Abstract
Different techniques such as hydrogen evolution, weight loss, electrochemical impedance spectroscopy, and potentiodynamic polarization measurement technique were used to determine the corrosion inhibition potential of 1-X-4-[4'-(-OCH3)-styryl] pyridinium iodides (X = CH3, C2H5, and C3H7) for stainless steel in 2 M HCl acid solution. The results from hydrogen evolution and weight loss techniques revealed that the inhibitors exhibited high inhibitory potential against corrosion of stainless steel in 2 M HCl, with inhibition efficiency increasing with inhibitor concentration. The anticorrosion performance of the compounds follows the order: III-C3H7 > II-C2H5 > I-CH3. Potentiodynamic polarization results revealed that the compounds played the role of mixed-type inhibitors, and the inhibitors molecules adsorbed on the surface of stainless steel according to the Langmuir adsorption isotherm. Furthermore, the inhibitors showed good performance at all temperatures (30-60 degrees C) studied and maintained protective ability at maximum temperature. On the basis of thermodynamic parameters, comprehensive adsorption (physisorption and chemisorption) for the studied inhibitors on stainless steel surface was suggested. SEM and EDX analysis confirmed the evidence of the formation of the adsorbed layer of inhibitor on the metal surface. A quantum chemical approach was adopted to predict the correlation between corrosion inhibition performance and molecular structure electronically. The data showed that the inhibition efficiency of the studied inhibitors increases with increasing immersion time (5, 30, 60 and 90 min) in the tested solution and this result implied that the studied inhibitors have a long-term effect as potent inhibitors.