Search results

Study of corrosion behaviour could benefit from quantum chemical calculation to investigate the role of adsorption of main anions such as OH⁻ and Cl⁻ on metallic surfaces. The purpose of this study is to report the quantum chemical study of aluminium immersed in NaOH, NaCl and HCl solutions and verifying the calculations by potentiodynamic and open-circuit potential (OCP) measurements.

The electrochemical evaluations based on potentiodynamic polarization and OCP experiments were carried out. For theoretical investigations, the quantum chemical calculation was performed. In this regard, the adsorption of Cl⁻, OH⁻ and H⁺ on aluminium surface was investigated. Furthermore, the natural bond orbital for the direction and magnitude of charge transfer interactions was calculated.

The calculations indicate that higher interaction energy between ions with the metallic cluster being modelled together with natural bond orbital calculations of direction and magnitude of charge transfer accurately predicts corrosion.

This paper shows that ions such as Cl⁻, OH⁻ and H⁺ cause the corrosion of aluminium in NaOH, NaCl and HCl environments. The overall theoretical data corroborate with experimental results.

The purpose of this study is to perform quantum chemical calculations based on the DFT method on four bipyrazoles used as corrosion inhibitors for the plain carbon (“mild”) steel in acid media to determine the relationship between inhibition efficiency and the molecular structure of inhibitors.

Several quantum chemical parameters, such as the charge distribution, energy and distribution of highest occupied molecular orbital and lowest unoccupied molecular orbital, the absolute electronegativity (χ) values and the fraction of electrons (△N) transferring from inhibitors to the steel surface, were calculated and correlated with inhibition efficiencies.

The results showed that the inhibition efficiency of bipyrazole increased with the increasing in EHOMO, and the areas containing N atoms were the most probable sites to donate electrons for adsorbing the inhibitor molecules onto the metal surface.

It is a useful method to investigate the mechanisms of reaction by calculating the structure and electronic parameters, which can be obtained by means of theoretical quantum theory. Thus, the behavior and mechanism of the organic inhibitors can be obtained. Quantum chemical method can also be used to guide the selection and molecular design of inhibitors.

This paper aims to investigate the corrosion inhibition ability of 4–(4-nitrophenyl) thiazol-2-amine (NPT) on the copper in 1 M HCl.

The corrosion inhibitory ability of NPT on the copper in 1 M HCl was studied by electrochemical impedance spectroscopy, scanning electron microscopy and atomic force microscopy. Theoretical calculations (molecular dynamics simulation, density functional theory and the nucleus independent chemical shift [NICS] as aromaticity indicator of the molecule) were also performed.

The corrosion inhibition efficacy of this compound was about 80%. Nyquist plots display a small arc contributed to the film or oxide layer resistance and a large loop associated with charge transfer resistance. The inhibitor adsorption was under Langmuir’s adsorption model. ΔG⁰_ads values point to the presence of physical and chemical adsorption. Results of quantum chemical calculations showed that NPT has better interaction with copper than NPTH⁺. NICS of NPT in benzene or thiazole rings was less negative compared to NICS of NPTH⁺. Thus NPT shows less aromaticity compared with NPTH⁺, showing NPT can have better interaction with copper than NPTH⁺. NPT had more negative E_int value and more interactions with the Cu relative to NPTH⁺, this result was in agreement with the results of quantum chemical calculations.

NPT is an efficient corrosion inhibitor for copper in HCl. Theoretical calculations showed that NPT can have better interaction with copper than NPTH⁺. The results of the theoretical studies were in good agreement with the experimental studies.

The main purpose of the present work is to introduce two new Schiff bases as corrosion inhibitors (CIs) for carbon steel (CS). The anti-corrosion performance of these Schiff bases having N and S heteroatoms in their structures was investigated and compared in 2 M HCl electrolyte. The inhibitory activity of these Schiff bases was also assessed.

Common electrochemical assays like potentiodynamic polarization and electrochemical impedance measurements were used to evaluate the ability of compounds in reduction of the rate of corrosion. Quantum chemical calculations (QCCs) were also used to examine the corrosion inhibitive and the process related to the electrical and structural characteristics of the molecules acting as CIs.

