Tailoring of Nepal-sourced plant extracts as anti-corrosive additives for mitigating rebar corrosion in reinforced concrete beam

The corrosive degradation of reinforcement metal in concrete structures is a significant concern, necessitating the search for anti-corrosive chemical options to classic concrete inhibitors. A cost-effective and non-toxic inhibitor for corrosion control of thermo-mechanically treated-mild steel (TMT-MS) rebar in reinforced concrete beams (RCBs) is explored in this investigation, using methanolic leaf extracts from four Nepali plants: Sesamum indicum L. (SiL), Elaeocarpus angustifolius Blume (EaL), Ziziphus budhensis (ZbL), and Tagetes erecta L . (TeL). The research involved in situ electrochemical analyses of half-cell potential (E _corr ) and electrical resistivity (E _ρ ), as well as the relevant surface analysis techniques. The anti-corrosion effectiveness, based on the E corr analysis, is correlated well with E ρ assessments. As the concentrations of the four plant extracts—SiL, EaL, ZbL, and TeL—increased from 500 to 4000 ppm in concrete paste, the E _corr of TMT-MS rebar shifted to a more noble potential than –126 mV (SCE), and the E _ρ increased more than 20 kΩ·cm after 168 days of exposure at ambient conditions, indicating a lower corrosion risk of the reinforcing TMT-MS rebar, compared to the control condition without plant extracts. The improved anti-corrosion effectiveness of these extracts is due to the adsorption of their phytocompounds onto the rebar surface in RCBs, as indicated by surface analysis. Chemical screening, ultraviolet-visible (UV-Vis), fourier transfer infrared (FTIR) spectrometry, and liquid chromatography-mass spectrometry (LC-MS), along with toxicity tests, identify non-toxic alkaloids, phenols, flavonoids, terpenoids, lipids, and saponins in the plant extracts, which function as anti-corrosive agents to help prevent early corrosion of reinforcing TMT-MS in RCBs.