Journal of Applied Electrochemistry, Vol.40, No.1, 39-47, 2010
The electrochemical corrosion behavior of sealed Ni-TiO2 composite coating for sintered NdFeB magnet
In this article, a protective sealed Ni-TiO2 composite coating (SCC) was prepared on sintered NdFeB magnet by pulse current electrodeposition and sol-gel combined technique. For a comparison, unsealed Ni-TiO2 composite coating (UCC) was also studied. The surface morphologies of composite coating were studied using scanning electron microscope (SEM). The structure of sealing layer was studied by Fourier transform infrared (FT-IR) spectrum. The anticorrosive properties of composite coating in neutral 3.5 wt% NaCl solution were evaluated by potentiodynamic polarization measurements and electrochemical impedance spectroscopy (EIS). In order to further investigate the anticorrosive properties of SCC, a long-term immersion test was carried out in neutral 3.5 wt% NaCl solution. The results of corrosion tests showed that due to the blocking effect of sealing layer, SCC can suppress the corrosion process by holding back the transfer or diffusion of corrosive medium, and therefore showed the excellent anticorrosive properties for sintered NdFeB magnet.
Keywords:Ni-TiO2 composite coating;Sintered NdFeB magnet;Sealing;Potentiodynamic polarization;Electrochemical impedance spectroscopy