Anticorrosive characteristics of imidazole derivative on carbon steel in 1 M HCl

The novelty of the work is to scrutinize for the first time the 4R,5S-2,4,5-tris(4-ethoxy-phenyl


Introduction
Corrosion is an electrochemical process that occurs between metallic materials and the environment, resulting in metal dissolution, process contamination, environmental damage, and economic losses [1,2].Corrosion impacts a wide range of materials, from integrated circuits to reinforced concrete bridges.Metallic materials, and especially carbon steel, which are the primary building blocks for many structures, are highly susceptible to corrosion when they come into contact with moist environments, are submerged in fresh or salt water, or are in the presence of more or less corrosive solutions [3,4].The assistance life of supported concrete structures has been extended by the development of numerous innovative materials and technologies.These methods, such as chloride extraction, cathodic protection, protective coatings and sealants, significant relegalization, and corrosion inhibitor pinnacles, can prevent and reduce steel consumption in concrete.
One of the most efficacious, beneficial, dynamic, and financially rewarding strategies for preventing metal rust is the benefit of organic inhibitors [5,6].Organic substances with heteroatoms of oxygen, nitrogen, and sulfur often enclose the ability to prevent rusting [7][8][9][10][11][12].Organic compounds possess unshared electrons in bonds of π and heteroatoms that can be readily given to a metal vacant d orbital, rendering them effective inhibitors.
Imidazole and its derivatives are extensively used in the treatment of bacterial, viral, inflammatory, and cancerous conditions [13,14].Furthermore, it has been proven that imidazole possesses outstanding corrosion inhibition capabilities for concrete structures.It may function as a corrosion inhibitor to stop environmental corrosion of carbon steel since it contains nitrogen atoms in the imidazole ring and conjugated π-electron system [15,16].
The primary novelty of our study lies in scrutinizing the performance of new imidazole derivatives, namely (4R,5S)-2,4,5-tris(4-ethoxyphenyl)-4,5-dihydro-1H-imidazole (TEPI), that was utilized as an organic inhibitor in acidic medium.To assess the performance of TEPI as an inhibitor and the corrosion rate of C35E, electrochemical methods were used.The C35E surface and its corrosive medium were scrutinized through the combination of scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and UV-vis spectroscopy, respectively.Furthermore, theoretical calculations based on density functional theory (DFT), Monte Carlo (MC), and molecular dynamic (MD) simulation were used to back up the experimental findings.

Materials
The material that operated as the working electrode in electrochemical measurements is carbon steel (C35E), and its weight and chemical composition are offered in Table 1.The surface area of C35E samples serving as electrodes was 1 cm 2 .After polishing the electrode surface with various grades of Sic paper and prior to being desiccated at ambient temperature, the samples were scoured with distilled water.http://dx.doi.org/10.5599/jese.2136 3 By diluting hydrochloric acid of 37 % with distilled water, a corrosive medium of 1M HCl was produced.The concentration range of TEPI was 1 mM to 1000 nM, while its molecular structure is shown in Figure 1.

Electrochemical measurements
The 3-electrode cell was adopted for the electrochemical exams, with a saturated calomel serving as the reference electrode, a platinum wire as the auxiliary electrode, and C35E as the working electrode with an area of 1 cm 2 .The C35E electrode was first immersed in the test medium for 1800 s to obtain a reliable, steady-state value of open circuit potential (Eocp).After measuring the open circuit potentials, the electrochemical exams took place.The electrochemical impedance spectroscopy (EIS) was conducted Eocp, in the frequency range between 100 kHz and 10 mHz, and ac amplitude of 10 mV peak-to-peak, using 10 points per frequency decade.EIS diagrams were simulated using Z-view.Then, potentiodynamic polarization (PDP) was enrolled at the potential of -800 to -100 mV at a sweep speed of 0.5 mV s -1 .Inhibition performances ( / %) taken from EIS and PDP were determined using equations ( 1) and (2).ii i where icorr° and icorr1 denote the corrosion current densities before and after TEPI addition.where Rp1 and Rp0 denote the polarization resistances prior and after TEPI addition, respectively, while  is the surface coverage degree.
For the uninhibited solution, data from electrochemical measurements were taken from our previously published study [17].This decision was made as the experiments were conducted under identical conditions and with the same equipment.

