Opuntiol: An Active Principle of Opuntia elatior as an Eco-Friendly Inhibitor of Corrosion of Mild Steel in Acid Medium

Abstract

The anticorrosion ability of Opuntia elatior fruit extract was tested on mild steel (MS) in 1 M HCl and H2SO4 media by a weight loss method at various temperatures, electrochemical experiments such as potentiodynamic polarization (PDS) and electrochemical impedance spectroscopy (EIS), and surface characterization techniques using scanning electron microscope (SEM) and X-ray diffraction (XRD) studies. The major phytoconsituent, opuntiol, was isolated chromatographically and characterized by infra-red (IR) and nuclear magnetic resonance (NMR) spectroscopic studies. Further, its corrosion inhibitive effect was investigated by PDS, EIS, SEM, and XRD studies. The results of the weight loss studies indicated that inhibition efficiencies were enhanced with an increase in concentration of extract and decreased with a rise in temperature. Adsorption of the extract on a mild steel surface obeyed the Temkin isotherm. Results of PDS revealed the mixed mode inhibitive action, and results of EIS studies confirmed the adsorption of the extract at the metal–solution interface. Further, SEM and XRD studies clearly revealed the film-forming ability of opuntiol on the surface of mild steel. Thus, the anticorrosion activity of O. elatior can be related to the presence of opuntiol.