Corrosion resistance of Nd–Fe–B sintered magnets with intergranular addition of Cu60Zn40 powders

Cu60Zn40 powders, as grain boundary modifiers, were added into Nd28.2Dy2.0FebalAl0.1Nb0.2Ga0.11B0.96 sintered magnets to improve the corrosion resistance of magnets. The corrosion resistance of magnets was investigated by polarization curve measurements in 3.5 wt% NaCl and 3.0 wt% NaOH solutions. It was found that the Cu60Zn40-added magnets had more positive corrosion potential Ecorr and much lower corrosion current density icorr than the Cu60Zn40-free one in both solutions, indicating the improvement of the corrosion resistance by Cu60Zn40 intergranular addition. Promotion of the electrochemical potential of the intergranular phase, formation of the Nd (Fe, Cu)2 phase, the uniform distribution of the Nd-rich phase and increase of the magnet density were found to be responsible for the improvement of the corrosion resistance.