Structure and Corrosion Resistance Characteristics of ZnAl/EP Coating on Bonded NdFeB Magnet

ZnAl/epoxy resin (ZnAl/EP) composite coating with a thickness of 30.5 mu m was prepared on bonded NdFeB magnetic ring. The morphologies and composition of ZnAl-EP/NdFeB were characterized by scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The surface roughness of samples was measured by 3D Laser Confocal Scanning Microscope (LCSM). The samples of prepared EP/NdFeB and ZnAl-EP/NdFeB were used for corrosion tests in potentiodynamic polarization method, electrochemical impedance spectroscopy (EIS) and neutral salt spray (NSS) test. The magnetic properties of samples were measured with a permanent magnet material measuring instrument. The corrosion current density (J(corr)) of ZnAl-EP/NdFeB is 1 order of magnitude lower than that of EP/NdFeB, reflecting the corrosion resistance of ZnAl-EP/NdFeB is much higher in contrast with the EP/NdFeB. Compared with the EP/NdFeB, the NSS test time of ZnAl-EP/NdFeB is increased from 72 to 936 h. In addition, the ZnAl-EP coating has no significant effect on the magnetic properties of NdFeB magnetic ring.