Corrosion Inhibitor Molecules Research Articles

EIS evaluation on the degradation behavior of rust-preventive oil coating exposure to NaCl electrolyte

The traditional evaluation on anti-corrosion performance of a rust-preventive oil is often time-consuming and of high cost. In this investigation, electrochemical impedance spectroscopy (EIS) has been employed to understand the degradation behavior of rust-preventive oil in contact with NaCl electrolyte, with a focus on analyzing the electrochemical responses that correspond to a different frequency range in the obtained EIS spectra. The results indicate that the obtained EIS spectra can be generally divided into four frequency ranges. The high-frequency range is influenced by the continuous seepage of NaCl electrolyte, and the sub-high frequency range can reflect the presence of reversed micelle formed by corrosion inhibitor molecules and water molecules. Besides, the mid-frequency range is associated with the adsorption process of corrosion inhibitor molecules at the oil-film/metal interface, and the low-frequency range is associated with the diffusion process of dissolved ferrous ions. An extended immersion will result in a continuous seepage of electrolyte into rust-preventive oil coating and degrade the adsorption of corrosion inhibitor molecules, leading to a poor corrosion protection performance of the oil coating. Therefore, it is believed that the proposed design can provide a method in evaluating the degradation behavior and corrosion protection performance of rust-preventive oil to underlying steel substrate by EIS measurement under a lower amplitude.

Theoretical Study and Virtual Screening of Nitrogen‐Containing Corrosion Inhibitors Based on Quantitative Structure–Activity Relationship

AbstractNitrogen‐containing corrosion inhibitors have a wide range of promising applications, and current conventional corrosion design and evaluation methods are largely based on empirical speculation and extensive exploratory experiments. Unfortunately, these efforts are often associated with high costs, long lead times, and a lot of “blind work.” In this work, we have computationally screened the quantum chemical parameters of five nitrogen‐containing corrosion inhibitor molecules and their corrosion inhibition properties by a molecular simulation method based on density functional theory calculations. The ultimate relationship between the corrosion inhibition efficiency (IE) of an adsorbent and its quantum chemical parameters was analyzed using linear regression by comparing the various quantum mechanical parameters of each inhibitor molecule, as well as the fraction of electrons (ΔN) that are transferred to the metal surface from the chemisorbed inhibitor molecule. Five different nitrogen‐containing corrosion inhibitor molecules were screened based on structural similarity. Meanwhile, their corrosion inhibition performance was evaluated using the most relevant structure–activity equations. The results showed that the synergistic effect between the corrosion inhibition performance and the orbital energies of highest occupied molecular orbital and lowest unoccupied molecular orbital was optimal under the HF/6‐31G(d) method, and the corresponding structure–activity relationship was established. Based on these results, a specific inhibitor molecule was found to have excellent corrosion inhibition performance with a predicted corrosion IE of up to 94.12 %.

Adsorption behavior of some green corrosion inhibitors on Fe (110) surface: The critical role of d-π interactions in binding strength

Wise selection and application of a green corrosion inhibitor requires a careful study of its adsorption mechanism at the metal surface. Herein, density functional theory calculations were carried out to investigate the adsorption behavior of six green corrosion inhibitor molecules on Fe(110) surface, i.e. serotonin, tyrosine, coumaric acid, histamine, vanillic acid, and lysine. Different adsorption configurations through the functional groups and aromatic rings were carefully examined for each molecule. The projected density of states, Bader charge values, charge density difference, and the ELF analysis were calculated For the energetically preferred adsorption configurations. Ab–initio molecular dynamics simulations were also performed to obtain the equilibrium structure for the adsorption of the molecules on the Fe(110) at 300 K in an acidic solution. The analyses reveal the critical role of π–d interactions, in the form of π–back donation, in determining the preferred adsorption configuration of the inhibitor molecules on the Fe(110). The adsorption energies were found to be in the range of −154.376 kJ/mol for lysine to −371.275 kJ/mol for coumaric acid. The adsorption energy data reveals that the molecules with larger π–networks have greater adsorption energies at the Fe (110) surface, and thus better corrosion protection efficiency.

