Synergistic Effect of Potassium Iodide with Some Heterocyclic Compounds on the Corrosion Inhibition of 304 Stainless Steel in Hydrochloric Acid Solution

The inhibitive effect of some heterocyclic organic compounds on the corrosion of 304 stainless steel (304 SS) in 1 M HCl was studied using weight loss, open potential circuit, potentiodynamic polarization and electrochemical impedance spectroscopy techniques at room temperature. The polarization curves revealed that these investigated compounds act as mixed-type inhibitors. Adsorption of these inhibitors on 304 SS surface was found to obey the Langmuir adsorption isotherm. Results showed that the corrosion rate of SS increased with raising temperature and decreased in the presence of investigated compounds. The highest inhibition efficiency of 70.1% was observed with these investigated compounds. An improved inhibition efficiency of 94.5% was observed with the mixture of these compounds and KI at 25 °C in 1 M HCl. This indicates that these compounds were assumed to adsorb on SS surface via physical adsorption. The reactivity of these compounds was analyzed through theoretical calculations based on semi-empirical theory. © 2017, Springer International Publishing AG.