Evaluation and Analyses of Rhizophora mangle L. Leaf-Extract Corrosion-Mechanism on Reinforcing Steel in Concrete Immersed in Industrial/Microbial Simulating-Environment

Abstract

Test-data from electrochemical monitoring methods were obtained from Rhizophora mangle L. leaf-extract admixed steel-reinforced concretes for detailing mechanism of the extract on steel-rebar corrosion in 0.5 M H2SO4 (simulating industrial/microbial environment). These electrochemical test-measurements, including corrosion potential, corrosion current and corrosion rate, were subjected to the analyses of probability distributions as per ASTM G16-95 R05 through the Kolmogorov-Smirnov goodness-of-fit test-statistics. Results showed that corrosion rate exhibited correlations with function of the natural plant-extract concentration and compact series of the inverse electrochemical noise resistance; the ratio of standard deviations of corrosion potential and corrosion current. Both the experimental and the correlated-prediction model identified Rhizophora mangle L. leaf-extract admixture concentrations that exhibited inhibition efficiency performance of η>70% on steel-rebar corrosion in the acidic test-medium. The adsorption isotherm modelling of the experimental and the predicted electrochemical test-results exhibited good agreements by following the Langmuir and Flory-Huggins isotherm fittings. In addition, the study identified physisorption as the prevalent corrosion-protection mechanism of the steel-rebar by the plant extract through both of the experimental and the correlated-prediction models of adsorption isotherm analyses.