Thin Films of a Complex Polymer Compound for the Inhibition of Iron Alloy Corrosion in a H3PO4 Solution.

The etching of iron alloy items in a H3PO4 solution is used in various human activities (gas and oil production, metalworking, transport, utilities, etc.). The etching of iron alloys is associated with significant material losses due to their corrosion. It has been found that an efficient way to prevent the corrosion of iron alloys in a H3PO4 solution involves the formation of thin complex compound films consisting of the corrosion inhibitor molecules of a triazole derivative (TrzD) on their surface. It has been shown that the protection of iron alloys with a mixture of TrzD + KNCS in a H3PO4 solution is accompanied by the formation of a thin film of coordination polymer compounds thicker than 4 nm consisting of TrzD molecules, Fe2+ cations and NCS-. The layer of the complex compound immediately adjacent to the iron alloy surface is chemisorbed on it. The efficiency of this composition as an inhibitor of iron alloy corrosion and hydrogen bulk sorption by iron alloys is determined by its ability to form a coordination polymer compound layer, as experimentally confirmed by electrochemical, AFM and XPS data. The efficiency values of inhibitor compositions 5 mM TrzD + 0.5 mM KNCS and 5 mM TrzD + 0.5 mM KNCS + 200 mM C6H12N4 at a temperature of 20 ± 1 °C are 97% and 98%, respectively. The kinetic parameters of the limiting processes of hydrogen evolution and permeation into an iron alloy in a H3PO4 solution were determined. A significant decrease in both the reaction rate of hydrogen evolution and the rate of hydrogen permeation into the iron alloy by the TrzD and its mixtures in question was noted. The inhibitor compositions 5 mM TrzD + 0.5 mM KNCS and 5 mM TrzD + 0.5 mM KNCS + 200 mM C6H12N4 decreased the total hydrogen concentration in the iron alloy up to 9.3- and 11-fold, respectively. The preservation of the iron alloy plasticity in the corrosive environment containing the inhibitor under study was determined by a decrease in the hydrogen content in the alloy bulk.

Insight into the corrosion inhibition performance of Jasmine flower extract on copper in sulfuric acid medium using experimental and theoretical calculation methods

BackgroundCopper is widely used in all areas of society, but it is easy to be corroded in corrosive media, which causes certain economic losses. Among many anti-corrosion methods, adding corrosion inhibitors is an efficient, convenient and common method. However, there are some shortcomings in traditional corrosion inhibitors, so it is urgent to develop an efficient corrosion inhibitor with no toxicity and low cost as well as no harm to the environment. MethodsThe corrosion performance of Jasmine flower extract (JFE) for copper in 0.5 mol/L sulfuric acid medium was studied by electrochemical test, and the microstructure and chemical composition of copper surface were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM) and atomic force microscope (AFM). The interaction mechanism between corrosion inhibitor molecules and copper was analyzed based on theoretical calculation. Significant findingsThe results show that JFE is an efficient and environment-friendly corrosion inhibitor. In a certain temperature range (298 ∼ 308 K), when the concentration of JFE is 500 mg/L, the corrosion inhibition efficiency (η) is not less than 94.0%. According to Langmuir adsorption model, the JFE adsorbs on the copper surface as a mixed type of inhibitor.

