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Article – Journal of Advanced Electrochemistry

Journal of Advanced Electrochemistry, Volume 2,Issue 4,2016 Pages 130-135


Corrosion Inhibitive Properties, Adsorption Behaviour and Synergistic Effect of Methanolic Extract of Crysophyllum albidum on Mild Steel Corrosion in HCl
M.A. Orokpo*, H.F. Chahul, J.I. Ona

The adsorption of Chrysophyllum albidum stem extract and corrosion inhibition properties on mild steel in 1.0 M HCl was investigated using weight loss and electrochemical linear polarization measurements. Inhibiton efficiencies of the plant extracts increased with increasing concentration but decreased with increasing time and temperature rise. The adsorption of the inhibitor on the mild steel surfaces was spontaneous and agrees with Langmuir and Freundlich adsorption isotherms. The values of activation energy of adsorbtion (Ea) and free energy of adsorbtion (ΔG0) obtained and other thermodynamic parameters shows that the adsorption mechanisms was a physical adsorption. FTIR analysis revealed the presence of phenolic compounds suspected to be Tannins and Phenolic acid. Micrographs from optical microscopy revealed that the extracts inhibited corrosion of mild steel in 1.0 M HCl. The addition of 0.05 M KI enhanced inhibiton efficiency of the plant extract. The inhibitory properties of stem bark extract of Chrysophyllum albidum (CA) on the corrosion of mild steel in 1.0 M HCl was investigated using weight loss and electrochemical linear polarization measurements. The plant inhibited the corrosion of the mild steel in the acid medium. The inhibition efficiencies of the inhibitor increased with increasing concentration but decreased with increasing temperature and immersion time. The adsorbtion of the inhibitor unto the surface of the mild steel was found to agree with both Langmiur and Freundlich adsorbtion Isotherms. The values of Ea was found to increase with increasing concentration of the inhibitor but decreased with increasing temperature, indicative of physisorption mechanism. All ΔG0 values obtained were negative and less than 80 kJmol-1, suggestive of a spontaneous adsorption. ΔH values obtained were all positive, indicative of an endothermic process. The kinetic study showed that the reaction followed a pseudo first order kinetics and the FTIR analysis revealed the presence of phenolic compounds suspected to be phenolic acid and tannins. Optical microscopy analysis revealed the presence of protective film upon adsorption of inhibitor onto the mild surface, which is responsible for the inhibition of corrosion. The inhibition efficiencies of the the various concentrations of the inhibitor was generally observed to increase by an average of 10% with the addition of 0.05 M KI, implying a positive synergistic effect between the extract and KI.



Keywords: Adsorption Isotherm; Crysophyllum albidum; Corrosion Inhibition; Physisorption; Synergism;