CORROSION BEHAVIOR OF HOT-WORKED ND-FE-B AND ND-FE-CU-B PERMANENT-MAGNETS

The corrosion resistance of hot-worked Nd-Fe-B and Nd-Fe-B-Cu magnets is studied. In atmospheric conditions, the corrosion rate is the same for sintered Or hot-worked magnets. In acidic solutions, however, the hot-worked magnet exhibit a lower corrosion resistance. In addition, the corrosion mechanism involved appears to differ due to the lower reactivity of the intergranular Nd-rich and B-rich phases. The addition of copper is found to strongly improve the corrosion resistance of hot-worked magnets. With an addition of only 2% Cu, the corrosion resistance of hot-worked magnets turns out to be higher than that of sintered Nd-Fe-B magnets in both environments, neutral and acidic.