AZ91D镁合金表面无铬转化膜/杂化复合涂层的耐蚀性能

Corrosion Resistance of Chromium Free Conversion Coating/Hybrid Composite Coating on AZ91D Magnesium Alloy

溶胶凝胶法制备的涂层性能优良,采用溶胶凝胶法、以正硅酸乙酯为主制备性能优良的涂层技术已很成熟,但用于镁合金的防护鲜有报道。为了提高AZ91D镁合金的耐蚀性能,先在其表面制备了无铬钼酸盐转化膜,然后采用有机/无机杂化溶胶凝胶的方法在转化膜表面制备杂化涂层,从而得到转化膜/杂化复合涂层。对复合涂层进行了红外光谱分析,并用扫描电镜(SEM)观察了其微观形貌,同时也对其进行了极化曲线和电化学阻抗谱分析。结果表明:二氧化硅和有机硅氧键通过溶胶凝胶反应,无机和有机间呈网络结构穿插在一起;复合涂层表面平整均匀,无开裂现象;转化膜层和转化膜/杂化复合涂层都可提高镁合金的耐蚀性,但后者的效果更加明显。

In order to improve the corrosion resistance of AZ91 D alloy, the chromium-free molybdate conversion coatings were pre-prepared on the alloy surface, and then the hybrid coatings were further fabricated on the surface of the pre-coatings by inorganic/organic sol-gel method to obtain the composite coating. The composite coatings were analyzed by IR spectroscopy, and the micro - morphologies of the coatings were observed by scanning electron microscope （SEM）. Moreover, the corrosion resistance of the coatings was evaluated by polarization curves and electrochemical impedance spectroscopy. Results showed that with the sol-gel reaction of SiO2 and organic silicon-oxygen bonds, the network structures between inorganic and organic interspersed with together. The composite coating possessed uniform and smooth surface without crack- phenomenon. Furthermore, both of conversion coating and conversion/hybrid coating could improve the corrosion resistance of Mg alloy, but the latter was better.