Performance and interaction mechanism of a new highly efficient benzimidazole-based epoxy resin for corrosion inhibition of carbon steel in HCl: A study based on experimental and first-principles DFTB simulations

Abstract

Thanks to their excellent properties, epoxy resins are the first choice for many engineering applications. In this regard, herein, a new epoxy resin, namely 1-(oxiran-2-ylmethyl-1H-benzo[d]imidazole (BIZ epoxy), was synthesized and characterized by nuclear magnetic resonance (1H, 13C NMR) and Fourier transform infrared-attenuated total reflection (FTIR-ATR)) techniques. The corrosion inhibition properties of prepared epoxy resin for carbon steel (CS) in 1.0 mol/L HCl were evaluated using electrochemical and scanning electron microscope (SEM) techniques. Furthermore, reactivity and interaction mechanisms between epoxy resin molecule and the iron surface were investigated using quantum chemical parameters (QCPs) and Density-Functional Tight-Binding (DFTB). Electrochemical studies by potentiodynamic polarization curves (PPC) and electrochemical impedance spectroscopy (EIS) showed that the BIZ epoxy acted as a barrier against the acid corrosion of CS with an inhibition efficiency of 93 % at 1 mmol/L. The adsorption of BIZ epoxy followed the Langmuir adsorption isotherm and was found to be a physicochemical process. The SEM analysis showed a significant difference in surface morphology of CS after inhibition due to the formation of a protective barrier. DFTB simulation of BIZ epoxy – Fe(110) surface revealed the formation of a chemical bond and several long-range van der Waals interactions. The projected density of states (PDOS) of isolated and adsorbed systems confirmed the physicochemical nature of interactions between inhibitor molecule and Fe(110) surface.