Corrosion resistance and photocatalytic activity evaluation of electrophoretically deposited TiO2-rGO nanocomposite on 316L stainless steel substrate

Abstract

Abstract TiO2-rGO nanocomposite coatings were obtained by electrophoretic deposition (EPD) technique of TiO2 nanoparticles and graphene oxide (GO) on stainless steel substrate. First, GO particles were synthesized using a modified Hummers' method. GO was reduced electrochemically to form a coating in the presence of nano-sized TiO2 particles. The influences of different parameters such as GO concentration, coupling co-electro-deposition parameters (electrophoretic duration and voltage) on thickness, surface morphology and, corrosion behavior of the as-synthesized TiO2-rGO nanocomposite coatings were systematically surveyed. The morphology and microstructure were investigated by field emission scanning electron microscopy (FE-SEM), Raman spectra and X-ray diffraction (XRD) techniques. Atomic force microscopy (AFM) was harnessed to evaluate the topography of the as-prepared GO powder. The bonding characteristics of as-synthesized and as-reduced GO were examined after deposition, by Energy Dispersive Analysis of X-Ray (EDX) and Fourier-transform infrared spectroscopy (FT-IR). Corrosion behavior of coatings and that of the pure TiO2 layer were evaluated by electrochemical impedance spectroscopy (EIS) and polarization techniques (by applying potentiodynamic polarization spectroscopy (PDS)). Detailed SEM studies showed that increasing EPD voltage brings about a coating with increased porosity and microcracks with higher thickness. In addition to that, the presence of rGO reduced corrosion current density (icorr) and shifted corrosion potential (Ecorr) toward more noble values in 3.5% NaCl at room temperature. Also, Analyses revealed that the optimum electrophoretically synthesized coating was obtained at GO concentration of 1 g/L, 30 V and 30 min at room temperature. The corrosion current density of the corresponding coating was remediated up to 0.2 μA cm−2, which means an anti-corrosion ability of about 30 times compared to TiO2-coated and bare 316L stainless steel. The results of impedance spectroscopic studies demonstrated that this coating renders as a barrier layer and resistance increased from 2.95 KΩ cm2 for TiO2-coated layer to 10.49 KΩ cm2 for the optimized layer.