Thin 1,2,4-Triazole Films for the Inhibition of Carbon Steel Corrosion in Sulfuric Acid Solution

Etching of steel items in sulfuric acid solution is used in various human activities (oil and gas industry, metal production, utilities, transport, etc.). This operation is associated with significant material costs due to corrosion losses of the metal. It has been found that an efficient way to prevent corrosion of steel in sulfuric acid solution involves the formation of thin protective films consisting of corrosion inhibitor molecules of triazole class on its surface. It has been shown that the protection of steels with a 3-substituted 1,2,4-triazole (3ST) in H2SO4 solution is accompanied by the formation of a polymolecular layer up to 4 nm thick. The 3ST layer immediately adjacent to the steel surface is chemisorbed on it. The efficiency of this compound as an inhibitor of corrosion and hydrogen absorption by steel is determined by its ability to form a protective organic layer, as experimentally confirmed by XPS and AFM data. The kinetic constants of the main stages of hydrogen evolution and permeation into steel in the H2SO4 solution were determined. A significant decrease in both the reaction rate of cathodic hydrogen evolution and the rate of hydrogen permeation into steel by the triazole in question was noted. It has been shown that the preservation of the metal plasticity in the acid medium containing the triazole under study is due to a decrease in the hydrogen concentration in the metal bulk.

Pyrazole acylhydrazone Schiff bases as magnesium alloy corrosion inhibitor: Synthesis, properties and mechanism investigation

Four novel pyrazole acylhydrazone Schiff bases were synthesized and tested as corrosion inhibitors for AZ91D in 0.5 wt.% NaCl solution. These inhibitors had good corrosion inhibition performance on Mg alloy. The results show that the aryl ring (Ar1) and aryl heterocyclic ring(Ar2) in the inhibitor molecules can improve the rigidity of the molecular structure and facilitate the adsorption of inhibitor molecules on the surface of magnesium alloy. The surface morphologies of magnesium alloy were observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The possible inhibition mechanism was studied by X-ray photoelectron spectroscopy (XPS). The results indicated that the corrosion inhibitor molecules deposited on the surface of AZ91D Mg alloy by cyclic voltammetry can form an effective protective film and improved the inhibition efficiency (92.2%) of corrosion inhibitors.

Nanomechanical Stability of Laterally Heterogeneous Films of Corrosion Inhibitor Molecules Obtained by Microcontact Printing on Au Model Substrates

Self-assembled monolayers of corrosion inhibitors of the mercaptobenzimidazole family, SH-BimH, SH-BimH-5NH2, and SH-BimH-5OMe, were formed on template-stripped ultraflat Au surfaces using microcontact printing, and subsequently analyzed using X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and AFM-force spectroscopy (AFM-FS) using a quantitative imaging (QI) mode. Printing of all used inhibitor molecules resulted in clear patterns and in slightly more compact films compared to immersion. The stability of the monolayers is further probed by AFM-FS. Adhesion values of laterally heterogeneous inhibitor-modified surfaces compared to bare Au surfaces, nonpatterned areas, and fully covered surfaces are analyzed and discussed. Microcontact printing confers a superior nanomechanical stability to imidazole-modified films of the printed surface patches as compared to homogeneously covered surfaces by immersion into the inhibitor solution.

Choline amino acid ionic liquids as green corrosion inhibitors of mild steel in acidic medium

The corrosion inhibition performance of three choline amino acid ionic liquids ([Ch][AA]ILs) for mild steel in 1 M HCl solution was evaluated by electrochemical analysis, gravimetric measurement, and surface morphological characterization in the temperature range of 298–328 K in this paper. The results of the polarization experiments show that [Ch][AA]ILs affect the cathode and anode reaction processes, proving that [Ch][AA]ILs are mixed corrosion inhibitors. Choline phenylalanine ionic liquids ([Ch][Phe]) exhibit the highest corrosion prevention efficiency among the three chosen corrosion inhibitors, as proven by SEM/EDS scanning, XPS analysis, and molecular dynamics simulation. The values of standard free energy of adsorption ΔGads range between − 20 kJ·mol-1 and − 40 kJ·mol-1, showing that inhibitor molecule adsorption on the metal surface involves both physical and chemical adsorption. According to the results of XPS research and quantum chemical calculations, the adsorption of corrosion inhibitor molecules on the metal surface is strongly related to the anions. The corrosion inhibitor molecules form a thick monolayer adsorption layer on the metal surface, preventing metal-corrosive media interaction. The molecular dynamics simulation findings reveal that the corrosion inhibitor molecules replace the solvent water or any other ions pre-adsorbed on the metal surface during the adsorption process, protecting the metal from corrosion.

