Electrochemical Impedance Spectroscopy EIS Research Articles

Review of the Application of Gravimetric and Electrochemical Techniques to Evaluate Corrosion Mechanisms in Metal Materials

Corrosion in carbon steels is a phenomenon that causes degradation of mechanical properties; iron alloys are susceptible to corrosion. Factors such as changes in temperature, pH of the medium, and humidity accelerate the corrosion process, and the oxides formed can generate irreversible changes to the material. The evaluation of surface corrosion is necessary to be able to predict in time, to be able to provide good maintenance whether by coatings, inhibitors, or anticorrosive paints, in an opportune way, and to avoid large economic and structural losses. Gravimetric techniques such as mass loss and electrochemical techniques such as Open Circuit Potential-OCP and Electrochemical Impedance Spectroscopy-EIS, help understand the different corrosion mechanisms, simulate real conditions, and generate reproducible studies with efficiency of time and interpretation. This work shows a brief review of gravimetric and electrochemical techniques applied to the evaluation of corrosion of carbon steels.

Sol-gel immobilization of lipase enzyme on FTO modified with silica-zirconia and gold nanoparticles films for design of triglyceride impedimetric biosensor

A novel electrochemical sensing platform was created using the formation of a sequence of films, over a conductive fluorine-doped tin oxide glass (FTO), obtained using the sol-gel method and the dip coating technique. Firstly, thin films of silica-zirconia mixed oxides were deposited, in sequence an ionic silsesquioxane film stabilizing and controlling the size of gold nanoparticles (6.5 ± 2.4 nm) was settled, and after the lipase enzyme, obtained from Candida rugosa, was entrapped into a silica film maintaining its operational stability. The films were characterized by scanning electron microscopy (SEM) with EDX, UV–Vis spectroscopy and X-ray photoelectron spectroscopy (XPS). The thickness of each film on the FTO glass was evaluated by optical profilometry. The presence of the enzyme on the platform was confirmed by cyclic voltammetry with the ρ-nitrophenyl palmitate method. This platform was applied successfully as a biosensor for tributyrin (TB) determination by electrochemical impedance spectroscopy EIS, showing low limit of detection (LD) of 1.86 μmol L−1 and high sensitivity of 5.37 μΩ μmol−1 L. The biosensor presented a low KMapp value of 22.69 μmol L− 1 and the Vmaxapp value of 85.57 μmol L−1 min−1 suggesting that the enzyme, immobilized with this method retained activity promoting a fast enzymatic reaction with the TB.

An examination of the effectiveness of the expired drug isoprinosine in preventing aluminum corrosion in alkaline solutions using both computational and experimental techniques.

A now-expired medication called isoprinosine was examined in NaOH (0.50 M) solutions as a potential novel inhibitor of aluminum corrosion. The inhibitory effectiveness of the isoprinosine compounds was examined utilizing different electrochemical tests (open circuit potential OCP, potentiodynamic polarization and electrochemical impedance spectroscopy EIS), surface examination and quantum calculations. Increases in isoprinosine concentration were seen to increase the inhibitory efficacy. It was discovered that the inhibitory action, which results in the inhibition of charge and mass transfer and protects the aluminum against harmful ions, was brought on by isoprinosine molecules adhering to the aluminum surface. Additionally, the surface morphology of Al dissolved in a 0.50 M NaOH solution without and with the existence of an isoprinosine molecule was analyzed using SEM/EDX and AFM techniques. Utilizing the optimized geometric parameters of the ground state molecules, FMO simulations and additional studies were executed successfully utilizing the density functional theory (DFT/B3LYP/6-311++G(d,p)). Based on the expected energies for the molecular carriers of charge, HOMO and LUMO. Calculations are also done for the AIM charges, Fukui functions, AIM charges, and excitation energies. Furthermore, molecular dynamic was simulated to explore the corrosion inhibition efficiency and mechanism of inhibition. The computational results are in the same agreement with experimental results, showing that isoprinosine can inhibit the corrosion of aluminum in 0.5 M NaOH.

