Electrochemical and Adsorption Behaviour of Diospyros mespiliformis on Annealed Carbon steel Corrosion in Hydrochloric Acid
R. S. Oguike *
Department of Chemistry, Corrosion Protection and Materials Science Laboratory, Abubakar Tafawa Balewa University, Bauchi, Nigeria and Department of Chemistry, Electrochemistry and Materials Science Research Laboratory, Federal University of Technology, Owerri, Nigeria
A. M. Kolo
Department of Chemistry, Corrosion Protection and Materials Science Laboratory, Abubakar Tafawa Balewa University, Bauchi, Nigeria
A. A. Ayuk
Department of Chemistry, Electrochemistry and Materials Science Research Laboratory, Federal University of Technology, Owerri, Nigeria
F. C. Eze
Department of Chemistry, Electrochemistry and Materials Science Research Laboratory, Federal University of Technology, Owerri, Nigeria
E. E. Oguzie
Department of Chemistry, Electrochemistry and Materials Science Research Laboratory, Federal University of Technology, Owerri, Nigeria
*Author to whom correspondence should be addressed.
Abstract
The interfacial activities of Diospyros mespiliformis on annealed carbon steel in 2 M HCl solution was studied by electrochemical methods; polarization and impedance spectroscopy measurements, while weight loss of the carbon steel at varying temperatures and gasometric method was studied. The results of the study revealed that D. mespiliformis mitigates the corrosion of carbon steel (FE164531) in HCl solution through adsorption. Results from Tafel plots suggest that Diospyros mespiliformis (DM) behaves predominantly as a cathodic inhibitor with highest inhibition efficiency (91%) at 1000 ppm. The Nyquist and Bode plots of the test solutions were similar in both inhibited and free medium and contained capacitive and inductive loops. Thermodynamic parameters suggest that D. mespiliformis is adsorbed on carbon steel mainly by physical adsorption. The values of enthalpy and entropy of adsorption suggests that DM adsorption on FE164531 surface was spontaneous. A good correlation was obtained following the percentage inhibition efficiencies calculated from all the techniques employed.
Keywords: Annealed carbon steel, Diospyros mespiliformis, corrosion inhibition, adsorption, hydrochloric acid