Development of data driven machine learning models for the prediction and design of pyrimidine corrosion inhibitors

Pyrimidines have been shown as promising nontoxic corrosion inhibitors for carbon steel in acid media that can replace toxic chemicals currently in use. However, the discovery of this important corrosion inhibitor has mainly be conducted by expensive trial and error experimental approaches. However, recent studies indicates that the use of machine learning can help in the speedy discovery of novel corrosion inhibitor molecules with minimal cost. In the present work, machine learning algorithms were utilized to develop predictive models for fifty-four (54) pyrimidines derivatives whose experimentally determined inhibition efficiencies data as corrosion inhibitors for carbon steel in hydrochloric acid medium are available in the literature utilizing the partial least square regression (PLS) and the random forest (RF). Seven descriptors were selected by PLS and used to develop the linear model. The variable importance results using the PLS indicates that molecular mass, molecular volume, electrophilicity, electronegativity, energy of the lowest unoccupied molecular orbital, electron affinity, and the logarithm of the partition coefficient were the main factors that determine the inhibition efficiencies. RF was used to capture the nonlinear nature of the data and to accurately predict the inhibition efficiency. Rigorous internal and external validation were performed using the PLS and RF to further verify the robustness and predictive ability of the models. The random forest yielded the best results with the mean standard error (MSE) of 32.602 compared to the PLS with MSE of 64.641. Both models were subsequently used for the prediction of five (5) new pyrimidines with very high inhibition efficiency. The result of this work can provide reference information and theoretical guidance for designing and synthesizing new and effective pyrimidines corrosion inhibitors.

Corrosion inhibition of Pichia sp. biofilm against mild steel corrosion in 1 M H2SO4

Pichia sp. was isolated from rotten gooseberry (Phyllanthus emblica) and monitored for corrosion inhibition properties by means of biofilm-forming ability. The corrosion inhibition potential of Pichia sp. was evaluated against mild steel corrosion in 1 M H2SO4 via standard weight loss, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization (PP) techniques. Further, Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) with energy dispersive X-ray (EDX), X-ray photoelectron (XPS) spectroscopy, and atomic force microscopic (AFM) techniques were employed for confirming the biofilm accumulation on the mild steel (MS) surface. The weight loss investigation was carried out at varying temperatures (283 K−303 K), which showed the increasing trend of inhibition efficiency (IE%), and decreasing trend of corrosion rate, along with increasing Pichia sp. isolate’s concentrations. Pichia sp. isolate has shown maximum corrosion inhibition efficiency (>90%) at 283 K with an optimum concentration of 9 × 106 (CFU/mL). However, temperature studies insisted on the physical adsorption of corrosion inhibitor molecules over the metal surface. EIS data revealed enhanced values of charge transfer resistance (Rct), when increasing Pichia sp. isolate concentrations. Potentiodynamic polarization (Tafel curve) investigation revealed that Pichia sp. isolate exhibited mixed-type corrosion inhibition, while predominantly controlling the anodic reaction. The surface analysis data revealed the adherence and anticorrosive nature of Pichia sp. isolate on the MS surface, and a possible corrosion inhibition mechanism has also been discussed.

