镁合金V-Ce转化膜的制备及性能  

Preparation and Corrosion Resistance Evaluation of Vanadium-Cerium Composite Conversion Coating on Magnesium Alloy

作　　者：贺旭东[1] 郭瑞光[1] 

机构地区：[1]西安建筑科技大学环境与市政工程学院,陕西西安710055

出　　处：《材料保护》2013年第11期44-46,50,共4页Materials Protection

基　　金：国家自然科学基金项目(20976143);教育部高等学校博士学科点专项科研基金(20096120110007)资助

摘　　要：为了提高偏钒酸铵、氟硅酸盐转化液制备的镁合金表面无铬转化膜的耐蚀性能，在该转化液中加入硝酸铈制备了V—ce复合转化膜。采用单因素试验对转化液中的有效耐蚀成分偏钒酸铵和硝酸铈的浓度和反应条件进行了优化；采用扫描电镜和能谱分析转化膜的形貌和成分，采用中性盐雾试验考察了膜层的耐蚀性能。结果表明：最佳转化膜成膜条件为1．20g／L偏钒酸铵、0．24g／L氟硅酸盐、4．00g／L硝酸铈，pH值为2．0～3．0，50℃，20～30min；最佳条件获得的转化膜主要由24％V，17％Ce，13％Mg，16％0（质量分数）组成，转化膜中的无定形结构和高含量的耐蚀钒、铈氧化物成分使其耐蚀性能显著提高，转化膜自腐蚀电位较基体正移了141mV，腐蚀电流密度仅为基体的1／26．耐盐雾时间达72h。Cerium nitrate was added into the ammonium metavanadate-fluosilicate conversion solution so as to improve the corrosion resistance of the Cr-free conversion coating on AZ31 Mg alloy while V-Ce composite conversion coating was afforded. The concentration of the effective anticorrosion ingredients in the conversion solution,ammonium metavanadate and cerium nitrate, and the reaction condition were optimized based on single factor orthogonal tests. The morphology and composition of the compos-ite conversion coating were analyzed with a scanning electron microscope and an energy dispersive spectrometer. Results indicated that the conversion solution with the optimized composition consists of 0. 24 g / L fluosilicate,4. 00 g / L cerium nitrate,and 1. 20 g / L ammonium metavanadate; and the optimal conversion solution pH value and temperature as well as conversion reaction time were suggested as 2. 0 ~ 3. 0 and 50 ℃ as well as 20 ~ 30 min, respectively. The V-Ce conversion coating obtained under the optimized condition consistd of 24% V( mass fraction; the same hereafter),17% Ce,13% Mg,and 16% O. Moreover,the amorphous structure and high contents of V and Ce oxides with good anticorrosion ability helped to greatly improve the corrosion resistance of the Mg alloy substrate. Namely,the corrosion potential of V-Ce conversion coating positively shifted by 141 mV as compared with that of the Mg alloy substrate; and its corrosion current density was only 1 /26 of that of the Mg alloy substrate, while it was able to endure salt-spray for 72 h.

关 键 词：V—Ce转化膜 镁合金 铈盐 偏钒酸盐 耐蚀性 

分 类 号：TG174.44[金属学及工艺—金属表面处理]