Evaluation of the corrosion inhibition potentials of green-tip forest lily (<i>Clivia nobilis</i>) <i>leaves extract</i> on mild steel in acid media

Abstract

Plant extracts are excellent alternatives as corrosion inhibitors because of availability, low toxicity, biodegradability and low cost. In this study, corrosion tests were performed on mild steel to evaluate the effect of concentration of inhibitor, varying immersion period and temperature on the corrosion inhibition properties of Clivia nobilis leaves extract. This was done in H₂SO₄ and HCl acid solutions using weight loss and gasometric methods. From the weight loss results, corrosion rate and degree of surface coverage were evaluated and plotted as a function of inhibitor concentration at various immersion times. The volume of the cathodic hydrogen gas evolved was also plotted as a function of inhibitor concentration. The efficiency of inhibition in H₂SO₄ and HCl solutions were also compared. It was observed that corrosion inhibition efficiency increased with increasing concentration of Clivia nobilis leaf extract but not with prolonged immersion period. Experimental data obtained at 313 and 333K fitted the Freundlich and Langmuir isotherms, suggesting adsorption of Clivia nobilis leaves extract on the metal surface. Activation energy data described the interaction as electrostatic.

Keywords: Extract, corrosion, inhibitor, concentration, leaves