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Inhibitive properties, thermodynamic and quantum chemical studies of alloxazine on mild steel corrosion in H2SO4
Abstract
Alloxazine (ALLOX) was tested as corrosion inhibitor for mild steel in 0.5 M H2SO4 solution using non-electrochemical technique (gravimetric and UV–Visible spectrophotometric measurements) at 303–333 K. ALLOX acts as inhibitor for mild steel in acidic medium. Inhibition efficiency increases with increase in concentration of ALLOX but decrease with rise in temperature. The adsorption of ALLOX was found to follow Temkin adsorption isotherm model. Both the activation and thermodynamic parameters governing the adsorption process were calculated and discussed. The adsorption follows a first-order kinetics. DFT study gave further insight into the mechanism of inhibition action of ALLOX.Research highlights► Alloxazine (ALLOX) is found to be a good inhibitor for the corrosion of mild steel in 0.5 M H2SO4. ► The adsorption of ALLOX on mild steel surface was found to accord with the Temkin adsorption isotherm and also follows the first-order reaction. ► The corrosion inhibition is satisfactorily discussed by both thermodynamic and kinetic parameters. ► The inhibitive mechanism is explained by UV–Visible spectroscopy and quantum chemical calculation results.
... The Freundlich isotherm (Figure 8, Freundlich) does not accurately represent an adsorption model for HKER at temperatures of 298 K and 308 K, respectively, the regression coefficients (R 2 ) being lower than 0.99. In the following, the Temkin isotherm and El-Awady's adsorption model will be comparatively presented using their respective linear expressions, represented by Equation (26) (Temkin) [32,51,52] and Equation (27) (El-Awady) [32,53], respectively. ...
... As can be seen from Equation (26) In the following, the Temkin isotherm and El-Awady's adsorption model will be comparatively presented using their respective linear expressions, represented by Equation (26) (Temkin) [32,51,52] and Equation (27) (El-Awady) [32,53], respectively. ...
... As can be seen from Equation (26), by plotting θ = f [ln(C−HKER)], straight lines are obtained, with the slope equal to 1/f and the intercept equal to [(1/f )lnK ads ], from which K ads is easily deduced [32,51,52]. By analogy, using Equation (27), from the plot of log θ 1−θ = f (logC), straight lines are obtained, with y-slopes and intercept equal to logK. ...
Reducing the impact of some biological fluids on bioimplants involves the control of surface characteristics by modeling the interface architecture and assembling ecofriendly thin films to retard corrosion. Therefore, a mixture of hydrolyzed keratin peptides (HKER) was investigated as a corrosion inhibitor for 304L stainless steel (SS) in physiological serum (PS), using electrochemical measurements associated with optical microscopy and atomic force microscopy (AFM). The tests, performed for various concentrations of the inhibitor at different temperatures, showed that the inhibition efficiency (IE) decreased with a rise in temperature and proportionally increased with the HKER concentration, reaching its maximum level, around 88%, at 25 °C, with a concentration of 40 g L−1 HKER in physiological serum. The experimental data best fitted the El-Awady adsorption model. The activation parameters (Ea, ∆Ha and ∆Sa) and the adsorption ones (∆Gads0, ∆Hads, ∆Sads) have highlighted a mixed action mechanism of HKER, revealing that physisorption prevails over chemisorption. AFM parameters, such as the average roughness (Ra), root-mean-square roughness (Rq) and maximum peak-to-valley height (Rp−v), confirmed HKER adsorption, indicating that a smoother surface of the 304L stainless steel was obtained when immersed in a PS-containing inhibitor, compared to the surface designed in blank solution, due to the development of a protective layer on the alloy surface.
... The degree of surface coverage (θ) was determined as IE/100 [16,38,42,51], taking into consideration its average values obtained from the potentiodynamic polarization (PDP) and, also, from the electrochemical impedance spectroscopy (EIS). ...
... According to the Temkin adsorption isotherm, θ is dependent on the inhibitor concentration as shown in Equation (3) [51]. ...
... Equation (3) is logarithmized and, after rearranging the terms, the linearized form of the Temkin adsorption isotherm is obtained (Equation (4)). where: K (L mol −1 ) represents the adsorption-desorption constant; α is a factor describing the inhibitor interactions with the substrate; the positive value of α indicates an attractive behavior of the inhibitor for the substrate; if α is negative, it suggests substrate repulsion for layer adsorption [51]. ...
Potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) were applied to study the inhibitory effect of N-acetylcysteine (NAC) on corrosion inhibition of carbon steel in hydrochloric acid solution. N-acetylcysteine influenced the iron dissolution to a greater extent than the hydrogen evolution reaction acting as a mixed inhibitor, predominantly anodic. The charge transfer resistance (Rct) gradually increased with the inhibitor concentration. From both methods, the inhibition efficiency (IE) reached a value of 89 ± 1% and NAC adsorption followed the Temkin isotherm. The value of adsorption Gibbs energy (ΔGadso), around −35 kJ mol−1, indicated a spontaneous adsorption and mixed action mechanism, with NAC chemical adsorption prevailing over physical one. New data will be reported by the computational study, that was performed using the density functional theory (DFT) method in aqueous phase. Quantum chemical descriptors were determined by B3LYP theory level with 6–31G+(d) basis set. Metropolis Monte Carlo atomistic simulation was used to reveal the adsorption configuration and interactions between acetylcysteine molecules and the carbon steel surface. Theoretical results were consistent with the experimental data, showing that the inhibitor action mechanism consisted of mainly chemisorption of its molecules on the carbon steel surface accompanied by van der Waals forces and electrostatic interactions.
... The value of E LUMO , on the other hand, is proportional to the molecule's ability to receive electrons [40][41][42]. A molecule with a higher E HOMO value and/or lower E LUMO value tend to have a higher %IE [43][44][45][46]. From Table 1, we can understand that all the calculated values of E HOMO and E LUMO strongly adhere to the following order: honey > mint, which matches well with that of the IE. ...
... Another useful parameter, dipole moment (µ), can be used to see the connection between the inhabitation and molecular structure of the inhibitor. In general, the higher value of µ reveals that the adsorption of the molecule into the metal surface is strong, and results in a higher value of IE [46,47]. We can see in Table 1 that the dipole moment of these two compounds is consistent with the order: honey is greater than the mint except for PM3 and RM1 methods, which explains the priority of honey over mint in inhibitory properties. ...
... The value of ELUMO, on the other hand, is proportional to the molecule's ability to receive electrons [40][41][42]. A molecule with a higher EHOMO value and/or lower ELUMO value tend to have a higher %IE [43][44][45][46]. From Table 1, we can understand that all the calculated values of EHOMO and ELUMO strongly adhere to the following order: honey > mint, which matches well with that of the IE. ...
Environment-friendly materials (e.g., Honey and Mint) are used as corrosion inhibitors for aluminum in hydrochloric acid (HCl) using both the density functional theory (DFT) at the B3LYP/6–31G* basis set level and semi-empirical methods (AM1, PM3, MINDO, and RM1). The aim of this study is to investigate the inhibition efficiency (%IE) in terms of their molecular structure. The quantum chemical parameters such as the highest occupied molecular orbital energy (EHOMO), the lowest unoccupied molecular orbital energy (ELUMO), the energy gap (ΔE), the charge on the reactive core, the hardness (η), and the total energy have all been computed. The MINDO method was used to measure the electronic energies and charge densities of the inhibitors that were used. Theoretical calculations were also carried out, with the findings correlating well with the experimental data. Gravimetry and gasometry measurements were used to investigate the effects of honey and mint on aluminum corrosion in a 1.0 M hydrochloric acid (HCl) solution. In acid solutions, honey and mint were found to be effective inhibitors of aluminum corrosion, with honey being the better option. Because of the adsorption of its components on aluminum surfaces, the inhibitory effect of the used inhibitors was addressed. The higher dipole moment of honey than that of mint caused the adsorption of honey on the aluminum surface better. The IEs measured by gravimetry and gasometry are almost identical
... The high values of a E and Δ * a H obtained in the presence of Nifuroxazid certifies that that aluminium dissolution becomes increasingly difficult as inhibitor concentration increases, confirming physisorption predominance [49,50]. This decrease in dissolution is linked to the gain of electrons that metal receives from inhibitor. ...
... This decrease in dissolution is linked to the gain of electrons that metal receives from inhibitor. Δ * a S values are positive in inhibitor presence, attesting that complex activated formation in the ratedetermining step is dissociative rather than associative and can be interpreted as desorption of the absorbed species [50], resulting in increased disorder [51]. ...
... The Berendsen thermostat ensures that the temperature control is upheld. The Condensed Phase Optimized Molecular Potential II (COMPASSII) forcefield is used to calculate the MC and MD of a system in condensed phase [16,27,33,44,[46][47][48][49][50][51]. The Radial Distribution Function (RDF) analysis was implemented on the complete MD trajectory [16,52,53]. ...
... As shown in Fig. 1, the electron distribution in HOMO and LUMO of the neutral species is nearly similar to those of the protonated species, indicating that the active centers that are responsible for donating and accepting electron in both forms are the same. As known, the higher the value of E HOMO , the greater the capability for a molecule to donate electrons, and therefore better the inhibition efficiency will be observed [51]. Inspection of Table 8 shows that the values of E HOMO (for both forms) follow the order of TBA > TEG, indicating that TBA has a greater ability to donate electrons to the Fe surface than the TEG molecule. ...
The aim of this research paper is comparing the effectiveness of two epoxies compounds (TBA and TEG) against the corrosion carbon steel (CS) in an acidic medium (0.5 M of H2SO4). To perform this study, many techniques and methods are used. Concern, the anti-corrosion tests were performed by weight loss, electrochemical techniques, and surface analysis. In order to confirm the experimental tests, computational calculation was used such as MC, DFT, and so on. The results show that the TBA has great corrosion efficiency than TEG. The SEM/EDS indicates that the surface of CS in the presence of TBA is clearer than TEG. It is crystal clear that these two inhibitors show good anti-corrosion behavior and the TBA inhibits the corrosion more than TEG.
... The values of Ea and A can be derived from the slope of the curve and the The activation enthalpy∆ H # was calculated from the relationship [19] As for the activation free energy, ∆ G # , it is calculated through a press relationship [20] G # =∆ H # -T∆S # …………………………….(13) ∆ ...
This study included the study of the efficiency of peppermint oil inhibition of aluminum corrosion in acidic medium HCl at concentrations (0.5, 1, 1.5, 2 M) on the corrosion rate in the presence and absence of the inhibitor peppermint oil at different concentrations (1000, 2000, 3000, 4000 ppm).In order to study the effect of changing the temperature (303, 313, 323, 333 K) on the corrosion rate in the absence and presence of the inhibitor, different concentrations of the inhibitor were chosen in addition to the acid concentration (1M). The experiments were carried out using the weight loss method to calculate the erosion rate. The expected heat of adsorption enthalpy was (-29.913 KJ/mol), with a negative sign indicates that the process is exothermic. The value of the free energy of adsorption ranged from (11.086-15.067 KJ/mol. (The results showed that Freundlich adsorption isotherm equation is the best fit to examine the adsorption process, also a scanning electron microscope. Showed the surface of aluminum before and after corrosion according to the results of the study, it was found that the used inhibitor reduces corrosion in acidic media. Its anti-corrosion efficacy also improves with increasing inhibitor concentration and with decreasing temperature.
... As known, DFT methods are the preferred methods in theoretical studies of corrosion inhibition, due to their ability to surmount one of the major drawbacks by ab initio methods, by including a possible low-cost part. The calculations presented in this work of all the parameters were performed at the same theoretical level as the geometry optimization [22,23]. For a better approach to the experimental conditions, all calculations were reoptimized by the self-consistent reaction field theory (SCRF) with the Polarized continuum model (PCM) to simulate the solvent environment. ...
