TiO2 nano-particle effect on the chemical and physical properties of Ni-P-TiO2 nanocomposite electroless coatings

Abstract

TiO2 nano-particles were used in electroless plating bath to obtain Ni/P/nano-composite coatings. The coatings were heat treated at 200, 400, 600 and 700 oC and their chemical and physical properties were investigated and it was found that 400 oC was the optimum temperature for the heat treatment of the coatings. The micro-hardness test of coatings showed that the composite coatings, which contain TiO2 nano-particles, exhibit better properties of microhardness. X-ray diffraction (XRD) analysis indicated that at 400 oC, Ni3P phase is formed, and when the heating temperature is 600 oC the presence of TiO2 particles is seen. We have used scanning Electron Microscopy (SEM) to measure the surface morphology of the composite and plane deposits. Weight loss measurement, Electrochemical Impedance Spectroscopy (EIS) and Potentiodynamic Polarization Spectroscopy were utilized to study the corrosion resistance of coatings in 3.5 %wt NaCl solution. Corrosion resistance experiments indicated that presence of TiO2 nano particles in the electroless coatings matrix improved the corrosion resistance of the coatings. Heat-treatment improved the corrosion resistance of the coatings up to 400 oC but heating above 400 oC caused a decrease in corrosion resistance. Wear behavior of the samples indicated that presence of TiO2 particles improve the wear resistance.