Superior inhibition action of the Mish Gush (MG) leaves extract toward mild steel corrosion in HCl solution: Theoretical and electrochemical studies

Abstract

This study is an effort in which a novel corrosion inhibitor, derived from a plant called Lamb's ear (locally known as Mish Gush), was employed to cut down the corrosion-related damages of the 1 M HCl solution on MS. The influence of various concentrations of MG extract (0–1600 ppm) in addition to several exposure times (0.5–24 h) were explored. Field-emission scanning electron microscopy (FE-SEM), Energy dispersive X-ray analysis (EDAX), Atomic force microscopy (AFM), and contact angle were carried out. The outcome of the FE-SEM and AFM illustrated that the MS surface laid bare to the corrosive media, experienced intense corrosion followed by a high roughness which then significantly decreased after the introduction of MG extract (MGe) to the solution. Raman extracted data underpinned the carbon-like film generation in the metal/solution interface; also, FT-IR illustrated the existence of several functional groups (e.g., CC and CH) which were in agreement with the ones existing in the MGe's molecules. Grazing-induced XRD signified that the incorporation of MGe in the solution resulted in the formation of less corrosion product on the surface in comparison with the blank sample. The MGe chemical structure and its existence on the surface were certified via UV–Vis analysis; Raman spectroscopy showed that a graphene-like film developed on the surface. Uncovering the MGe's corrosion-preventive film characteristic on the surface was accomplished through Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PP) measurements. The outcome suggested that the rise in the MGe concentration in the solution, as well as exposure time, increased the inhibition efficiency proportionally which maximized to 96% after 4 h of exposure to the solution incorporated 1200 ppm of MGe. Computations showed that the MGe followed a mixed-type inhibition. Also, it was found that the most probable adsorption isotherm for the inhibitor deposition was Langmuir. Besides the experiments, theoretical studies based on Molecular dynamics (MD), Monte Carlo (MC), and Density functional theory (DFT) were performed. These studies confirmed the adsorption of inhibitors on the metallic surface through the reactive sites of the inhibitor molecules.