A series of organic compounds derived from isoxazole, namely 4a, 4b, 4c, 4d, 4e, 4f, 4g and 4h were studied as corrosion inhibitors for mild steel in order to investigate the influence of different substitutions on the overall intrinsic properties such as boundary orbital energies (EHOMO, ELUMO), energy gap ∆E, electronegativity χ, absolute hardness η, and softness σ, fraction of transferred electrons ∆N; and local such as natural atomic populations and Fukui indices. For this purpose, theoretical studies have been carried out by the DFT density functional theory at the level of the B3LYP functional and the 6-31G (d,p) basis set. As well as, the simulation study of the molecular dynamics was carried out on the surface of Fe (110) in order to understand in depth, the adsorption behavior of the studied inhibitors. Indeed, in this context, the impact of the different groups in the inhibitors before and after adsorption on the iron surface. The optimized structures, electronic parameters, FMOs, Fukui functions and thermodynamic parameters were evaluated to identify candidates appropriate for application as corrosion inhibitors. The results of the global descriptors of the eight isoxazole derivatives showed that these descriptors are almost similar except for compound 4c, these studied inhibitors act in a similar manner. Moreover, the molecular dynamics results also discovered that these inhibitors represent a better reactivity as a result of the negative value of the adsorption energy of all the studied compounds which shows that, these adsorbed systems are more stable and stronger. The results of the dynamic descriptors found by MDS were in excellent coherence with the quantum study results.
... The force of electrostatic adsorption is a function of the difference between the charges carried by the inhibitor and the surface of the metal, which is itself a function of the difference between the corrosion potential of the metal and its potential for zero charges in the corrosive medium considered [18,22] as well as the physically adsorbed substances, which condense rapidly on the metal but are easily degraded by desorption when the temperature increases. ...
... The physisorption retains the identity of the adsorbed molecules and is based on three kinds of interacting forces: hydrogen bonds, polar force, and van der Waals force. The force of electrostatic adsorption is proportional to the difference between the charges carried by the inhibitor and the metal's surface, which is proportional to the difference between the metal's corrosion potential and its potential for zero charges in the corrosive medium under consideration [24,28] as well as the physically adsorbed substances, which condense rapidly on the metal but are easily degraded by desorption when the temperature increases. ...
... In this context, two crucial energy parameters, LUMO (E LUMO ) and HOMO (E HOMO ), are directly linked to a molecule's electron-accepting and electron-donating capacity, respectively. Existing literature [77,78], reports have consistently demonstrated that an increase in E HOMO and a decrease in E LUMO enhance the interaction of a corrosion inhibitor molecule with a metal surface. E LUMO specifically signifies the molecule's ability to accept electrons from the d-orbitals of the metal surface, while E HOMO represents its inclination to donate electrons to suitable acceptor species, primarily the d-orbitals of the metal. ...
The research on green sources of corrosion inhibitors has gained significant traction in recent times due to their cost-effectiveness and environmentally friendly nature. In this study, we assessed the synergistic inhibitory impact of hydrosol extract (H-EX) derivatives obtained from T. Capitata (L.) Cav. on the corrosion of copper alloy (brass) in a 3% NaCl environment, employing a combination of experimental and computational approaches. The chemical composition of H-EX was analyzed through Gas Chromatography-Mass Spectrometry (GC–MS), revealing that Carvacrol (CA) constitutes the predominant compound at 98.01%. In addition, minor constituents include Acetovanillone Acetate (A-AC) at 1.41% and Eugenol (EU) at 0.58%. We assessed the corrosion inhibition properties using various electrochemical techniques, including Open Circuit Potential (OCP), Potentiodynamic Polarization (PDP), and Electrochemical Impedance Spectroscopy (EIS) measurements. The results unequivocally indicate the substantial anti-corrosion efficacy of H-EX, with an impressive inhibition efficiency (ƞEIS (%)) of 90.20% at a concentration of 1(g/L). Notably, H-EX exhibits characteristics of a cathode-type inhibitor, and its adsorption onto brass follows the Langmuir adsorption isotherm. Furthermore, H-EX demonstrates excellent inhibitory activity across a broad temperature range, spanning from 298 K to 338 K. The examination of surface morphology using Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Spectroscopy (EDX) reveals the formation of a robust protective film on the brass surface in the presence of H-EX. Our computational chemistry investigations, employing Density Functional Theory (DFT) with two functionals (B3LYP and M062X) at the 6–311++G(d,p) level, along with Monte Carlo (MC) simulations and the radial distribution function (RDF) tool, affirm the inhibitory performance of the eco-friendly H-EX compounds and their synergistic inhibitory effects on the metal surface. Moreover, MC simulation studies shed light on the synergistic and inhibitory interactions between the various components within the studied extract. Notably, the CA-AC-A-EU mixture demonstrates the most potent synergistic impact and offers the most effective protection for the metal surface, outperforming other combinations (i.e., CA-EU, CA-AC-A, and EU-AC-A), with adsorption energies of −114.80 Kcal/mol and −738.41Kcal/mol in gas and aqueous media, respectively. In conclusion, our study showcases the potential of using DFT and Monte Carlo (MC) simulations to enhance our understanding of the synergistic effects of natural extract-based inhibitors. This knowledge can significantly contribute to the design and production of more efficient and cost-effective mixed corrosion inhibitors.
... According to the literature, when ΔG°a ds in less than or equal to −20 kJ mol −1 , adsorption occurs by developing electrostatic attraction force between the inhibitor active center and negatively charged metal surface (physisorption), while if ΔG°a ds exceeds −40 kJ mol −1 , adsorption occurs by developing a coordination bond between the inhibitor and metal surface. 48 Our measurements show that the process involves both physisorption and chemisorption mechanisms (mixed type), with values ranging from −32 to −40 kJ mol −1 . The negative values of the ΔG°a ds parameter may be used to infer spontaneous adsorption and the stability of the adsorbent layer on C-steel externality. ...
A novel series of polymeric ionic liquids (ILs) based on benzimidazolium chloride derivatives, namely, 1,3-diheptyl-2-(2-phenyl-propyl)-3H-benzimidazol-1-ium chloride (IL1), 1,3-dioctyl-2-(2-phenyl-propyl)-3H-benzimidazol-1-ium chloride (IL2), and 1,3-Bis-decyl-2-(2-phenyl-propyl)-3H-benzoimidazol-1-ium chloride (IL3), were synthesized and chemically elucidated by Fourier transform infrared spectroscopy, ¹H NMR, ¹³C NMR, and elemental analysis. Their influence as corrosion suppressors were investigated for C-steel corrosion in 1 M HCl, by weight loss (WL), potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS) methods, revealing that their exclusive addition decreased corrosion with mounting concentrations. These assays demonstrated that novel ILs are efficient inhibitors at relatively low dosages. The efficacy of the synthesized ILs reached 79.7, 92.2 and 96.9%, respectively, at 250 ppm and 303 K. Parameters for activation and adsorption were calculated and are discussed. The Tafel polarization results demonstrated that the investigated ILs support the suppression of both cathodic and anodic reactions, acting as mixed type inhibitors. Langmuir’s adsorption isotherm was confirmed as the best fitted isotherm, describing the physical–chemical adsorption capability of used ILs on the C-steel surface with the change in the free energy of adsorption, ΔG°ads = 32.6–37.2 kJ mol–1. The efficacy of the synthesized ILs was improved by increasing the doses, and the temperature reached 86.6, 96.1, and 98.4%, respectively, at 318 K. Surface morphology was proved by Fourier Transform Infrared spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscopy (AFM), and then, changes in test solutions were checked by Ultraviolet–visible spectroscopy. Theoretical modeling (density functional theory and Monte Carlo) revealed the correlation between the IL’s molecular chemical structure and its anticorrosive property.
... From the Fig. 5, the shape of the blank impedance spectra presents a capacitive loop at high frequencies attributed to the charge transfer and inductive loop at low frequencies attributed to desorption phenomena of the SO 2− 4 ions [7,20]. In the presence of the inhibitor and for low concentrations (10 − 6 M and 10 − 5 M), we obvious the similar impedance spectra with adding a small loop at high frequencies attributed to the adsorption of the inhibitor formed a film on the surface of the electrode [20,21]. In fact, for the concentrations superior to 10 − 5 M the loop that attributed to desorption phenomena was disappearing, that indicate a good inhibition effect. ...
... These are usually accompanied by the dissolution of metal, thereby leading to the failure of the material. Metals and alloys deployed to the service in such harsh environments must be protected since acid enhances the rate of dissolution of metals (Obi-Egbedi et al., 2011;Singh 2012). This can be done by adding some species into the solution with which the metallic surface is in contact to inhibit corrosion reaction which will help in the reduction of corrosion rate. ...
... This fact indicates that the former has the highest electrondonating capacity to the unoccupied d orbitals of Fe atoms, whereas the second has the highest tendency to accept electrons from sites of high electron density of the metal surface. For the ΔE gap value, it has been considered that lower values of ΔE gap provide good inhibition efficiencies [79]. The phytochemical compounds with the lowest ΔE gab values were the caffeic and chlorogenic acid. ...
... Therefore, repulsion can be considered to occur between absorbed glycine molecules, which should be related to the steric hindrance effect of polar molecules. 40,41 In addition, the standard adsorption free energy (ΔG ads 0 ) formula is as follows: ...
In this study, the inhibition effect of glycine on TiN corrosion in hydrogen peroxide (H2O2) solution was studied through polishing experiments, static corrosion tests, and electrochemical tests. According to the results of electrochemical impedance spectroscopy, 3 wt% glycine exhibited an inhibition efficiency of more than 78% for TiN corrosion due to the greatly increased charge transfer resistance at the TiN/solution interface after its addition. Scanning electron microscopy, atomic force microscopy, and Fourier transform infrared spectroscopy analysis provided evidence that glycine molecules adsorbed on the TiN surface to form a protective film to prevent corrosion. Adsorption isotherm studies demonstrate that spontaneous, mixed physical and chemical adsorption occurs, which follows the Temkin model. The corrosion inhibition mechanism was investigated by X-ray photoelectron spectroscopy. The results show that glycine molecules can prevent TiN from being oxidized to titanium oxide, thus reducing the corrosion intensity. This study is of importance in solving the problem of a too fast corrosion rate of TiN in an oxidizing environment.
... The lowest unoccupied orbital energy (ELUMO) reflects its ability to accept electrons. Furthermore, the difference between the two is the energy gap (ΔE); the smaller its value, the stronger the adsorption of the molecules on iron, and the better effect [48]. From Table 5, the energy gap (ΔE) of SPMD is smaller than that of PMD, indicating that SPMD has a stronger electron-donating ability [49]. ...
1H-Perimidine (PMD) and 1H-perimidine-2-thiol (SPMD) were developed as inhibitors for reinforcing steel in a simulated concrete pore (SCP) solution. Electrochemical measurements, contact angle experiments, scanning electron microscopy (SEM) and quantum chemical calculations were used to investigate the corrosion performance and adsorption mechanisms. The experimental results showed that owing to the structure of SPMD containing a 2-position sulfhydryl group, SPMD is superior to PMD as a corrosion inhibitor for HRB400 reinforced steel in the SCP solution, and its corrosion efficiency can reach more than 80%. Moreover, the introduction of nitrogen and sulfur atoms into the inhibitor not only can coordinate with Fe atoms to form strong bonds but also is useful for preventing charge transfer in the metal corrosion process. More importantly, the perimidine derivatives can spontaneously adsorb on iron, and the adsorption process obeys the Langmuir isotherm. The research results show that the perimidine derivatives can improve the durability of concrete structures.
... Weight loss is one of the most widely used methods in the study of corrosion, due to its simplicity and the reliability of the measurements offered by this technique [46]. We investigate the inhibition efficiency of the new synthesis inhibitors 6NE1 and 6NI2 in various concentrations at a range of temperatures (298-328 K) after 12 h of immersion in the acidic solution using the weight loss measurements. ...
