Electrochemical, Adsorption and Surface Morphological Studies of Terminalia mantaly Extract as a Corrosion Inhibitor for Mild Steel

ABSTRACT This study investigates the corrosion inhibition potential of Terminalia mantaly ethanol leaf extract on mild steel in 0.3M HCl using Fourier Transform Infrared Spectroscopy (FTIR), Gas Chromatography-Mass Spectrometry (GC-MS), Potentiodynamic Polarization (PDP), and Scanning Electron Microscopy (SEM). FTIR analysis confirmed the presence of functional groups such as hydroxyl (-OH), carbonyl (C=O), and aromatic (C=C) groups, which facilitate adsorption onto the metal surface. GC-MS identified bioactive compounds, including fatty acids, esters, and phenolics, known for their corrosion inhibition properties. Electrochemical studies revealed that the extract acts as a mixed-type inhibitor, predominantly affecting the anodic reaction, with inhibition efficiency increasing from 62.67% at 0.2 g/L to 78.18% at 0.6 g/L. Adsorption studies showed that the inhibition mechanism follows the Freundlich isotherm, suggesting multilayer adsorption. Thermodynamic analysis indicated that the adsorption process is spontaneous and majorly physisorptive. SEM micrographs confirmed the formation of a protective layer on the steel surface, reducing corrosion damage. These findings highlight Terminalia mantaly extract as a sustainable, eco-friendly corrosion inhibitor, offering a promising alternative to synthetic inhibitors in acidic environments.