Eco-Friendly Inhibitors for Mild Steel Corrosion in Hydrochloric Acid

The corrosion of Mild Steel in hydrochloric acid (HCl) containing Indian Neem (Azadirachta Indica), Ankado (Calotropis Gigantea) and Hibiscus Rosa-Sinensis (Jasud) Leaves Extracts has been studied by weight loss and potentiodynamic polarization methods. In plain HCl, the corrosion rate increases with the acid concentration and temperature. At a constant acid concentration, the inhibition efficiency (IE) of Neem, Ankado and Jasud leaves ark increases with the inhibitor concentration. As a constant inhibitor concentration, the IE (Inhibition Efficiency) decreases with the increase of acid concentration. The IE of inhibitors increases in the order: Ankado Neem Jasud. As temperature increases, percentage of inhibition decreases. Plots of Langmuir, Freundlich's and Temkin's adsorption isotherm results in a straight line suggest that the inhibitors cover both the anodic and cathodic regions through general adsorption. The values of activation energy and free energy of adsorption indicated physical adsorption on mild steel surface. Polarization study reveals that the inhibitors functions as a mixed inhibitor.