Corrosion Inhibiting by Some Organic Heterocyclic Inhibitors Through Langmuir Adsorption Mechanism on the Al-X (X = Mg/Ga/Si) Alloy Surface: A Study of Quantum Three-Layer Method of CAM-DFT/ONIOM

Abstract

The physicochemical attributes of inhibitor → metal & metal alloys nanosheet can be one of the fundamental factors for recognizing determining and selecting the Langmuir adsorption through IR, NMR, NQR, NBO, UV–VIS, HOMO/LUMO, and charge distribution and other quantum attributes. Then, the fluctuation of occupancy of natural bond orbitals has been estimated for pyridine → Al–Al, pyridine → Al–Mg, pyridine → Al–Ga, pyridine → Al–Si; 2-picoline → Al–Al, 2-picoline → Al–Mg, 2-picoline → Al–Ga, 2-picoline → Al–Si; 3-picoline → Al–Al, 3-picoline → Al–Mg, 3-picoline → Al–Ga, 3-picoline → Al–Si, 4-picoline → Al–Al, 4-picoline → Al–Mg, 4-picoline → Al–Ga, 4-picoline → Al–Si, and 2,4-lutidine → Al–Al, 2,4-lutidine → Al–Mg, 2,4-lutidine → Al–Ga, and 2,4-lutidine → Al–Si through the Langmuir adsorption process due to concerning the nitrogen atom in the benzene ring of related heterocyclic compounds becoming close to the monolayer nanosurface of aluminum and its alloys. Nuclear magnetic resonance has certainly has focused on the aluminum shielding in the intra-atomic interaction with magnesium, gallium, and silicon and simultaneously interatomic interaction with nitrogen atoms in organic heterocyclic inhibitors through variety of high, medium, and low layers of ONIOM method. In addition, on the basis of the computed amounts of UV–VIS spectra for pyridine and its family adsorbing on the Al alloy surface, there are maximum adsorption bands between 150 and 240 nm. Two maximum adsorption bands for pyridine, 2-picoline, 3-picoline, and 4-picoline are at 200 nm and 250 nm. Besides, it has been observed two maximum adsorption bands for 2,4-lutidine around 170 nm and 210 nm, respectively.