Corrosion protection of carbon steel by two newly synthesized benzimidazol-2-ones substituted 8-hydroxyquinoline derivatives in 1 M HCl: Experimental and theoretical study

Two new organic compounds composed of 8-hydroxyquinoline and benzimidazol-2-one units have been successfully prepared, and identified by different spectroscopic methods (IR, NMR and Elemental analysis). The synthesized heterocyclic namely 1-((8-hydroxyquinolin-5-yl)methyl)-3-(prop‑1-en-2-yl)-1H-benzimidazol-2(3H)-one (HMPB) and 1,3-bis((8‑hydroxy-quinolin-5-yl)methyl)-1H-benzimidazol-2(3H)-one (BHMB) are assessed as corrosion inhibitors for carbon steel (CS) in 1 M hydrochloric acid media utilizing gravimetric measurements, electrochemical impedance spectroscopy, potentiodynamic polarization and UV − visible spectroscopy at 298 K. The inhibiting action is more pronounced by BHMB compared to HMPB and affected a maximum value of 91% at the 10⁻³ M attributed to BHMB and 89% achieved by HMPB, the shift in corrosion potentials obtained suggested that the two compounds are cathodic-type inhibitors. The adsorption of benzimidazol-2-ones substituted 8‑hydroxy-quinoline derivatives on the carbon steel surface follows the Langmuir adsorption isotherm and was found to involve chemisorption. The EIS spectra expressed principally as a slightly depressed semi-circle shape corresponding to a single time constant in Bode diagrams for the two organic compounds in the both concentration and temperature effects. In addition, all thermodynamic parameters such as ΔG_ads ^∘ E_a, ΔS_a and ΔH_a were estimated and discussed. Finally, the combination of density functional theory (DFT) and Monte Carlo simulations were used to understand the regions in the BHMB and HMPB molecules where interaction with steel surface can occur.