Mechanistic insight into adsorption and anti-corrosion capability of a novel surfactant-derived ionic liquid for mild steel in HCl medium

A novel cetylpyridinium picrate ionic liquid (CPP) was synthesized and investigated for its corrosion inhibition trait on mild steel (MS) substrate in 1 M HCl. The molecular structure of CPP was elucidated by FT-IR and NMR spectroscopy. Gravimetric experiment, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization technique (PP) were used to quantify the corrosion inhibition efficiency of CPP. Gravimetric results at 30 degrees C showed an appreciably high inhibition efficacy of 90.79% at an extremely low concentration of CPP (8 x 10-7 M) which is further raised with temperature attaining maximum protection of 99.04% at 70 degrees C at the same concentration. Adsorption of CPP at MS-electrolyte interface was ideally compatible with Langmuir adsorption isotherm. Surface analysis by X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDS), contact angle measurement, and FT-IR spectroscopy confirms that CPP forms an organic-inorganic hybrid protective layer to prevent the surface from corrosive ions. Scanning electron microscopy (SEM) micrographs accentuated reduced heterogeneity of metal surface in the presence of adsorbed CPP. The computational methods (DFT, fukui indices calculation, and MD simulation) were exploited to envisage the inhibition mechanism of CPP.