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Corrosion protection of sintered NdFeB magnets by CAPVD Ti 2 N coating
Author(s) -
Ali A.,
Ahmad A.
Publication year - 2009
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.200805132
Subject(s) - materials science , neodymium magnet , coating , corrosion , tafel equation , metallurgy , titanium nitride , scanning electron microscope , titanium , nitride , nickel , composite material , magnet , electrochemistry , layer (electronics) , electrode , chemistry , physics , quantum mechanics
Sintered NdFeB magnets have poor corrosion resistance and are readily susceptible to corrosion under different environmental conditions. Cathodic arc physical vapour deposited (CAPVD) titanium nitride coating for sintered NdFeB permanent magnets has been investigated in this paper. Tafel extrapolation was employed to study the corrosion behaviour in 3.5% NaCl solution at ambient temperature. The adhesive strength of the coating was estimated with the help of the scratch test. The surface chemistry and coating morphologies were studied with scanning electron microscope (SEM). X‐Ray diffraction (XRD) was used for qualitative phase analyses of coatings and substrate. The properties of CAPVD titanium nitride coating were compared with electrodeposited multilayer nickel–copper–nickel coating. It was figured out that the CAPVD titanium nitride coating had better adhesion strength and shifted the free corrosion potential (FCP) of the system towards positive potential, providing protection to the NdFeB substrate. However, the corrosion rate of CAPVD titanium nitride coating was more than the electrodeposited multilayer nickel–copper–nickel coating. The magnetic properties remained comparable.