Cobalt/graphene electrodeposits: Characteristics, tribological behavior, and corrosion properties

Cobalt/graphene composite coatings were electrodeposited from the baths containing 0.1-0.5 g/L graphene particles. The effect of graphene particles on structure, morphology, hardness, tribological behavior, and corrosion of the coatings was studied. The results revealed that the pyramidal morphology of the pure Co film became smaller at low graphene concentrations, and changed to needle-shaped at the high concentrations. The presence of graphene in the composite films resulted in the reduction of the cobalt crystallite size and thereby increased the hardness of the coatings. The hardness of Co/0.2 g/L graphene composite coating was 530 Hv that was about 1.6 times higher than the pure Co film. The composite coatings also had better tribological behavior than the steel substrate and the Co film. The lowest volume loss achieved in a composite coating deposited from a bath with 0.2 g/L graphene particles. The most corrosion resistance samples were those electrodeposited from baths with 0.2-0.4 g/L graphene particles. The corrosion current density of these samples in 3.5 wt% NaCl solution was <1 mu A/cm(2).