Investigation of polyphenol derivative extraction from Terminalia catappa leaves and assessment of their corrosion inhibition performance on CB300 steel in saline solution

Abstract

This research investigates the extraction of polyphenolic compounds from Terminalia catappa leaves and their application as a natural corrosion inhibitor for CB300 steel in saline solution. The parameters for key extraction, as solvent ratio, temperature, and extraction duration, were tuned to enhance polyphenol yield. The optimal conditions were identified as a 1:1 ethanol-water solvent ratio, extraction at 60 °C, and a heating duration of 30 minutes. The composition of the extract was analyzed using UV-Vis and FTIR spectroscopy, which confirmed the presence of polyphenolic functional groups. The effectiveness of preventing corrosion was measured using SEM, EDX, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS). The results indicated that the extract created a protective layer on the steel surface, diminishing corrosion activity. The corrosion rate was decreased by 42.39% relative to the control at an optimum concentration of 0.004% in a 3.5% NaCl solution. Nevertheless, elevated extract concentrations marginally reduced inhibitory efficacy owing to heightened acidity. This study illustrates the efficacy of the extract from Terminalia catappa leaves as a sustainable and environmentally friendly corrosion inhibitor for steel structures in marine settings.