•Synthesis and characterization of new Schiff base from Imidazo(1,2-a)pyridine and invistigation of their ability to to inhibit corrosion of mild steel in 1.0 M HCl.•The study is based on ...electrochemical techniques and DFT quantum chemical calculations.•Their inhibition efficiency depends on their concentration and their molecular structure.•The electron-accepting ability of compounds affects their adsorption properties.•There is a good correlation between theoretical and experimental results.
In this work, we report a study on the synthesis and characterization, using several spectroscopic techniques such as IR, 13C NMR, 1H NMR and mass spectroscopy, of a new series of Schiff bases based on imidazo(1,2a)pyridine (IMP) scaffold, and the evaluation of their ability to inhibit the corrosion of mild steel in 1M HCl by mass loss techniques, Potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and quantum chemistry calculation based on density functional theory (DFT).
The obtained results show that these inhibitors, namely (E)-N-(2-phenylimidazo(1,2-a)pyridin-3-yl)-1-(1H-pyrrol-2-yl)methanimine (IMP1), (E)-N-(2-phenylimidazo(1,2-a)pyridin-3-yl)-1-(thiophen-2-yl)methanimine (IMP2) and (E)-1-(5-nitrothiophen-2-yl)-N-(2-phenylimidazo(1,2-a)pyridin-3-yl)methanimine (IMP3), act only by reducing the cathode area without changing the mechanism of the cathodic reaction, and that the effectiveness of the inhibition increases with increasing concentration of the inhibitors. The adsorption of the studied compounds on the surface of mild steel follows the Langmuir isotherm model. And finally, we highlighted the existence of a correlation between the molecular structure of the tested inhibitors and their anticorrosion activity.
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Chemical hardness is considered to be a useful theoretical descriptor in many experimental and theoretical studies and this concept has several important applications in chemistry. In this study, an ...equation for atomic hardness is proposed. Following the equation for atomic hardness which is based on charges, ionisation energies and electron affinities of atoms, a new equation is obtained for the calculation of the chemical hardness of groups and molecules using the atomic hardness equation and the principle of chemical hardness equalisation. Molecular chemical hardness may be calculated using α and β parameters of atoms in a molecule or group through the use of the obtained molecular hardness equation. Furthermore, the advantage of this equation over other equations in the literature is that using this equation the chemical hardness of the charged groups and molecules can also be calculated. Besides, the relationship between molecular hardness and charge of molecule is examined using the results obtained from the new molecular hardness equation, and the partial charges of atoms in molecules are calculated with the help of derived equations.
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The development of green corrosion inhibitors is a challenging task as it has to comply with strict environmental regulations. Ionic liquids (ILs) have recently been proposed as ...promising corrosion inhibitors. The present paper reports on two ILs designed to act as green and efficient high-temperature corrosion inhibitors. The prepared ILs, namely, choline formate (ChF) and choline acetate (ChA), are composed of biologically active ions. To elucidate their structure and corrosion inhibition effect on mild steel in 5% HCl the ILs were subjected to characterization tests like proton nuclear magnetic resonance (1H NMR), carbon nuclear magnetic resonance (13C NMR) and Fourier Transform infra-red (FT-IR) spectroscopy and corrosion tests like weight loss measurements, potentiodynamic polarization measurements (PDP), and electrochemical impedance spectroscopy (EIS). The effectiveness of the inhibition (%IE) increased with increasing concentrations and temperature up to 50 °C. ChF and ChA exhibited the highest inhibition efficacies of 96.9% and 99.5%, respectively at a temperature of 50 °C and concentration of 2 × 10−3 M. Above 50 °C their inhibition performance diminished, displaying an efficacy of 77.6% for ChF and 79.3% for ChA at 80 °C. The results of polarization measurements suggested mixed type behavior of inhibitors, and adsorption followed Langmuir adsorption isotherm. Furthermore, surface studies like scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) revealed protecting capability of the investigated inhibitors. FT-IR, and Raman spectroscopic studies revealed the adsorption of ILs on the Fe surface, and an ultra-violet visible (UV–vis.) spectroscopy study confirms the formation of Fe2+- ILs complex. X-ray Photoelectron Spectroscopy (XPS) was conducted to study the formation of corrosion products and protective film over the mild steel surface. Density functional theory (DFT) calculations and molecular dynamics (MD) simulations were also done to understand the inhibition mechanism of ILs.
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•DDA shows excellent corrosion inhibition performance for Q235 steel in H2SO4.•The solubility and toxicity of DDA were evaluated by theory.•Surface morphology of Q235 steel was ...examined by SEM and AFM.•The adsorption process of DDA follows Langmuir adsorption isotherm.•Experimental results were supported by DFT and molecular dynamics calculations.
3,3-Dithiodipropionic acid (DDA) as a potential corrosion inhibitor for Q235 steel in 0.5 M H2SO4 solution was examined. A variety of research approaches including electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), scanning electron microscopy (SEM), atomic force microscopy (AFM), and computational techniques were employed. The toxicity and solubility of DAA were reasonably assessed. Its inhibition efficiency can reach approximately 93% when the optimal concentration is 5 mM. The results of PDP curves manifest that DDA is a mixed type corrosion inhibitor. EIS data indicate that the charge transfer resistance increases with increasing concentration of DDA. Gibbs free energy obtained from the Langmuir isotherm model suggests that DDA molecules hinder the acid attack mainly by chemisorption. Surface topography analysis strongly confirmed the electrochemical findings. Moreover, the simulation results based on density functional theory (DFT) calculation and molecular dynamics (MD) simulations supported the successful interfacial adsorption of DDA on Fe(1 1 0) surface.
