Evaluation of Corrosion Inhibition of Mercapto Functional Compounds for Mild Steel in 1M Hydrochloric Acid Solution During Immersion Time

Corrosion inhibition effect of 2-mercaptobenzimidazole (MBI) and 2-mercaptobenzoxazole (MBO) compounds on steel in hydrochloric acid solution was investigated by electrochemical impedance spectroscopy (EIS) and it was observed that both of these compounds have corrosion inhibition effect on mild steel. Evaluation of electrochemical behavior in test solutions showed that by increasing the immersion time from 15 to 300 min corrosion resistance of samples are increased and at the same immersion time MBI have the better corrosion inhibition in comparison to MBO. Quantum chemical calculations were performed using Hyperchem7 software for MBI and MBO. The results of calculations showed superior inhibition efficiency of MBI in comparison to MBO, which could be attributed to the more negative charge of pyrole-like nitrogen atom in comparison to oxygen atom. This can cause easier protonation and consequently adsorption on the metal surface occurs easily. J. Color Sci. Tech. 4(2010), 65-70 © Institute for Color Science and Technology.