Preparation of Ni–Mo/GO composite coatings with strengthened mechanical properties and enhanced corrosion resistance

Abstract

Ni–Mo/GO coatings in thickness of 1.5–3 μm were electrodeposited from a citrate bath containing nickel sulfate, sodium molybdate, GO and SDS. The impacts of GO nanosheets on the surface morphology, structure, mechanical properties and corrosion resistance of the Ni-Mo matrix were explored. Ni-Mo alloy shows an amorphous phase with a smooth and compact surface. The codeposited graphene oxide can refine Ni-Mo microstructure, but also can lead to rougher surfaces with defects. Coefficient of friction (COF) of Ni-Mo matrix decreased, and wear resistance and hardness increased in the presence of GO. The corrosion resistance of Ni–Mo/GO would be improved only if GO concentration exceeded 0.2 g L−1. The preferred concentration of GO was 0.2–0.3 g L−1, which showed satisfactory anti-corrosion performance. The corrosion resistance depends not only the amount of GO present but also its dispersed arrangement and distribution. A higher content of GO, a dispersion of particles parallel to the substrate and uniform GO distribution in the metallic matrix can hinder the diffusion of corrosive species, leading to an improved corrosion resistance.