Ultraviolet-visible spectroscopy
To better comprehend how the TEPI interacts with the C35E surface in an aggressive medium, as well as the development of iron-TEPI complexes, the inhibited and uninhibited solutions of 1.0 M HCl were subjected to UV-visible spectroscopy employing a JASCO V-700 UV-Visible spectrophotometer before, and after 3 days of C35E submersion.

Combination of scanning electron microscopy and energy dispersive X-ray.
The surface morphologies of C35E exposed to 1M HCl medium without and with 0.001M of TEPI for 24 hours at 303 K were investigated by SEM.It normally operates with an EDX unit and an acceleration voltage of 20 kV.SEM results obtained in the absence of the inhibitor were taken from the work already published by our research team [18].

Monte Carlo and molecular dynamic simulations
Materials Studio 8 software was used to evaluate the TEPI adsorption processes on the C35E surface.The Fe (110) surface simulation was carried out by putting the surface crystal in a cell measuring 2.732.703.71nm 3 using a 6-couche slab model for each layer, making up an (11×11) unit cell.The liquid phase was made up of 500 H2O, 5Cl -, and 5H3O + .On top of the liquid layer, a 40vacuum layer was created to prevent interaction between the surface and periodic repeating planes.The simulations were carried out at 303 K under NVT ensemble control using an Andersen thermostat.The simulation was performed by Forcite code in a COMPASS force field for 1000 ps with a time step of 0.1 fs.The diffusion of Cl − , H3O + , and H2O in inhibitor membranes was also simulated [27,28].

The polarization curves
Figure 2 depicts the polarization graphs at 303 K prior and after multiple amounts of TEPI added in the 1 M HCl medium.Table 2 supplies details on the relevant extrapolated electrochemical indices, such as corrosion potential (Ecorr), corrosion current (icorr), and cathodic and anodic Tafel slopes (c and a).A preliminary analysis of Tafel branches revealed that adding TEPI to the acidic environment lessens both anodic and cathodic current densities, implying that the presence of TEPI limits both C35E dissolving and cathodic hydrogen evolution.Furthermore, it is evident that the inhibitory effect of TEPI on the reduction of hydrogen (H + ) is considerably greater than on the C35E dissolution reaction.It is also noted that the cathodic segments of the polarization current potential curves result in Tafel lines that are nearly parallel.This phenomenon reveals that the process of hydrogen evolution remains unchanged with the addition of TEPI.Most likely, the reduction of http://dx.doi.org/10.5599/jese.2136 5 hydrogen ions on the C35E surface takes place mostly through a charge transfer mechanism [29].In this manner, the surface area available for H + ions became reduced while the actual reaction mechanism remains unaltered.Table 2 clarifies that TEPI amounts have a small effect on c but a big impact on a.Also, the a deviations display that TEPI affects the anodic process kinetics.The practically constant values of c for TEPI suggest that it was initially adsorbed onto the C35E surface and hindered by simply obstructing the C3E active sites without changing the cathodic mechanism.
The Ecorr value moved in the positive direction after the TEPI was added, and its shift is less than 27.66 mV, inferring that the TEPI performs as a mixed-type corrosion inhibitor [30].However, as the amount of TEPI rises, the icorr decreases, which could be owing to the TEPI adsorbing on the C35E surface.The inhibition efficiency rose with the TEPI amount, getting 97.7 % at 1 mM imidazole.TEPI offers high performance relative to the imidazoles mentioned in the literature, and this is due to the molecule's high electron densities provoked by the existence of π-electrons in the imidazole and ethoxy phenyl rings and lone pair electrons in nitrogen atoms.