In this work, we studied the inhibitory effect of two indazole derived compounds named 2-methyl-6-nitro-2Hindazole (6NI2) and 1-ethyl-6-nitro-3a,7a-dihydro-1H-indazole (6NE1) on the corrosion of C38 steel in 1 M HCl solution, using electrochemical impedance spectroscopy, potentiodynamic polarization, and mass loss measurements in different concentrations and temperatures (298 K, 308 K, 318 K, and 328 K). The results showed that the efficiency of our compounds increases with the increase of inhibitor concentration in the solution to reach maximum values of 94.73% and 96.49% at 10–3 M of 6NE1 and 6NI2, respectively. The increase in temperature negatively influences the inhibition efficiency of both compounds down to 79.04% and 80.10% at 10−3 M of 6NE1 and 6NI2, respectively, at 382 K. Thermodynamic and kinetic parameters controlling the adsorption process are calculated and discussed. The polarization curves show that both 6NE1 and 6NI2 act as mixed-type inhibitors. The adsorption mode of 6NE1 and 6NI2 obeys the Langmuir adsorption isotherm. In addition, the Nyquist curves showed that the increase of the inhibitor concentration results in the increase of the charge transfer resistance and the decrease of the double layer capacity. The surface of the C38 steel was investigated using SEM and EDS technics. DFT calculations and Molecular dynamics simulations have approved the correlation of the inhibition efficiency with the experimental study of our inhibitors.
... This research employed a PAE inhibitor that was decently soluble in 1M HCl. In contrast to previous research [15,40,41], it was not necessary to combine it with an organic solvent before adding it to the corrosive medium. This appears to be related to PAE's chemical composition. ...
Corrosion inhibitors generated from plants and organic compounds are critical for achieving a greener environment. In this work we investigated the corrosion inhibition of pomegranate arils extract (PAE) for mild steel in 1M HCl by potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), and profilometry measurements. The effects of PAE concentration (100, 200, 400 mg L–1) and temperature (298, 313, and 333 K) on the PAE inhibition efficiency were evaluated. Polarization measurements revealed that PAE was a mixed anodic-cathodic inhibitor. Corrosion inhibition efficiency was around 74% at a PAE concentration of 400 mg L–1 at 298K. However, at 333 K, the corrosion current density in the solution containing 400 mg L–1 of PAE was measured to be 1.28 mA cm-2, which was higher than that in the blank solution (0.92 mA cm-2). This increase in corrosion rate at 333 K demonstrates the negative influence of high temperatures on PAE inhibition efficiency. The PAE green inhibitor was discovered to have a physical adsorption characteristic and to obey the Langmuir adsorption isotherm.
... Depending on the potential sweep, the sample can be oxidized (anodic curve) or reduced-passivated (cathodic curve). The behavior of metal or ceramic alloys can be easily determined using electrochemical principles [84]. Fig. 6 shows the potentiodynamic curves for the studied thin films in the Hank and Fusayama solution and Table 7 shows the obtained values for corrosion potential (E corr ), Pitting potential (Ep), corrosion current density (j corr ) and corrosion rate (Cr). ...
To determine the possibility of using new thin films architectures as biocompatible materials, an experimental and computational study was performed to evaluate the mechanical, tribological, and corrosion properties in simulated physiological media (saliva and blood plasma) of Zr, ZrN, and ZrN/Zr coatings, deposited by PVD magnetron sputtering. The crystalline structure and chemical composition were well correlated with high resistance to plastic deformation, wear, and corrosion, making these materials excellent candidates for functionalizing and protecting dental prostheses. The predominant wear mechanism under consideration was abrasion, which was reduced when using ceramic ZrN coating as a base for the superficial Zr thin film. When exposed to simulated body fluids, these materials exhibited high corrosion resistance, which was demonstrated by potentiodynamic measurements. These results are consistent with those predicted by Density Functional Theory computational models, which showed that electron transfer associated with the wear mechanism is kinetically impeded, as a consequence of the large energy barriers for this process associated with the adsorption of the molecular species on the ZrN surface. Additionally, calculated adsorption energies indicated that urea (from the simulated saliva solution) interacts strongly with the surface. This interaction was associated to the formation of passivating protective layers, which is a key mechanism to protect against corrosion, acting in synergy with the kinetic barriers.
... The DE (2.4887 eV) value indicates a high tendency to react and increase the inhibitors' adsorption ability over the metal surface. 73,83,84 The energy of HOMO and LUMO are related with the (v, g, r and x) are calculated using Eqs. (15)(16)(17)(18)(19)(20). ...
This study deals with the preparation and corrosion inhibition investigations of pyrazoline-sulfonamide hybrid, namely 4-((3-methyl-5-oxo-4,5-dihydro-1H-pyrazol-4-yl)diazenyl) benzene sulfonamide 4. Elemental analysis, Fourier transform infrared spectroscopy, 1H nuclear magnetic resonance (1H NMR), and 13CNMR spectra investigated the pyrazoline-sulfonamide structure. The mild steel corrosion inhibition was investigated in 1 M HCl and 3.5% NaCl solutions using various techniques, including electrochemical, gravimetric, and microscopic techniques. The inhibition efficiency was 95.4 and 87.7% at 500 ppm inhibitor in 1 M HCl and 3.5% NaCl, respectively. The positive values of ∆Hads (44.184 and 31.403 kJ/mol, in 1 M HCl and 3.5% NaCl, respectively) indicate that inhibitor adsorption is an endothermic process. Moreover, the high values of Kads (0.281 and 0.148 M-1) indicate more significant adsorption and thus stronger inhibitory efficiency. Langmuir adsorption isotherm was used to evaluate mild steel corrosion inhibition by pyrazoline-sulfonamide. Experimental data agree with data obtained from B3LYP density functional theory calculations. Therefore, based on the experimental and theoretical data, pyrazoline-sulfonamide is recommended as a corrosion inhibitor of mild steel in aqueous media.
... In addition, since the values of Ea are all less than 80 kJ/mol [17] [18], physical adsorption of TDG on aluminium surface was proposed. The values of Ea for the corrosion process, both in the absence and presence of TDG, are greater than 20 kJ mol -1 and this suggests that the entire process is controlled by surface reaction [19]. ...
Thiodiglycolic acid acts as an accelerator of corrosion of aluminium in hydrochloric acid solution and
cannot be used as corrosion inhibitor for aluminium in acid solution. This can be attributed to the fact
that it is unable to form a passivation layer on the aluminium surface.
... In addition, since the values of Ea are all less than 80 kJ/mol [17] [18], physical adsorption of TDG on aluminium surface was proposed. The values of Ea for the corrosion process, both in the absence and presence of TDG, are greater than 20 kJ mol -1 and this suggests that the entire process is controlled by surface reaction [19]. ...
Thiodiglycolic acid acts as an accelerator of corrosion of aluminium in hydrochloric acid solution and
cannot be used as corrosion inhibitor for aluminium in acid solution. This can be attributed to the fact
that it is unable to form a passivation layer on the aluminium surface.
... Table 8 shows the thermodynamic parameters for the manufactured ionic liquids adsorption in 1 M HCl at various temperatures. Table 6 Corrosion rate and inhibition efficiency (C.R, % I) data gotten from mass loss for aluminum alloy AA6061 in 1 M HCl with and without different concentrations of inhibitors (Ia-c) at 308 K and 318 K. Generally, the standard adsorption free energy value of À20 kJ mol À1 or less negative are related to an electrostatic interaction between charged aluminum metal surfaces (physical adsorption), while those of À40 kJ mol À1 or more negative are charge transfer or sharing from the ionic liquid's molecules to the aluminum metal surface which produces coordination bonds which are related to chemical adsorption [34]. The typical free energy of ionic liquids adsorption onto aluminum values was found to be from À31.8 to À35.5 kJ mol À1 . ...
Three newly ionic liquids namely, 1-bnzyl-2-methyl-3-octyl-1H-imidazol-3-ium bromide, 1-bnzyl-3-decyl-2-methyl-1H-imidazol-3-ium bromide, and 1-bnzyl-3-dodecyl-2-methyl-1H-imidazol-3-ium bromide are synthesized and their chemical structures characterized via different spectra techniques (FT-IR, elemental analysis, and ¹H-NMR). The corrosion inhibition of newly ionic liquids was evaluated on aluminum alloy in 1M HCl at varied exposure temperatures (298–318 K) and varied concentrations via various experimental and theoretical methods for example mass loss, electrochemical, spectral, and computational calculations. The results illustrate that these types of ionic liquids inhibit corrosion of aluminum in acid solution with maximum inhibition efficiency was reached 83.2 % at 298 K. The inhibition efficiency increases with the addition of zinc sulfate which has a synergistic impact which was reached to 92.7%. Also, the concentration of ionic liquids and the kind of cation have an impact on the obtained results. The existence of these inhibitors in the acidic solution improves the charge transfer resistance and lessens the double-layer capacitance. The Langmuir adsorption isotherm governs the adsorption of these inhibitors' molecules on the aluminum alloy surface, and they behave as mixed-type inhibitors. The outputs reveal that the computational calculations match the experimental data rather well.
In daily life, corrosion is an inevitable problem. Metal corrosion control is crucial for technical, financial, health, and environmental reasons. One of the finest methods for preventing corrosion in metals and metal alloys involves the application of inhibitors. Toxicity of the environment caused by synthetic inhibitors has increased the use of green corrosion inhibitors which are biodegradable, are nontoxic, and do not include heavy metals. In addition, these are affordable, easily accessible, and renewable. The majority of the natural products have the required components for their use as a good source of green corrosion inhibitors. These components help with the adsorption of these substances on metals or alloys to produce a coating that protects the surface and prevents corrosion. The numerous forms of green corrosion inhibitors are briefly covered in this chapter, with a focus on the discussion of the various characteristics of the green corrosion inhibitors documented in the literature.
This study investigated the relationship between the molecular structure and the corrosion inhibition efficiency of three corrosion inhibitors for steel in acidic media using the DFT method. First, the molecular conformations of the three compounds were optimized and the populations of charges and frontier orbitals were obtained at the B3LYP/6-311G level. Quantum chemical parameters were also obtained by calculations, including the highest occupied molecular orbital energy (EHOMO), the energy gap (ELUMO−EHOMO), the total energy of the molecule, the dipole moment and the number of electrons transferred (ΔN). The results of the correlation between quantum chemical parameters and inhibition efficiencies demonstrated that the inhibition efficiency of the inhibitors increased with the decrease of ELUMO-EHOMO and the increase of ΔN. The regions with nitrogen and oxygen atoms are the sites most likely to bond with iron atoms by donating electrons.
Carbon dioxide (CO2) is frequently present in oil and gas fields, and its use in CO2 flooding for enhanced oil recovery is growing. However, CO2 is highly corrosive to steel in oilfield fluid. The effective and economical method for controlling corrosion is the addition of corrosion inhibitors for carbon steel materials. Thio-compounds of small size have shown potential as corrosion inhibitors to enhance the performance of imidazoline inhibitors. In this study, several small thio-derivatives inhibitors including mercaptoethanol (ME), thiourea (TU), mercaptoacetic acid (TGA), and 2-mercaptobenzimidazole (MBI) were compared to inhibit the CO2 corrosion. They were used as synergists to enhance corrosion inhibition of oleic imidazoline (OIM) on carbon steel in CO2-saturated brine at 60°C. The corrosion inhibition was evaluated using weight loss and electrochemical techniques, while the surface was characterized using atomic force microscopy (AFM). Additionally, quantum chemical calculations were conducted to investigate the mechanism of corrosion inhibition. The results demonstrate that the MBI, with its aromatic group, exhibited superior corrosion inhibition performance compared with ME, TGA, and TU. The surface characterization revealed no pitting and localized corrosion at 10 ppm of inhibitor. A proposed interaction model suggests that OIM becomes protonated and forms a coadsorption layer with MBI on the carbon steel surface through electrostatic attraction. MBI adsorbs onto iron through a bidentate binding-N-S-bridge connection, effectively preventing carbon steel corrosion in the CO2 environments. This research contributes to establishing a structure-properties relationship for thio-chemicals, aiding in the development of more efficient corrosion inhibitors.
