Corrosion evaluation for recycled Nd-Fe-B sintered magnets

Abstract The chemical stability is an important concern for Nd-Fe-B sintered magnets with respect to their practical applications. In our present study, recycled Nd-Fe-B sintered magnets with excellent magnetic properties have been fabricated from waste Nd-Fe-B sintered magnets as well as their corrosion behavior were investigated and compared with the original waste magnets. We find both magnets to exhibit approximately similar corrosion processes, corrosion rates, and magnetic properties. Moreover, potentiodynamic polarization curves and electrochemical impedance spectroscopy results reveal that both magnets exhibit similar corrosion thermodynamics and kinetics. For comparison, the recycled magnets have a slightly higher rare earth content and more Nd-rich grain boundary phase in their microstructure compared with those of the original waste magnets, but with a negligible influence to the corrosion resistance of the magnets. We conclude that the recycling process has no adverse influence on the performance of these magnets, thus demonstrating the applicability of the recycled Nd-Fe-B sintered magnets.