A Theoretical Approach to the Study of Some Plant Extracts as Green Corrosion Inhibitor for Mild Steel in HCl Solution (original) (raw)
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Jurnal Teori dan Aplikasi Fisika, 2022
Steel is a material that has low resistance to corrosion when interacting with a corrosive environment. The application of natural extracts as green inhibitors is able to provide good performance in inhibiting corrosion of steel with high inhibition efficiency. Natural extracts that are effective and efficient as corrosion inhibitors on steel are those which in their compound structure contain heteroatom groups (such as O, N, S, P) and aromatic rings. This work provides an important comparative overview for the development of green inhibitor natural extracts in steel. The results of theoretical studies based on quantum mechanics with the DFT method at the atomic level based on molecular orbitals, chemical quantum parameters, and adsorption characteristics show results that are in accordance with experimental studies. The frontier molecular orbital (FMO) plot shows the distribution of electron density in the HOMO-LUMO region as a predictor of the active site of the inhibitor molecule interacting with the steel surface. Quantum chemical parameters such as ionization potential (I), electron affinity (A), absolute electronegativity (χ), hardness (η), softness (σ), fraction of electrons transferred (ΔN), electrophilicity (ɷ), and electron backdonation (ΔEback-donation) was calculated to obtain a correlation between the electronic properties of the inhibitor molecule and the corrosion inhibition potential. The results of the calculation of the quantum chemical parameters show the reactivity of the inhibitor molecule which has a very good potential to interact and bind strongly to the steel surface. This has the potential to make the inhibitor molecule have a high inhibition efficiency. Chemical adsorption and/or physical adsorption by forming complex compounds between inhibitor molecules and the steel surface are corrosion inhibition mechanisms to protect steel from a corrosive environment.The development of future studies should be able to display the mechanism of interaction and inhibition of inhibitor molecules in more detail and systematically at the atomic level on several metal surfaces such as Fe, Al, Cu, and others.
The resolution of ambiguity usually associated with the characterisation of adsorption process of the plant extracts as corrosion inhibitors for metal corrosion was achieved through the use of Adejo-Ekwenchi adsorption isotherm using the case of corrosion inhibition of mild steel corrosion in 2 M HCl by ethanol leaf extract of Hyptis suaveolens poit. The study was carried out using the weight loss method at the temperature range of 301 K to 313 K. The inhibition efficiency, %IE, was found to decrease with increase in temperature, suggestive of physical adsorption (physisorption) mechanism. The observed decrease in the value of parameter b of the Adejo-Ekwenchi isotherm is a confirmation of a physisorption for adsorption of this extract onto the metal surface. By the use of R2 and Gads this adsorption would be thought to well fit into Langmuir, Freundlich, Temkin and El-Awady. But the adsorption process best fit the Langmuir isotherm, as resolved through the Adejo-Ekwenchi isotherm. Implicitly, this is one clear case of emerging trends for sustainable development and human capacity building as focus is now on plant extracts, away from synthetic inhibitors, as eco-friendly inhibitors for metal corrosion prevention due reasons like cost, strict environmental regulations, renewability and biodegradability. The design and development of new and effective inhibitors will only be possible if adsorption of inhibitor onto the metal surface is clearly understood.
Journal of Advanced Chemical Sciences, 2017
The use of Ficus carica (FC) and Vitellaria paradoxa (VP) as corrosion inhibitors using weight loss measurements at 303, 313, 323 and 333 K has been reported. In this present study, quantum chemical studies using the molecular-modelling program hyperchem are employed to give an insight into the mechanism of inhibition of FC and VP. The quantum chemical parameters obtained in this study include Energy of highest occupied molecular orbital, EHOMO (eV), energy of lowest unoccupied molecular orbital, ELUMO (eV), energy gap, EL-H, (eV), dipole moment, (D) absolute electronegativity, hardness, ionization potential, and electron affinity. The values of quantum chemical descriptors obtained reveal that both FC and VP inhibited the corrosion of aluminium but FC shows better performance. The presence of alkaloids, glycosides, saponins and tannins (having –C=O, C-OH, C=C, OH -CH3, etc groups) was found to have contributed greatly to the inhibition process by interacting with the aluminium surf...
