Investigation on corrosion inhibition and adsorption mechanism of triazine-thiourea derivatives at mild steel / HCl solution interface: Electrochemical, XPS, DFT and Monte Carlo simulation approach

Abstract

Abstract The corrosion inhibition behavior of synthesized triazine-thiourea compounds, namely, 1,3-bis(5,6-diphenyl-1,2,4-triazin-3-yl)thiourea (BTT) and 1,3-bis(5H-[1,2,4]triazino[5,6-b]indol-3-yl)thiourea (BTI) on mild steel in 15% HCl solution was investigated by using gravimetric and electrochemical corrosion testing methods at different experimental conditions. BTT was found more efficient corrosion inhibitor than BTI. It was observed from experimental outcomes that at optimum concentration (200 ppm) and 303 K temperature, BTT was 98.5% efficient towards the corrosion protection of mild steel in 15% HCl solution. The surface morphological study of uninhibited and inhibited samples was performed by FESEM and AFM analysis. Adsorption of both inhibitor molecules on the surface of mild steel obeyed Langmuir adsorption isotherm. XPS analysis was performed to determine the binding energy and elemental composition of adsorbed inhibitor molecules on the surface of mild steel. DFT and Monte Carlo simulation (MCS) was performed to get more insight into the protection mechanism adopted by inhibitor molecules.