Effect of Phosphate Treatment on the Corrosion Resistance of Nd–Fe–B Anisotropic Magnetic Powder

Anisotropic Nd–Fe–B hydrogenation disproportionation desorption recombination powder with high corrosion resistance was prepared by phosphoric acid treatment. The treated samples baked at temperatures higher than 250 °C exhibited high corrosion resistance. In addition, the change ratio of coercivity before and after the anticorrosion test was within 5%. Microstructural observations indicated the formation of a uniform phosphate layer with a small amount of Nd oxide at high baking temperatures.