Corrosion resistance of NdFeB sintered magnets with intergranular addition of Cu₆₀Zn₄₀ powders

Cu₆₀Zn₄₀ powders, as grain boundary modifiers, were added into Nd_28.2Dy_2.0Fe_balAl _0.1Nb_0.2Ga_0.11B_0.96 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 Cu₆₀Zn ₄₀-added magnets had more positive corrosion potential E _corr and much lower corrosion current density i_corr 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.