Synergistic effects and hydrogen bonded interaction of alkyl benzimadazoles and thiourea pair on mild steel in hydrochloric acid

Synergistic hydrogen bonded interaction and corrosion protection properties of alkyl benzimidazoles and thiourea pair on mild steel in hydrochloric acid at different temperatures have been studied by polarization, electrochemical impedance spectroscopic studies (EIS), adsorption, surface studies and computational methods. The extent of synergistic interaction increases with temperature. Quantum chemical approach was used to calculate some electronic properties of the molecules. The inhibition efficiencies and the global chemical reactivity relate to total energy, EHOMO, ELUMO and gap energy (ΔE). Thiourea interacts with benzimidazoles up to a bond length of approximately 2.20 Å. This interaction may be due to the development of a hydrogen bond between thiourea and benzimidazoles. This synergistic interaction offer extended inhibition efficiency toward mild steel in hydrochloric acid. The corrosion inhibition efficiencies and the global chemical reactivity relate to total energy, EHOMO, ELUMO and gap energy (ΔE).