Rare earth passivation and corrosion resistance of zinc coated NdFeB magnets

Rare earth passivation was conducted on Zn coated NdFeB magnets by chemical reaction to enhance the corrosion resistance performance. Morphologies, microstructures and compositions of different passivated coatings were studied by X-ray diffraction, field emission scanning electron microscopy, and X-ray photoelectron spectroscopy, respectively. The corrosion behavior was evaluated by electrochemical measurement and neutral salt spray test. The results show that the rare earth passivation can enhance the corrosion resistance of Zn coated NdFeB magnets. When the concentration of cerium nitrate is 5 g/L, the passivated specimens can achieve the longest NSS time of 360 h, which is 144 h longer than that of the pristine Zn/NdFeB magnets. The passivation layer on the Zn coating surface contributes to the enhancement of the magnets’ corrosion resistance.