Effective acid corrosion inhibitors for X60 steel under turbulent flow condition based on benzimidazoles: electrochemical, theoretical, SEM, ATR-IR and XPS investigations

The corrosion inhibition properties of two benzimidazole derivatives 2-(2-Bromophenyl)-1H-benzimidazole (BHB) and 2-(2-Bromophenyl)-1-methyl-1H-benzimidazole (BMB) for X60 steel in 1 M HCl solution were investigated under laminar and turbulent flow conditions. Experimental methods (electrochemical impedance spectroscopy, linear polarization and potentiodynamic polarization) were complemented with scanning electron microscopy, attenuated total reflectance infrared spectroscopy and X-ray photoelectron spectroscopy. The results obtained all agree that the protonation of BHB and BMB facilitated their protective adsorption on the steel. Although turbulent flow condition increased the corrosion rate, BHB and BMB provided significant corrosion protection for the carbon steel in the acid medium. The presence of a methyl group on the benzimidazole ring conferred greater corrosion inhibition property on BMB when compared with BHB. Theoretical calculations provided more insight into the inhibitor–steel interaction at the atomic and molecular levels.