Electrochemical measurements were obtained from steel-reinforced concrete samples immersed in 0.5 M H2SO4 medium, for simulating industrial/microbial environment, to assess the corrosion-inhibition effects of two admixtures. Cymbopogon citratus (C. citratus) leaf-extract was used in comparison with the well-known but toxic inhibitor, Na2Cr2O7 (sodium dichromate) as a reference. Equal mass fractions, as percentage by mass/weight of cement (wt%) for concrete mixing, of the plant-extract and Na2Cr2O7 were admixed separately in steel-reinforced concrete samples immersed in the industrial/microbial simulating-environment. From these, corrosion-rate by linear polarization-resistance (LPR) and corrosion-potential as per ASTM(1) C876-15 were measured and statistically analyzed as per ASTM G16-13. Corrosion-potential results showed that both admixtures reduced corrosion risk as per ASTM C876-15 criteria. However, high concentrations of C. citratus leaf-extract surpassed the highly effective performance of Na2Cr2O7 at inhibiting reinforcing-steel-corrosion in the test-medium. The 0.417 wt% C. citratus leaf-extract exhibited optimal inhibition efficiency, η = 92.36% in the study. In comparison, the 0.250 wt% Na2Cr2O7 exhibited the highest inhibition effectiveness performance of η = 83.96% among the concentrations of Na2Cr2O7 chemical inhibitor. These indicate prospects on the suitability of C. Citratus leaf-extract as an environmentally friendly corrosion inhibitor in the industrial/microbial service environment that are discussed in the study.
Key words: steel-reinforcement corrosion, Cymbopogon citratus (C. citratus) leaf-extract, industrial/microbial simulating environment, environmentally friendly inhibitor, corrosion rate, corrosion potential, inhibition efficiency