Corrosion behaviour of Ni/WC-MoS2 composite coatings prepared by jet electrodeposition with different MoS2 doping concentrations

Abstract

This study aimed to evaluate the corrosion behaviour of composite coatings with MoS2 doping. Herein, the jet electrodeposition technique was used to prepare Ni/WC-MoS2 composite coatings with different MoS2 doping concentrations. Then, the composition, morphology, surface contact angle and so on, 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 corrosion mechanism of composite coatings in the corrosion process was also analysed. Results indicated 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. As the MoS2 doping concentration increased, the hydrophobic surface angle of the coating could be increased up to 132.5 °. After the corrosion test in 3.5 wt% NaCl solution, the surface of the composite coating without MoS2 doping showed severe pitting corrosion. Therefore, the hydrophobicity allowed the Ni/WC-MoS2 composite coating to offer excellent corrosion resistance with a predominantly uniform corrosion mechanism. The improved corrosion resistance of the composite coatings was attributed to the enhanced surface morphology and hydrophobicity. The more pronounced surface roughness and hydrophobicity helped the coating to trap air and form ‘air pockets’ when in contact with the corrosive medium, thereby 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) and corrosion rate (CR) of 0.0193 μA·cm−2 and 2.2446E-4 mm/a, respectively. Thus, the Ni/WC-MoS2 composite coatings behaved with better corrosion resistance than Ni/WC composite coatings.