Phytochemical Constituent and Anti-corrosion Properties of the Root Extract of Phyllanthus mellerianus (Nvo-nkwu) Plant on Mild Steel in 1.5M HCl Medium

The research reports on the phytochemical constituents and anti-corrosion properties of the root extract of Phyllanthus mellerianus on mild steel in 1.5M HCl. The powdered root was extracted with ethanol and concentrated with a rotary evaporator. The phytochemical constituents’ were achieved through GC-MS, FTIR and wet analysis. The anticorrosion properties were investigated via weight loss, hydrogen evolution techniques, and SEM analysis. The phytochemical investigation reveals the presence of tannins, flavonoids, phenols, and terpenoids at reasonable percentages. At different temperatures of 303K, 313K, and 323K, the inhibition efficiency, enthalpy, entropy, activation energy, Gibbs free energy, and adsorption isotherms were extrapolated with some models. The inhibition efficiency increased with an increase in the concentration of the extract, an indication of the inhibitive property of the root extract. This was supported through the extrapolation of Gibbs free energy, activation energy, enthalpy, and entropy change. The thermodynamic variable shows that the mechanism of inhibition was physisorption, whereas the kinetics study confirmed a first-order kinetic on the corrosion of mild steel in hydrochloric acid. The values of the linear regression R2 confirm the inhibitive impact of the root extract on mild steel in an acid medium. The presence of the heteroatoms N, O, and S in the root extracts of Phyllanthus mellerianus has been attributed to their inhibitory effectiveness.