Electrochemical impedance spectroscopy
The corrosion behavior of C35E in the acidic medium prior and after TEPI addition was investigated by measuring electrochemical impedance spectroscopy (EIS), and its outcomes are displayed in Figure 3.All collected impedance spectra display simply one depressed half-circle bonded to charge transfer during the corrosion process [31], and their size improves with rising TEPI concentration.The impedance loops do not produce perfect half-circles, typically ascribed to the roughness of the metal interface and/or frequency dispersion [32].Comparable capacitive loops might illustrate that, in the lack or presence of TEPI, the charge transfer mechanism controls the electrode reactions.The capacitive loop clearly grows when TEPI is present, showing a strong inhibiting impact of TEPI.A single-phase angle peak can be seen in the Bode graphs (Figure 4), implying a single time constant.The peak amplitude at intermediate frequency becomes more extensive as the concentration of TEPI increases, indicating the adsorption of more TEPI molecules on the C35E steel surface.This leads to a reduced metal dissolution rate [33].To derive the EIS information, the EIS spectra were simulated by applying the equivalent circuit portrayed in Figure 3, and the acquired information is tabulated in Table 4.In this circuit, Rs stands for the resistance of the electrolyte solution, CPE denotes the constant phase element characterizing the double-layer capacitance (Cdl), while Rp stands for the polarization resistance.To suit the EIS half-circles, CPE has been swapped for Cdl [34]: (3) where A denotes the coefficient of CPE, n denotes the exponent of CPE (dependent on a degree of surface roughness), i denotes the imaginary unit and  the angular frequency.As a result, Cdl is determined by employing the formula below [34]: Table 3 displays that χ 2 (Chi-square is the fitting precision) was close to 0.001, offering that this model provided an outstanding match for the EIS spectra.The Rp values expand with increasing TEPI amounts, whereas the Cdl values reflect an opposite trend, which might result from greater coverage on the C35 surface by TEPI adsorption, leading to improved inhibition performance.The diminution in Cdl implies a decline of the local dielectric constant and/or growth in the thickness of the electrical double layer, implying that the TEPI molecules perform via adsorption on the C35E/solution interface [35].Furthermore, the readings of n in the presence of TEPI were higher than in the absence of TEPI, signifying growth in the homogeneity of the C35E surface with adsorbed inhibitor [30].It is clear that the inhibition effectiveness was inhibitor amount dependent, reaching 98.3 % at 0.001 M, proving that TEPI is a potent corrosion inhibitor for C35 in the acidic medium.

Temperature influence and activation factors
The temperature has a powerful impact on corrosion rate and inhibitor performance, particularly in acidic medium.Corrosion happens more quickly as the temperature increases.The performance of inhibition of TEPI was investigated at various temperatures varying from 303 to 333 K prior and after the addition of 0.001 M TEPI for examining the mechanism of inhibition and estimating activation factors of the corrosion process by exploiting PDP experimentations presented in Figure 5.The related electrochemical indices are gathered in Table 4.
Figure 5 and data in Table 4 demonstrate that the growth in icorr becomes apparent when the temperature augments prior and after the addition of TEPI and that the improvement in the uninhibited solution is more noticeable when compared to the rise in the inhibited solution, meaning that the temperature rise slows the process of adsorption of TEPI molecules on the C35E surface.The effectiveness only dropped by 5.1 % when TEPI was present in the temperature range, demonstrating the potent inhibitory power of TEPI and its independence from temperature [35].The information on temperature influence was exploited to determine the activation kinetic parameters through Arrhenius and the transition-state relationships, Equations ( 5) and ( 6): where A denotes the Arrhenius pre-exponential factor, T is temperature, R is the universal gas constant, h denotes the Planck's constant, N denotes the Avogadro number, Ea symbolizes the energy of apparent activation, Ha denotes the enthalpy, and Sa denotes the entropy of apparent activation.
The magnitudes of Ea, Sa, and Ha listed in Table 5 were determined from the slope of Arrhenius plots (Figure 6a) and the intercept and slope of the transition state plots (Figure 6b), respectively.5 shows that the magnitude of Ea is augmented when TEPI is present, strongly pointing out that TEPI molecules are fixed to the C35E surface through physical adsorption (electrostatic interactions) [36].The corresponding magnitude of Ha for TEPI is higher than in its absence, suggesting that the dissolution of C35E becomes slower in the presence of TEPI.Furthermore, the magnitudes of Ha are both positive and reflect the endothermic character of the C35E dissolution process [37,38].Related magnitudes of Sa for TEPI were negative in its absence or presence in the medium.Besides, the magnitude of Sa for TEPI is higher than in its absence, exhibiting a rise in the disorder during the transformation of the reactants into activated complexes.

