Inhibition of Mild Steel Corrosion in the Presence of Fatty Acid Thiosemicarbazides

Selected thiosemicarbazides of fatty acids with C₁₁-C₁₈ carbon atoms were synthesized and evaluated as corrosion inhibitors of mild steel (MS) in 1 N hydrochloric acid (HCl) and 1 N sulfuric acid (H₂SO₄) by weight loss and potentiodynamic polarization methods. The values of activation energy and free energy of adsorption of all the thiosemicarbazides were calculated to investigate the mechanism of corrosion inhibition. The potentiodynamic polarization studies, carried out at room temperature, revealed that all the compounds blocked the corrosion reactions. The adsorption of all the thiosemicarbazides on the MS surface in both the acid solutions was found to obey Temkin’s adsorption isotherm. All of these compounds showed good inhibition efficiency (IE) in both acids. The IE of these compounds was found to vary with the nature and concentration of the compounds, solution temperature, immersion time, and nature of the acids. Electrochemical impedance spectroscopy was also used to investigate the mechanism of corrosion inhibition.