NdFeB磁体表面化学镀Ni-Co-p合金及其耐腐蚀性能研究

采用化学镀方法制备Ni-Co-P三元合金镀层以改善NdFeB磁体的耐腐蚀性能.优化了镀液配方以及施镀工艺,研究了镀液pH值和金属离子配比(Co2 ]/Ni2 Co2 ])对沉积速度和镀层成分的影响,测量了NdFeB基体和不同镀层在3.5%(质量分数,下同)NaCl溶液中的极化曲线.结果表明,随镀液pH值增加,沉积速度提高,镀层中Co含量升高,Ni含量和P含量逐渐降低;随镀液中Co2 比例增加,沉积速度下降,镀层中Co含量升高,Ni和P含量降低.化学镀Ni-Co-P合金后的NdFeB磁体在3.5%NaCl溶液中的腐蚀速度降低了约两个数量级;当镀液金属离子配比Co2 ]/Ni2 Co2 ]=0.3时,镀层耐腐蚀性能最好,且优于相同施镀条件下所得到的Ni-P镀层.

Electroless Deposition of Ni-Co-P Deposit on NdFeB Permanent Magnets and Its Corrosion Resistance Property

Electroless Ni-Co-P ternary alloy deposits were prepared by optimizing the bath composition and operating conditions to improve the corrosion resistance of NdFeB permanent magnets.The effects of pH and metallic ion ratio(Co~(2+)]/Ni~(2+)+Co~(2+)]) on plating rate and deposit composition were investigated.Polarization curves of NdFeB matrix with and without Ni-Co-P deposits in 3.5%(mass fraction)NaCl solution were examined.It is found that the plating rate and the cobalt content of the deposit increase with increasing pH,while the nickel and phosphorus contents decrease.With increasing metallic ratio,the plating rate decreases and the cobalt content of the deposit increases with a simultaneous decrease in the nickel and phosphorus contents.The polarization curves exhibit that the corrosion rate of NdFeB magnets decreases by two orders of magnitude in 3.5%NaCl solution after electroless plating with the Ni-Co-P deposits.A metallic ion ratio at 0.3 in the bath solution achieved the best corrosion resistance.