Quantum mechanics calculations have been applied within the framework of the density functional theory (DFT) to five major molecules of Aloes extract namely; Anthranol (AN), Aloin-Emodin (AE), Aloin Barbaloin (AB), Chrysophanol glycoside (CN) and Rutin (RT) recently investigated as corrosion inhibitor for mild steel in 1.0 M HCl in order to determine the structural and electronic parameters of the molecules responsible for imparting on the extract its high inhibition efficiency as corrosion inhibitor. The electronic parameters calculated include: E HOMO , E LUMO , energy gap () etc,. The calculated results show that all the molecules have high propensity as electron donors, have low and (high reactivity), are good nucleophiles characterized by low values of , and the energy change associated with the charge transfer to the mild steel surface E, are all favourable (negative). Our result confirms the generally held assumption that there is a synergistic effect between the different organic molecules present in plant extracts towards enhancing the corrosion inhibition of these extracts on metals and alloys in varied aggressive media.
South African Journal of Chemistry, 2019
The inhibitive performance of Sapium ellipticum leaf extract as green corrosion inhibitor for carbon steel in varying concentrations in hydrochloric acid has been investigated. To determine the adsorption strength and phenomenon of inhibition, density functional theory was adopted to model the molecular structure of the extract. Also to evaluate the inhibition efficiency weight loss, electrochemical method and statistical modelling was employed. Optimum inhibition efficiency of 89 % was achieved from electrochemical study at conditions of 1.5 g L-1 SE concentration, temperature of 303 K and 1 M HCl, respectively. The electrochemical study signifies that the phenomenon of inhibition is under mixed control and the inhibition process is in accordance with Langmuir isotherm. Fourier transform infrared spectroscopy (FTIR) of the corrosion particles and surface examination (SEM) confirms the existence of the protective film on the metal surface through the adsorption of extract species.
Root and root bark extracts of Xylopia aethiopica (XE) have been evaluated as corrosion inhibitors for mild steel in aerated 0.1 M HCl and H 2 SO 4 solutions by gravimetric method. The inhibition efficiency increases with increase in inhibitor concentrations. Adsorption mechanisms for the adsorptions of XE extracts' molecules were predicted using the following adsorption isotherms (Langmuir, Freundlich, Temkin and El-Awady) by linear regression. With the aid of Chi-square (X 2) statistic, the best fitted adsorption isotherms were selected. Physisorption mechanisms have been proposed for the extracts in the studied acidic media. Quantum chemical calculations gave some electronic properties of the molecules of XE extracts so as to ascertain any correlation(s) between the corrosion inhibition and molecular structures. 1.0 Introduction Mild steel and its alloys have proved to be strategically important materials and have extensive uses in fertilizer, oil and metallurgical industries. Engineering systems depend upon corrosion protection for their reliability, performance and safety. However, the applications of steel in industrial acid cleaning, acid pickling, acid descaling and oil well acidizing, involve contacts between acidic media and steel which cause the metal to corrode [1]. The use of corrosion inhibitors had been shown to be the most effective and efficient practical way of preventing metal corrosion. The toxicity of most synthetic corrosion inhibitors have brought severe criticisms against their uses because they pose environmental hazards, therefore, the use of natural products of plant origin as corrosion inhibitors at present is encouraged because they are eco-friendly. Most of the efficient corrosion inhibitors contain nitrogen, oxygen, sulphur, double and triple bonds. The availabilities of lone pairs of electrons and π bonds existing in their molecules have been reported to inhibit metal corrosion in acidic media by adsorption on metal surfaces via these sites. These inhibition