Hydrogen induced corrosion mechanism in NdFeB magnets

An investigation was conducted comparing the corrosion behavior of NdFeB magnets in flowing hydrogen and in the beat and humidity of an autoclave. The results show that corrosion is both macroscopically and microscopically similar in both environments. In both cases, the corrosion progressed most rapidly in those areas where the magnetic orientation 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.