Electrodeposited nickel/alumina composite coating on NdFeB permanent magnets |
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Authors: | H Zhang Y W Song Z L Song |
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Affiliation: | 1. Ningbo Institute of Material Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (P.R.China);2. Institute of Solid State Physics, Chinese Academy of Sciences, Heifei 230001 (P.R.China) |
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Abstract: | NdFeB magnets are highly susceptible to corrosion in various environments. A nickel/alumina composite coating for NdFeB magnets was investigated in this paper. The microstructures of electrodeposited nickel coating and nickel/alumina composite coating were determined by scanning electron microscope (SEM). The corrosion behavior of nickel coating and nickel/alumina composite coating in 3.5 wt% sodium chloride solution was studied by polarization curves and electrochemical impedance spectroscopy (EIS). The results show that the nickel coating and nickel/alumina composite coating can both provide adequate protection to the NdFeB substrate. Furthermore, the free corrosion potential of nickel/alumina composite coating is more positive and the passivation region is more obvious compared with nickel coating, and the capacitance loop diameter of nickel/alumina composite coating is significantly larger than that of nickel coating. With the increase in immersion time, a flat of passivation film is formed on the surface of nickel/alumina composite coating, resulting in excellent corrosion resistance after 288 h immersion in 3.5% sodium chloride solution according to EIS testing. |
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Keywords: | corrosion resistance electrodeposited NdFeB permanent magnets nickel/alumina composite coating |
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