Chemical hardness is an important reactivity property of matter and chemical hardness that is defined as the resistance towards electron cloud polarization or deformation of chemical species is a ...measure of stabilities and reactivities of molecules. In the present report, a new method that is useful in terms of calculation of chemical hardness of molecules is presented. Display omitted
•A new method for calculation of molecular hardness is presented.•Molecular hardness can be calculated using atomic ionization energy and electron affinity values through the new method.•The agreement was obtained with experimental data.
The chemical hardness introduced by Pearson in 1960s is an extremely useful theoretical descriptor. It is apparent that principles such as hard and soft acids and bases (HSAB) and maximum hardness principle (PMH) related with the chemical hardness provide theoretical justifications and explanations for many issues in chemistry. In the present report, a new molecular hardness equation to calculate chemical hardness of functional groups and molecules is derived utilizing the relationship with charge of the electronic energy for atoms, Density Functional Theory, and Datta’s global hardness equalization principle. The reliability of the new equation is assessed by comparison with experimental data, the results of Datta’s geometric mean equation, and molecular hardness values obtained in the present work. The new equation provides the opportunity to calculate the chemical hardness of molecules from first ionization energies (IE1), first electron affinities (EA1) and second ionization energies (IE2) of atoms in the molecules.
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The mutually corroborated density functional theory (DFT) and molecular dynamics (MD) simulation methodology were employed to evaluate the inhibition performance of three thiourea ...derivatives (Inh1, Inh2, and Inh3) on carbon steel corrosion. Experimental results have shown that the corrosion rate follows the order: Inh3>Inh2>Inh1. Quantum chemical descriptors such as the frontier orbital energies (EHOMO and ELUMO), the energy gap between ELUMO and EHOMO (ΔE), dipole moment (μ), and Fukui index have been calculated and discussed. Some significant factors such as solvent, temperature, and coverage have been considered when investigating the adsorption of aforementioned thiourea derivatives on Fe(110) surface. Our results provide important atomic/molecular insights into the anticorrosive mechanism of inhibitor molecules, which could help in understanding the organic-metal interface and designing more appropriate organic corrosion inhibitors.
•Arginine is a good corrosion inhibitor compared to other amino acids studied.•The agreement between theoretical and experimental results was obtained.•Basic amino acids such as arginine acts as ...powerful electron donator.
Amino acids are biologically important organic compounds in the human body which contain two important functional groups namely: –NH2 (amine) and –COOH (carboxylic acid) in their structures. In the present work, corrosion inhibitive performance amino acids such alanine (Ala), methionine (Met), aspartate (Asp), asparagine (Asn), lysine (Lys), arginine (Arg) and histidine (His) were investigated. All quantum chemical calculations related to these amino acids at the B3LYP/6-31G++(d, p) HF/6-31G++(d,p) methods were performed. Corrosion inhibition effects of the subject amino acids were discussed not only in the gas phase but also in the water phase, acetic acid and formic acid. Furthermore, molecular dynamic simulations employing Monte Carlo sampling approach were applied to search for the most stable configuration and adsorption energies for the interaction of the amino acid corrosion inhibitors on Cu (111)/50 H2O interface. A good correlation between theoretical data and experimental data has been obtained. Moreover, arginine that is a basic amino acid the best corrosion inhibitor among amino acids, considered in this study.
Display omitted Typical energy profile plots for arginine/Cu (111)/50 H2O system obtained during 5 cycles of the Monte Carlo simulation process.
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•We obtained the habit information of α-Fe obtained by the “Morphology” module.•The adsorption of pyrrole, furan, and thiophene on Fe(110) surface were studied by DFT ...calculations.•Our DFT modeling provided a reasonable micro-explanation to the empirical rule.
Steel is an important material in industry. Adding heterocyclic organic compounds have proved to be very efficient for steel protection. There exists an empirical rule that the general trend in the inhibition efficiencies of molecules containing heteroatoms is such that O<N<S. However, an atomic-level insight into the inhibition mechanism is still lacked. Thus, in this work, density functional theory calculations was used to investigate the adsorption of three typical heterocyclic molecules, i.e., pyrrole, furan, and thiophene, on Fe(110) surface. The approach is illustrated by carrying out geometric optimization of inhibitors on the stable and most exposed plane of α-Fe. Some salient features such as charge density difference, changes of work function, density of states were detailedly described. The present study is helpful to understand the afore-mentioned experiment rule.
Lattice energy, which is a measure of the stabilities of inorganic ionic solids, is the energy required to decompose a solid into its constituent independent gaseous ions. In the present work, the ...relationships between lattice energies of many diatomic and triatomic inorganic ionic solids are revealed and a simple rule that can be used for the prediction of the lattice energies of inorganic ionic solids is introduced. According to this rule, the lattice energy of an AB molecule can be predicted with the help of the lattice energies of AX, BY and XY molecules in agreement with the experimental data. This rule is valid for not only diatomic molecules but also triatomic molecules. The lattice energy equations proposed in this rule provides compatible results with previously published lattice energy equations by Jenkins, Kaya, Born-Lande, Born-Mayer, Kapustinskii and Reddy. For a large set of tested molecules, calculated percent standard deviation values considering experimental data and the results of the equations proposed in this work are in general between %1–2%.
•A simple lattice energy calculation technique is introduced.•We obtained a good agreement with experimental data.•Calculated percentage deviation values are between %1 to 2.
