Preparation of Ni–W–SiO2 nanocomposite coating and evaluation of its hardness and corrosion resistance

In this paper, nanocomposite coatings were obtained by electrochemical codeposition of SiO2 nano-particles (diameter 30–40 nm) with Ni–W on mild steel surface. The structure and microstructure of coatings was separately analyzed by X-ray diffraction (XRD) and scanning electron microscope (SEM). The corrosion resistance of the samples was evaluated by potentiodynamic polarization (Tafel) and electrochemical impedance spectroscopy (EIS). Results indicated that nano-SiO2 had a prodigious impact on the microstructure, composition and structure of electroplated coating by remarkable effect on its electrodeposition process. Ni–W–SiO2 coatings showed higher hardness in comparison with the Ni–W coating. Hardness values of Ni–W–SiO2 coatings ranged from 768 to 823 HV and the coating obtained in bath containing 10 g/L nano-SiO2 showed a maximum hardness (about 823 HV). Apart from that, significant influence had been observed on corrosion resistance by the SiO2 nano-particles. Electrochemical test results demonstrated that Ni–W–SiO2 coatings exhibited a generally less protective performance compared with amorphous Ni–W coating.