Corrosion behavior of Ni/WC nano-structured composite layers synthesized by electrochemical method

Abstract

Ni/WC nano-structured composite coatings were developed by electrodeposition method from a nickel plating electrolyte containing WC nanoparticles (diameter size of ~60 nm). The corrosion behavior of Ni/WC nano-structured composite coatings and pure Ni coating were comparatively investigated in wet conditions in the solution that simulates the primary water of Pressurized Water Reactors (PWRs). The morphology and chemical composition of the obtained coatings before was observed through scanning electron microscopy (SEM) connected to an energy dispersive X-ray system (EDX). The open circuit potential (OCP) and Electrochemical Impedance Spectroscopy (EIS) methods were used to evaluate the corrosion behavior, at room temperature. The nanohardness of pure Ni and Ni/WC nanocomposite coatings was tested by nanoindentation technique. SEM-EDX analyze proved that WC nanoparticles were successfully incorporated into Ni matrix. Presence of WC nanoparticles in the nickel matrix transforms surface morphology from regular pyramidal to irregular global and changes the crystallizations of nickel matrix to smaller and thinner crystallites. Ni/WC nanocomposite coating revealed a higher nanohardness value in comparison with pure Ni coating. The corrosion resistance of Ni/WC nanocomposite coating is higher under similar experimental conditions as compared with pure nickel layers, proving an enhancement of corrosion resistance.