Pulse-reverse electrodeposition of Ni-Co/graphene composite films with high hardness and electrochemical behaviour

This study reports the production of functional Ni-Co/graphene coating obtained by pulse-reverse current (PRC) electrodeposition method in Ni-Co plating bath containing graphene (Gr) to be co-deposited. Effects of graphene concentration on the morphology, microstructure, microhardness, and electrochemical behaviour of the resulting Ni-Co/graphene thin film were investigated. It was found that Gr introduced into the electrolyte and its concentration affected the composition as well as the structure of the composite coatings. A higher Gr concentration in the electroplating bath led to a higher Co concentration in Ni-Co alloy coatings. Ni-Co alloys and Ni-Co/Gr composite coatings exhibited a compact surface under PRC current, an average crystallite size in the range of 8–10 nm, and a solid solution structure of Ni (Co). The electrochemical behaviour of the composite coating improved with increasing Gr content, but decreased with higher Gr concentration (0.8 g/l). Ni-Co/Gr nanocomposite coating also exhibited a higher microhardness of 610 HV than monolithic Ni-Co coating of 458 HV.