Mechanical Engineering Department, Covenant University, Ota, Nigeria; Chemical, Metallurgical and Materials Engineering Department, Tshwane University of Technology, Pretoria, South Africa
Okeniyi, J.O., Mechanical Engineering Department, Covenant University, Ota, Nigeria; Loto, C.A., Mechanical Engineering Department, Covenant University, Ota, Nigeria, Chemical, Metallurgical and Materials Engineering Department, Tshwane University of Technology, Pretoria, South Africa; Popoola, A.P.I., Chemical, Metallurgical and Materials Engineering Department, Tshwane University of Technology, Pretoria, South Africa
Electrochemical monitoring techniques were employed in this study to assess anticorrosion performance of Phyllanthus muellerianus leaf-extract on concrete steel-reinforcement in 0.5 M H2SO4, used for simulating industrial/microbial environment. For this, steel-reinforced concretes admixed with different concentrations of the natural plant leaf-extract were partially immersed in the acidic test-solution and subjected to electrochemical monitoring of corrosion potential, corrosion current and corrosion rate. Test responses analysed as per ASTM G16-95 R04, showed that the corrosion rate correlated, r = 84.93%, ANOVA p-value = 0.0403, with the leaf-extract concentration admixed in concrete and the ratio of the standard deviation of potential to the standard deviation of current. These identified the 0.3333% Phyllanthus muellerianus (per weight of cement) with optimum effectiveness at inhibiting steel-reinforcement corrosion both by the experimental model, η = 91.66±2.51%, and by the prediction from the correlation fitting model, η = 85.54±14.44%. Fittings of both the experimental and the predicted data followed the Flory–Huggins and the Frumkin adsorption isotherms which suggest prevalent mechanism of physical adsorption (physisorption) of the extract on steel-rebar surface. These support the use of Phyllanthus muellerianus as environmentally-friendly admixture for inhibiting concrete steel-reinforcement corrosion in the industrial/microbial service-environment. © 2014, Sociedade Portuguesa de Electroquimica. All rights reserved.