Magnetic and corrosion characteristics of Nd-Fe-B magnet with various surface coatings

Various surface coatings, including duplex Ni(undercoat)/Cr(topcoat), multilayer Ni/Cu/Ni/Cr, Zn, bright Ni, bright Au, and black epoxy were applied to improve the corrosion resistance of the Nd-Fe-B magnet. The corrosion behavior of the surface-coated magnets was studied using Normal and Acetic Acid Salt Spray Tests. The influence of coating and corrosion on the magnetic properties was also investigated. It was found that the duplex Ni/Cr coating provided the best corrosion protection with little deterioration in the magnetic properties during the corrosion process.