abilities of corrosion inhibitors have been shown to depend on [2, 3]: (i) the chemical structure of the compound, (ii) the surface charge of the metal, and (iii) the type of interactions between the inhibitor molecules and the metal surface. In corrosion inhibition studies, many methods of investigation have been employed and they include: gasometric [4], electrochemical impedance spectroscopy [5, 6, 7], weight loss [8, 9, 10, 11, 12], polarization [13, 14], UV/visible spectrophotometric [15], and so on. These aforementioned techniques involve the measurements of change in hydrogen gas evolved, change in spectrum/graph generated due to change in electrical current of electrolytes, change in weight loss of metal, change in corrosion reaction temperature, change in electrical resistance of an electrolyte (majorly) due to accumulation of gaseous molecules on the electrode, change in the shape of spectrum and wavelength of absorption maxima respectively. The use of any of the mentioned techniques depends on the economic buoyancy of the researcher. In any case, results obtained from any of these techniques are valid and reliable. However, the weight loss method of monitoring corrosion rate is useful because of its simple application and reliability. Quantum chemical calculation is usually used to study the correlations between the corrosion inhibition and molecular properties of inhibitors. Recently, Density Functional Theory (DFT) has become an attractive theoretical method because basic parameters for even huge complex molecules at low cost. Also, the application of DFT now extends to explanation of some empirical molecular properties such as corrosion inhibition with quantum mechanics. Therefore, DFT is a very powerful technique to probe the inhibitor/surface interaction and to analyze experimental data [2]. The need for a cheap, renewable, easily available and eco-friendly source of material as corrosion inhibitor has therefore attracted us to investigate the mild steel corrosion inhibition properties of Xylopia aethiopica in acidic media. 2.0 Experimental 2.1 Materials preparation The sheet of mild steel used has the following composition (%): C 0.05; Mn 0.6; P 0.36; Si 0.3; balance Fe. The mild steel sheet was mechanically press-cut into coupons of dimension 5 × 2 × 0.04 cm. These coupons were
TECHNOLOGIES AND MATERIALS FOR RENEWABLE ENERGY, ENVIRONMENT AND SUSTAINABILITY: TMREES19Gr, 2019
To solve the problem of environmental pollution during the metal cleaning process, new compounds extracted from biodiesel such as Pyropyl-Gallate (L1), Pyrogallol (L2), 4-Methyl-catecho (L3) and Protocatechuic-acid (L4) were investigated as green corrosion inhibitors by using density functional theory (DFT) and Molecular dynamic simulation (MDS) methods. The computed quantum chemical parameters obtained from DFT for instance the total energy , the energy of the highest occupied molecular orbital , the energy of the lowest unoccupied molecular orbital , the dipole moment µ and the polarizability (α) indicate that those examined molecules were efficient corrosion inhibitor. The tested molecules present a general planar structure. This structure unit may be in favor of the important interaction zone if the molecule adsorbed on the metal surface at nearly 0° contact angle. As can be seen from Molecular electrostatic potential (MEP), it is clear that more electron rich regions are largely located around the heteroatoms and the conjugated double bonds, means that L1, L2, L3 and L4 can promote the formation of a complex on the metal surface by transferring electrons and forming a coordinate covalent bond through the chemical adsorption. From MDS study, the binding energy of the adsorption system (Inhibitor-Fe) is more important, showing that this adsorption system is very stable, and has high inhibitory efficiency. According to the study of quantum chemistry, the oxygen atoms of the molecules tested can give electrons to the unoccupied iron orbital "d" to form coordination bonds while the orbital π of aromatic rings can accept electrons from the iron orbital "d" to form coordination bonds. A good agreement was found between DFT and MDS methods.
