Preparation of Ni/graphene hydrophobic composite coating with micro-nano binary structure by poly-dopamine modification

In this study, poly-dopamine (pDA) was used to prepare a nickel-graphene (GR) composite coating on 45# steel by utilizing the electrodeposition techniques. The pDA has two advantages for the Ni/GR@pDA composite coatings: (1) improving the dispersion of graphene in the aqueous solution; (2) enhancing the bonding force between GR and the substrate. The high resolution transmission electronic microscope (HRTEM) and the energy dispersive spectroscope (EDS) confirmed that GR was coated with a layer of pDA, which is the product of the situ spontaneous oxidative polymerization reaction of dopamine (DA). Dispersion test result showed that the modified GR could disperse in the aqueous solution stably for more than 4 h. The dispersion of GR was improved obviously. The friction-wear and corrosion experiments indicated that the performance of composite coating was raised significantly than the pure Ni coating. Because the grains of the composite coating were refined, the micro-nano binary structure was formed on the coating surface. Hence the hydrophobicity of the coating was greatly improved.