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通过测量稀土转化膜生长微观形貌、稀土转化膜生长曲线、成膜反应表观活化能、成膜电位时间曲线及Tafel曲线,研究电镀锌稀土转化膜成膜动力学。结果表明:稀土转化膜的生长分为快速生长、缓慢生长、平稳生长3个阶段,3个阶段生长速率与单位面积转化膜质量均呈抛物线关系,形成具有保护性能的膜层;其中第一、二阶段成膜反应的活化能分别为18.17,28.93 kJ.mol-1,具有较快的反应速率,第三阶段成膜反应的活化能为42.41 kJ.mol-1,反应速率相对较慢。此外,成膜反应还与外因成膜温度和成膜时间有关,升高温度可缩短转化膜成膜的时间,有利于转化膜的形成,成膜温度在25~35℃之间,成膜时间在120~180 s之间,膜层具有较好的耐蚀性能。
The growth kinetics of rare earth conversion coating was investigated by measuring the growth morphology, rare earth conversion coating growth curve, the apparent activation energy of film forming reaction, the potential time curve of membrane potential and Tafel curve. The results showed that the growth of rare earth conversion coating was divided into three stages: rapid growth, slow growth and steady growth. The growth rate of three stages showed a parabolic relationship with the mass per unit area of conversion coating to form a protective layer. Among them, The activation energy of the second-stage film-formation reaction was 18.17 and 28.93 kJ · mol-1, respectively. The activation energy of the third-stage film-forming reaction was 42.41 kJ · mol-1 and the reaction rate was relatively slow. In addition, the film forming reaction is also related to the external film forming temperature and the filming time. Increasing the temperature can shorten the film forming time of the conversion film, which is favorable for the formation of the conversion film. The film forming temperature is between 25 and 35 DEG C, In 120 ~ 180 s, the film has good corrosion resistance.