Microstructural, surface and electrochemical properties of electrodeposited Ni-WC nanocomposites coatings

Abstract

In this work, we study the influences of nano-sized WC particles (diameter size of ∼50 nm), concentrations on the structure, surface morphology, mechanical and electrochemical properties of Ni-WC composite coatings electrodeposited on pretreated copper substrates. The corrosion behavior of Ni-WC composite coatings was studied by the potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods in two corrosion media (0.1 M HCl) and (3.5% NaCl). EDS analysis affirms that WC is the incorporated particles and nickel is the blinder metal. The incorporation of WC particles in the nickel matrix forms heterogeneous deposits that contain deep and narrow pores. XRD pattern indicates good crystal structure with (110), (111), (200) and (311) preferred growth orientations. The reinforcement of Ni matrix by nan-sized WC particles refines the grains size of the coatings. Microhardness and roughness of the deposits increase with the increase of WC concentration in the electrolyte bath. Based on the lowest corrosion density and the highest charge transfer resistance value, corrosion tests show that the samples 4 g/L and 1 g/L immersed in the corrosive media of 3.5% NaCl and 0.1 M HCl are the optimum conditions, respectively.