SYNTHESIS, CHARACTERIZATION, AND COMPARATIVE STUDY OF PYRIDINE DERIVATIVES AS CORROSION INHIBITORS OF MILD STEEL IN HCl MEDIUM

Radical catalysis has been used to achieve addition of dodecanethiol and mercaptoacetic acid to 4-vinylpyridine (4VP), giving 4-(dodecylthiaethyl)pyridine (DTEP) and 4-pyridylethylthia-acetic acid (PETAA). The purified monoadducts have been characterized using 1H NMR and 13C NMR spectroscopy. Inhibition of the corrosion of mild steel in 1M HCl by 4VP, DTEP, and PETAA has been investigated at 308K using weight loss measurements, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) methods. The results obtained show that PETAA is the best inhibitor and its inhibition efficiency (E %) increases with the inhibitor concentration, reaching up to 93% for DTEP at 10-3M. Potentiodynamic polarization studies clearly revealed that the inhibitors changed the mechanism of hydrogen evolution and that they acted as mixed inhibitors but most effectively in the cathodic range.