Electroless Ni-W-P Coating and Its Nano-WS2 Composite: Preparation and Properties

The ternary alloy Ni-W-P and its WS2 nanocomposite coatings were successfully obtained on low-carbon steel using the electroless plating technique. The sodium tungstate (Na2WO4) concentration in the bath was varied to obtain Ni-W-P deposits containing various Ni and P contents. WS2 composite was obtained with a suitable concentration of Na2WO4 in Ni-P coating. These deposits were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray analysis (EDX) studies. The corrosion behavior was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) studies in 3.5 wt % NaCl solutions, and the corrosion rates of the coatings for Ni-P, Ni-W-P, and Ni-W-P-WS2 were found to be 2.571 x 10(-5), 8.219 x 10(-7), and 7.986 x 10(-7) g/h, respectively. An increase in the codeposition of alloying metal tungsten (W) enhanced the corrosion resistance and microhardness and changed the structure and morphology of the deposits. Incorporation of WS2 nanoparticles to Ni-W-P alloy coating reduced the coefficient of friction from 0.16 to 0.11 and also helped in improving the corrosion resistance of the coating further.