Corrosion Inhibition of Mild Steel by Ethanolic Terminalia microcarpa Decne Leaf Extracts in 3.5% NaCl Solution: A Gravimetric and Surface Analysis Studies

Mild steel is widely used but vulnerable to corrosion, with conventional inhibitors posing toxicity risks. This study evaluated the leaf extracts of Terminalia microcarpa Decne, also locally known as kalumpit, as a green corrosion inhibitor for mild steel in a 3.5% NaCl solution. The prepared extracts, characterized by FTIR, were found to contain phytochemicals with inhibition potential. Weight loss measurements showed that inhibition efficiency was concentration-dependent, but was not influenced by immersion time. SEM and UV-vis spectroscopy confirmed the formation of a protective surface barrier on the metal. The adsorption process followed a Temkin isotherm model, consistent with physical adsorption. These findings indicate that Terminalia microcarpa Decne leaf extracts are a promising and safe alternative for corrosion inhibition.