HYDROGEN-INDUCED CORROSION MECHANISM IN NDFEB MAGNETS

An investigation was conducted comparing the corrosion behavior of NdF eB magnets in flowing hydrogen and in the beat and humidity of an auto clave. The results show that corrosion is both macroscopically and mic roscopically similar in both environments. In both cases, the corrosio n progressed most rapidly in those areas where the magnetic orientatio n of the Nd2Fe14B matrix grains was perpendicular to the outer surface . A corrosion mechanism involving the reaction of hydrogen-either as a pure gas or as a by-product of the decomposition of water vapor-with the neodymium-rich grain boundary phase is proposed. (C) 1996 American Institute of Physics.