Adsorption isotherm
The thermodynamic details of the adsorption process assist in comprehending the inhibition mechanism for an inhibitor on the metal surface.Physical and chemical adsorption are two main kinds of interactions that may characterize molecular adsorption [39].In this context, the surface coverage values () (defined by Eq. ( 2)) for different TEPI concentrations can be calculated from the EIS data (Table 3) to present the best adsorption isotherm.Multiple attempts have been undertaken to fit the  values to adsorption isotherms, including Langmuir, Temkin, and Frumkin, as illustrated in Figure 7.The correlation coefficient (R 2 ) values and the slopes of the straight lines depicted in Figure 7 remain relatively close to unity for Temkin and Frumkin.At the same time, for Langmuir, http://dx.doi.org/10.5599/jese.2136 9 they are equal to unity.Therefore, the Langmuir adsorption isotherm demonstrates the best potential adsorption model of the TEPI molecules onto the C35E surface in the acidic medium, which may be formulated in linear terms as follows [32]: where Kads denotes the adsorption equilibrium constant.Equation ( 8) links Kads value to Gibbs free energy Gads 0 [32]: where R denotes the constant of universal gas and 55.55 stands for H2O concentration.The values of Gads 0 and Kads are listed in Table 6.The high magnitude of Kads demonstrates that TEPI molecules adsorb powerfully on the C35E surface [39].The Gads 0 value means the TEPI molecules are chemisorbed at the C35E surface [40].The TEPI molecules contributing lone electron pairs and/or electrons and Fe empty orbitals work together to form chemical bonds with Fe unfilled orbitals.

UV-visible spectroscopy
The complexation process between Fe ions and the inhibiting molecules can be utilized to investigate the underlying mechanism of anticorrosion prevention of carbon steel since Fe is an essential element of C35E.The earlier study, however, revealed that a modification in wavelength with the increase or decrease in absorbance implies the development of a complex involving Fe and molecules present in the corrosive medium [41].The UV-visible spectrum of TEPI in the acidic medium prior to C35E submerging showed two absorption bands at 210 and 273 nm because of an n-π* and π-π* electronic transitions, resulting from the heteroatoms lone pair on the pyridine ring (Figure 8).After 3 days of C35E submerging, the bands appeared to have shifted blue (the first to 207 nm and the second to 255 nm), with a rise in absorbance.These modifications occurred probably due to the formation of complexes among Fe 2+ ions and TEPI species in the acidic medium.

