Corrosion Behavior of NdFeB-Based Nanocrystalline Permanent Magnets

The corrosion properties of epoxy-bonded nanocrystalline magnets made from rapidly quenched NdFeB-based powders with compositions varying from the Nd-rich to the Fe-rich range and with Co, Nb additives and that of their principal single phases as well as that of intensively milled Nd2Fe14B/alpha-Fe nanocomposites with up to 35 wt.-% alpha-Fe in aqueous buffer solution with pH 5 (and pH 8.4) are evaluated. With increasing Fe content and corresponding microstructural modifications a change in the corrosion mechanism and an improvement of the corrosion resistance is detected.