Mg及Mg合金表面稀土转化处理及其耐蚀性研究

RARE EARTH CONVERSION TREATMENT FOR Mg AND ITS ALLOYS AND THEIR CORROSION PERFORMANCE

利用电化学极化技术和交流阻抗技术对高纯Mg、Mg合金AZ91D及AM6 0B在 5种稀土盐溶液中的成膜情况及被膜金属在 3.5 %NaCl溶液中的腐蚀行为进行了研究 .极化测试结果表明 ,稀土转化处理能使高纯Mg及Mg合金AM 6 0B的耐蚀性能得到一定程度的提高 ,但对AZ91D的耐蚀性能却几乎没有任何改善 .EIS测试结果显示 ,稀土转化膜在 3.5

In this paper corrosion performance of a high-purity Mg and two Mg alloys,AZ91D and AM60B treated or not by five different rare earth salt solutions (RESS) respectively are studied using EIS,potentiodynamic polarization and E vs t curves.With the exception of AZ91D,rare earth conversion treatment can improve the corrosion resistance of the other materials to some extent.The protectiveness of the coatings was enhanced at the initial stage and then deteriorated with immersion time in NaCl solution.The enhancement can be attributed to the transition of rare earth and Mg oxide/hydroxide in RECC to more stable thermodynamically substances in the presence of water,which can improve the compactness of RECC and subsequently enhances their barrier effect at the beginning of exposure.The deterioration may be due to the continuous dissolution and destruction resulted from aggressive media,which advance towards coating/substrate interface and finally destroy the intactness of coatings.