SEM/EDX analysis
Figure 9 shows the scanning electron micrographs of C35E samples prior and after 24 h of soaking in 1 M HCl, without and with 1 mM of TEPI at 303 K. Figure 9a1 displays the polished steel sample without flaws other than polishing scratches.In Figure 9b1, the specimen surface was poorly harmed, with profound holes indicating severe corrosion.When TEPI was added to the 1 M HCl medium, the C35E surface area exhibited a few small pinholes and low damage (Figure 9c1), demonstrating its strong ability to reject corrosive ions.This ability generally results from TEPI adsorption on the C35E surface by developing a protective and compact film.
The EDX spectra presented in Figures 9a2-8c2 show characteristic peaks of prevailing elements such as Fe, C, Mn and Cr, constituting C35E samples (cf.Table 1).Also, the presence of oxides visible through the O peak is prominent for C35 samples left in 1.0 M HCl, without and with the presence of 1 mM TEPI inhibitor.
Table 7 summarizes all EDX results presented as wt.% and at.% of identified elements of C35E samples before and after 24 hours of immersion in 1.0 M HCl, without and with 1 mM TEPI.It appears that the at.% of chlorine ions in the absence of TEPI is 46.30%, whereas it decreases to 0.38 % in its presence.The reduction of Cl -ions in the presence of TEPI suggests that this inhibitor can be deposited on the C35E surface, protecting against attack by Cl -ions.The percentage of atomic content of iron (Fe) for C35E immersed in the 1M HCl is 46 %.However, when C35E was dipped in the optimal concentration (1 mM) of TEPI, it increased to 83.29 %.This increase suggests that the presence of TEPI hinders the dissolution reaction of C35E in the acidic solution.Additionally, the percentage atomic content of oxygen (O) significantly decreased from 46.30 to 33.66 %.Conversely, the percentages for nitrogen (N) show a notable increase from 0 to 3.76 % in the presence of TEPI.These findings confirm the presence and formation of a protective film of TEPI on the C35E surface in 1 M HCl.

Properties of TEPI based on DFT calculations
Quantum computing based on the DFT method allows us to support experimental conclusions.To do this, we started by determining the exact geometry of the evaluated inhibitor for its neutral (TEPI) and protonated (TEPI-H) forms, optimizing the geometry of each form without any geometric restrictions, and identifying the frontier molecular orbital density distributions and other quantum chemical descriptors for each form.
Figure 10 shows the most stable configuration of the inhibitory molecule in its TEPI and TEPI-H forms.The distribution of HOMO and LUMO molecular orbitals and the electron density mapped with the iso-surface of the electrostatic potential (ESP) are shown in Figure 11.A closer analysis of HOMO distribution shows that it has a total localization of electron density at surface level.This suggests a high electron-donating capacity due to many local sites favoring the adsorption of this molecule to the metal surface in question.However, the LUMO distribution takes place at the level of an ethoxyphenyl structure, and the dihydro-imidazole of the molecule studied shows that these two parts are ready to receive electrons.These HOMO and LUMO distribution properties may lead to parallel adsorption with the Fe(110) metal support.This observation is well illustrated by the calculation of the electron density mapped with the iso-surface of the electrostatic potential (ESP) (Figure 11).The potential areas, both positive and negative, are represented by the colors red and blue, respectively.Oxygen and the non-protonated nitrogen atoms are the sites most vulnerable to electrophilic attack, further promoting adsorption power on the metal surface.The values of the calculated descriptors are presented in The HOMO (LUMO) energy value is associated with the electron-donating (accepting) ability of the corrosion inhibitor [42].The high energy value of the HOMO indicates that it is easier for the TEPI to donate electrons to empty d orbitals in metals, which facilitates good adsorption and increases the value of corrosion inhibition efficiency.
In general, a low value of (ΔE) signifies that the molecule strongly interacts with the metal surface and acts as an effective corrosion inhibitor [43].While it is difficult to discuss this parameter without comparing it with that of a similar compound, it is important to note that the energy gap of the TEPI in neutral and protonated forms is low (Table 8), especially in the protonated form, compared to numerous of mentioned corrosion inhibitors [43,44].This observation confirms that the TEPI can easily adsorb on the metal surface, causing higher protection.The calculated global reactivity descriptors show that this molecule has a high nucleophilic power.This is consistent with the value of the calculated electron transfer index (0.319 and 0.182 for TEPI and TEPI-H, respectively), which, according to Koopmans, improves corrosion inhibition effectiveness [45].The high values of the dipole moment and the polarizability of the proposed molecule (the dipole moment and the polarizability for the neutral form are 3.173 D and 413.496 a.u, respectively, and are 7.955 and 417.187D for the protonated form) are also in agreement with this conclusion.
The calculated quantum descriptors show high structural chemical reactivity for both forms, with high inhibitory efficacy, which was experimentally proven.

