Corrosion Inhibition Efficiency of Tamarindus Indica Leaves Extracts on Mild Steel in Hydrochloric Acid

Abstract

Tamarindus indica leaves extract was used as a green corrosion inhibitor for mild steel in 1 M hydrochloric acid (HCl) under varied conditions using weight loss technique. The inhibition efficiency, thermodynamics, kinetics and mechanism of inhibition by Tamarindus indica leaves extract on the mild steel were determined. The inhibitor's concentrations used for the study were 0.0g/15ml (blank), 0.2g/15ml, 0.4g/15ml, and 0.6g/15ml, at the temperatures of 28°C (301K), 40°C (313K), 50°C (323K), and 60°C (333K). The results obtained showed that the inhibition efficiency of the inhibitor was inversely proportional to the temperature, but directly proportional to the concentration of inhibitor in the acid. The maximum efficiency of 79.68%, was observed at 28°C (301K) and at a concentration of 0.6g/15ml. The heat of adsorption and free energy (ΔGads) calculations yielded negative values. This indicates that the reaction between the inhibitor molecules and the metal surface was favorable since all the calculated values were negative. As the concentration of the inhibitor increased, the negativity of the ΔGads increased; suggesting physical adsorption. The data obtained fitted in the Langmuir and Temkin adsorption isotherms at lower temperatures. The results from the phytochemical analysis showed that saponins, were absent, but the extract has tannins, phenolic compounds, alkaloids, cardiac glycosides and flavonoids.