Quantum Chemical Studies on the Corrosion Inhibition of Mild Steel by Piperidin-4-One Derivatives in 1 M H<sub>3</sub>PO<sub>4</sub>

Abstract

The corrosion inhibition properties of 2,6-diphenylpiperidin-4-one (DPP) (1A) and 2,6-diphenyldihydro-2H-thiopyran-4(3H)-one (DPDT) (1B) for mild steel in 1 M phosphoric acid were studied using weight loss, potentiodynamic polarization and electrochemical impedance spectroscopic techniques. The effect of temperature on the corrosion behavior of mild steel has been examined in the temperature range 303 -328 K. The inhibition efficiency increases with increasing inhibitor concentration but decreases with increasing temperature. Potentiodynamic polarization studies indicated the mixed nature of inhibitors. The adsorption of the inhibitors on mild steel surface obeyed the Langmuir adsorption isotherms. The density functional theory (DFT) at the B3LYP/6-31G (d) basis set level was performed on 1A and 1B to investigate the correlation between molecular structure and the corresponding inhibition efficiency (%). The quantum chemical parameters such as EHOMO, ELUMO, the energy gap (E), hardness (η), softness (S), dipole moment (µ), electron affinity (A), ionization potential (I), the absolute electronegativity (χ), the fraction of electron transferred (N), electrophilicity index (ω), the back-donation (EBack-donation) and Mulliken population analysis have been calculated.

The Corrosion Inhibition Effect of Triazinedithiol Inhibitors for Aluminum Alloy in a 1 M HCl Solution

“…Similarly, the value of E LUMO reflects the ability of the molecule to accept electrons [32]. A molecule with a lower energy gap means a better inhibition ability, because the value of energy needed to remove an electron from the last occupied orbital is lower [33]. From Table 4, a higher E HOMO value and lower energy gap were found in the DBN molecule, which demonstrated that DBN had an anti-corrosion capability superior to DAN.…”

Glyceral Trinitrate: As Potential Corrosion Protector for Mild Steel in Acid Medium Along with Paint-coated Steel in a Saline Environment

“…The inhibitor geometrical structure was optimized completely with the program package GAUSSIAN 09 followed by B3LYP procedure [25][26][27] within the basic set of 6-31G 28 . All the quantum chemical parameters of electronegativity (χ), dipole moment (µ), global hardness (η), E LUMO E HOMO , Global softness (σ), ∆E, ∆N were discussed for the studied compound.…”

Corrosion Inhibition Potential of Thiosemicarbazide Derivatives on ALuminium: Insight from Molecular Modelling and QSARs Approaches

“…In an acidic solution, the hydrogen evolved can cause a reduction of the nitro group in TSC 3 which can aid the desorption of TSC 3 thus making it a less effective corrosion inhibitor than TSC 2 and TSC 5 Absolute hardness, electronegativity, and softness are indicators of reactivity that are derived from electronic energy (E) with respect to the number of electrons (N) at a constant external potential t(r) [29]. The absolute hardness and softness reactivity descriptors are associated with the description of soft and hard solutions through the acid and base theory [30][31] established that the hardness of all atoms in a molecule is actually equalized, and molecular hardness equals the geometric mean of component atoms' chemical hardness [32]. The transfer of electrons between chemical species occurs in every reaction and in contrast to hard molecules, soft molecules are affected by charge transfer.…”