Nd^(3+)对烧结Nd-Fe-B化学镀Ni-P合金结合力和耐蚀性的影响

Effects of Nd^(3+) on Adhesion And Corrosion Resistance of Electroless Ni-P Coating on Sintered Nd-Fe-B Magnets

在化学镀液中添加Nd3+,研究其浓度对Ni-P镀层与烧结Nd-Fe-B磁体的结合力和施镀后磁体耐蚀性的影响。测定添加不同浓度Nd3+镀液中所得Ni-P镀层与磁体的结合力,以及镀层在3.5%NaCl(质量分数,下同)溶液中的极化曲线,并结合中性盐雾实验表征施镀后磁体耐蚀性。结果表明,添加2.5g·L-1Nd3+时,Ni-P镀层与Nd-Fe-B磁体的结合力从6.4MPa提高至25.2MPa;施镀后磁体的自腐蚀电位从–0.382V升高到–0.148V,自腐蚀电流密度从4.52μA·cm-2降低到0.07μA·cm-2,耐盐雾腐蚀时间达到256h,磁体耐蚀性显著提高。

Ni-P coatings were deposited on sintered Nd-Fe-B magnets through the addition of Nd^3＋ in the electroless plating solution. The effects of Nd^3＋ concentration on the adhesion and corrosion resistance of the coatings were investigated. The adhesions between the magnets and the Ni-P coatings were measured in different Nd＋ concentration plating solutions, and the polarization curves of the coatings in 3.5% （mass fraction） NaCl solution were plotted, the magnet corrosion resistances were characterized by neutral salt spray experiment. The results showed that the addition of Nd^3＋ could significantly improve the adhesion and corrosion resistance of Ni-P coatings on magnets. When increasing Nd^3＋ up to 2.5 g·L^-1, the adhesion strength of the Ni-P coating to Nd-Fe-B magnet was enhanced from 6.4 to 25.2 MPa. Synchronously, the corrosion potential Ecorr of the coated magnets in 3.5% NaCl solution increased from -0.382 to -0.148 V, the corrosion current density Icorr decreased from 4.52 to 0.07 μA·cm^-2, and the coated magnets could be as long as 256 h free of corrosion in the neutral salt spray, reflecting the improvement of corrosion resistance.