Study of Cerium and Lanthanum Conversion Coatings on AZ63 Magnesium Alloy Surface

摘要:

采用扫描电子显微镜，X射线能谱，Tafel 极化曲线和电化学阻抗谱法研究了铈镧转化膜对AZ63镁合金耐蚀性能的影响。结果表明，铈和镧的复合转化膜比单一稀土膜的表面更加均匀致密，对镁合金的耐蚀性有明显改善。双稀土转化膜的缓蚀效果随着浸泡成膜时间的增长而增加。延长时效时间有助于铈和镧的进一步氧化，耐蚀性能先增后减，时效48 h膜层的耐蚀效果最好

Abstract:

The influence of cerium and lanthanum conversion coatings on AZ63 magnesium alloy surface was investigated by Tafel polarization curves, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). The results show that the dual rare-earth conversion film treated in the mixture solution containing cerium nitrate and lanthanum nitrate is denser and more uniform than that in single rare-earth solution. EDX and XPS analysis demonstrates that the coatings are composed of rare earth oxides and hydrated hydroxides. The cerium and lanthanum conversion coatings can improve the corrosion resistance of AZ63 magnesium alloy evidently. The inhibition effect of dual rare-earth film on magnesium alloy increases with the increase of immersion time. With the extension of aging time, the inhibition effect increases first and then decreases. The coating aged for 48 h possesses the best inhibition effect