The adsorption of ethanolic root extract of Portulaca oleracea as corrosion inhibitor for the corrosion of mild steel in H 2 SO 4 medium at the temperature range of 305K to 315 K was studied using weight loss method and characterized using the common adsorption isotherms. The inhibition efficiency, IE%, was found to increase with both increase in the inhibitor concentration and rise in temperature. The increase in IE% with rise in temperature is suggestive of chemisorption. The adsorption best fitted the Langmuir, El-Awady, Temkin and Adejo-Ekwenchi isotherms. Evaluated values of free energy, ΔG ads , of the adsorption process were found to be all negative, indicative of spontaneity of the adsorption process and values obtained through the Temkin were above -20 kJ/mol, supportive of the chemisorption. The fact that the slopes and intercepts of the ideal Langmuir isotherm (ILI) plots were not unity and zero, respectively, signifies a deviation from this isotherm but the deviation cannot be said to be much as ΔG ads values obtained through modified Langmuir isotherm (MLI) are not quite different from those of ILI. The adherence of the adsorption to the Temkin isotherm is evidence evident of chemisorption, which was made evidently made clear from the Adejo-Ekwenchi b parameter. The exact number of water molecules replaced by inhibitor molecules could not be ascertained by Bockris-Swinkels isotherm.
The adsorption of ethanolic root extract of Portulaca oleracea as corrosion inhibitor for the corrosion of mild steel in H 2 SO 4 medium at the temperature range of 305K to 315 K was studied using weight loss method and characterized using the common adsorption isotherms. The inhibition efficiency, IE%, was found to increase with both increase in the inhibitor concentration and rise in temperature. The increase in IE% with rise in temperature is suggestive of chemisorption. The adsorption best fitted the Langmuir, El-Awady, Temkin and Adejo-Ekwenchi isotherms. Evaluated values of free energy, ΔG ads , of the adsorption process were found to be all negative, indicative of spontaneity of the adsorption process and values obtained through the Temkin were above -20 kJ/mol, supportive of the chemisorption. The fact that the slopes and intercepts of the ideal Langmuir isotherm (ILI) plots were not unity and zero, respectively, signifies a deviation from this isotherm but the deviation cannot be said to be much as ΔG ads values obtained through modified Langmuir isotherm (MLI) are not quite different from those of ILI. The adherence of the adsorption to the Temkin isotherm is evidence evident of chemisorption, which was made evidently made clear from the Adejo-Ekwenchi b parameter. The exact number of water molecules replaced by inhibitor molecules could not be ascertained by Bockris-Swinkels isotherm.
Journal of Bio- and Tribo-Corrosion, 2020
The purpose of this study is to identify the green corrosion inhibitors of brass in a 3% NaCl solution. Potential corrosion inhibition compounds extracted from the essential oil (EO) and the hydrosol (HY) of Moroccan Thymbra capitata (L.) Cav. (Lamiaceae) were tested and characterized. Gas chromatography coupled with mass spectrometry (GC-MS) method was used to identify the chemical composition in EO and HY. The electrochemical analysis was conducted using potentiodynamic polarization curves and impedance spectroscopy (EIS) techniques. The results obtained show a high percentage of carvacrol for both EO (85.96%) and HY (98.04%). In addition, the corrosion rate of brass decreased with increasing concentrations of EO and HY in the presence of 3% NaCl. Unexpectedly, the maximum inhibition efficiency was recorded for HY (93.04%) then for EO (84.90%) in a 3% NaCl medium. The protective film adsorbed on the brass surface when using the two green extracts was analyzed using scanning electron microscope (SEM), coupled with energy-dispersive X-ray analysis (EDX). The surface morphology showed a good inhibition for HY compared to that of EO. Computational studies, using density function theory (DFT) and Monte Carlo (MC) simulations, confirmed the experimental results, this allowed us to understand that the high inhibition efficacy of HY is likely associated with the synergistic effect between carvacrol and eugenol despite this latter low percentage (0.50%) in our extract. This study also enabled us to suggest an inhibition mechanism of carvacrol and the synergistic effect between carvacrol and eugenol, which increase the corrosion inhibiting effect of HY.