Effects of graphene oxide and current density on structure and corrosion properties of nanocrystalline nickel coating fabricated by electrodeposition

Abstract

Protective coatings with superior corrosion resistance and enhanced mechanical properties are still greatly required when applied in challenging environments. In this paper, nickel-graphene oxide nanocrystalline coatings with uniform structure have been fabricated by co-electrodeposition technique. Effects of graphene oxide (GO) in plating solution and applied current density on structural, composition, crystallite size and corrosion-resistant properties of electrodeposited Ni-GO nanocrystalline coatings were compared and investigated systematically. The deposited coatings have a compact, crack-free, silver-gray appearance with lower surface roughness, exhibiting colonies-like morphology. The presence and uniform distribution of graphene oxide on the surface as well as inside nickel coating were confirmed. The crystallite size and crystal plane orientation have no significant alteration in the presence of graphene oxide. The preferred orientation of (200) crystal plane of pure Ni is changed to low energy (111) plane for Ni-GO composites. The average roughness Ra of Ni-GO is 3–5 nm. Ni-GO coating contains 2.6–3.9 wt% GO, 95.5–96.9 wt% Ni and some oxygen. With the increase of GO, the corrosion resistance first enhanced to a maximum at 0.2 g L−1 GO. When GO exceeds a certain value, agglomeration occurred, causing uneven dispersion of GO and heterogeneous coarse surfaces. The anti-corrosion capability was enhanced by the incorporation of GO due to the grain refinement and the uniform dispersion of impermeable GO. Current density could change the structure and anti-corrosive features of Ni-GO coating. The Ni-GO nanocrystalline coating possesses enhanced performance, which has a promising application prospect in harsh environments.