The electrochemical measurements indicate that both Schiff bases acted as the efficient CIs of CS in 2 M HCl electrolyte. The adsorption of the Schiff base on the surface of the CS caused the corrosion to be inhibited. The change of Gibbs energies indicated that both physical and chemical interactions are involved in the adsorption of NNS and SNS on CS surfaces. The predicted QCCs of the CIs neutral and positively charged versions were well-aligned with those obtained by electrochemical experiments.

Using electrochemical experiments and quantum chemical modelings, two new Schiff bases, N-2-((2-nitrophenyl)thio)phenyl)-1-(pyrrole-2-yl)methanimine (NNS) and N-2-((2-nitrophenyl)thio)phenyl)-1-(thiophen-2-yl)methanimine (SNS), were evaluated as anti-corrosion agents for CS in 2 M HCl electrolyte. The DFT calculations were considered to compute the quantum chemical parameters of the inhibitors.

This study aims to investigate the inhibition performance of an aqueous extract of Matricaria recutita chamomile on the corrosion of S235JR steel in 0.5 M NaCl by using electrochemical impedance spectroscopy (EIS) and polarization measurements.

The inhibition performance was investigated using EIS and polarization measurements. Surface analysis demonstrates the presence of a protective layer on the steel surface in the presence of the extract. Quantum chemical parameters calculated for the molecules contained in the aqueous extract are interpreted to predict the corrosion inhibition efficiency of the considered extract.

The inhibition efficiency of chamomile aqueous extract for S235JR steel increases with increasing amounts of plant concentration and with an increase in the immersion time. The optimal inhibition efficiency of chamomile extract, 98.90 per cent, was achieved for S235JR steel when immersed in 15 per cent v/v of extract concentration for 2 h. The surface analysis in the absence and presence of the chamomile extract confirmed the formation of a protective layer on steel surface. The quantum chemical calculations allowed to explain the great inhibition efficiency values by interpreting the calculated quantum parameters.

This is the first study carrying out an experimental and theoretical investigation on M. recutita chamomile as a green corrosion inhibitor, with interesting potential industrial applications.

This paper aims to study inhibitory effect of 4-aminothiophenol on the corrosion of mild steel (MS) in 0.5 M HCl.

In this study, electrochemical experiments, quantum chemical calculations, potentiodynamic measurements, linear polarization resistance and scanning electron microscopy were used.

The experimental results suggest that this compound is efficient corrosion inhibitor and the inhibition efficiencies increase with increasing their (from 0.5 to 10.0 mM.) concentrations. This reveals that inhibitive actions of inhibitors were mainly due to adsorption on mild steel surface. The adsorption of these inhibitors was found to obey Langmuir adsorption model. The computed quantum chemical features show good correlation with empirical inhibition efficiencies.

The 4-aminothiophenol is suitable inhibitor for application in closed-circuit systems against corrosion. The study is original and has great impact in industrial area. The obtained theoretical results have been adapted with the experimental data.

The purpose of this paper is to investigate the surface properties, particle sizes and corrosion inhibition performance of sodium dodecyl sulfate (SDS) in the presence of imidazolium-based ionic liquid as an additive. Up to now, different properties of alone surfactants and ionic liquids have been studied. However, few studies have been devoted to mixed ionic liquid and surfactant. The significance and novelty of this research is the investigation of 1-methylimidazolium trinitrophenoxide ([MIm][TNP]) as ionic liquid effects on SDS corrosion behavior.

The inhibition effect of [MIm][TNP], SDS and their mixtures on mild steel surface in 2 M hydrochloric acid (HCl) solution was examined by electrochemical impedance spectroscopy, potentiodynamic polarization (PDP), scanning electron microscopy (SEM), atomic force microscopy and quantum chemical calculations as well as dynamic light scattering (DLS) and surface tension measurements to discuss surface properties of studied solutions.

Based on the results, ionic liquid/SDS mixtures significantly indicated better inhibition properties than pure surfactant solution. PDP curves indicated that the studied compounds act as mixed-type of inhibitors. The critical micelle concentration, surface properties and particle sizes were investigated from the surface tension measurements and DLS results.

Adsorption of the inhibitors on the steel surface obeyed the Villamil adsorption model. SEM was used for surface analysis and verified the inhibition efficiency of mixed IL/SDS system. Quantum chemical calculations were performed using density functional theory, and a good relationship between experimental and theoretical data has been obtained.