Notwithstanding diverse proposed methods for metal corrosion prevention, inhibitors are still the most popular. Undoubtedly, efficiency is the first and foremost important parameter for a proper inhibitor selection. But in some cases, the applied inhibitor could not reduce an acceptable portion of corrosion owing to multiple limiting factors. Unfortunately, contemporary researchers are not interested in pursuing a critical constructivist viewpoint on this issue and most of the inhibitors have been abandoned simply because of their low efficiency. However, with a scientific and conscious look over the inhibitors’ configuration and environmental stimuli, inhibitors’ proficiency can be simply reached at the highest possible. Fortunately, concerning the imposed biological standards, the importance of optimization and inhibitors’ innovative application is now more momentous than previous decades. Structural modification and correct inclusion of functional groups (i.e., aromatic rings, π–system, heterocyclic rings, heteroatoms, alkyl chains, substituents, polymer chains and monomers) in inhibitors configuration is the most simple but constructive approach for tuning inhibitors’ performance. But alongside the proper structure, attention should also be paid to the environmental stimuli. Environmental stimuli, including the immersion time, inhibitor concentration, temperature, media and metal type, are important influential variables that can impose numerous limitations on the impact of the utilized corrosion inhibitor. The main aim of this advanced and critical review is the creation of a modern perspective to choose a prosperous potential inhibitor and create new ideas to design specific potential inhibitors suitable for different industries and applications. Although smart corrosion inhibitors have overcome many available obstacles in traditional inhibitors, one step further, the provided futuristic suggestions in the present work try to solve the few available issues in this class of inhibitors to claim more durable protection.
Two newly synthetic nontoxic dipyridine-based ionic liquids (PILs) with the same chain lengths and different polar groups were investigated: bispyridine-1-ium tetrafluoroborate (BPHP, TFPHP) with terminal polar groups Br and CF3, respectively, on Carbon steel (CS) in 8M H3PO4 as corrosion inhibitors. Their chemical structure was verified by performing ¹HNMR and ¹³CNMR. Their corrosion inhibition was investigated by electrochemical tests, especially as mass transfer with several characterizations: Scanning electron microscope/Energy dispersive X-ray spectroscopy (SEM–EDX), UV–visible, Atomic force microscope, Atomic absorbance spectroscopy, X-ray Photoelectron Spectroscopy and Gloss value. Theoretical calculation using density functional theory by calculating several parameters, molecular electrostatic potential, Fukui Indices, and Local Dual Descriptors were performed to demonstrate the reactivity behavior and the reactive sites of two molecules with a concentration range (1.25–37.5 × 10–5 M) and temperature (293–318 K). The maximum inhibition efficiency (76.19%) and uniform coverage were sufficient for BPHP at an optimum concentration of 37.5 × 10–5 M with the lowest temperature of 293 K. TFPHP recorded 71.43% at the same conditions. Two PILs were adsorbed following the El-Awady adsorption isotherm, including physicochemical adsorption. The computational findings agree with Electrochemical measurements and thus confirm CS's corrosion protection in an aggressive environment.
Purpose
This study aims to prevent mild steel (MS) against corrosion in 0.5 M HCl solution, 2-amino-4-methoxy-6-methyl-1,3,5-triazine was used. The effectiveness of the compound as a corrosion inhibitor was studied via electrochemical, surface and theoretical calculation techniques.
Design/methodology/approach
For concentrations ranging from 0.5 to 10.0 mM, almost similar polarization resistances were obtained from electrochemical impedance spectroscopy (EIS) and linear polarization resistance tests. It also investigated inhibitive activity of 2-amino-4-methoxy-6-methyl-1,3,5-triazine on the steel surface using scanning electron and atomic force microscope instruments. Langmuir adsorption is the best matched isotherm for the adsorption of the inhibitor to the steel surface.
Findings
EIS method was used to determine inhibition efficiency, which was determined to be 95.7% for 10.0 mM inhibitor containing acid solution. Density functional theory’s predictions for quantum chemistry agreed well with the other experimental results.
Originality/value
The methods used in this study are effective and applicable; the used organic inhibitor is 2-amino-4-methoxy-6-methyl-1,3,5-triazine; and protective effectiveness is important, which is crucial for the task of MS corrosion prevention.
A new Lavandula angustifolia extract was prepared to investigate the anti-corrosion effect against mild steel in corrosive environment. Inhibitory performance of green extract was examined in detail with electrochemical, morphological, as well as quantum chemical calculation analyses. The effects of inhibitor concentration and exposure time were examined to describe the inhibition behavior. Physical and chemical adsorption kinds happen between the surface of the steel and Lavandula angustifolia extract. Furthermore, surface analysis studies were applied to justify the formation of protective adsorption coating occurred on the surface of steel. Quantum chemical calculation results are also in good consistent with other experimental outcomes.
Carbon dioxide often exists in oil and gas fields, and CO2 flooding is also increasingly used to enhance oil recovery. CO2 is highly corrosive to steel in oilfield fluid. The effective and economical method for controlling corrosion is the addition of corrosion inhibitors for carbon steel materials. Small thio-compounds have been found effective to enhance corrosion inhibition of imidazoline inhibitors. In this study, several small thio-derivatives inhibitor including mercaptoethanol (ME), thiourea (TU), and mercaptoacetic acid (TGA) and 2-mercaptobenzimidazole (MBI) were compared to inhibit the CO2 corrosion. They were used as synergists to enhance corrosion inhibition of oleic imidazoline (OIM) for carbon steel at 60 °C in CO2-saturated brine. The corrosion inhibition was investigated by weight loss and electrochemical methods. The surface was characterized by scanning electron microscopy (SEM). The mechanism of corrosion inhibition was studied by quantum chemical calculations. The results show that the MBI with the aromatic group gave the best corrosion inhibition than that of ME, TGA, and TU. The surface characterization showed no pitting and localized corrosion at 10 ppm of inhibitor. The model of interaction is proposed that OIM is protonated and coupled with MBI by electrostatic attraction to co-adsorb on the carbon steel surface. MBI adsorbs on Fe by a bidentate binding-N-S-bridge connection, which effectively prevents the corrosion of carbon steel in the CO2 environment. The research provides a structure-properties relationship of thio-chemicals to develop more effective corrosion inhibitors.
Carbon dioxide often exists in oil and gas fields, and CO2 flooding is also increasingly used to enhance oil recovery. CO2 is highly corrosive to steel in oilfield fluid. The effective and economical method for controlling corrosion is the addition of corrosion inhibitors for carbon steel materials. Small thio-compounds have been found effective to enhance corrosion inhibition of imidazoline inhibitors. In this study, several small thio-derivatives inhibitor including mercaptoethanol (ME), thiourea (TU), and mercaptoacetic acid (TGA) and 2-mercaptobenzimidazole (MBI) were compared to inhibit the CO2 corrosion. They were used as synergists to enhance corrosion inhibition of oleic imidazoline (OIM) for carbon steel at 60 °C in CO2-saturated brine. The corrosion inhibition was investigated by weight loss and electrochemical methods. The surface was characterized by scanning electron microscopy (SEM). The mechanism of corrosion inhibition was studied by quantum chemical calculations. The results show that the MBI with the aromatic group gave the best corrosion inhibition than that of ME, TGA, and TU. The surface characterization showed no pitting and localized corrosion at 10 ppm of inhibitor. The model of interaction is proposed that OIM is protonated and coupled with MBI by electrostatic attraction to co-adsorb on the carbon steel surface. MBI adsorbs on Fe by a bidentate binding-N-S-bridge connection, which effectively prevents the corrosion of carbon steel in the CO2 environment. The research provides a structure-properties relationship of thio-chemicals to develop more effective corrosion inhibitors.
Purpose
The purpose of this study is to investigate starch mucor (SM) in potassium iodide (KI) as corrosion inhibitor of aluminium in hydrochloric acid (HCl) medium.
Design/methodology/approach
The SM in KI was characterized by gravimetric, scanning electron microscopy, electrochemical impedance spectroscopy measurements, potentiodynamic polarization and gas chromatography-mass spectrometer techniques. The inhibition efficiency was optimized using response surface methodology.
Findings
The result revealed that the inhibitor inhibited corrosion at a low concentration with the rate of inhibition increasing as the concentration of the inhibitor increased. The inhibition efficiency increases as the temperature was increased with slight incorporation of the inhibitor (SM in KI). This indicates that the corrosion control is both inhibitor (SM in KI) and temperature dependent.
Originality/value
The research results can provide the basis for using SM in KI as corrosion inhibitor of aluminium in HCL medium. Mixed-type inhibitor nature of SM was proved by cathodic and anodic nature of the polarization curves.
The addition of corrosion inhibitors can effectively improve the hazards posed by the corrosion of carbon steel in circulating cooling water. From the economic and environmental perspective, it makes sense to develop eco-friendly corrosion inhibitors that can be monitored online. In the present work, three polyaspartic acid (PASP) derivatives modified with benzothiazole compounds (R-ABT: R=H, Me and OMe) were synthesized as fluorescent green corrosion inhibitors for the first time, which have good thermostability and allow online detection by fluorescence spectroscopy. The corrosion performance of three inhibitors on carbon steel in cooling water was investigated using the electrochemical test, weight loss measurement, scanning electron microscopy (SEM), atomic force microscopy (AFM), contact angle test, X-ray photoelectron spectroscopy (XPS), DFT and molecular dynamic (MD) simulation. The electrochemical tests indicate that all three derivatives are mixed-type inhibitors and their corrosion inhibition capacity is ranked as follows: PASP-OMe-ABT (96.45%) > PASP-Me-ABT (91.38%) > PASP-H-ABT (89.38%). The three inhibitor molecules improve the carbon steel surface by physisorption and chemisorption as shown by weight loss tests and surface analysis. XPS analysis further confirms the presence of a compound film on the metal surface. Meanwhile, the difference in the radial distribution function and diffusion coefficient of the three derivatives on the Fe (110) surface was also in-depth revealed by quantum chemical calculation based on density functional theory (DFT) and the molecular dynamics (MD) simulation. The theoretical data obtained strongly support the experimental results and confirm that the introduction of methoxy enhances the corrosion inhibition performance.
Biopolymer chitosan (CS), chitosan grafted acrylamide based titanium dioxide (CS-g-PAM/TiO2) and magnetite (CS-g-PAM/Fe3O4) hybrid nanocomposites have been synthesized through free radical graft co-polymerization and successfully validated as corrosion inhibitors for mild steel in 15 % HCl solution. The synthesized compounds have been characterized through FTIR, APC, XRD and TEM. The thermal stability of the nanocomposites was established by TGA. The anticorrosive performance was determined through gravimetric measurements and by electrochemical study. According to EIS technique it was observed that CS-g-PAM/TiO2 and CS-g-PAM/Fe3O4 showed maximum 97.19 % and 95.49 % efficiency respectively. Langmuir adsorption isotherm is obeyed in each case. The activation and adsorption parameters have been determined from isotherm study. FESEM and AFM confirmed better adsorption layer formed by composites over mild steel surface. The elemental composition of the metal samples was proved by the XPS investigation. DFT and ANOVA test further corroborates the experimental results.
The synergistic effect and the synergistic mechanism of oleic imidazoline (OIM) and mercaptoethanol (ME) as carbon steel corrosion inhibitors were studied by the weight-loss and electrochemistry theoretical methods in 3.5wt.% NaCl aqueous solution saturated by CO2 at 60°C. Both the weight-loss and the electrochemistry experiment results show that the synergistic effect between OIM and ME greatly improves the corrosion inhibition performance of the mixture corrosion inhibitors. The inhibition efficiency of the mixture corrosion inhibitors is high up to 96.56% when the ratio of OIM and ME is 3 to 1. The quantum chemical parameters calculated at the B3LYP/6-311++G(d,p) level show that OIM can be preferentially adsorbed for its low energy gap. The molecular dynamic simulation results also indicate that OIM is preferentially adsorbed onto the Fe(110) surface with a adsorption energy of -1583.7 kcal·mol⁻¹. The adsorbed OIM molecules form a film with voids and ME molecules fill in the voids forming a bilayer film. The bilayer film becomes the most condensed and the thickest when the molar ratio of OIM and ME is 3 to 1 in NaCl aqueous solution saturated by CO2. The film can effectively prevents the carbon steel from corrosion because the corrosive medium is blocked by the film. As a result, the mixture corrosion inhibitors of OIM and ME with the ration of 3 to 1 presents the best synergistic effect and the synergistic mechanism is a bilayer adsorption mechanism. The results can provide a helpful guideline for further studying the synergistic effect of the mixture inhibitors of OIM and other chemicals.
