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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。
The environment-friendly rare earth conversion coating was prepared on the surface of AZ91D magnesium alloy by using Ce (SO4) 2-H2O2 solution system, and Ni (NO3) 2 and sodium dodecyl benzene sulfonate were added to the treatment solution to improve the film formation at room temperature effect. The microstructure, elemental composition and microstructure of rare earth conversion coatings on magnesium alloy surface were studied by SEM, EDS, XRD and GIXD methods. The self-corrosion potential tracking method was used to study the film formation process of magnesium alloy in rare earth solution. Compared with Ni (NO3) 2, the additive sodium dodecyl benzene sulfonate can effectively improve the compactness and corrosion resistance of the conversion coating. The self-etching current density of the conversion film obtained by adding sodium dodecylbenzenesulfonate was reduced from 7.41 × 10 -5 A / cm 2 to 2.20 × 10 -5 A / cm 2 compared with the conversion film obtained from the additive-free treatment liquid , The potential-time curve of the second phase of the film-forming time reduced from 5min to 2min. The main components of the rare earth conversion film are Mg, Al, O and Ce. Additive Ni (NO3) 2 and sodium dodecyl benzene sulfonate can respectively increase the content of Ce in the conversion coating from 18.92% to 22.32% and 25.08%. The RXD and GIXD studies showed that the conversion coatings obtained in all solutions were amorphous.