Evaluation of Ficus krishnae plant leaves extract as a potent green and sustainable corrosion inhibitor for low-carbon steel in 1.0 M HCl medium

Ficus krishnae plant leaf extract (FKLE) has been utilized to mitigate the corrosion of low-carbon steel (LCS) in a 1M HCl environment. The efficacy of FKLE on LCS has been evaluated using weight loss measurements, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization (PDP) techniques. Maximum corrosion inhibition efficiencies of 98.31%, 94.31%, and 96.39% have been observed via weight loss, EIS, and PDP methods respectively, at an optimal concentration of 150 ppm FKLE. The inhibitor molecules have reduced both anodic and cathodic reactions in the acidic medium, demonstrating mixed-type inhibition behavior. Corrosion control has occurred through adsorption phenomena, adhering to the Langmuir adsorption isotherm. Thermodynamic analysis has indicated that the inhibition process is spontaneous and exothermic. Scanning electron microscope (SEM) and transmission electron microscope (TEM) images have revealed severe damage to the LCS surface in the absence of FKLE, while significant protection has been provided in its presence. Atomic force microscopy (AFM) images have shown reduced surface roughness on the corroded LCS surface with FKLE addition. Water contact angle (WCA) measurements have demonstrated that FKLE-treated LCS surfaces possess increased hydrophobicity, whereas untreated LCS surfaces remain more hydrophilic, enhancing susceptibility to acid attack.