NdFeB磁体表面化学镀Ni-P合金防腐研究

Effect of Electroless Deposition on the Corrosion Resistance Property for NdFeB Permanent Magnets with Surface Coating of Ni-P Alloy

摘要:

采用正交试验法对NdFeB磁体表面化学镀镍磷合金的工艺进行了优化，测量了镀层和基体在3．5％（ω）NaCl溶液、10％（φ）盐酸和20％（ω）NaOH溶液中的腐蚀速度，以及在3．5％NaCl溶液中的极化曲线和电化学阻抗谱，对比分析了在酸性和碱性条件下所得Ni-P镀层的结构和表面形貌。结果表明，采用EIS谱图及等效电路模型可对镀层和磁体在介质中的电化学参数进行拟合分析，化学镀Ni-P合金能够显著改善NdFeB磁体的耐腐蚀性能，且酸性条件下所获得的镀层为非晶态结构，表面胞状组织呈密集连续分布，耐腐蚀性能更佳。

Abstract:

The coating technics by electroless deposition with Ni-P alloy on the surface of NdFeB magnets were optimized by orthogonal experiments. The microstructure and morphology of NdFeB magnets with electroless Ni-P deposit from an acidic bath and an alkaline bath were studied and compared. The corrosion rates of Ni-P deposites and substrate were measured in the NaCl solutions of 3.5wt%, the HCl solutions of 10vot% and the NaOH solutions of 20wt%. The corrosion characteristics of Ni-P deposits were evaluated for the two baths by electrochemical potentiodynamic polarization and impedance techniques. The results show that both deposits enhanced the corrosion resistance of substrate. The Ni-P deposit from the acidic bath provides a better protection due to the amorphous structure, and the continuous and compact cystiform microstructure on the surface of coatings.