The inhibition properties of 2-mercaptobenzothiazole (MBI) and its synergism with oleic imidazoline (OIM) for carbon steel in CO2-saturated brine solution were investigated by electrochemical, weight loss measurements, surface analysis and quantum chemical calculations. The effectiveness of MBI for OIM was also compared to the other sulfur-containing corrosion inhibitors such as 2-mercaptothanol (ME), mercaptoacetic acid (TGA), and thiourea (TU). The results show that a mixture of MBI and OIM gave a better synergistic corrosion inhibition than that of ME, TGA, and TU. OIM is protonated and coupled with MBI by hydrogen bonding to co-adsorb on the carbon steel surface. MBI adsorbs on Fe by a bidentate binding-N-S-bridge connection, which effectively prevents the carbon steel from CO2 corrosion.
We investigated the effect of the 2-mercaptobenzothiazole concentration on the sour-corrosion behavior of API X60 pipeline steel in an environment containing H2S at 25°C and in the presence of 0, 2.5, 5.0, 7.5, and 10.0 g/L of 2-mercaptobenzothiazole inhibitor. To examine this behavior, we conducted open-circuit potential (OCP), potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) tests. Energy dispersive spectroscopy and scanning electron microscopy were also used to analyze the corrosion products. The results of the OCP and potentiodynamic polarization tests revealed that 2-mercaptobenzothiazole reduces the speed of both the anodic and cathodic reactions. An assessment of the Gibbs free energy of the inhibitor (ΔG
⊖ads
) indicated that its value was less than −20 kJ·mol−1 and greater than −40 kJ·mol−1. Therefore, the adsorption of 2-mercaptobenzothiazole onto the surface of the API X60 pipeline steel occurs both physically and chemically, the latter of which is particularly intentional. In addition, as the ΔG
⊖ads
value was negative, we could conclude that the adsorption of 2-mercaptobenzothiazole onto the surface of the pipeline steel occurs spontaneously. The EIS results indicate that with the increase in the 2-mercaptobenzothiazole inhibitor concentration, the corrosion resistance of API X60 steel increases. An analysis of the corrosion products revealed that iron sulfide compounds form on the surface. In summary, the results showed that an increase in the inhibitor concentration results in a decrease in the corrosion rate and an increase in inhibitory efficiency. Additionally, we found that the 2-mercaptobenzothiazole adsorption process on the API X60 steel surfaces in an H2S-containing environment follows the Langmuir adsorption isotherm and occurs spontaneously.
Now a days green corrosion inhibitors are highly in demand to mitigate corrosion of metal and alloys due to their non-toxicity as well as the absence of heavy metal and toxic compounds in comparison to the organic corrosion inhibitors. Since in the past research conducted on vitamin B12 as a corrosion inhibitor, the study of thermodynamic and kinetic parameters was lacking, the present work is focussed on the temperature dependence of corrosion on Vit B12(Vitamin B12) for the mild steel surface which is an influencing parameter in the present day to day industrial problems. There is a desirable need for efficient inhibitors which work well in high temperatures too. So the present study consciously restricts itself to Vit B12, a naturally occurring corrosion inhibitor. VitB12 is a water-soluble vitamin and also called cobalamin. It is an ecofriendly organometallic compound, has many adsorption sites, and is thus a promising candidate for corrosion retardation. The Potentio-dynamic Polarisation and Electrochemical Impedance Spectroscopy (EIS) are the two techniques that have been used in the analysis of the corrosion inhibition efficiency of Vit B12. It has been observed that the addition of inhibitor Vit B12, shows an enhancement in the Rct (charge transfer resistance) and a decrease in the capacitance layer Cdl value, which indicates the formation of a protective layer over the mild steel surface. The study of thermodynamic and kinetic parameters of the inhibitor adsorption over the mild steel was performed through temperature study. The surface morphology in the absence and presence of Vit B12 on the mild steel was analyzed by FE-SEM where the smooth surface is visible in the presence of inhibitor which shows the protective behavior of Vit B12.
An ab initio density functional theory (DFT) calculation revealed
the electronic properties of azomethine functionalised epoxy,
namely, 4-((oxiran-2-yl)methoxy)-N-(4-(4-(4-((oxiran-2-yl)methoxy)-
benzylideneamino)phenoxy)benzylidene)benzenamine (DSBE) and
amine based curing agent namely diethylenetriamine (DETA), triethylenetetraamine(TETA) and para-phenylenediamine (PPD)
responsible for its adsorption on the mild steel surface. The frontiers
molecular orbitals (FMOs) and the corresponding energies as
well as global softness values revealed the reactive nature of the
studied organic molecules. The probable trends of the chemical
properties of different amine cured epoxy have been predicted.
The insights of the adsorption of these organic molecules have
been visualized through density functional tight binding calculation.
It revealed that these organic molecules are able to adsorb
onto targeted metal surface viz. Fe(110), FeO(110) and Fe2O3(110)
plane through charge density sharing occurring at the moleculeiron
layer interface. Thus, a complete theoretical insight analysis
and modelled simulated adsorption study provided a clear picture
regarding the adsorptions of the organic molecules onto metallic
surfaces.
Designing efficient corrosion inhibiting molecules is very important prior to its synthesis and analysis of the anticorrosive property. In this regards, the double azomethine functionalised highly π-conjugated aromatic organic compounds possessing strong and moderate electron activating groups, namely, 4,4'-{1,4-phenylenebis[(E)-methanylylidene-(E)-azanylylidene]}diphenol (TA); 2,2'-{1,4-phenylenebis[(E)-methanylylidene-(E)-azanylylidene]}di(pyrimidine-4,6-diol) (TAD) and 2,2'-{1,4-phenylenebis[(E)-methanylylidene-(E)-azanylylidene]}di(pyrimidine-4,6-dithiol) (TADT) were synthesized and characterised. Subsequently, the in-depth electronic properties were explored using ab initio density functional theory and local reactivity analysis. Afterwards, the interaction spontaneity and mechanism, along with equilibrium adsorption configurations onto Fe(110) surface was probed employing Monte Carlo simulation approach. Additionally, non-covalent interactions within a molecular structure and after its adsorption onto a targeted iron surface were explored using reduced density gradient analysis. Consequently, the obtained results have been explained and the expected corrosion inhibition mechanism, as well as the inhibition capability, have been predicted. © 2022 CSIR-Central Mechanical Engineering Research Institute Durgapur, India.
The influence of inhibitor concentration and temperature on the corrosion behaviour of steel in molar HCl solution has been investigated by weight loss method. Results obtained show that the inhibitory effect of 2-phenylthieno(3, 2-b)quinoxaline (P4) increases with increasing P4 concentration to attain the highest value (95%) at 5 10 -4 M. The determination of the corrosion rate at the temperature range (308 -353K) indicates that E% decreases with rise of temperature. Arrhenius law and its transition equation lead to estimate activation parameters of corrosion process. P4 inhibits well steel at moderate temperature and adsorbs according to the Langmuir isotherm. Plots of logarithm of corrosion rate function of the reciprocate of temperature as well as Van't hoff and Gibbs equations facilitated the access to thermodynamic parameters such as equilibrium constant, adsorption heat and adsorption entropy. The various parameters of activation and adsorption may be a good tool to discuss manner of adsorption of organic compound. Attempt to correlate molecular structure to quantum indices was made.
Clotrimazole (CTM) [1-[(2-chlorophenyl)-diphenyl-methyl]imidazole], an antifungal drug, was investigated as a corrosion inhibitor for aluminium in HCl using weight loss method. CTM inhibited the corrosion of aluminium in HCl. The inhibition efficiency increased with increase in the concentrations of CTM to reached 90.90% at 1 x 10 -4 M, but decreased with increase in temperature. Phenomenon of physical adsorption is proposed for the inhibition and the process followed the Langmuir adsorption isotherm and kinetic / thermodynamic model of El-Awady et al. The mechanism of adsorption inhibition and type of adsorption isotherm were proposed from the trend of inhibition efficiency with temperature, E a , ∆G ads , and Q ads . Quantum chemical calculations results show that CTM possesses a number of active centres concentrated mainly on the imidazole moiety of the molecule. The highest occupied molecular orbital (HOMO), and the lowest unoccupied molecular orbital (LUMO) were also found around the nitrogen atoms and the cyclic of the benzene rings.
The corrosion rates in the presence of nizoral (NZR), an antifungal drug, as mild steel corrosion inhibitor in 0.1 M H 2 SO 4 was measured by the weight loss method in the temperature range from 30 – 50 o C. Results obtained revealed that NZR acts as an inhibitor for mild steel in sulphuric acid solution. Inhibition efficiency increased with increase in concentration of the inhibitor but decreased with increase in temperature. The addition of KI increased the inhibition of NZR to a considerable extent. The experimental results suggest that the presence of iodide ions in the solution stabilized the adsorption of Nizoral molecules on the mild steel surface thereby improving the inhibition efficiency of Nizoral. The adsorption characteristics of the inhibitor were approximated by Langmuir adsorption isotherm and kinetic/thermodynamic adsorption model of El-Awady et al. Mechanism of physical adsorption is proposed from the activation and thermodynamic parameters calculated.
The corrosion and inhibitor adsorption processes in mild steel/1-methyl-4[4′(-X)-styryl] pyridinium iodides (X: H, CH3 and OCH3)/hydrochloric acid systems was studied at different temperatures (25–60°C) by means of hydrogen evolution (HE) and weight loss (WL) measurements. It was found that the studied compounds exhibit a very good performance as inhibitors for mild steel corrosion in 1.5M HCl. Results show that the inhibition efficiency increases with decreasing temperature and increasing concentration of inhibitors. Good agreement between the results obtained from hydrogen evolution and weight loss measurements was appeared. It has been determined that the adsorption for the studied inhibitors on mild steel complies with the Langmuir adsorption isotherm at all studied temperatures. The kinetic and thermodynamic parameters for mild steel corrosion and inhibitor adsorption, respectively, were determined and discussed. On the bases of thermodynamic adsorption parameters, comprehensive adsorption (physisorption and chemisorption) for the studied inhibitors on mild steel surface was suggested. A good correlation between the substituent type and the inhibition efficiency of inhibitors through the application of Hammet relationship was obtained. Results show that with increasing the donor property of the substituent, the inhibition efficiency of the inhibitor is increased in the order: I-H
The initial-rate kinetics of the flavin reductase reaction catalysed by biliverdin-IXβ reductase at pH 7.5 are consistent with a rapid equilibrium ordered mechanism, with the pyridine nucleotide binding first. NADPH binding to the free enzyme was characterized using stopped-flow fluorescence quenching, and a K(d) of 15.8 μM was calculated. Equilibrium fluorescence quenching experiments indicated a K(d) of 0.55 μM, suggesting that an enzyme-NADPH encounter complex (K(d) 15.8 μM) isomerizes to a more stable 'nucleotide-induced' conformation. The enzyme was shown to catalyse the reduction of FMN, FAD and riboflavin, with K(m) values of 52 μM, 125 μM and 53 μM, respectively. Lumichrome was shown to be a competitive inhibitor against FMN, with a K(i) of 76 μM, indicating that interactions with the isoalloxazine ring are probably sufficient for binding. During initial experiments it was observed that both the flavin reductase and biliverdin reductase activities of the enzyme exhibit a sharp optimum at pH 5 in citrate buffer. An initial-rate study indicated that the enzyme obeys a steady-state ordered mechanism in this buffer. The initial-rate kinetics in sodium acetate at pH 5 are consistent with a rapid-equilibrium ordered mechanism, indicating that citrate may directly affect the enzyme's behaviour at pH 5. Mesobiliverdin XIIIα, a synthetic biliverdin which binds to flavin reductase but does not act as a substrate for the enzyme, exhibits competitive kinetics with FMN (K(i) 0.59 μM) and mixed-inhibition kinetics with NADPH. This is consistent with a single pyridine nucleotide site and competition by FMN and biliverdin for a second site. Interestingly, flavin reductase/biliverdin-IXβ reductase has also been shown to exhibit ferric reductase activity, with an apparent K(m) of 2.5 μM for the ferric iron. The ferric reductase reaction requires NAD(P)H and FMN. This activity is intriguing, as haem cleavage in the foetus produces non-α isomers of biliverdin and ferric iron, both of which are substrates for flavin reductase/biliverdin-IXβ reductase.
