Electrodeposition and corrosion behavior of nano-structured Ni-WC and Ni-Co-WC composite coating

Abstract

Composite coating of metallic-ceramics tungsten carbide (WC) in nickel matrix has been achieved by direct current (DC) electrodeposition using watt's bath solution on stainless steel substrate. The deposition parameters such as current density, bath temperature, and stirring rate were maintained at constant levels for all the coating configurations. The surface morphologies, microstructure, and chemical composition of the composite coating were studied using scanning electron microscope (SEM), X-ray diffraction (XRD), and energy dispersive analyzer x-ray system (EDX), respectively. The surface morphology and microstructure analysis showed that the composite coatings form cauliflower-like grain colonies, grain size was calculated from Scherrer equation it was less than 60 nm for all composite coating. Micro hardness of composite coating was increased by increasing WC load in solution and decreasing grain size. The electrochemical corrosion behavior of composite coating was evaluated by potentiodynamic polarization measurements and electrochemical impedance spectroscopy (EIS) in aerated 0.5 mol/l H2SO4 at room temperature, showing passivation behavior of all composite coating, good protection of Ni-8g/l WC on stainless steel substrate.