度,膜层耐蚀性提高。通过Pearson相关分析可知,膜层耐蚀性主要受致密度及孔隙率的影响,同时也受膜厚、物相等其他特征参量的影响。而电解液各组分通过影响上述微观结构特征参量从而影响膜层性能。

Abstract:

Micro-arc oxidation coatings were prepared on AZ91D magnesium alloy by changing the collocation of Na₂SiO₃, NaOH, KF and NaAlO₂ based on simplex-centroid mixture design. The effects of electrolyte components on the formability and corrosion resistance of the coating were investigated. The results show that the obtained regression equation is very significant and has high prediction accuracy. Pareto analysis shows that the four electrolytes have significant effects on the corrosion resistance of the coating. Response surface analysis shows that increasing the concentration of Na₂SiO₃ or NaAlO₂ can significantly improve the corrosion resistance of the coating. But the combination of the two is detrimental to the improvement of the corrosion resistance. The main salt is very important for increasing the coating formability and corrosion resistance. When the electrolyte does not contain the main salt, the coating formability and corrosion resistance are very poor. The appropriate increase of NaOH and KF concentration in the electrolyte containing the main salt is also beneficial to improve the corrosion resistance. According to Pearson correlation analysis, the corrosion resistance primarily depends on the coating density and porosity, and is also affected by other characteristic parameters such as thickness and composition. The components of the electrolyte affect the properties of the coating through influencing the above microstructure parameters.