The adsorption of [(4-hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)-(4-methoxy-phenyl)-methyl]-urea on iron in phosphoric media was studied by using electrochemical technique. The adsorption mechanism was investigated using adsorption isotherms. The experimental data fit localized adsorption models. The values for free energy of adsorption, ΔGads0, were also calculated at each surface coverage, θ of the studied compound by applying the mathematical model of Bockris Swinkels adsorption isotherm. The variation of free energy of adsorption ΔGads0 with surface coverage, was interpreted in terms of deviation from ideal condition assumed in Langmuir model. A possible adsorption model of HPU2 molecules on to the metal surface was suggested.
The corrosion inhibition of 2-hydrazino-4,7-dimethylbenzothiazole on low carbon steel in industrial water has been investigated at different temperatures and fluid velocities at different concentrations of the inhibitor using mass loss, potentiodynamic polarization and electrochemical impedance spectroscopy measurements. The results showed that corrosion resistance increased by increasing the inhibitor concentration. Optimization of the three variables has been made and correlating the results obtained using Box–Wilson statistical method. The adsorption process on low carbon steel surface obeys Flory–Huggins isotherm. The values of ΔGads obtained suggest that, the adsorption process of 2-HMBT on low carbon steel is chemisorption. The activation energy increased with increasing the concentration of inhibitors leading to decrease of the pre-exponential factor, and the entropy of activation increased negatively in the presence of inhibitor. SEM was used to identify the film formed on the metal surface.
The corrosion of commercial aluminium alloy sheets in different concentrations of H2SO4 and HCl solutions was studied using the weight loss technique from 303 K to 313 K. The difference in corrosion rate of aluminium in H2SO4 and HCl solutions without inhibitor was attributed to difference in activation energies of the metal acid solution reaction. Pre-exponential factors derived from the Arrhenius plot for both acids were observed to be approximately the same value at constant temperature and concentration. 2-acetyl pyridine-(4-phenyl) thiosemicarbazone (PTSC) was used as corrosion inhibitor. The maximum % inhibitor efficiencies obtained were 76% and 28% in HCl and H2SO4 solutions respectively at concentration of 5 × 10-4 M at 303 K. Mechanism of physical adsorption is proposed. PTSC was found to obey the Langmuir isotherm at 303 K and 313 K in H2SO4 solution but obeyed the Flory-Huggins isotherm at 323 K in HCl solution. First order type of reaction mechanism was obtained from the kinetic treatment of the weight loss data. The difference in inhibition behaviour of PTSC in both acid solution has been explained in terms of metal corrodent inhibitor interaction.
The corrosion of iron and aluminium has been investigated in 0.1 M HCl acidic solutions in the presence of different concentrations of SDBS at different temperatures (303, 318, and 333 K). With this aim, the corrosion rate of iron and aluminum was determined by using gravimetric and potentiostatic methods. Semi-logarithmic current potential curves were drawn by potentiostatic measurements at different temperatures. By using these curves, the electrochemical parameters (Icorr, Ecorr, Rp) were calculated. The activation energy (Ea) was calculated with the Arrhenius equation at different concentrations of inhibitor. The adsorption of SDBS on metal surface has been carried out with Langmuir adsorption isotherm and the curves of isotherm have been obtained. According to experimental results, SDBS is more effective in inhibiting aluminium corrosion. The inhibition effect of SDBS decreases with an increase of temperature.
The inhibition of corrosion of aluminium in HCl by solution mixtures of derivatives of thiosemicarbazone at 303-313 K and concentration range of 1 × 10-5 to 5 × 10-4 M has been studied using weight loss technique. The thiosemicarbazone derivatives used are 2-acetyl- pyridine-(4-phenylthiosemicarbazone) (PTSC), 2-acetylpyridine-(4- phenyl-iso-methylthiosemicarbazone) (PIMTSC) and 2-acetylpyridine-(4-phenyl-iso-ethylthio-semicarbazone (PIETSC). They were mixed in doublet: PTSC + PIMTSC (PM), PTSC + PIETSC (PE) and PIMTSC + PIETSC (ME) and in triplet PTSC + PIMTSC + PIETSC (PME). The maximum inhibition efficiency is in the order ME > PE > PME > PM. The inhibition efficiency increases with increase in iso group in the mixtures, which was attributed to interaction of the molecules resulting to exposing of the adsorption sites. Physical adsorption mechanism has been proposed for the mixture used. Kinetic treatment of the results gave a first order type of mechanism.
The effect of purine, as a safe inhibitor,was investigated by measuring the corrosion of Al in 1.0Mdeaerated
stirred H3PO4 solution at 25 ◦C. Measurements were conducted under various experimental conditions
using polarization and impedance measurements, complemented with EDX examinations of the electrode
surface. According to these results, purine alone showed a poor inhibition effect. Addition of I− ions
enhanced the inhibition efficiency of purine. The synergistic effect is attributed to enhanced adsorption
of purine by the adsorbed I− ions. Potentiodynamic polarization studies showed that purine alone and the
mixture of purine and I− ions act as mixed-type inhibitors for the corrosion of Al in 1.0MH3PO4 solution.
The impedance diagram exhibited three time constants or semi-circles of which the sizes are dependent
on inhibitor concentration and immersion time. The capacitive time constant at high frequencies may be
related to the oxide film itself. The second capacitive time constant at low frequencies can be attributed
to oxide film dissolution. The inductive loop at medium frequencies may be attributed to the relaxation
of adsorbed charged intermediates. Inhibition via hydrogen bond formation is also discussed here.
The inhibitive effect of 2,3-diaminonaphthalene (2,3-DAN) for corrosion of aluminum in 1 M HCl was investigated using hydrogen evolution technique at 30 and 40°C. Quantum chemical calculation results showed that 2,3-DAN molecule possessed planar structure with a number of active centers, which aided the adsorption process. The Mulliken charge density, the highest occupied molecular orbital (HOMO), and the lowest unoccupied molecular orbital (LUMO) were found mainly focused around nitrogen atoms and the cyclic of the benzene as well. The presence of 2,3-DAN molecules in the corrosive medium (1 M HCl solution) inhibits the corrosion process of aluminum and as the concentration of 2,3-DAN increases the inhibition efficiency also increases but decreases with rise in temperature. The corrosion inhibition of 2,3-DAN was discussed in terms of blocking of the Al surface by adsorption of the molecules of the inhibitor at the active centers. It was found that the adsorption of 2,3-DAN onto the Al surface followed the Langmuir adsorption isotherm and 2,3-DAN adsorbed on Al surface probably by physisorption. The proposed physisorption mechanism was supported by the calculated values of Ea, Qads, and ΔGads.
A newly synthesized azo compound, namely 8-quinolinol-5-azoantipyrine (HQAP), was studied as an inhibitor for the corrosion of mild steel in 1M HCl. Results of weight loss and Tafel polarisation measurements show that this compound has fairly good inhibiting properties for steel corrosion in acidic bath, with efficiency around 96% at a concentration of 10!3 M. The inhibition is of a mixed anodic-cathodic nature. Langmuir isotherm is found to provide an accurate description of the adsorption behaviour of the investigated azo compound. Some thermodynamic parameters such as the adsorption heat, adsorption entropy and adsorption free energy have been calculated by employing thermodynamic equations. Kinetic parameters such as the apparent activation energy and pre-exponential factor have been calculated and discussed.
The semi-empirical ZINDO/1 method is used to calculate the electronic structure and thermodynamic properties of aniline trimers adsorbed onto cluster models of the Al(100) and Fe(100) surfaces. The effects of progressive oxidation and protonation of the trimers on corrosion inhibition are interpreted in terms of these calculations.
The effects of single o-phenanthroline and the mixture of various concentrations of NaCl and 0.0002 M o-phenanthroline on the corrosion of cold rolled steel in 1.0–4.0 M phosphoric acid have been investigated by using weight loss method and polarization method. The present study revealed that cold rolled steel in phosphoric acid has been more efficiently inhibited by o-phenanthroline in the presence of NaCl than single o-phenanthroline, and inhibition efficiency increases with increasing concentration of NaCl in the presence of 0.0002 M o-phenanthroline. At a relative higher concentration of NaCl, there is the synergistic effect between o-phenanthroline and NaCl. The adsorption of inhibitor accords with the Langmuir adsorption isotherm. Polarization studies show that the inhibitor mainly acts as a mixed type inhibitor for steel in 1.0 M phosphoric acid. Thermodynamic parameters such as adsorption heat, adsorption entropy and adsorption free energy are obtained from experimental data of the temperature studies of the inhibition process at four temperatures ranging from 30 to 45 °C. The kinetic data such as apparent activation energy and pre-exponential factor at different concentrations of the inhibitor are calculated, and the effects of the apparent activation energy and pre-exponential factor on the corrosion rate of cold rolled steel are discussed. At 40 °C, in 1.5–4.0 M phosphoric acid, the concentration pre-exponential factor and acid concentration constant are calculated, the synergistic effect has been observed too, and the inhibition efficiency of mixture slowly decreases with increasing concentration of phosphoric acid. A new equation has been used to explain the dependence of corrosion rate on acid concentration. The inhibition action is satisfactorily explained by using both thermodynamic and kinetic models. The results obtained from weight loss method and polarization method are in good agreement.
Molecular orbital theoretical calculations based on the modified neglect of differential overlap (MNDO) method were performed on some substituted methyl pyridines and substituted ethane derivatives in common use as corrosion inhibitors for iron in acid media. New correlations of corrosion rates with the energy of the highest occupied molecular orbital (E{sub HOMO}), the energy gap or difference between the lowest unoccupied molecular orbital and the highest occupied molecular orbital (E{sub LUMO}-E{sub HOMO}), and Hammett`s parameter Ï were presented. Absolute electronegativity (Ï) values and the fraction of electrons (ÎN) transferred from substituted pyridine and ethane compounds to iron in the bulk metal were calculated and correlated with corrosion rates for the first time.
2,3-Quinoxalinedione (QD) was tested as corrosion inhibitor for mild steel in 1M HCl solution using electrochemical (potentiodynamic polarisation) and non-electrochemical technique (weight loss and UV–vis spectrophotometric measurement). Results of weight loss and Tafel polarisation measurements showed that this compound has fairly good inhibiting properties for steel corrosion in acidic bath, with efficiencies of around 88% at a concentration of 10−3M. The inhibition is of a mixed anodic–cathodic nature. Langmuir isotherm is found to provide an accurate description of the adsorption behaviour of the investigated compound. Negative value was calculated for the energy of adsorption indicating the spontaneity of the adsorption process. The formation of complex between metal cations and 2,3-quinoxalinedione is also proposed as additional inhibition mechanism of mild steel corrosion.
Acenaphtho [1,2-b] quinoxaline (AQ) was tested as a novel corrosion inhibitor for mild steel in 0.5M H2SO4 solution using chemical technique at 30°C. AQ acts as an effective inhibitor for mild steel in acidic medium. Inhibition efficiency increased with increasing concentration of AQ. Langmuir isotherm was found to provide an accurate description of the adsorption behaviour of the investigated compound. A zero-order kinetics relationship with respect to mild steel was obtained with and without AQ from the kinetic treatment of the data. DFT study gave further insight into the mechanism of inhibition action of AQ.
A theoretical study of benzimidazole (BI) and two of its derivatives namely 2-methylbenzimidazole (2-CH3BI) and 2-mercaptobenzimidazole (2-SHBI) recently used as corrosion inhibitors for mild steel in 1M HCl was undertaken by considering Density Functional Theory (DFT) at the B3LYP/6-311G++(d,p) level. The properties most relevant to their potential action as corrosion inhibitors has been calculated in the neutral and protonated form: EHOMO, ELUMO, energy gap (ΔE), dipole moment (μ), electronegativity (χ), global hardness (η) and the fraction of electrons transferred from the inhibitor molecule to the metallic atom (ΔN). The theoretical results are in agreement with the experimental data.
