Journal of Physical & Theoretical Chemistry, 2017

The study examined corrosion inhibition of corrosion inhibition of 5-methyl-2H-imidazol-4carboxaldehyde and 1H-Indole-3-carboxaldehyde on mild steel in acidic medium using weight loss and Density Functional Theory (DFT) methods. DFT calculations were carried out at B3LYP/631+G** level of theory in aqueous medium on the molecular structures to describe electronic parameters. The values of thermodynamic parameters such as free energy of adsorption (ΔGoads), adsorption equilibrium constant (Kads), adsorption entropy (ΔSoads), adsorption enthalpy (ΔHoads) and activation energy (Ea) were calculated, analyzed and discussed. The adsorption process on mild steel surface showed that 4-methylimidazol-5-carboxaldehyde and Indole-3-carboxaldehyde obeyed Freundlich and Temkin adsorption isotherms respectively. Also, the molecular parameters associated with inhibition efficiency such as EHOMO, ELUMO, band gap energy (ELUMOEHOMO), softness (S), electron affinity (EA) and number of electrons transf...

Density Functional Theory (DFT) method was used to study the corrosion inhibition characteristics of 2-phenylimidazo[1,2-a]pyridine (2PIP) and 2-(m-methoxyphenyl)imidazo[1,2-a]pyrimidine (2MPIP) on mild steel. Quantum chemical parameters such as highest occupied molecular orbital energy (EHOMO), lowest unoccupied molecular orbital energy (ELUMO), the energy gap, chemical hardness, softness, dipole moment, absolute electronegativity, electrophilicity index and the fraction of electron transferred were calculated and correlated to inhibition efficiency of the studied molecules. Low energy band gaps coupled with structural stabilities should favour the adsorption of protonated molecules on metal surface at low concentrations and before the adsorption equilibrium. However, at high concentrations and towards equilibrium desorption of the protonated would be rapid due charge repulsion and molecular distortion from planarity which would facilitate the adsorption of neutral molecules on metal surface at equilibrium.

2020

The adsorption behavior of Benzimidazol-2-one (Bz), 5-Methylbenzimidazol-2-one(CH3Bz) and 5-Chlorobenzimidazol-2-one (ClBz) as inhibitors for mild steel corrosion in HCl 1M have been studied computationally using density functional theory (DFT) calculations with the hybrid B3LYP functional. The calculations were focused on the protonated forms of the molecules under study, seeing that these classes of inhibitors can easily be protonated in acidic medium. The most preferred protonation centers were determined proton affinity (PA). Fukui indices have been computed to evaluate the nucleophilic and electrophilic sites of atoms in the molecule. The interaction of the inhibitors with the iron surface was studied by calculating the combined energy (Ecom) and the free energy of adsorption ( ΔG°ads ). Observable correlation was found between experimental corrosion inhibition efficiency and the theoretical data. The molecular dynamics (MD) and Monte Carlo (MC) simulations used show that all i...

Corrosion Science, 2011

The corrosion inhibition performances of three corrosion inhibitors on mild steel in acidic medium, namely 1,3-thiazole (TA), 2-amine-1,3-thiazole (2-ATA), and 4-amine-1,3-thiazole (4-ATA), were theoretically evaluated using quantum chemistry calculations and molecular dynamics simulations both in gas phase and aqueous phase. The frontier orbital energy, global activity, and Fukui indices were studied. Adsorption energy of corrosion inhibitors on iron surface was calculated. Furthermore, a prediction of iron crystal morphology was performed, and the surface energies were obtained. The results indicate that Fe (1 1 0) surface possesses the lowest surface energy. 4-ATA shows the highest reaction activity among the three molecules. The binding energies of the corrosion inhibitor molecules and iron surface follow the order 4-ATA > 2-ATA > TA.

Corrosion Science, 2021

This work aims to investigate the corrosion inhibition of the mild steel in the 1 M HCl solution by 1octyl-3-methylimidazolium hydrogen sulphate 1-butyl-3-methylimidazolium hydrogen sulphate, and 1-octyl-3-methylimidazolium chloride, using electrochemical, weight loss, and surface analysis methods as well as the full quantum-mechanical treatment. Polarization measurements prove that studied compounds are mixedtype inhibitors with a predominantly anodic reaction. The inhibition efficiency obtained from the polarization curves is about 80-92% for all of the 1-octyl-3-methylimidazolium salts with a concentration higher than 0.005 mol/l, while it is much lower for 1-butyl-3-methylimidazolium hydrogen sulphate. The values measured in the weight loss experiments (after seven days) are to some extent higher (reaching up to 98% efficiency). Furthermore, we have shown that the influence of the alkyl chain length on the inhibition efficiency is much larger than that of the anion type. Furthermore, we obtain a realistic model of a single molecule on iron surface Fe(110) by applying the Density Functional Theory calculations. We use the state-of-the-art computational approach, including the meta-GGA strongly-constrained and appropriately normed semilocal density functional to model the electronic structure properties of both free and bounded-to-surface molecules of 1-butyl-, 1-hexyl-, and 1-octyl-3-methylimizadolium bromide, chloride, and hydrogen sulphate. From the calculations we extract, the HOMO/LUMO gap, hardness, electronegativity, and charge transfer of electrons from/to molecules-in-question. It supports the experimental findings and explains the influence of the alkyl chain length and the functional group on the inhibition process.

