Primary investigation of corrosion resistance of Ni-P/TiO2 composite film on sintered NdFeB permanent magnet

摘要

In this paper, an electroless nickel plating and sol-gel combined technique used to prepare the Ni-P/TiO2 composite film on sintered NdFeB permanent magnet is described and the composite film was characterized by X-ray diffraction (XRD), environmental scanning electron microscopy (ESEM), and energy dispersive X-ray spectrometer (EDX). The corrosion resistance of Ni-P/TiO2 film was studied by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The self-corrosion current density (i(corr)) of Ni-P/TiO2 composite film is 2.38 mu A/cm(2) in 0.5mol/L H2SO4 Solution about 33% of that of Ni-P coating and 0.22 mu A/cm(2) in 05mol/L NaCl solution about 14% of that of Ni-P coating, respectively. In 0.5mol/L H2SO4 and 0.5mol/L NaCl solutions, the polarization resistance (Rp) of the composite film is 12.5k Omega cm(2) and 120 Omega cm(2), about 1.6 and 2 times that of Ni-P coating, respectively. The results indicate that Ni-P/TiO2 composite film has a better corrosion resistance than Ni-P coating. (C) 2008 Elsevier B.V. All rights reserved.