Development of electroless Ni–P/nano-WC composite coatings and investigation on its properties

• The Ni–P–WC nanocomposite coatings are synthesized by electroless method.
• Microhardness is greatly improved by adding WC nanoparticles and heat treatment.
• Ni–P–WC coatings showing high corrosion resistance in the salty environment

In this study, a Ni–P–WC nanocomposite coating was prepared by electroless deposition methods, modifying the typical Ni–P coating through the addition of WC nano-particles. The morphology, structure, microhardness and corrosion resistance of the Ni–P–WC coating and conventional Ni–P coating were analyzed by using the optical stereoscopic microscopy (OSM), scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), anodic polarization curve and electrochemical impedance spectroscopy (EIS). It was observed that WC nano-particles and Ni–P deposited homogeneously on the Ni–P matrix, electroless deposited composite coatings exhibit an amorphous structure of the nickel matrix in which crystalline tungsten carbide is incorporated. The microhardness of the coating increased due to the existence of the nano-particles, and it will be improved after heat treatment. According to the results of corrosion testing in the 3.5 wt.% sodium chloride solution, the electroless Ni–P–WC coatings showed significantly improved corrosion resistance due to its special structure, compared to a conventional Ni–P electroless coating, even after 40 days immersion, it also exhibited good corrosion resistance ability.