The effect of iodide ions on the inhibitive performance of 2,3-diaminonaphthalene (2,3-DAN) in 1M HCl for aluminium corrosion has been studied using hydrogen evolution (gasometry) measurements at 30 and 40°C. Results obtained showed that the presence of 2,3-DAN molecules in the corrosive medium (1M HCl solution) inhibits the corrosion process of aluminium and as the concentration of 2,3-DAN increases the inhibition efficiency also increased at the studied temperatures. A synergistic effect was observed between KI and 2,3-DAN. The experimental results suggest that the presence of iodide ions in the solutions stabilized the adsorption of 2,3-DAN molecules on the metal surfaces and, therefore improve the inhibition efficiency of 2,3-DAN. Phenomenon of physical adsorption is proposed for the inhibition and the process followed the Freundlich adsorption isotherm. The activation energy (Ea), heat of adsorption (Qads) and free energy of adsorption for the corrosion process (ΔGads) have been evaluated at the different temperatures and the values support the results obtained. Some quantum chemical parameters and the Mulliken charge densities for 2,3-diaminonaphthalene were calculated by the AM1 Semi-empirical method to provide further insight into the mechanism of inhibition of the corrosion process.
Quinolin-5-ylmethylene-3-{[8-(trifluoromethyl)quinolin-4-yl]thio}propanohydrazide (QMQTPH) was synthesized, characterized and tested as a corrosion inhibitor for mild steel in 1M and 2M HCl solution using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Polarization resistances calculated from the EIS measurements were in good agreement with those obtained from direct current (DC) polarization measurements. The mild steel samples were also analyzed by scanning electron microscopy (SEM). The results showed that QMQTPH is an excellent inhibitor for mild steel in acid medium. The inhibition was assumed to occur via adsorption of the inhibitor molecule on the metal surface. It acts as an anodic inhibitor. In the 30° to 60°C temperature range, the QMQTPH adsorption follows Langmuir isotherm model. The protection efficiency increased with increasing inhibitor concentration in the range 10−5−10−3M, but slightly decreased with increasing temperature.
The corrosion inhibition of mild steel in 1M HCl solution by cefotaxime sodium has been studied by Tafel polarization, electrochemical impedance spectroscopy (EIS) and weight loss measurement. The inhibitor showed 95.8% inhibition efficiency at optimum concentration 300ppm. Results obtained revealed that inhibition occurs through adsorption of the cefotaxime on metal surface without modifying the mechanism of corrosion process. Potentiodynamic polarization studies suggest that it is a mixed type of inhibitor. Electrochemical impedance spectroscopy techniques were also used to investigate the mechanism of corrosion inhibition.
The corrosion protection of mild steel in a 2.5M H2SO4 solution by 4,4-dimethyloxazolidine-2-thione (DMT) was studied at different temperatures by measuring changes in open circuit potential (OCP), potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS). Corrosion current densities calculated from EIS data were comparable to those obtained from polarisation measurements. Results showed that DMT inhibited mild steel corrosion in a 2.5M H2SO4 solution and indicated that the inhibition efficiencies increased with the concentration of inhibitor, but decreased proportionally with temperature. Polarisation curves showed that DMT is a mixed-type inhibitor. Changes in impedance parameters suggested the adsorption of DMT on the mild steel surface, leading to the formation of protective films. The DMT adsorption on the mild steel surface followed the Langmuir adsorption isotherm. The kinetic and thermodynamic parameters for dissolution and adsorption were investigated. Comprehensive adsorption (physisorption and chemisorption) of the inhibitor molecules on the mild steel surface was suggested based on the thermodynamic adsorption parameters.
The adsorption of 3-(4-amino-2-methyl-5-pyrimidyl methyl)-4-methyl thiazolium chloride (AMMPTC) or vitamin B1 at the mild steel surface from hydrochloric acid (HCl) solution is studied using chemical techniques. The surface coverage with the adsorbed AMMPTC is used to calculate the free energy of adsorption, ΔGads0, of AMMPTC using Bockris–Swinkels isotherm. The dependence of free energy of adsorption, ΔGads0, with surface coverage, θ, is ascribed to surface heterogeneity of the adsorbent. The effect of AMMPTC is discussed from the viewpoint of adsorption model. The adsorption of AMMPTC molecules on the surface occurs without modifying the kinetic of corrosion process which is of first order with respect to mild steel.
Weight loss measurements and potentiostatic polarization studies show that 2-hydrazino-6-methyl-benzothiazole (HMBT) acts as an effective inhibitor for the corrosion of mild steel in 1 N HCl and 1 N H2SO4. It behaved predominantly as cathodic inhibitor in HCl and mixed inhibitor in H2SO4. Hydrogen permeation studies also show that HMBT acts as an effective cathodic inhibitor by decreasing hydrogen permeation current through mild steel surface. The adsorption of HMBT on mild steel from 1 N HCl and 1 N H2SO4 is found to obey Langmuir's adsorption isotherm.
The corrosion inhibition of mild steel in 1M HCl by benzylidene-pyridine-2-yl-amine (A), (4-benzylidene)-pyridine-2-yl-amine (B) and (4-chloro-benzylidene)-pyridine-2-yl-amine (C) has been studied at 25°C using electrochemical and weight loss measurements. Polarization curves reveal that the used compounds are mixed type inhibitors. Results show that inhibition efficiency increases when the inhibitor concentration increases. The inhibition efficiency changes with the type of functional groups substituted on benzene ring. The experimentally obtained adsorption isotherms follow the Langmuir equation. The effect of temperature on the corrosion behavior in the presence of 10−2M of inhibitors was studied in the temperature range of 25–43°C. The associated activation energy of corrosion and other thermodynamic parameters have been determined. It has been found that all those schiff base compounds are excellent inhibitors.Obvious correlation was found between corrosion inhibition efficiency and quantum chemical parameters, using the linear and non-linear QSAR models. The obtained theoretical results have been compared with the experimental results.
The corrosion inhibitive effects of Pachylobus edulis exudate gum for mild steel in 2 M H2SO4 and influence of potassium halide additives on the inhibition efficiency were investigated using hydrogen evolution and thermometric methods at 30°–60°C. Inhibition efficiency was determined by comparing the corrosion rates in the absence and presence of additives. The trend of inhibition efficiency with temperature was used to propose the mechanism of inhibition. It was found that the exudate gum acts as an inhibitor for acid-induced corrosion of mild steel. Inhibition efficiency (%I) of the exudate gum increased with an increase in concentration of the exudate gum and synergistically increased on addition of potassium halides but decreased with increase in temperature. Inhibitor adsorption characteristics were approximated by Temkin adsorption isotherm at all the concentrations and temperatures studied. The phenomenon of physical adsorption is proposed from the activation parameters obtained.
The effect of inhibitor concentration and temperature on the corrosion process of copper–nickel alloy in presence of naphthylamine (NA) and phenylenediamine (PDA) in 5% HCl has been investigated by weight loss technique. Maximum value of inhibitor efficiency was 85.6% for NA at 35°C and 0.085M inhibitor concentration, while the lower value was 1% at 55°C and 0.01M in the presence of PDA. Two mathematical models were used to represent the corrosion rate data: second order polynomial model and exponential model. Non-linear regression analysis shows that the first model was better than the second model with high correlation coefficient.
The inhibition of the corrosion of mild steel in hydrochloric acid solutions by 4-amino-5-phenyl-4H-1,2,4-trizole-3-thiol (APTT) inhibitor was studied using weight loss technique. Basic kinetic parameters of the corrosion inhibition process were obtained by reaction kinetic equations. Rustles show that the inhibition increases with increasing of inhibitor concentration. Kinetic calculations show that the maximum value of time for which the corrosion rate increases twice the initial one, while time for which the mass of the sample subjected to corrosion decreases twice the initial one were at 8×10−4M of APTT. The dynamics were described by an exponential kinetic equation of self-accelerating reactions in the absence of inhibitor and by an equation of a zero order in its presence.
The molecular behavior of some pyridine derivatives as corrosion inhibitors of iron and aluminum in acid media, were studied quantum electrochemically. The calculations were made for three conditions; isolated inhibitor molecule, metal cluster, and finally polarized continuum media. It is concluded that for aluminum the vertical adsorption through nitrogen atom is prevailing, while for iron both vertical and planar adsorptions (through π electrons of aromatic ring) are possible, but the vertical is predominant. The inhibitor chemical potential (μ) and the extent of charge transfer (ΔN) to the metal were determined. A linear correlation between each of these and the inhibition efficiencies are demonstrated. Finally, from the calculated de-solvation free energy values as a function of dielectric constant, it is observed that there is an abrupt decrease in the free energies as the inhibitor molecule enters EDL. Also the calculated de-solvation free energies show a linear correlation with experimental inhibition efficiencies.
The corrosion inhibition of aluminium in HCl solution in the presence of exudate gum from Raphia hookeri at temperature range of 30–60°C was studied using weight loss and thermometric techniques. The exudate gum acts as an inhibitor in the acid environment. The inhibition efficiency increases with increase in inhibitor concentration but decreases with an increase in temperature. The inhibitive effect of the Raphia hookeri exudate could be attributed to the presence of some phytochemical constituents in the exudate which is adsorbed on the surface of the aluminium metal. The exudate gum was found to obey Temkin adsorption isotherm and Kinetic–Thermodynamic Model of El-Awady et al. at all the concentrations and temperatures studied. Phenomenon of physical adsorption is proposed from the activation parameters obtained. Thermodynamic parameters reveal that the adsorption process is spontaneous.
The interfacial behavior of fluconazole (FLC) between aluminium and hydrochloric acid has been investigated by using weight loss technique at 30–50°C. The results showed that fluconazole is an excellent corrosion inhibitor for aluminium in acidic medium. Inhibition efficiency increased with increase in the concentrations of fluconazole but decreased with rise in temperature. The adsorption of the inhibitor on the aluminium surface is found to accord with Temkin adsorption isotherm. Some thermodynamic and activation parameters have been calculated and analysed. The mechanism of physical adsorption is proposed from the values of Ea and ΔGads° obtained. The correlation of inhibition effect and molecular structure of fluconazole was then discussed by quantum chemistry study to further provide insight into the mechanism of the inhibitory action.
The inhibition effect of bis-thiadiazole derivatives (BTDs) against the corrosion of mild steel in 1M HCl solution was studied by weight loss, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization methods. All the BTDs exhibited >90% inhibition efficiency at concentration as low as 40ppm. The adsorption of BTDs obeyed Langmuir adsorption isotherm. Both thermodynamic and activation parameters were calculated and discussed. Polarization curves indicate that they are mixed type of inhibitors. All the BTDs were adsorbed physically at lower concentration where as chemisorption was favoured at higher concentration.
Ketoconazole (KCZ) has been evaluated as a corrosion inhibitor for mild steel in aerated 0.1M H2SO4 by gravimetric method. The effect of KCZ on the corrosion rate was determined at various temperatures and concentrations. The inhibition efficiency increases with increase in inhibitor concentration but decrease with rise in temperature. Adsorption followed the Langmuir isotherm with negative values of ΔGads0, suggesting a stable and a spontaneous inhibition process. Quantum chemical approach was further used to calculate some electronic properties of the molecule in order to ascertain any correlation between the inhibitive effect and molecular structure of ketoconazole.
The inhibiting effect of four sulfa drugs compounds (e.g. sulfaguanidine, sulfamethazine, sulfamethoxazole and sulfadiazine) on mild steel corrosion in 1.0M HCl solutions were evaluated using both galvanostatic polarization and weight loss techniques. All the examined sulfa drug compounds reduce the corrosion of mild steel. Among the compounds studied, sulfadiazine exhibited the best inhibition efficiency and sulfaguanidine the lowest. The inhibition efficiency goes through a maximum for sulfaguanidine while it increases continuously with concentration to a limit with sulfadiazine, sulfamethoxazole and sulfamethazine respectively. Galvanostatic polarization measurements indicate that all the examined compounds are of mixed inhibitor type with predominant cathodic effectiveness. Moreover, the results revealed a better performance for these compounds as corrosion inhibitors in HCl than in H2SO4 solutions. Also, the corrosion inhibition mechanism is discussed.
