Application of Peperomia pellucida leaves extract as a green corrosion inhibitor for mild steel in 1.0 m hydrochloric acid solution

Abstract

The inhibition efficiency of Peperomia pellucida (PP) leaves extract against the corrosion of mild steel in 1 M hydrochloric acid was investigated by weight loss and electrochemical methods. The inhibition efficiency (%I) decreased with increase in temperature. Results from weight loss, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) studies revealed that PP acted as a good inhibitor and inhibition efficiency reached 98.1 % at 1000 ppm inhibitor concentration. The values for Gibbs free energy (ΔG = -18.79 kJ mol^-1 at 343 K) were negative, indicating that the adsorption of PP on the surface of mild steel is spontaneous. The values of ΔG also indicated that adsorption of PP on the mild steel surface was by physisorption and the generated data fitted the Langmuir adsorption isotherm. A decrease in entropy with increase in PP concentration was also observed. At 1000 ppm inhibitor concentration, ΔH = -32.58 kJ mol^-1 was obtained. The negative value of ΔH indicated the exothermic nature of the  orrosion process and adsorption of PP molecules on mild steel surface. Activation energy increased with a rise in PP concentration. Polarization studies revealed that PP acts as a mixed type inhibitor. Results of weight loss and electrochemical studies validate the use of Peperomia pellucida as inhibitor for corrosion of mild steel in acidic medium

Keywords: Corrosion, inhibition efficiency, inhibitor, mild steel, Peperomia pellucida