Integrated Experimental and Theoretical Assessment of Novel Bis-pyridinium Ionic Liquid Derivatives as Potent Corrosion Inhibitors for N80 Steel in 15% HCl
摘要
This study investigates the corrosion inhibition of N80 carbon steel in 15% HCl at 303 K and 363 K using four novel ionic liquid derivatives (OCMP-4, OCMP-3, NCMP-4, and NCMP-3). Surface analysis, computational methods, weight loss measurements, and electrochemical techniques were employed. Weight loss measurements showed that corrosion rates decreased significantly with the addition of 5 × 10−3 M of the inhibitors, from 25 mm/year without inhibitors to 1.16 mm/year (OCMP-4), 0.61 mm/year (OCMP-3), 0.55 mm/year (NCMP-4), and 0.31 mm/year (NCMP-3), indicating a protective layer formation. Electrochemical impedance spectroscopy revealed strong adsorption of NCMP-3 on the steel surface, achieving over 90% inhibition efficiency and forming a protective layer within 24 h. Electrochemical studies demonstrated that temperature and exposure time affect inhibition efficiency, shifting the mechanism from cathodic to anodic with increasing temperature. Adsorption of all four molecules on the N80 carbon steel surface was spontaneous and physicochemical, obeying Langmuir's law. Profilometry, Raman spectroscopy, and SEM confirmed the formation of the protective layer. Density functional theory (DFT) calculations showed the following trend in energy gaps: ΔEgap (NCMP-3) < ΔEgap (NCMP-4) < ΔEgap (OCMP-3) < ΔEgap (OCMP-4), suggesting that NCMP-3 is the most reactive, which aligns with experimental inhibition efficiencies. Density functional tight-binding (DFTB) and molecular dynamics simulations revealed the parallel adsorption of the inhibitors onto the iron surface, resulting in the formation of covalent bonds. These findings offer valuable insights into the temperature and exposure time dependence of ionic liquid inhibitors, thereby enhancing our understanding of their corrosion protection mechanisms.
Graphical Abstract