The corrosion inhibition of mild steel in 1M H2SO4 using polyacrylamide (PA) in the presence of iodide ions was studied at 30–60°C using weight loss and hydrogen evolution methods. Results obtained showed that inhibition efficiency increased with increase in concentration of PA and decreased with increase in temperature. The inhibition efficiency of PA synergistically increased on addition of KI. The adsorption of PA alone and in combination with iodide ions on the metal surface is found to obey Freundlich, Temkin and Flory–Huggins adsorption isotherms at all temperatures studied. Phenomenon of physical adsorption is proposed from the values of Ea and ΔGads° obtained. Synergism parameter evaluated is found to be greater than unity for all concentrations of PA indicating that the enhanced inhibition efficiency of PA caused by addition of iodide ion is only due to synergism. Adsorption of PA and (PA+KI) on to mild steel surface is spontaneous.
The corrosion inhibition of cold rolled steel in 0.5M sulfuric acid in the presence of tween 60 and sodium chloride (NaCl) has been investigated by using weight loss and electrochemical techniques. The inhibition efficiency increases with increasing tween 60 concentration at the same temperature, but decreases with increasing temperature studied. A synergistic effect exists when tween 60 and chloride ions are used together to prevent cold rolled steel corrosion in 0.5M sulfuric acid at every experimental temperature. The polarization curves show that tween 60 is a cathodic inhibitor, while the complex of tween 60 and NaCl is a mixed-type inhibitor. The experimental results suggest that the presence of chloride ions in the solution stabilizes the adsorption of tween 60 molecules on the metal surface and improves the inhibition efficiency of tween 60. The adsorption of single tween 60 follows the Temkin adsorption isotherm, but the complex accords with the Langmuir adsorption isotherm. Some thermodynamic parameters such as adsorption heat, adsorption entropy and adsorption free energy has been calculated by employing thermodynamic equations. Kinetic parameters such as apparent activation energy and pre-exponential factor have been calculated and discussed.
Corrosion inhibitive performance of 2-aminopyrimidine (APr), 2,4-diaminopyrimidine (dAPr), 2,4-diamino-6-hydroxy-pyrimidine (dAHPr) and 2,4,6-triaminopyrimidine (tAPr) during the acidic corrosion of steel surface was investigated using three methods, MP2, ab initio Hartree–Fock and density functional theory (DFT). Quantum chemical parameters such as the highest occupied molecular orbital energy (EHOMO), the lowest unoccupied molecular orbital energy (ELUMO), energy gap (ΔE), dipole moment (μ), sum of the total negative charge (TNC), molecular volume (MV), electronegativity (χ), chemical potential (Pi), global hardness (η), softness (σ) and the fraction of electrons transferred (ΔN), were calculated. Furthermore, the interaction energies of the inhibitors with the iron surface were studied. A good correlation was found between the theoretical data and the experimental results.
By considering adsorption processes of organic compounds as being determined by the electronic distribution in the “anchoring”
group of an adsorbate, a correlation has been derived between adsorption measurements and Hammett‐like substituent constants
through the use of Linear Free Energy Relations (LFER). The analysis is extended to corrosion inhibitors by assuming that
the mechanism of inhibition by organic molecules is chemisorption and that the energetics of the corrosion process per se are unaffected by the addition of substituents on the parent compound.
The validity of hybrid and nonlocal DFT methods are tested on examples of systems which are difficult to model by way of quantum chemistry techniques. The electron affinities for the oxygen and fluorine atoms were calculated. The exothermicity, the barrier for the fluorine atom reaction with the hydrogen molecule, and the energy of the H–F bond and its distance were computed with DFT methods, as well as, with ROHF, MPn, and QCISD(T) ab initio methods. The computations were performed by using various basis sets, with 6‐311++G(3df,3pd) as the largest. The obtained results are compared with the experimental values. The results of the Becke3LYP hybrid method is in qualitative agreement with experimental results and in the majority of the cases reassembles the high cost QCISD(T) calculation results. Considering the modest computational cost for DFT methods, Becke3LYP/6‐311+G(2d,2p) is suggested as the standard theory model for computation, and Becke3LYP/6‐311++G(3df,3pd) as the model for generating highly accurate results. They should be applicable to relatively sizable chemical systems. © 1996 American Institute of Physics.
The inhibition performance of mebendazole, a drug, on mild steel in molar hydrochloric acid solution was studied by weight loss and electrochemical methods. The maximum inhibition efficiency 96.2% was observed in presence of 2.54 × 10−4 M inhibitor. Polarization measurements showed that the inhibitor is mixed type. Data obtained from EIS studies were analyzed to model inhibition process through appropriate equivalent circuit models. The results obtained from the different methods are in good agreement. The various thermodynamic parameters of dissolution and adsorption processes were evaluated in order to elaborate adsorption mechanism. Adsorption of inhibitor obeyed Langmuir adsorption isotherm model.
2,3-diphenylbenzoquinoxaline (2,3DPQ) has been synthesized and its inhibiting action on the corrosion of mild steel in 0.5 M H2SO4 has been assessed by weight loss method at 30 °C. The results of the investigation show that this compound has excellent inhibiting properties for steel corrosion in sulphuric acid. Inhibition efficiency increases with increase in the concentration of the inhibitor. The adsorption of 2,3DPQ onto the mild steel surface followed the Langmuir adsorption model with the free energy of adsorption of −11.4 kJ mol−1. Quantum chemical calculations were employed to give further insight into the mechanism of inhibition action of 2,3DPQ.
The synergism between red tetrazolium (RT) and uracil (Ur) on the corrosion of cold rolled steel (CRS) in H2SO4 solution is first investigated by weight loss, potentiodynamic polarization, and atomic force microscope (AFM). Effects of inhibitor concentration (25–500 mg l−1), temperature (20–50 °C), and acid concentration (1.0–5.0 M) on synergism are discussed systematically. The results reveal that RT has a moderate inhibitive effect, and its adsorption obeys the Freundlich adsorption isotherm. For Ur, it has a poor effect. However, incorporation of RT with Ur significantly improves the inhibition performance, and produces synergistic inhibition effect.
A generalized concept of philicity is introduced through a resolution of identity, encompassing electrophilic, nucleophilic, and radial reactions. Locally, a particular molecular site may be more prone to electrophilic attack or another may be more prone to nucleophilic attack, but the overall philicity of the whole molecule remains conserved. Local philicity is by far the most powerful concept of reactivity and selectivity when compared to the global electrophilicity index, Fukui function, local softness, or global softness because it contains information about almost all of the known global and local descriptors of chemical reactivity and selectivity.
Recently (1) the rate data for the generalized nucleophilic displacement reaction were reviewed.
The effect of 2,5-bis(4-pyridyl)-1,3,4-thiadiazole (4-PTH) on the corrosion of mild steel in acidic media (1 M HCl, 0.5 M H2SO4, 1 M HClO4) has been investigated using weight loss measurements, electrochemical impedance spectroscopy and potentiodynamic polarisation. These studies have shown that 2,5-bis(4-pyridyl)-1,3,4-thiadiazole is good inhibitor for mild steel in 1 M HCl, 0.5 M H2SO4 and 1 M HClO4 solutions, the better performances are seen in the case of 1 M HCl solutions. But in 1 M HClO4, the 4-PTH stimulates corrosion at low concentrations. Polarisation curves indicate that the 4-PTH is a mixed-type inhibitor in all acidic media and E (%) is temperature-dependent. Adsorption on the mild steel surface follows the Langmuir isotherm model in all acidic media. The electronic properties obtained using the Hartree-Fock AB initio 3-21G quantum chemical approach, were correlated with the experimental efficiencies. (c) 2005 Elsevier Ltd. All rights reserved.
The density functional theory (DFT) at the B3LYP/6-31G (d,p) and B3LYP/6-311G(d,p) basis set levels and ab initio calculations using the HF/6-31G (d,p) and HF/6-311G(d,p) methods were performed on four rhodanine azosulpha drugs (namely 5-sulfadiazineazo-3-phenyl-2-thioxo-4-thiazolidinone, 5- sulfamethazineazo-3-phenyl-2-thioxo-4-thiazolidinone, 5-sulfadimethoxineazo-3-phenyl-2-thioxo- 4-thiazolidinone, and 5-sulfamethoxazoleazo-3-phenyl-2-thioxo-4-thiazolidinone) used as corrosion inhibitors for mild steel in acidic medium to determine the relationship between the molecular structure of the rhodanine azosulpha drugs and inhibition efficiency(%IE). The quantum chemical parameters/descriptors, namely, EHOMO (highest occupied molecular orbital energy), ELUMO (lowest unoccupied molecular orbital energy), the energy difference (ΔE) between EHOMO and ELUMO, dipole moment (μ), electron affinity (A), ionization potential (I), the absolute electronegativity (X), absolute hardness (η), softness (σ), polarizability (α), the Mulliken charges, and the fraction of electrons (ΔN) transfer from inhibitors to iron, were calculated and correlated with the experimental %IE. Quantitative structure activity relationship (QSAR) approach has been used, and a composite index of some quantum chemical parameters/descriptors was performed to characterize the inhibition performance of the studied molecules. The results showed that the inhibition efficiency (%IE) of the rhodanine azo sulfa drugs studied was closely related to some of the quantum chemical parameters/descriptors but with varying degrees of correlation coefficient (R2). The %IE also increased with the increase in EHOMO and decrease in EHOMO−ELUMO; and the areas containing N atoms are the most possible sites for bonding to the metal iron surface by donating electrons to the metal. The HOMO orbitals consist of 61.73–63.04% double bonded S atom (7(S)), and most of the rest are concentrated on the rhodanine group; so, the rhodanine molecule plays an important role in bonding of sulfa drugs with metal atom in the corrosion process. The calculated/estimated %IE of the compounds studied was found to be close to the experimental %IE. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010
The corrosion inhibition of cold rolled steel in 0.5 M sulfuric acid in the presence of 8-hydroxyquinoline and sodium chloride (NaCl) has been investigated by using weight loss and electrochemical techniques. The inhibition efficiency increases with increasing concentration of 8-hydroxyquinoline at the same temperature, but decreases with increasing temperature studied. A synergistic effect exists when 8-hydroxyquinoline and chloride ions are used together to prevent cold rolled steel corrosion in 0.5 M sulfuric acid at every experimental temperature. The polarization curves show that 8-hydroxyquinoline is a cathodic inhibitor, while the complex of 8-hydroxyquinoline and NaCl is a mixed-type inhibitor. The experimental results suggested that the presence of chloride ions in the solution stabilizes the adsorption of 8-hydroxyquinoline molecules on the metal surface and improved the inhibition efficiency of 8-hydroxyquinoline. The adsorption of single 8-hydroxyquinoline follows the Temkin adsorption isotherm, but the complex accords with the Langmuir adsorption isotherm. Some thermodynamic parameters such as adsorption heat, adsorption entropy and adsorption free energy have been calculated by employing thermodynamic equations. Kinetic parameters such as apparent activation energy and pre-exponential factor have been calculated and discussed.
Corrosion inhibition efficiencies of 3-amino-1,2,4-triazole (3-ATA), 2-amino-1,3,4-thiadiazole (2-ATDA), 5-(p-tolyl)-1,3,4-triazole (TTA), 3-amino-5-methylmercapto-1,2,4-triazole (3-AMTA) and 2-aminobenzimidazole (2-ABA) on steel in sodium chloride media were investigated using Tafel extrapolation method. Potentiostatic current–potential curves were utilized to derive corrosion potentials (Ecorr), corrosion current densities (icorr), surface coverage degrees (θ) and corrosion inhibition efficiencies (η, %). 2-ABA was found to have the highest inhibition efficiency in both, 2.5 and 3.5% aqueous NaCl media. For all the inhibitors studied, surface coverage and inhibition efficiency values were found to increase with increasing concentration of the compound concerned. Inspection of the θ values indicate that the adsorption process obeys the Temkin isotherm for TTA and 2-ABA, but the Langmuir isotherm is followed by 3-ATA, 2-ATDA and 3-AMTA.