Evaluation of Corrosion Behaviour of Ni/Wc-Mos2 Composite Coatings Prepared by Jet Electrodeposition with Different Mos2 Doping Concentrations

Abstract

The jet electrodeposition technique was used to prepare Ni/WC-MoS2 composite coatings with different MoS2 doping concentrations. The composition, morphology, surface contact angle etc., of coatings’ surfaces, were characterised. The corrosion behaviour of the composite coatings with different nano-MoS2 doping concentrations was investigated in 3.5 wt.% NaCl. The results exhibited that the MoS2-doped composite coatings had fewer surface micro-defects than Ni/WC coatings. Micro-nano structures such as "cauliflower" and nodules occurred on the coating’s surface with MoS2 doping. The hydrophobic surface angle of the coating could be increased up to 132.5 °as the MoS2 doping concentration rises. After corrosion test in 3.5wt.% NaCl solution, the surface of the composite coating without MoS2 doping showed severe pitting corrosion. The improved corrosion resistance of the composite coatings was attributed to the enhanced surface morphology and hydrophobicity. The more significant surface roughness and hydrophobicity helped the coating to trap air and form "air pockets" when in contact with the corrosive medium, blocking the corrosion process of Cl-. The Ni/WC-5 g/L MoS2 composite coating had more positive corrosion potential (Ecorr) than other coatings, with a minimum corrosion current density (Icorr) of 0.0193 μA·cm-2 and a minimum corrosion rate (CR) of 2.2446E-4 mm/a.

Keywords: Nano-MoS2, Ni/WC-MoS2 composite coating, Surface morphology, Hydrophobicity, Corrosion behaviour