Adsorption-controlled corrosion protection of mild steel in acidic environment using Xanthosoma undipes leaf extract: An integrated electrochemical and SEM analysis

The increasing emphasis on sustainable corrosion control has stimulated extensive exploration of naturally derived inhibitors as alternatives to conventional chemical additives. Xanthosoma undipes (locally known as Talas Beneng), an indigenous Indonesian taro species, contains a variety of bioactive constituents—including flavonoid derivatives, polyphenolic compounds, and polymeric carbohydrates—that exhibit strong affinity for metallic interfaces. In the present investigation, the corrosion protection capability of leaf extract derived from this plant was systematically evaluated for API 5 L Grade B steel exposed to a 1 M hydrochloric acid environment. The inhibitor performance was examined across a concentration range of 0 to 500 ppm. Spectroscopic characterization using Fourier Transform Infrared analysis was conducted to elucidate the functional moieties responsible for surface interaction, while electrochemical behavior was assessed through potentiodynamic polarization and impedance-based measurements. Morphological changes on the steel surface were further examined using scanning electron microscopy. The spectroscopic results confirmed the presence of heteroatom-containing and aromatic functional groups, which are known to promote interfacial adsorption. Electrochemical measurements revealed a pronounced decrease in corrosion activity, with optimal performance observed at 200 ppm, corresponding to an inhibition efficiency of 74.48%. Impedance analysis demonstrated a notable increase in charge transfer resistance, signifying enhanced barrier properties of the adsorbed layer. Surface observations corroborated these findings, showing significantly reduced surface damage and a more uniform morphology in the presence of the inhibitor. Overall, the results substantiate the potential of X. undipes leaf extract as a viable green corrosion inhibitor for steel structures operating in acidic media.