A Preparation Method and Effects of Al-Cr Coating on NdFeB Sintered Magnet

摘要

The 50μm Al-Cr coating on NdFeB sintered magnets was prepared through dipping in solution, shaking dry and heating at 300°C. The morphology and composition of the Al-Cr coating were investigated with SEM and EDS. The corrosion resistance of NdFeB sintered magnets with and without the Al-Cr coating on was analyzed by the normal salt spray, the polarization curves and electrochemical impedance spectroscopy. The magnetic properties were measured with a hysteresis loop tracer. The results show that the Al-Cr coating forms an overlapping structure and Al flakes lies nearly parallel to the substrate, which improves the anticorrosion abilities and enduces normal salt spray test from 10h to 100h. The corrosion potential of NdFeB sintered magnets with and without the Al-Cr coating moves positively from -0.67V to -0.48V, which is in accordance with Nyquist and Bode plots. The Al-Cr coating influences magnetic properties of NdFeB sintered magnets little.