Surface analysis and interface properties of a newly synthesized quinoline-derivative corrosion inhibitor for mild steel in acid pickling bath: Mechanistic exploration through electrochemical, XPS, AFM, contact angle, SEM/EDS, and computational studies

Abstract

The two novel heterocyclic quinoline derivatives, 5-(methoxymethyl)-2-methylquinolin-8-ol (QO) and 5-((2-hydroxyethoxy)methyl)-2-methylquinolin-8-ol (QOOH) are examined in this work for their ability to adsorb against the corrosion of mild steel (MS) in a molar hydrochloric acid (HCl) media. After the synthesis of these two compounds, we proceeded some analytical methods such as the nuclear magnetic resonance of the proton and the carbon (1H NMR and 13C NMR). Potentiodynamic polarization (PDP), electrochemical frequency modification (EFM), and impedance spectroscopy (EIS) were the methods used in the experimental examination. The results indicated that the inhibitory efficacy of QO and QOOH increases with concentration. Both inhibitors exhibit mixed type behavior, according to the findings of polarization. Following that order was QO's and QOOH's inhibitory efficiencies 93.20% (QO) > 88.84% (QOOH). The Langmuir adsorption model is used in the adsorption process of these two chemicals. A barrier layer encasing the MS was shown to exist by Scanning electron microscope (SEM), energy dispersive X-ray analysis (EDS), atomic force microscopy (AFM), contact angle, and X-ray photoelectron spectroscopy (XPS) were all used in the examination of the surface characterization. The Density functional theory (DFT) findings suggest that inhibitors with electron-accepting capabilities exhibit the strongest interactions with the iron surface.