利用Tafel曲线、阻抗谱分析、NaCl水溶液点滴实验和扫描电镜观察等手段, 研究了温度对AZ91D镁合金的植酸转化膜表面形貌及耐蚀性的影响. 结果表明: 当温度为25 ℃ ～35 ℃时转化膜的耐蚀性较好, 温度过高或过低都会使转化膜的耐蚀性变差; 转化膜表面的裂纹是在干燥处理过程中由于表层转化膜体积收缩而产生的; 镁合金表面形成的植酸转化膜应属于电子导体, 该层膜的形成阻碍了腐蚀介质与镁合金基体的接触, 同时抑制腐蚀产物的扩散, 对镁合金起到了较好的防护作用.
AZ91D magnesium alloy, was treated in solutions of phytic acid at different temperature. SEM, Tafel and EIS were adopted and spot test was carried out to investigate the influence of processing temperature on appearance and corrosion resistance of conversion coating. Results show that the phytic acid conversion coating have better corrosion resistance when magnesium alloy was treated in a temperature range between 20 ℃ and 35 ℃. The corrosion resistance would become poor of the coatings prepared at temperature beyong the above range. The appearance of cracks on the conversion coating surface may be resulted from dehydrating in the process of desiccation. The conversion coating is a kind of coating that hinders the contact between corrosion medium and matrix metal and inhibits the diffusion of corrosion products.
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