汽车用镁合金铈盐改性硅烷复合膜的耐蚀性

目前镁合金表面稀土-硅烷化改性多采用复合工艺,简单硅烷化处理研究较为少见。将不同含量的硝酸铈直接添加到KH-550硅烷溶液中,应用简单化学浸渍法在AZ91D压铸镁合金表面制备了铈盐改性硅烷复合膜;通过点滴腐蚀试验、全浸腐蚀试验和电化学交流阻抗谱评价了铈盐改性复合膜的耐蚀性能,利用扫描电子显微镜和椭偏仪分析了铈盐改性复合膜的表面微观形貌和厚度。结果表明:与硅烷膜相比,铈盐改性硅烷复合膜较均匀、致密、平整,厚度明显增加;随着硝酸铈含量的增加,铈盐改性硅烷复合膜的耐蚀性能先上升后下降,当硝酸铈掺杂量达到0.50 g/L时,复合膜的耐蚀性能最佳;随盐水浸泡时间的延长,复合膜的低频阻抗值先增大后减小,表明其具有一定的"自修复"能力。

Corrosion Resistance of Ce-Doped Silane Composite Coatings on AZ91D Magnesium Alloy for Automobile

KH-550 silane coatings doped with different concentrations of cerium nitrate were prepared on AZ91D die-cast magnesium alloy by simple chemical dipping.The corrosion resistance of the Ce-doped silane composite coatings was evaluated by drop test,immersion corrosion test and electrochemical impedance spectroscopy.The surface morphology and thickness of the Ce-doped silane composite coatings were characterized by scanning electron microscope and ellipsometer.Results indicated that the Ce-doped silane composite coatings were more uniform,denser and smoother than the single silane coating,and the thickness was also increased obviously.The corrosion resistance of the Ce-doped silane composite coatings was first increased and then decreased with the increase of the content of cerium nitrate.The corrosion resistance of the composite coatings was the best when the content of cerium nitrate was up to 0.50 g/L.With the increase of immersion time in 5％ NaCl solution,the low frequency impedance of the Ce-doped silane composite coatings was increased firstly and then decreased,which showed that the Ce-doped silane composite coatings had the "self-healing" ability to a certain degree.