2021

One of the ways of reducing metal corrosion and its devastating effects is by using organic corrosion inhibitors. This is because of the π-conjugation in their moieties, their ability to donate electrons to the metal’s vacant d-orbitals, and their low lying LUMO orbitals for accepting electrons as well from the metal, all these improve their adsorption on the metal surface. (E)-5-((4-benzoylphenyl)diazenyl)-2-hydroxybenzoic acid (AD4) was synthesized via the coupling reaction of p-aminobenzonephenone and Salicylic acid, characterized via FTIR, UV/Vis, 1H-NMR, and 13C-NMR spectroscopy. The melting point of AD4 is 103oC–106oC indicating that it is thermally stable and pure. Gravimetric and potentiodynamic polarization techniques were employed to obtain the corrosion rates (Cr) and percentage inhibition efficiency (%IE) at different concentrations of the inhibitor and at different temperatures. The thermodynamic parameters like Enthalpy, ∆Hoads, Entropy, ∆Soads and free energy of adsor...

Journal of Bio- and Tribo-Corrosion, 2019

In the present work, a new organic inhibitor, namely (2(-4(chloro phenyl-1H-benzo[d]imidazol)-1-yl)phenyl) methanone (CBIPM), that has an inhibitive effect on the ordinary steel corrosion in 5.0 M HCl has been studied using electrochemical measurements (potentiodynamic polarization and electrochemical impedance spectroscopy). The obtained results showed that the inhibition efficiency increased with concentration and reached 98.6% at 10 −3 M. In addition, the CBIPM takes its performance at the temperature range of 298-328 K. The adsorption of the inhibitor on the ordinary steel was well described by the Langmuir isotherm. On the other hand, the establishing of correlation between the molecular structures of quantum chemistry indices was carried out using the density functional theory.

Journal of Chemical Information and Modeling, 2015

The inhibition effect of N,N′-bis(1-(3,5-dihydroxyphenyl)ethylidene)propane-1,3-diamine was studied on steel corrosion in 1 M hydrochloric acid solutions. The density functional theory was applied to calculate quantum chemical parameters such as the highest occupied molecular orbital energy, the lowest unoccupied molecular orbital energy, electron affinity, global electrophilicity index, the fraction of electron transferred, global nucleophilicity index, and Mulliken charges. According to quantum calculation, the diamine compound showed high interaction and effective adsorption on steel surface and high inhibition efficiencies and therefore nitrogen atoms of inhibitor indicated more tendencies for the electrophilic effect in the adsorption. Electrochemical impedance and potentiodynamic polarization indicated that this material has excellent inhibiting features in very low concentrations. The influence of DC trend on the explanation of electrochemical noise data was evaluated by polynomial fitting and the optimum polynomial order m = 4 was obtained. Noise resistance and the inhibition efficiency was calculated and compared in different methods. The theory of shot noise in frequency domain was used to obtain the electrochemical event charge. The corroded surface of steel in the absence and existence of thiazole compound was studied by Atomic force microscopy.

Journal of the Turkish Chemical Society Section A: Chemistry, 2019

Density Functional Theory (DFT) calculation at B3LYP level of theory and 6-31G* basis set was applied on some triazole derivatives of pyrimidine which led to the optimization of their structures, generation of electronic and other important Quantum chemical descriptors such as the energy of the highest occupied molecular orbital (EHOMO), the energy of the lowest unoccupied molecular orbital (ELUMO), energy band gap (ΔE), Dip E), Dipole Moment (μ)), chemical hardness (η),), chemical softness (σ)), global electronegativity σ =1η = − (2 (EHOMO − E L U M O)) (χ) and number of transferred electrons (ΔE), Dip N) using SPARTAN'14 Software. The obtained results shows a good correlation between the chemical structures of the inhibitors and their experimental inhibition efficiencies (%IEs). The ranking of these efficiencies (%IEs) nicely matched with the order of a good number of the generated descriptors but with a varying degree of correlation as majority of the descriptors indicates that I-4 is the best inhibitor among the data set. Furthermore, molecular dynamic (MD) simulations were carried out to search the best adsorption configuration of the inhibitor on the steel (1 1 0) surface using Material Studio 8.0. The obtained results of MD simulations suggest that the interaction was as a results of the chemical adsorption on the steel surface, since the binding energy > 100 Kcalmol-1 for all the inhibitors and the best adsorption energy was found to be-488.07 Kcalmol-1 (I-4). This observation are in good agreement with the DFT results and the experiment findings. Thus; this study provides a valuable approach and new direction to novel steel corrosion inhibitor discovery.

Albaydha University Journal, 2023

The inhibitive action of a new Benzimidazole derivation, 3H-2-Methyl-1,2,4-Triazepino [2,3-a] Benzimidazole-4 (5h)-one (MTB), for the corrosion of mild steel in one molar hydrochloric acid solution was investigated. Corrosion tests has been conducted using weight loss measurement electrochemical method and scanning electron microscopy associated with energy dispersion spectrometer (SEM/EDS). The results showed increasing inhibition efficiency with increasing the inhibitor concentration and reach to 98% at 1×10-2 M. The thermal studies indicated that the newly synthesized MTB inhibited the corrosion of mild steel by its adsorbing on the specimen surface via both physisorption and chemisorption mechanism. The adsorption process of MTB on the mild steel surface obeys Langmuir adsorption isotherm and act as mix-type inhibitor. The analysis of surface morphology confirmed the thermal results by showing the MTB molecules on the mild steel surface. Various DFT parameter like HOMO and LUMO energy, gab energy (∆E), electronegativity (χ), softness (), global hardness (η) were derived for MTB molecules and correlated with experimental results.