Abstract:Ni-P coatings were deposited on sintered Nd-Fe-B magnets through the addition of Nd3+ in the electroless plating solution. The effects of Nd3+ 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 Nd3+ could significantly improve the adhesion and corrosion resistance of Ni-P coatings on magnets. When increasing Nd3+ 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.