Electrochemical Study of Corrosion Inhibition of Mild Steel in Acidic Solution Using Gnetum africana Leaves Extracts

Weight loss and electrochemical (open circuit potential (OCP), linear sweep voltammetry (LSV) and Potentiodynamic polarization (PDP)) techniques were used to assess the effectiveness of Gnetum africana leaves extracts as corrosion inhibitor for mild steel in 1.0 M hydrochloric acid (HCl) solution at 30-45°C. It was found that Gnetum africana leaves extracts retarded the dissolution of mild steel in 1.0 M HCl solution. The inhibition efficiency increased with increase in extract concentration and did reasonably well at increased temperature, which is suggestive of physical and chemical adsorption mechanism. Open circuit potential shows reduction of resistance polarization Rp with the addition of the Gnetum africana extract. Potentiodynamic polarization result suggests that Gnetum africana extracts functioned as mixed-type inhibitor. The adsorption of Gnetum africana extracts onto the mild steel surface followed Langmuir and Temkin adsorption isotherm models. The mechanism of physisorption of the extracts onto the mild steel surface is proposed from the trend of inhibition efficiency with temperature which is corroborated by the values of activation parameters obtained from the experimental data.