LAUSR

Abstract Aqueous extracts of the fruit shell of Hymenaea stigonocarpa were tested as an eco-friendly corrosion inhibitor for mild steel in 0.5 mol L−1 H2SO4. Corrosion data were obtained from potentiodynamic polarization and electrochemical impedance experiments. Surface analysis was carried out by scanning electron microscopy, Fourier-transform infrared spectroscopy, and ultraviolet-visible spectrophotometry. The steel corrosion rate decreased in the presence of the fruit shell extract. Inhibition efficiency reached a maximum of ~90%. Activation energy of the inhibited corrosion process increased 2.5 times compared with the uninhibited process. Organic molecules present in the plant extract were detected on the steel surface. The development of an inhibitor film was modeled by the Langmuir isotherm. The fruit shell extract acted as a corrosion inhibitor decreasing the rate of hydrogen evolution.