SULPHURIC ACID CORROSION OF MILD STEEL IN THE STEM EXTRACTS OF Cnidoscolus aconitifolius PLANT
B. U. UGI *
Department of Pure and Applied Chemistry, Corrosion and Electrochemistry Research Group, University of Calabar, P.M.B. 1115 Calabar, Nigeria
I. E. UWAH
Department of Pure and Applied Chemistry, Corrosion and Electrochemistry Research Group, University of Calabar, P.M.B. 1115 Calabar, Nigeria
P. C. OKAFOR
Department of Pure and Applied Chemistry, Corrosion and Electrochemistry Research Group, University of Calabar, P.M.B. 1115 Calabar, Nigeria
EKERETE JACKSON
Department of Chemistry, University of Uyo, P.M.B. 1017, Uyo, Akwa Ibom State, Nigeria
S. E. EJIM
Department of Pure and Applied Chemistry, Corrosion and Electrochemistry Research Group, University of Calabar, P.M.B. 1115 Calabar, Nigeria
N. E. NYA
Department of Pure and Applied Chemistry, Corrosion and Electrochemistry Research Group, University of Calabar, P.M.B. 1115 Calabar, Nigeria
*Author to whom correspondence should be addressed.
Abstract
Alkaloid and nonalkaloids extracts of Cnidoscolus aconitifolius stem is reported as corrosion inhibitor of mild steel in 2.0 M H2SO4. Conventional weight loss measurements and Tafel polarization technique are employed to study the effect on mild steel corrosion in H2SO4 solutions. The weight loss result revealed that both plant extracts are excellent corrosion inhibitors. Electrochemical polarization data revealed mixed mode of inhibition. The increase in %IE with change in concentration of the extracts suggests the strong adsorption of active molecules leading to the formation of a protective layer on the mild steel surface. It was found that adsorption of both stem extracts followed Langmuir adsorption isotherm model.
Keywords: Weight loss, Langmuir isotherm, activation energy, corrosion current density, inhibition efficiency, Cnidoscolus aconitifolius