Synthesized of Novel Imidazole-derived Schiff Base as a Corrosion Inhibitor of Carbon Steel in Acidic Medium Supported by Electrochemical and DFT Studies

In this work, a newly synthesized imidazole derivative, namely (N,N'E,N,N'E)-N,N'-(thiophene-2,5-diylbis(methanylylidene))bis(1Hbenzo[ d]imidazol-2-amine) which is donated as (SJ1), was tested as an inhibitor in controlling the corrosion of carbon steel in 0.1 M hydrochloric acid solution by using open circuit potential (OCP), potentiodynamic polarization (PDP), at four different temperatures (293, 303, 313 and 323 K) and various of SJ1 concentrations. Furthermore, the surface morphology was investigated using both the Atomic force microscopy (AFM) and Scanning Electron Microscope (SEM), respectively. The effect of using different concentrations of SJ1 and temperature was also investigated. SJ1 was synthesized and characterized via using the UV-Vis, mass spectroscopy, 1H NMR and 13C NMR spectroscopy, and the element analysis CHN. The experimental results shown that SJ1 can consider as an excellent corrosion inhibitor for carbon steel in 0.1 hydrochloric acid solution, by presence of SJ1 the corrosion of carbon steel was significantly suppressed. The inhibition efficiency is increased with increasing the inhibitor concentration but is decreased with the increases of temperature, and the optimum inhibition efficiency by 0.5 mM of SJ1 is 96%. The adsorption behavior of SJ1 onto the surface of the carbon steel in the acidic environment was investigated and found is obeyed the Langmuir adsorption isotherm. Also, both the thermodynamic and kinetic parameters are computed and discussed. The observed results of the free energy of adsorption ΔGads of -38.12 kJ mol-1 suggested that adsorption of SJ1 onto the surface of carbon steel has both types of interaction physisorption/chemisorption. The modeling methods were conducted by using the density functional theory (DFT/B3LYP) to study the electronic properties of SJ1 to discover the correlation between the molecular structure and the inhibitor efficiency. Both the experimental and simulation results were in good agreement with each other in this concern and authorize that SJ1 is an effective inhibitor.