Optimizing the performance of a composite corrosion/scale inhibitor for CO2 flooding wells

To solve the corrosion and scaling problems of CO2 flooding wells, a novel composite corrosion and scale inhibitor FIQC-APES was developed in the study. Two agents with high performances were identified from six corrosion inhibitors and five scale inhibitors based on quantum chemical calculations, electrochemical methods, and static scale inhibition tests. After optimizing the reagent ratio, the two agents were devised and combined together to create a new composite corrosion and scale inhibitor for CO2 flooding wells. Finally, the protective performance of the composite agent was evaluated under simulated working conditions. The results revealed that a ratio of corrosion inhibitor (FIQ-C) to scale inhibitor (APES) (2:1) was the optimal ratio for composite corrosion and scale inhibitors. On metal surface and calcite crystal surface, corrosion inhibitor and scale inhibitor molecules could be stably adsorbed. The composite corrosion and scale inhibitor had a good protective effect on H-grade sucker rods, N80 pipes, and P110 pipes under the simulated conditions of CO2 flooding wells (CO2 partial pressure was 4 MPa). The corrosion rate was less than 0.045 mm/y. The corrosion and scale inhibition rates were respectively more than 96% and 95%, suggesting that the corrosion and scale inhibition performances of the composite inhibitor met the requirements for oilfield protection. The study suggested that FIQC-APES could act as a novel inhibitor for controlling corrosion and scale in CO2 flooding wells.

Novel cationic aryl bithiophene/terthiophene derivatives as corrosion inhibitors by chemical, electrochemical and surface investigations

Two novel bithienyl fluorobenzamidine derivatives namely, 4-([2,2′:5′,2′′-terthiophen]-5-yl)-2-fluorobenzamidine hydrochloride salt (MA-1615), 5′-(4-amidino-3-fluorophenyl)-[2,2′-bithiophene]-5-carboxamidine dihydrochloride salt (MA-1740) were synthesized, characterized and their corrosion inhibition properties were evaluated by electrochemical methods for carbon steel (C-steel) in 1 M HCl. Experimental investigations revealed that the inhibition effectiveness of the investigated inhibitors (INHs) by the Tafel polarization method followed the order: MA-1740 (96.9%) > MA-1615 (95.6%), demonstrating higher efficiency than inhibitors of similar structure reported in the literature. The investigated bithiophene derivatives exhibit mixed-type corrosion inhibition characteristics by blocking the active sites on the surface of C-steel. EIS study revealed that the INHs behave as interface-type corrosion inhibitors. UV–Visible spectrometric measurements confirmed a complex formation between the Fe2+ cation released during the corrosion reactions and inhibitor molecules.

Capturing the synergistic effects between corrosion inhibitor molecules using density functional theory and ReaxFF simulations - A case for benzyl azide and butyn-1-ol on Cu surface

We have employed DFT and ReaxFF simulations to explain synergism between benzyl azide (BA) and butyn-1-ol (BOL) molecules for copper. DFT computed HOMO-LUMO gaps (eV) follow the trend: BA-BOL (5.58) < BA (5.85) < BOL (7.07); while the interaction energy magnitudes, |Eint| (eV) for most stable configurations on Cu (111) surface follow the trend: BA-BOL (2.55) > BA-BA (2.11) > BOL-BOL (0.62) validating synergism. Lateral interactions between NBA-HBOL are possibly responsible for synergism. ReaxFF simulations, although significantly faster, agree qualitatively with DFT. Thus, an intelligent use of DFT and ReaxFF can help expedite screening of synergistic inhibitors for industrial applications.

Unraveling the microstructural properties of cement-slag composite pastes incorporated with smart polymer-based corrosion inhibitors: From experiment to molecular dynamics

Incorporation of corrosion inhibitor into the cement-slag composite pastes can effectively improve the resistance to seawater erosion. However, corrosion inhibitor inevitably affects the microstructures and transport properties of cement-slag composite pastes, which poses a great challenge for the engineering application prospects of the composite pastes modified by corrosion inhibitor. In this paper, a smart organic polymer with hydrophilic and hydrophobic components is designed as corrosion inhibitors, and a combination of experiments and molecular dynamics (MD) simulations is employed to investigate the effect of this smart polymer-based corrosion inhibitor on cement-slag composite pastes under seawater erosion. Experiments show that this smart polymer-based corrosion inhibitor has profound effect on the hydration properties, pore structures and ions resistance of cement-slag composite pastes, with an optimum content of approximately 6%. MD simulations reveal the nano-mechanism by which this smart polymer-based corrosion inhibitor hinders water and ion transport in the calcium aluminate-silicate hydrate (CASH) nanopores. Analysis suggests that strong electrostatic interactions, originating from the CaCASH-Oinhibitor pairs and the H-bond networks, are the primary sources of the corrosion inhibitor-CASH bonding mechanism. Besides, the migration rates of water and ions are reduced as the large cluster structures formed among the corrosion inhibitor molecules, water molecules and erosive ions.