The purpose of this paper is to study the corrosion inhibition performance of an eco-friendly drug clozapine on the corrosion of copper in 1.0 M nitric acid and 0.5 M sulfuric acid solutions.

The corrosion inhibition nature of inhibitor molecule was evaluated by weight loss, electrochemical impedance spectroscopy and potentiodynamic polarization studies. An attempt was made to correlate the molecular properties of neutral and protonated forms of inhibitor molecule using quantum chemical calculations. The effect of temperature on the corrosion inhibition efficiency was also studied using electrochemical impedance spectroscopy. The potential of zero charge was determined to explain the mechanism of corrosion inhibition.

The studies on corrosion inhibition performance of clozapine showed that it has good corrosion inhibition efficiency on the corrosion of copper in 1.0 M nitric acid and 0.5 M sulfuric acid solutions. The adsorption of clozapine molecules onto the copper surface obeyed the Langmuir adsorption isotherm. The value of free energy of adsorption calculated is very close to −40 kJmol⁻¹, indicating that the adsorption is through electrostatic coulombic attraction and chemisorption. The decrease in the value of energy of activation with the addition of inhibitor also shows the chemisorption of the inhibitor on the metal surface. The potential of zero charge and quantum chemical studies confirmed that the protonated molecules also get involved in the corrosion inhibition process through physisorption.

The present work indicates that clozapine can act as a good corrosion inhibitor for the corrosion of copper in acid media.

The purpose of this investigation is to study the corrosion behavior of iron and aluminum in HCl and NaOH media by means of theoretical and experimental approaches.

For theoretical investigations, the quantum chemical calculation was performed. In this regard, the adsorption of OH⁻ and Cl⁻ on iron and aluminum surfaces was investigated. Furthermore, the natural bond orbital for the direction and magnitude of charge transfer interactions were calculated. In addition, the electrochemical evaluations based on potentiodynamic experiments were carried out.

The quantum chemical calculation results showed that the charge transfer from OH⁻ to the iron surface is more than that from Cl⁻, and also the charge transfer from Cl⁻ is more than that from OH⁻ to aluminum cluster. Furthermore, these anions donate more electrons to the iron cluster than to the aluminum cluster. The experimental data showed that the rate of corrosion of iron in 1.0M NaOH solution was less than in 1.0M HCl solution. The corrosion of aluminum in HCl solution was less than that in NaOH solution. The rate of corrosion of iron in both solutions was less than that of aluminum.

The findings of this paper indicate that calculations based on the natural bond orbital analysis of the charge transfer rates from OH⁻ and Cl⁻ to the iron or aluminum surfaces, and their comparison with experimental results, exhibited excellent agreement.

The purpose of this paper is to investigate the inhibitive properties of black pepper extract (BPE) for aluminium in 1M hydrochloric acid (HCl) medium.

Gravimetric, electrochemical impedance spectroscopy, galvanostatic polarization, scanning electron microscopy with energy dispersive X-ray examinations (SEM-EDX) techniques were used to study the corrosion inhibitive study.

The gravimetric measurement indicates that inhibition efficiency shows direct proportional relation with concentration of inhibitor. The impedance results illustrates that there was a presence of protective layer of inhibitor adsorbed on the metal/solution interface. Polarization outcome showed that BPE is mixed type inhibitor. The existence of adherent layer of inhibitor on the Al surface was confirmed by SEM-EDX. Quantum chemical calculations were performed using the density functional theory at B3LYP/6-31G(d) level of theory to evaluate the activity of inhibitor molecules present in extract towards the corrosion inhibition of Al.

Due to the presence of large number of compounds in the extract, it becomes difficult to understand the most active compound responsible for inhibition. However, from gas chromatography mass spectrometry and quantum data, the approximation has been made that the major compound piperine present in the extract can be most probable component responsible for the inhibition activity. Further calculation of binding energy between Al and inhibitor molecules can be performed using Material Studio software.

The extract can be used in cleaning and etching solutions. It can be used to limit the loss of Al metal during etching process.

BPE can be used as a potential source of eco-friendly corrosion inhibitor for Al in HCl medium.