Tithonia diversifolia Extract as An Eco-friendly, High-temperature Corrosion Inhibitor for 304 Stainless Steel in Acidic Solution: Experimental and Quantum Chemical Studies

Abstract In the present work, Tithonia diversifolia (Hemsl) A. Gray leaf extract (TDLE) was utilized as an eco-friendly and high-temperature corrosion inhibitor for 304 stainless steel (SS) in 1 M HCl. The performance of TDLE was studied electrochemically using potentiodynamic polarization and electrochemical impedance spectroscopy techniques. The surface of the metal was characterized using scanning electron microscopy (SEM). The quantum chemical method was also studied to understand the inhibition process. Leaves were extracted with demineralized water at 90°C. The adsorption behavior of TDLE best matches Langmuir's adsorption isotherm. The isotherm assumed that the adsorbed species occupies only one surface site to form a monolayer of inhibitor on the metal surface with no interactions from other adsorbed species. The corrosion inhibition efficiency increases with solution temperature, reaching 98.48% at 65°C in the presence of 3.5 g/L TDLE. SEM images show significant improvement of the 304 SS surface with TDLE. A quantum chemical study indicates that methyl 3.5-dicaffeoyl quinate is the most active inhibitor in TDLE.