Quantum chemical study of inhibition of the corrosion of mild steel in 1 M hydrochloric acid solution by newly synthesized benzamide derivatives

• Published in: Research on chemical intermediates 2014-03, Vol.40 (3), p.1069-1088
• Main Authors: Belfilali, I., Chetouani, A., Hammouti, B., Louhibi, S., Aouniti, A., Al-Deyab, S. S.
• Format: Article
• Language: English
• Subjects: Catalysis; Chemistry; Chemistry and Materials Science; Inorganic Chemistry; Physical Chemistry
• ISSN: 0922-6168; 1568-5675
• DOI: 10.1007/s11164-013-1022-6

The inhibitory effect of some new synthesized benzamide compounds on corrosion of mild steel in 1  M HCl solution has been studied by use of weight loss measurements and the electrochemical techniques potentiodynamic polarization and electrochemical impedance spectroscopy. The inhibiting action is more pronounced with increasing concentration. Inhibition efficiency is maximum (approximately 99 %) at 10 −3   M . Polarization measurements also show that the compounds act as mixed inhibitors. The cathodic curves indicate that reduction of protons at the mild steel surface occurs as a result of a pure activating mechanism. EIS measurements reveal increased transfer resistance with increasing inhibitor concentration. The presence of heteroatoms increases inhibition efficiency without causing a drastic change in adsorption mechanism, which follows the Langmuir isotherm model. Significant correlations were obtained between inhibition efficiency with the chemical indexes calculated, by use of the standard software Gaussian03, on the basis of density functional theory (DFT) at the B3LYP/6-31G** level of theory, indicating that variation of inhibition with inhibitor structure may be explained in terms of electronic properties. The effect of temperature on the corrosion behaviour of steel in 1  M HCl without and with inhibitors at 10 −3   M was studied in the temperature range from 308 to 333 K, and the associated activation energy was determined.