Thermodynamic and Electrochemical Investigation of 2-Mercaptobenzimidazole as Corrosion Inhibitors for Mild Steel C35E in Hydrochloric Acid Solutions

Abstract

-2-Benzimidazolethiol (BIZT) was tested as a corrosion inhibitor for mild steel in 1 M HCl solution using different techniques: weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The corrosion processes were inhibited by adsorption of BIZT on to the mild steel surface, manner increasing in inhibitor concentration accompanies with corrosion rate decreases, inhibition efficiencies increase and surface coverage degree increases. The rate of corrosion of mild steel rapidly increases with temperature over the temperature range of 298K to 328K both in absence and presence of inhibitor. Quantum chemical parameters are calculated using the Density Functional Theory method (DFT). Correlation between theoretical and experimental results is discussed. Langmuir adsorption isotherm fits well with the experimental data. The protection efficiency increases with increasing inhibitor concentration (in the range 2,5 .10 -4 -30,0 .10 -4 M) and temperature too. the thermodynamic parameters, such as adsorption equilibrium constant (K ads), free energy of adsorption (ΔG ads), adsorption heat (ΔH ads) and adsorption entropy (ΔS ads) values were calculated and discussed.