Electroless Ni-W-P/WS2 ternary composite coatings

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 × 10¿5, 8.219 × 10¿7, and 7.986 × 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 WS2nanoparticles 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.