Inhibition behavior of nitrogen-doped carbon dots on X80 carbon steel in acidic solution

In order to restrain the corrosion issue in the picking process of metal materials, nitrogen-doped carbon dots (NCDs) with a size of 2 ~ 4 nm have been fabricated via hydrothermal synthesis with citric acid and thiourea as precursors. The corrosion inhibition behavior of NCDs on X80 carbon steel were investigated in 0.1 M HCl solutions with electrochemical experiments, the weight loss method, and surface morphology analysis. The Tafel curves showed that the inhibition efficiency reached as high as 92.98% at the NCDs concentration of 10 mg·L−1, indicating that NCDs had significant anti–corrosion capacity for X80 carbon steel. Impedance spectroscopy data revealed that the diameter of the capacitive reactance increased with increasing the NCDs concentration. More corrosion inhibitor molecules can be adsorbed on the metal surface instead of water molecules, which enhanced corrosion resistance of carbon steel. Weight loss experiment and surface morphology analysis strongly supported the results of electrochemical experiments. In addition, the NCDs adsorption at X80 surface followed the Langmuir adsorption isotherm, which was mainly dominated by physical adsorption.

Study on fine lines and undercut suppression of printed circuit board prepared by electrolytic etching

PurposeThe purpose of this paper is to study an electrolytic etching method to prepare fine lines on printed circuit board (PCB). And the influence of organics on the side corrosion protection of PCB fine lines during electrolytic etching is studied in detail.Design/methodology/approachIn this paper, the etching factor of PCB fine lines produced by new method and the traditional method was analyzed by the metallographic microscope. In addition, field emission scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were used to study the inhibition of undercut of the four organometallic corrosion inhibitors with 2,5-dimercapto-1,3,4-thiadiazole, benzotriazole, l-phenylalanine and l-tryptophan in the electrolytic etching process.FindingsThe SEM results show that corrosion inhibitors can greatly inhibit undercut of PCB fine lines during electrolytic etching process. XPS results indicate that N and S atoms on corrosion inhibitors can form covalent bonds with copper during electrolytic etching process, which can be adsorbed on sidewall of PCB fine lines to form a dense protective film, thereby inhibiting undercut of PCB fine lines. Quantum chemical calculations show that four corrosion inhibitor molecules tend to be parallel to copper surface and adsorb on copper surface in an optimal form. COMSOL Multiphysics simulation revealed that there is a significant difference in the amount of corrosion inhibitor adsorbed on sidewall of the fine line and the etching area.Originality/valueAs a clean production technology, electrolytic etching method has a good development indicator for the production of high-quality fine lines in PCB industry in the future. And it is of great significance in saving resources and reducing environmental pollution.

Application of hollow mesoporous organosilica nanoparticles as pH and redox double stimuli-responsive nanocontainer in the controlled release of corrosion inhibitor molecules

