Corrosion inhibition performance of ethanol extract leaves of Cucurbita pepo (Pumpkin) on mild steel in acidic media

Abstract

The use of inorganic and synthetic organic compounds as corrosion inhibitors is becoming unpopular due to environmental concerns. The focus of most corrosion mitigation research is now on the use of environmentally friendly substances. This paper reports on the use of the ethanol extract of the leaves of Cucurbita pepo against the corrosion of mild steel in 1.0 M solution of hydrochloric acid using weight loss and linear polarization measurements at 303- 333 K. The plant extract was found to retard the corrosion of steel coupons in the acid media at 95 % inhibition efficiency thereby functioning as a good corrosion inhibitor against the dissolution of steel in 1.0 M solution of hydrochloric acid. Apparent activation energy values in the inhibited systems (16.42 kJ/mol, 16.52 kJ/mol/17.26 kJ/mol, 19.34 kJ/mol) were found to be greater than that of the free acid solution (10.48 kJ/mol) showing the adsorption of the plant extract on the steel surface to be by physical mechanism. In the study, values of enthalpy, Δ?^∗ were all negative showing the exothermic nature of the corrosion and inhibition processes while free energy values for the inhibition processes at 303 K and 333 K were -16.48kJ/mol and -15.59 kJ/mol respectively revealing the inhibition of mild steel in the acid media by the plant extracts to be spontaneous.

Keywords: Acid, Adsorption, Corrosion, Mild steel, Temperature, Weight loss