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Electrodeposited nickel/alumina composite coating on NdFeB permanent magnets
Author(s) -
Zhang H.,
Song Y. W.,
Song Z. L.
Publication year - 2008
Publication title -
materials and corrosion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.487
H-Index - 55
eISSN - 1521-4176
pISSN - 0947-5117
DOI - 10.1002/maco.200804107
Subject(s) - materials science , passivation , nickel , coating , neodymium magnet , corrosion , dielectric spectroscopy , composite number , scanning electron microscope , metallurgy , microstructure , composite material , electrochemistry , magnet , electrode , chemistry , layer (electronics) , physics , quantum mechanics
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.