Phytochemical, Weight-Loss, and Scanning Electron Microscopy Studies of Ficus ottoniifolia leaf extract as a green corrosion inhibitor for mild steel

Bio-based materials like plant extracts, natural polymers, gums, Agricultural waste, amino acids, and carbohydrates, because of their natural origin, biodegradability, and non-accumulative properties serve as excellent sustainable substitutes to many inorganic corrosion inhibitors that pose toxicity concerns. This study investigated the phytochemical composition, corrosion inhibition performance, and surface protective behavior of Ficus ottoniifolia leaf aqueous extract as a green corrosion inhibitor for mild steel in 0.5 M HCl. Fresh leaves were collected, authenticated, air-dried, pulverized, and extracted in hot distilled water. The Phytochemical screening revealed eight major classes of bioactive constituents, with terpenoids and flavonoids occurring in the highest concentrations, supported by saponins, glycosides, alkaloids, phenols, steroids, and tannins. Weight-loss measurements for over four weeks, showed a consistent decrease in corrosion rate with increasing inhibitor volume (5 - 20 mL) and immersion time, with the 20 mL extract achieving the strongest inhibitory effect. Peak inhibition efficiency occurred between 300 and 350 hours, attributed to excellent formation and stabilization of an adsorbed protective film, after which a gradual decline was observed due to film weakening. SEM analysis revealed severe surface degradation on uninhibited steel, while samples exposed to 20 ml extract exhibited smooth morphology, minimal corrosion, and sustained protection even after 672 hours immersion. These findings positions Ficus ottoniifolia extract as a viable alternative to synthetic inhibitors owing to its long-term efficacy in acidic environments.