Okeniyi, Joshua Olusegun and Loto, C. A. and Popoola, Abimbola Patricia Id (2015) Investigating the corrosion mechanism of Morinda lucida leaf extract admixtures on concrete steel rebar in saline/marine simulating environment. International Journal of Electrochemical Science, 10 (12). pp. 9893-9906. ISSN 14523981
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In this paper, measurements of corrosion test data from steel reinforced concrete samples immersed in 3.5% NaCl, for simulating saline/marine environment, were analysed for investigating corrosion mechanism by Morinda lucida leaf extract admixtures on the steel rebar. Corrosion potential as per ASTM C876-95 R99, corrosion current by zero resistance ammeter and corrosion rate from linear polarization resistance instrument were subjected to the Weibull probability distribution as per Kolmogorov-Smirnov goodness of fit criteria. From this, electrochemical noise resistance was modelled through the ratio of Weibull standard deviation of corrosion potential to that of Weibull standard deviation of corrosion current after which the modelled noise resistance and the plant extract concentration were correlated with the corrosion rate. Results from these analyses of electrochemical test data showed that excellent correlation, of R = 98.07%, Nash-Sutcliffe Efficiency = 96.18% and ANOVA p-value = 0.0456, exists between the corrosion rate as a function of the plant extract concentration and the noise resistance. The correlation model obtained exhibited good agreements with experimental results in inhibition efficiency performance of the admixture on steel reinforcement corrosion in the test medium. By these, 3.333 g/L Morinda lucida (per volume of concrete mixing water) exhibited optimal inhibition efficiency, η = 90.59±2.52 (by correlation prediction) or η = 89.27±3.94 (by experimental model), on the concrete reinforcing steel corrosion in the study. Adsorption isotherm fittings of the correlation prediction and experimental results showed that they both followed the Langmuir isotherm, which indicated physical adsorption (physisorption) as the prevalent mechanism of Morinda lucida leaf extract on the concrete steel rebar. © 2015 The Authors.
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