AZ31镁合金表面钼酸盐转化膜的制备与耐蚀性能  

Preparation and corrosion resistance of molybdate conversion coatings on AZ31 magnesium alloy

作　　者：刘俊瑶 李锟[1] 雷霆[1] 

机构地区：[1]中南大学粉末冶金国家重点实验室,长沙410083

出　　处：《粉末冶金材料科学与工程》2016年第1期137-145,共9页Materials Science and Engineering of Powder Metallurgy

基　　金：国家高技术研究发展计划自助项目(SS2015AA032101);中南大学粉末冶金国家重点实验室开放基金资助项目

摘　　要：以Na2Mo O4为主盐,与氧化剂H2O2、成膜促进剂NaF和Na2Si O3一起组成化学转化液,在AZ31镁合金表面制备钼酸盐转化膜,利用扫描电镜和X线光电子能谱仪分析转化膜的形貌和组成,通过电化学阻抗测试研究转化膜在3.5%Na Cl溶液中的腐蚀行为,并讨论成膜机理,研究转化液中Na2Mo O4浓度与p H以及成膜温度和时间对薄膜结构与耐腐蚀性能的影响。结果表明:转化液的优化组成为0.2 mol/L Na2Mo O4+0.12 mol/L NaF+0.014mol/L Na2Si O3+0.012 mol/L H2O2;优化工艺条件为p H=5,温度60℃,转化时间30 min;转化膜为黄棕色,主要由Mg Mo O4,Mg F2,Mo O2,Mo O3和Mg Si O3组成,转化膜宏观上完整均匀,存在网状微裂纹;钼酸盐转化膜能有效提高AZ31镁合金的耐腐蚀性能,对基体合金有一定的保护作用。The chemical conversion solution was composed of Na2 Mo O4 as the main salt, H2O2 as oxidant, NaF and Na2 Si O3 as accelerants. A yellowish-brown molybdate conversion coating was formed on AZ31 Mg alloy surface through the chemical conversion solution. The morphology and composition of the coating were studied by scanning electron microscopy（SEM） and X-ray proton spectrometry（XPS）. Corrosion behavior of the conversion coating in 3.5% Na Cl solution was evaluated by electrochemical impedance spectrum and a coating film formation mechanism was discussed.The results show that the optimal chemical conversion solution is composed of 0.2 mol/L Na2 Mo O4, 0.12 mol/L NaF, 0.014 mol/L Na2 Si O3 and 0.012 mol/L H2O2 with p H value of 5, and the processing factors are soaking 30 min at of 60 ℃. The molybdate conversion coating fabricated under this optimization conditions is complete and uniform as well as has a net-like micro-crack structure with Mg Mo O4, Mg F2, Mo O2, Mo O3 and Mg Si O3 as main components. The molybdate conversion coating can effectively improve the corrosion resistance of AZ31 Mg alloy and play a protective role for the basal body.

关 键 词：镁合金 钼酸盐 化学转化膜 耐蚀性能 硅酸盐 

分 类 号：TG178[金属学及工艺—金属表面处理]