Microstructure and properties of oxalate conversion coating on AZ91D magnesium alloy  

作　　者：蒋永锋 周海涛 曾苏民 

机构地区：[1]School of Materials Science and Engineering,Central South University

出　　处：《中国有色金属学会会刊：英文版》2009年第6期1416-1422,共7页Transactions of Nonferrous Metals Society of China

基　　金：Project(20070420821)supported by the China Postdoctoral Science Foundation;Project supported by the Special Project for Postdoctoral Scientific Research of Hunan Provincial Scientific and Technology Department of China;Project supported by the Postdoctoral Foundation of Central South University,China

摘　　要：The oxalate coating formed on AZ91D magnesium alloy by chemical conversion treatment methods in oxalate salt solutions was investigated.The surface morphologies and chemical composition of coating were examined using scanning electron microscopy(SEM)equipped with energy dispersive analysis of X-ray(EDX).Electrochemical impedance spectroscopy(EIS), potentiodynamic polarization curves and salt spray tests were employed to evaluate corrosion protection of the coating to substrate in 5%NaCl solution.The mechanism of coating formations was also considered in details.The results indicate that a compact and dense surface morphology with fine particle clusters of the oxalate coating on magnesium alloy is presented,which mainly consists of oxide or/and organic of Mg,Al and Zn.And the anti-corrosion of the magnesium after oxalate conversion treatment is better than that of the magnesium substrate.The results of salt spray test for oxalate coating is evaluated as Grade 9 according to ASTM B117. The electric resistance of oxalate chemical conversion coating to substrate is below 0.1Ω.The oxalate coating formed on AZ91D magnesium alloy by chemical conversion treatment methods in oxalate salt solutions was investigated. The surface morphologies and chemical composition of coating were examined using scanning electron microscopy （SEM） equipped with energy dispersive analysis of X-ray （EDX）. Electrochemical impedance spectroscopy （EIS）, potentiodynamic polarization curves and salt spray tests were employed to evaluate corrosion protection of the coating to substrate in 5% NaCl solution. The mechanism of coating formations was also considered in details. The results indicate that a compact and dense surface morphology with fine particle clusters of the oxalate coating on magnesium alloy is presented, which mainly consists of oxide or/and organic of Mg, Al and Zn. And the anti-corrosion of the magnesium after oxalate conversion treatment is better than that of the magnesium substrate. The results of salt spray test for oxalate coating is evaluated as Grade 9 according to ASTM B117. The electric resistance of oxalate chemical conversion coating to substrate is below 0. 1Ω.

关 键 词：AZ91D镁合金 化学转化膜 草酸盐 微观结构 膜性能 扫描电子显微镜 防腐涂层 电化学阻抗谱 

分 类 号：TG146.22[一般工业技术—材料科学与工程]