The stimuli-responsive release could reduce the waste of the corrosion inhibitor and realize the accurate repair of corroded region. In this work, hollow mesoporous organosilica nanoparticles (HMON) were first synthesized by silica-etching chemistry tailoring method. Then, HMON were encapsulated with 2-mercaptobenzothiazole (MBT) corrosion inhibitor molecules to build an intelligent corrosion inhibitor system, i.e., MBT@HMON. The microstructure and frame composition of the synthesized HMON were characterized. After the successful encapsulation of MBT into HMON, the release kinetics of MBT from HMON under different dithiothreitol (DTT) concentration and pH conditions were investigated. Finally, the corrosion inhibition performance of MBT@HMON for copper alloy was evaluated in 3.5 wt% NaCl solution by weight loss test and electrochemical impedance spectroscopy (EIS). The results show that the controlled release of corrosion inhibitor MBT from HMON could be realized by tuning the redox and pH conditions of corrosion medium. When the appropriate concentration of MBT@HMON was added into the corrosion medium (1.6 g·L−1 in this work), the corrosion of cooper alloy was greatly inhibited. This simple and general strategy of introducing corrosion inhibitors loaded HMON directly into the corrosion medium offers a new prospect for the application of nanocontainers in the intelligent corrosion protection of metallic materials.

Assessment of N-(4H-1,2,4-triazol-4-yl)octanamide as hydrochloric acid corrosion inhibitor for mild steel

The present study demonstrates a method to manipulate the adsorption behavior of corrosion inhibitor molecules through structural modification leading to significant enhancement of the corrosion inhibition efficiency. A weak corrosion inhibitor molecule 4-amino 1,2,4 triazole (AT) was structurally modified to N-(4H-1,2,4-triazol-4-yl)octanamide (OAT) through the attachment of an octanoyl chain as the hydrophobic tail. Probing of the adsorption behavior of both AT and OAT on mild steel in 1 M HCl using gravimetric, polarization, and electrochemical impedance spectroscopy (EIS) techniques revealed a change of the adsorption mechanism from physisorption to chemisorption due to the structural modification and the corrosion inhibition efficiency improved from 65 % (for 10 mM AT) to 99 % (for 0.3 mM OAT). OAT exhibited a temperature-independent inhibition efficiency of more than 99 % in 30−60 °C range. X-ray photoelectron spectroscopy (XPS) study indicated chemisorption of OAT molecules on the steel surface through nitrogen atoms of the triazole ring, resulting in the formation of a self-assembled monolayer (SAM). Finally, the efficacy of the OAT SAM to protect mild steel from corrosion in HCl medium was demonstrated using scanning electrochemical microscopy (SECM) and scanning electron microscopy (SEM).

Understanding the relationship between the structural properties of three corrosion inhibitors and their surface protectiveness ability in different environments

All-atom molecular simulations and chemical quantum calculations were used to understand the effect of the environment on the surface adsorption of corrosion inhibitor (CI) molecules. Three CIs abbreviated: TEPA, iTEPA and HC-iTEPA studied in this work, were selected to systematically investigate the influence of the alkyl tail, N-pendant group, imidazoline and benzene rings, on the CIs adsorption behavior. A relationship is provided between their structural properties and their surface protectiveness ability in different environments. Chemical quantum calculations revealed the electron distribution in inhibitors structures, indicating their ability to accept/donate charges from the Fe atoms in vacuum and in water solvation. The quantum molecular parameters in water solvation anticipated higher electron transfer ability of iTEPA in aqueous conditions compared to TEPA and iTEPA, thus, leading to stronger adsorption on iron surface, corroborated by the molecular dynamics (MD) classical simulations. MD simulations showed that nearly 53%, 39%, 59% reduction in adsorption energies was detected for single inhibitor molecule of TEPA, iTEPA, and HC-iTEPA shifting from water to CO2-saline media, respectively. The formation of water double adsorption layer contributed to decreasing the CIs adsorption energies by the larger surface separation distances spotted in the density profiles. Nevertheless, the multi-inhibitors study revealed strong adsorption of TEPA and iTEPA on the iron surface, while HC-iTEPA neglected cooperative adsorption and aggregated as a spherical-like micelle with lower surface coverage propensity. Radial distribution functions g(r) explored the preferential interactions of inhibitor-H2O and inhibitor-CO2 that guided the CIs adsorption conformation. Self-diffusivity coefficients of competing adsorbates with the three CIs were found to be one to two orders of magnitude lower near the interface than in the bulk.