Comprehensive assessment of corrosion inhibition mechanisms of novel benzimidazole compounds for mild steel in HCl: An experimental and theoretical investigation

Abstract This study set out to examine the corrosion inhibiting properties of two novel benzimidazole derivatives, namely 1,4-bis(2-(4-chlorophenyl)-1H-benzo[d]imidazol-1-yl)butane (IM-Cl) and 1,4-bis(2-phenyl-1H-benzo[d]imidazol-1-yl)butane (IM-H) towards mild steel in HCl solution. In this study, gravimetric, electrochemical and scanning electron microscopy (SEM) techniques were applied to gain a detailed understanding of inhibition effects of IM-Cl and IM-H on steel corrosion. Also, the present study aimed to explore the relationship between functional properties of the inhibitor molecules and their adsorption capacities on the MS surface with the aid of computational methods. Experimental results obtained by weight loss, potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) measurements revealed that tested compounds had a good anticorrosion capacity. Chloride substituted benzimidazole demonstrated the best inhibition performance reaching 93% at 5 × 10−3 mol/L. The polarization technique (PDP) showed that the target molecules belonged to mixed-type inhibitors, preventing simultaneously anodic and cathodic reactions. Besides, the interactions mode between benzimidazole derivatives and mild steel surface followed the Langmuir adsorption model, and physical and chemical interactions assisted the adsorption mechanism of both compounds. EIS measurements illustrated that the imidazole derivatives made a positive impact on the mild steel corrosion process by increasing the polarization resistance with an increase in the concentration of the inhibitors. SEM analyses were performed to examine the surface morphology of uninhibited and inhibited steel and demonstrated good protection of the mild steel surface in the presence of tested compounds. Further, the temperature and immersion time effects on inhibition performances of benzimidazole were examined to evaluate the stability of these compounds under different operating conditions. Additionally, information extracted from theoretical approaches using Density Functional Theory (DFT) and molecular dynamics (MD) studies is in agreement with those obtained by experimental methods, which corroborate the strong anticorrosion activity of benzimidazole compounds under investigation.