Preparation of cerium oxide based environment-friendly chemical conversion coating on magnesium alloy with additives

添加剂作用下制备环境友好型铈基镁合金稀土转化膜(英文)

Ce（SO4）2？H2O2 solution was adopted to prepare a chemical conversion coating on AZ91D magnesium alloy.Additives of Ni（NO3）2 and sodium dodecyl benzene sulfonate were applied to improving the coating formation.SEM,EDS,XRD and GIXD were adopted to study the coating morphology,structure and composition,and the potential change curve in the treating solution was recorded to study the coating growth.Sodium dodecyl benzene sulfonate makes a remarkable improvement in the coating compactness,and shortens the time in the second stage of the coating formation from 5 min to 2 min.Compared to Ni（NO3）2,sodium dodecyl benzene sulfonate makes the more remarkable effect on the corrosion resistance improvement,since it can decrease the current density of corrosion from 7.41×10-5 A/cm2 to 2.20×10-5 A/cm2.The additives of Ni（NO3）2 and sodium dodecyl benzene sulfonate can enhance the Ce content from 18.92% to 22.32% and 25.08% in the coating,respectively.The XRD and GIXD results indicated that all the conversion coating formed in different solutions exhibit amorphous structure.

采用Ce(SO4)2-H2O2溶液体系在AZ91D镁合金表面制备环境友好型稀土转化膜,并在处理液中添加Ni(NO3)2和十二烷基苯磺酸钠以提高室温下的成膜效果。采用SEM、EDS、XRD、GIXD等方法研究镁合金表面稀土转化膜的微观形貌与元素组成以及微观结构,采用自腐蚀电位跟踪法对镁合金在稀土溶液中的成膜过程进行研究。添加剂十二烷基苯磺酸钠比Ni(NO3)2能更有效地提高转化膜的致密性与耐腐蚀性能。与从不含添加剂处理液中得到的转化膜相比较,添加十二烷基苯磺酸钠得到的转化膜的自腐蚀电流密度从7.41×10-5A/cm2降低到2.20×10-5A/cm2,电位?时间曲线第二阶段的成膜时间从5min缩短到2min。稀土转化膜的主要成分为Mg、Al、O和Ce。添加剂Ni(NO3)2和十二烷基苯磺酸钠可分别将转化膜中Ce元素的含量从18.92%增加到22.32%和25.08%。RXD与GIXD研究表明在所有溶液中得到的转化膜均为非晶态结构。