初期腐蚀行为
( 1．北京科技大学材料科学与工程学院 腐蚀与防护中心， 北京 100083；
2．中国科学院 金属研究所金属腐蚀与防护国家重点实验室， 沈阳 110016)
摘 要: 采用室内加速的方法， 利用金相显微镜、扫描电镜和X射线衍射等手段对AZ91D镁合金在含微量SO2工业污染环境中的初期腐蚀层形貌以及腐蚀产物进行了分析和研究。结果表明： SO2加速镁合金的腐蚀，随着SO2含量增加， 镁的腐蚀速率加快。镁合金的初期腐蚀具有局部腐蚀的特征。 腐蚀优先从α相基体开始，腐蚀初期在材料表面生成一层保护性的含有MgO和Mg(OH)2的薄膜。 SO2降低了薄液层的pH值， 增强溶解过程， 促进可溶性MgSO3·6H2O和MgSO4·6H2O腐蚀产物的生成， 使表面膜失去保护作用，加速镁合金的后期腐蚀。
关键字: SO2；大气环境； AZ91D镁合金； 腐蚀
（ 1. Corrosion and Protection Center, School of Materials Science and Technology, University of Science and Technology Beijing, Beijing 100083, China;
2. State Key Laboratory for Corrosion and Protection, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China）
Abstract: The initial surface morphology of corrosion layer, corrosion products and structure of rust layer for AZ91D magnesium alloy in SO2 industrial polluted atmosphere were analyzed by metallographic observation, SEM and XRD. The results show that corrosion rate increases with increasing SO2 content in the atmosphere. The initial attack has the characteristics of localized corrosion. Corrosion starts from α phase, and MgO and Mg(OH)2 form at first, which provide a protective layer. SO2 decreases pH in the electrolyte layer, accelerates dissolution process, and promotes the formation of MgSO3·6H2O and MgSO4·6H2O. These soluble corrosion products result in the loss of protection function and the acceleration of corrosion. Meanwhile, cracks appear with continuation of corrosion, which provide the paths for oxygen and other corrosion pollutants filtering into matrix, further resulting in severe localized corrosion.
Key words: SO2; atmosphere; AZ91D magnesium alloy; corrosion