Monte Carlo and molecular dynamic simulation results
To evaluate the properties of the proposed TEPI molecule as a corrosion inhibitor and to show its behavior with respect to the metallic surface, Monte Carlo (MC) and molecular dynamic (MD) simulations were performed.The objective of this simulation was to determine the lowest adsorption energy of our molecule when it is in contact with the iron surface by looking for its spontaneous configuration both in a vacuum and in an aqueous medium and finding its binding and interaction energy.
Recall that the binding and interaction energies are calculated from the energy of the total energy of the entire system (ETotal), the energy of the inhibitor (EInhibitor), and the energy of the Fe (110) surface (ESurface) according to equations ( 9) AND (10).
Figure 12 shows the adsorption configuration of the TEPI inhibitor molecule on the metal surface, with the structural arrangement leading to the most stable adsorption energy.The energy results of this simulation, performed in aqueous medium, are summarized in Table 9.
The results of this study suggest that the proposed molecule can be a good corrosion inhibitor for steel since it has a high affinity towards the metallic surface.Its mode of adsorption is parallel and nearby, with significant adsorption energies in both phases.This adsorption energy becomes very high even in a corrosive medium (presence of H2O, H3O + and Cl -), which indicates an easy and stronger interaction between the TEPI organic molecule and steel.TEPI can adsorb efficiently on the metal surface in its neutral or protonated form thanks to the oxygen and nitrogen atoms of the imidazole ring and the phenyl rings.The presence of the oxygen atoms strengthens the polarity of the tails (ethoxyphenyl) of the molecule, which allows effective coverage of the surface and improves its inhibition properties.
To confirm these results and predict the binding energy, a molecular dynamic simulation was performed, and the equilibrium of the system was evaluated and confirmed by the stable average values of the energy fluctuations, taking into account the temperature factor (at experimental temperature 303 K).This simulation showed that the molecule can efficiently adsorb onto the surface while maintaining its orientation.The data in of the molecule with the Fe surface are very high and positive, suggesting a high stability of the adsorbed molecule [46,47].
The results of the MD and MC simulations show high adsorption of the two forms studied on Fe (110), which indicates that the inhibitor studied is highly effective against the corrosion phenomenon, as was already reported in the experimental section.

Corrosion inhibition mechanism
PDP findings confirmed the mixed nature of TEPI adsorption with the predominant cathodic type.Furthermore, the values of adsorption and thermodynamics parameters show that adsorption processes are both chemically and physically based.Therefore, the mechanism of corrosion inhibition could be explained by the adsorption process of the inhibitor onto the metal surface.It is reasonable to assume that TEPI molecules in the HCl medium may exist in the protonated form in equilibrium with the equivalent neutral molecular form according to: TEPI + xH + ↔ (TEPIH) x+ (11) At first, a significant number of Cl -ions from the HCl medium was adsorbed onto the positively charged C35E surface, creating a negative charge region.Subsequently, the protonated (TEPIH) + would be electrostatically adsorbed (physisorption) on this newly generated negatively charged surface, forming a protective film (FeCl -TEPIH + )ads and thus preventing the anodic corrosion reaction.Similarly, the cathodic reaction mechanism can be described as follows: Fe + H + → (FeH + )ads (12) (FeH + )ads + e -→ (FeH)ads + H + + e -→ Fe + H2 ↑ The protonated (TEPIH) + ions were also adsorbed in the cathodic sites, where they compete with H + for electrons, reducing the production of H2.
In addition to physisorption, chemisorption can occur by the displacement of pre-adsorbed water molecules from the C35E /aqueous medium interface.The O atoms (ethoxy) and/or N atoms of the imidazole ring might establish coordination bonds with the vacant d-orbital of iron atoms using their free electron pairs.Furthermore, the excess negative charge collected on the C35E surface can be transferred from the iron d-orbital to the empty π* orbital of TEPI molecules (retro-donation) (Figure 13), boosting TEPI adsorption on the C35E surface.Finally, the adsorbed inhibitor layer was formed on the C35E surface, acting as a barrier between C35E and 1 M HCl medium and preventing acid corrosion of C35E steel.

