Surface modification of carbon steel by ZnO-graphene nano-hybrid thin film

Abstract

Application of corrosion resistant coatings is one of the most widely used means of protecting steel. Zinc coated (galvanize) steel, is well known for galvanic protection of steel substrates and nowadays, particular attention has been paid to the coupling of graphene oxide (GO) with metallic materials, in order to lessen corrosion rate. In this research, an isopropanol supercritical reducing environment prepared to make zinc ions bond directly with graphene oxides, to form a button shape hybrids of ZnO-Graphene (ZnOG). The hybridized bonding between zinc and graphene oxide is confirmed by Fourier Transform Infra-Red analysis. And the morphology revealed, using a Field Emission Scanning Electron Microscope. ZnOG dip-coated thin film on a carbon steel St.32 substrate, was further analyzed by X-ray diffraction study and Energy Dispersive Spectroscopy (EDS) on the micrographs to verify the presence of ZnOG buttons on the surface. Polarization plots show that ZnOG has lowest corrosion rate in both 3.5 wt% NaCl and wet H2S electrolytes, with respect to conventional or GO composited galvanize steel. In fact non-hybridized GO in galvanize coating, increases corrosion rate in wet H2S by 14 times. This is further verified by Warburg formation of Nyquest impedance plots, that GO flakes make a path for corrosive ion diffusion across the coating. But hybridizing GO into the coating, provides a robust barrier against corrosion. In conclusion, Mott-Schottky analysis revealed ZnO semiconductor properties, even for conventional hot dip galvanize steel.