Total-Corrosion Effects of Anthocleista Djalonensis and Na2Cr2O7 on Steel-Rebar in H2So4: Sustainable Corrosion-Protection Prospects in Microbial/Industrial Environment

This paper studies total-corrosion effects of Anthocleista djalonensis (green natural-plant) and Na2Cr2O7 (well-known inhibitor, but environmentally-hazardous chemical) on steel-reinforcement in concrete immersed in 0.5 M H2SO4, simulating microbial/industrial environment. Equal-mass models of the plant leaf-extract and of Na2Cr2O7 were employed as admixtures in steel-reinforced concrete samples immersed in the test-system, from which macrocell corrosion measurements were obtained and analysed as per ASTM G109-99a. Results showed that only the 3.33 g/L Anthocleista djalonensis, among the equal-mass models of leaf-extract and the chemical admixtures, was outperformed by the 3.33 g/L Na2Cr2O7 in total corrosion reduction effects. In the study, 5.00 g/L Anthocleista djalonensis exhibited optimal effectiveness, = 93.77%, on the total-corrosion effect of concrete steel-reinforcement. The many Anthocleista djalonensis admixtures that exhibited better inhibition than Na2Cr2O7 admixtures indicates positive prospects of the plant as an eco-friendly and sustainable corrosion-protection alternative for the toxic chemical in microbial/industrial environment

Modelling Rhizophora Mangle L Bark-Extract Effects on Concrete Steel-Rebar in 0.5 M H2SO4: Implications on Concentration for Effective Corrosion-Inhibition

In this paper, electrochemical test-data were obtained from 0.5 M H2SO4-immersed steel-reinforced concrete admixed with different Rhizophora mangle L bark-extract concentrations and subjected to modelling analyses for studying corrosion-inhibition effectiveness. For this, macrocell current from zero-resistance ammeter and corrosion-rate from linear-polarization resistance instruments were respectively subjected to total-corrosion modelling as per ASTM G109-99a and statistical-distribution modelling as per ASTM G16-95 R04. Further analyses of these modelled test-results showed that the corrosion-rate correlated excellently (R = 95.04%, Nash-Sutcliffe efficiency = 90.33%, p-value = 0.037) with function of the bark-extract concentration and the total-corrosion from the steel-reinforced concrete samples. In agreements, both experimental and correlation fitting models identified 0.167% Rhizophora mangle L bark-extract with good corrosion-inhibition efficiency, η = 73.30% (experimental) or η = 60.81% (correlation prediction). These bare implications on macrocell technique usage for complimenting identification of admixture concentration for effective corrosion-inhibition of concrete steel-rebar in the microbial/industrial simulating-environment studied