汽车用冷轧板表面三种磷化膜的耐蚀性比较

在汽车用冷轧板表面制备了铁系磷化膜、锌-钙系磷化膜和锰系磷化膜。使用扫描电镜和能谱仪观察了三种磷化膜盐雾腐蚀前后的形貌,并分析了元素组成。使用电化学工作站测量了三种磷化膜的交流阻抗谱,并拟合得到电荷转移电阻。结果表明:铁系磷化膜腐蚀前后的形貌存在显著差异;锌-钙系磷化膜腐蚀前后晶粒形状发生改变,并且在晶粒表面明显可见微小的蚀坑;锰系磷化膜腐蚀前后的形貌差别不太明显。以电荷转移电阻为评价指标,三种磷化膜的耐蚀性都好于冷轧板的耐蚀性。锰系磷化膜的耐蚀性最好,其次为锌-钙系磷化膜,铁系磷化膜的耐蚀性最差。

Comparison of Corrosion Resistance of Three Kinds of Phosphating Films on Surface of Cold-Rolled Plate for Automobile

Iron phosphating film,zinc-calcium phosphating film and manganese phosphating film were prepared on the surface of cold-rolled plate for automobile.The morphology and elemental composition of three phosphating films before and after satt spray corrosion were observed and analyzed by scanning electron microscopy and energy disperse spectroscopy,and the alternating current impedance spectra of three kinds of phosphating films was measured by electrochemical workstation and charge transfer resistance was obtained by fitting the alternating current impedance spectra.The results showed that the morphology of iron phosphating film before and after corrosion was significantly different,while the morphology of manganese phosphating film before and after corrosion was not significantly different.The grain shape of zinc-calcium phosphating film was changed before and after corrosion,and tiny pits appeared obviously on the grain surface.Taking the charge transfer resistance as evaluation index,the corrosion resistance of three kinds of phosphating films wasbetter than that of cold-rolledplate,and the corrosion resistanceof manganese phosphating film was thebest,followed by zinc-calcium phosphating film,and the corrosion resistance of iron phosphating film was the worst.