Ni-P化学镀层对NdFeB永磁材料耐腐蚀性的改善

Effect of Electroless Ni-P Plating on Corrosion Resistance of NdFeB Magnets

测量了不同类型Ni-P化学镀试样和基体的孔隙率,以及在HCl、NaCl和NaOH溶液中的腐蚀速率,比较了不同类型Ni-P化学镀试样在3.5%NaCl溶液中的极化曲线,对比分析了酸性和酸碱复合条件下所得Ni-P镀层的表面形貌。结果表明:化学镀Ni-P合金能显著改善NdFeB永磁体的耐腐蚀性和致密性,且以弱碱性化学镀为底层,酸性化学镀为表层的酸碱复合镀层的致密性和耐腐蚀性最佳,单一酸性镀层的耐腐蚀性又优于碱性镀层。

The porosity of different types of Ni-P deposits and substrate were measured and the corrosion rates were studied in 3.5% NaCl, 10% HCl and 20% NaOH solutions. The corrosion characteristics of different types of Ni-P deposites in 3. 5% NaCl solution were envaluated by electrochemical potentiodynamic polarization curves. The microstructure of electroless Ni-P deposits in acidic and acidic-alkaline compositing baths were compared. The results showed that all the types of deposits could enhance the densification and corrosion resistance of substrate. The acidicalkaline composite deposits composed of alkaline Ni-P plating as bottom film and acidic Ni-P plating as top film could provide the best protection, and the corrosion resistance of single acidic Ni-P deposit was better than that of single alkaline Ni-P deposit.