Conclusion
The findings of this investigation reveal that TEPI is a good inhibitor of C35E steel corrosion in 1 M HCl at 303 K.It has been encountered that when the amount of TEPI rises, the effectiveness values for inhibition rise noticeably, achieving about 97 % in 1 mM HCl.According to the findings of PDP, TEPI is functioning as a mixed-type inhibitor.Adsorption of TEPI on the C35E steel surface in 1 M HCl rules the Langmuir adsorption isotherm model.Both SEM and UV-vis confirm that TEPI has an adsorption action on the surface of the C35E.In the same way, the calculated quantum descriptors show high structural chemical reactivity for both forms, with high inhibitory efficacy as experimentally proven.The results of the MD and MC simulations show strong adsorption of the two forms studied on Fe (110), providing better protection for the steel in question.

2 )EFigure 2 .
Figure 2. PDP segments for C35E corrosion in 1 M HCl ahead of and after TEPI addition

2 Z r / W cm 2 Figure 3 .Figure 4 .
Figure 3. EIS plots of C35E corrosion in 1 M HCl prior and after TEPI addition

Figure 5 .
Figure 5. PDP segments for C35E corrosion in 1 M HCl without (a) and with 1 mM of TEPI (b) undertemperatures varying from 303 to 333 K

Figure 6 .
Figure 6.Arrhenius (a) and the transition-state (b) plots for C35E dissolution in 1 M HCl prior and after the addition of 1 mM TEPI

Figure 7 .
Figure 7. Various isotherm models for C35E in 1 M HCl with 1 mM TEPI at 303 K

Figure 8 .
Figure 8. UV-visible absorption spectra of 1 M HCl containing 0.001M of TEPI prior and after C35E dipping

Figure 9 .
Figure 9. SEM/EDX for C35E prior (a) and after 24 hours of soaking in 1 M HCl (b) and with 1 mM of TEPI (c) at 303 K (a1) and (b1) images are taken from 18.

Figure 12 .
Figure 12.Top and side views of the equilibrium adsorption geometries of TEPI and TEPI-H on the Fe (110) surface in aqueous medium

Table 1 .
Chemical composition and element weights of carbon steel C35E

Table 4 .
PDP factors for C35E corrosion in 1 M HCl without and with 1 mM of TEPI under temperatures varying from 303 to 333 K

Table 5 .
Ea, Ha and Sa values for C35E dissolution in 1 M HCl prior and after the addition of 1 mM TEPI

Table 7 .
Percentages of atomic and weight contents of elements of C35E surface in the absence and presence of 0.001M TEPI obtained from EDX spectra

Table 8 .
Calculated values of quantum chemical descriptors of TEPI in aqueous medium generated from the B3LYP/6-31G(d,p) level

Table 9 .
The output energies calculated by MC simulation for adsorption of the studied inhibitor on Fe (110) surface in vacuum and aqueous medium *dEads -change in adsorption energy, dNi -change in the quantity of molecules adsorbed

Table 10 .
MD simulation of TEPI and TEPI-H onto a Fe (110) surface at 303 K yielded interaction and binding energies Table 10 also indicate that the binding energies http://dx.doi.org/10.5599/jese.213615