CORROSION BEHAVIOR OF NDFEB WITH CO AND V ADDITIONS

Two NdFeB materials were selected for study. The first is referred to as a base or standard alloy with a composition of (NdDy)15FebalAl0.7B6 , and the second is similar, Nd13.5Dy1.5FebalCo5V4AlB8, but alloyed wi th Co and V. The corrosion behavior of magnets made with these two mat erials is compared by two different techniques, autoclave testing at e levated temperature and pressure for 96 h, and dc electrochemical test ing in an aqueous electrolyte. For the former, the base alloy exhibite d poor corrosion resistance with a weight loss on the order of 270 mg/ cm2. Significantly, the Co-V-treated samples yielded excellent corrosi on resistance, showing no change in weight. Two types of electrochemic al tests were performed on electrodes of each material, potentiodynami c polarization and constant potential in sodium sulfate solutions at p H from 1.5 to 4.4. Consistent with the autoclave tests, electrochemica l experiments show lower currents for the Co-V alloys.