A Theoretical Study On The Mechanism Of The Inhibition Efficiency Of Benzimidzole And Its Derivates

The inhibition performance of four corrosion inhibitors in HCl mild steel corrosions, including benzimidazole, 2-methylbenzimidazole,2-amidobenzimidazole,2-mercaptobenzimi- dazole about the molecular structure, the adsorptive process on metal and the diffuseness in the molecular film,has been theoretically evaluated by quantum chemistry calculations and molecular dynamics simulations.The relationship between inhibitor efficiency of Benzimidazole and its derivates and their electronic properties of molecules has been carried out by using the quantum chemistry calculation,at the level of B3LYP with the 6-31G base set, and consided the effects of solvent and appling PCM model.It is found that 4 inhibitor molecules are planar strucure with conjugate system.2-mercaptobenzimidazole bears the highest reactivity among the four molecules.and 2-amidobenzimidazole possesses two electrophilic attack centers, which enables multi-center adsorption of the molecule on the metal surfaces And the inhibition efficiencies have a good linearity relation with the energy of the highest occupied molecular orbital(EHOMO).the energy field (ΔE). the global hardness(η)and dipole moment(μ) of the inhibitor molecules in the liquid phase.In addition, 2-mercaptobenzimidazole on Fe(001) surfaces was studied by using the Dmol3 module of Material Studio 4.0 software. In same while gravimetric and polarization techniques were used to investigated the molecule as corrosion inhibitor of A3 steel in 6% hydrochloric acid. Results manifest that 2-mercapto- benzimidazole adsorb on hollow site and lose electron to Fe forming coordinate bond to inhibite the electron on Fe, The corrosion inhibitor efficiencies of the molecule is 94.8% and the consistency of it with the higher efficiencies is in 0.05% to 0.1% The molecule is cathode protecting-type corrosion inhibitor which agreeing with the result from theorical calculation.Molecular dynamics simulations was performed to model the diffuse behavior of corrosive medium in corrosion inhibitors film and the combinatibe process of benzimidazole and its derrivants on metallic surfaces in vacuum or liquid,using Discover module,NVT ensemble and Compass force field,The result show four moleculars adsorb parallelly on metal in vacuum which the higher adsorption energy is and the better inhibition efficiencies. However in water. 2-mercaptobenzimidazole and 2-amidobenzimidazole adsorb on Fe(001) of which the function group is the adsorptive center and adsorptive angle is 65o and 20o respectively.The others adsorb parallelly which in agreement with the result from quantum chemistry.then.the diffuseness coefficient,the Cohesive energy,theoretic sequence of inhibition efficiencies and dynamic process of moleculars adsopting on matel. were caculated to discuss the interaction and clarify the inhibiting mechanism.