Electrochemical, microstructural and theoretical validation of 2-(2-Bromophenyl)-1H-benzimidazole as inhibitor for C1018 steel during very aggressive CO2 corrosion

This work is motivated by the lack of research papers reporting benzimidazole derivatives in very aggressive CO2-corrosion systems. We appraise the inhibitive performance of 2-(2-bromophenyl)-1 H Benzimidazole (BPHB) in CO2-saturated 3.5 % sodium chloride (NaCl) + 50 ppm acetic acid (HAc) without and with 1 M hydrochloric acid (HCl) using electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), scanning electron microscopy (SEM) and x-ray diffraction (XRD). We augment results from these techniques with molecular dynamics simulations and density functional theory, as computational modelling techniques. In the absence of HCl, the inhibitor adsorbs firmly on the steel surface, displays a strong cathodic influence on corrosion potential (E-corr) and current density (i(corr)), and minimizes both general and pitting corrosion with similar to 80 % efficiency. The presence of HCl furnishes abundant H+ ions that significantly diminish the cathodic influence of BPHB, blocks its firm adsorption and, although it reduces the extent of general and pitting corrosion, lowers its efficiency to similar to 70 %. Computational modelling techniques confirm electrochemical and surface probe results. The nitrogen atoms and CC bonds in the imidazole ring are the centers that facilitate BPHB adsorption. The inhibitor adsorbs in such a way as to maximize surface coverage. However, adsorption is more energetically favored in the absence of HCl, based on E-ads calculations.