Materials Science Forum, Vol.475-479, 2151-2154, 2005
Electrochemical impedance spectroscopy of Nd-Fe-B magnet prepared by spark plasma sintering
Electrochemical impedance spectroscopy (EIS) tests of anisotropic Nd-Fe-B magnets prepared by spark plasma sintering (SPS) technique were carried out to investigate their corrosion kinetics in different solutions. According to the Nyquist and Bode diagrams, convenient equivalent circuit was modeled and the values of the proposed equivalent circuit components were calculated. It was found from the EIS plot formats that the electrochemical reaction of SPS Nd-Fe-B magnets was controlled by the step of surface charge transfer i.e. activation polarization in alkaline solution, while controlled by step of active substances adsorption on the magnet surface in salt and acidic solutions. Compared with conventional sintered Nd-Fe-B magnets, the SPS Nd-Fe-B magnets possess better chemical stability in saline and weak acidic environment.