Investigation of Ti/Al2O3 + TiO2 and Ti + TiO2/Al2O3 + TiO2 hybrid coatings as protection of ultra-light Mg–(Li)–Al–RE alloys against corrosion

Low corrosion resistance is a significant problem of magnesium alloys, particularly ultra-light magnesium-lithium alloys. Surface treatment is one way to improve their corrosion resistance. The paper presents the results of tests of Ti/Al2O3 + TiO2 and Ti + TiO2/Al2O3 + TiO2 coatings obtained in a hybrid process combining PVD and ALD methods and ALD coating of Al2O3 + TiO2 type obtained on AE42 (Mg–4Li–2RE) and LAE442 (Mg–4Li–4Al–2RE). Structural studies were performed using scanning and transmission electron microscopy (SEM and TEM), atomic force microscopy and EDS and XPS spectroscopic methods. Potentiodynamic tests and electrochemical impedance spectroscopy EIS in 0.05 M NaCl solution were performed to determine the electrochemical properties of the tested materials. Moreover, tests of surface wettability and tribological properties using the ball-on-disc method were performed. Based on the analysis of anodic polarisation curves and Tafel analysis, it was found that the Ti + TiO2/Al2O3 + TiO2 coating showed the best potentiodynamic properties on both substrates. In particular, on the magnesium-lithium substrate, the value of the polarisation resistance of this hybrid coating is Rpol = 14 × 103 Ω × cm2, and the value of the corrosion current is jcorr = 0.4 µA/cm2. For the uncoated LAE442 substrate, the polarisation resistance is Rpol = 1.05 × 103 Ω × cm2, and the corrosion current value is jcorr = 5.49 µA/cm2. This improvement is due to the synergistic effect of the combined PVD and ALD technologies. The study confirmed the impact of hybrid coatings on improving the anti-corrosion and tribological properties of ultra-light magnesium alloys.

Graphene-Binding Peptide in Fusion with SARS-CoV-2 Antigen for Electrochemical Immunosensor Construction.

The development of immunosensors to detect antibodies or antigens has stood out in the face of traditional methods for diagnosing emerging diseases such as the one caused by the SARS-CoV-2 virus. The present study reports the construction of a simplified electrochemical immunosensor using a graphene-binding peptide applied as a recognition site to detect SARS-CoV-2 antibodies. A screen-printed electrode was used for sensor preparation by adding a solution of peptide and reduced graphene oxide (rGO). The peptide-rGO suspension was characterized by scanning electron microscopy (SEM), Raman spectroscopy, and Fourier transform infrared spectroscopy (FT-IR). The electrochemical characterization (electrochemical impedance spectroscopy—EIS, cyclic voltammetry—CV and differential pulse voltammetry—DPV) was performed on the modified electrode. The immunosensor response is based on the decrease in the faradaic signal of an electrochemical probe resulting from immunocomplex formation. Using the best set of experimental conditions, the analytic curve obtained showed a good linear regression (r2 = 0.913) and a limit of detection (LOD) of 0.77 μg mL−1 for antibody detection. The CV and EIS results proved the efficiency of device assembly. The high selectivity of the platform, which can be attributed to the peptide, was demonstrated by the decrease in the current percentage for samples with antibody against the SARS-CoV-2 S protein and the increase in the other antibodies tested. Additionally, the DPV measurements showed a clearly distinguishable response in assays against human serum samples, with sera with a response above 95% being considered negative, whereas responses below this value were considered positive. The diagnostic platform developed with specific peptides is promising and has the potential for application in the diagnosis of other infections that lead to high antibody titers.

Corrosion Resistance and Electrical Conductivity of Hybrid Coatings Obtained from Polysiloxane and Carbon Nanotubes by Electrophoretic Co-Deposition.

Nanocomposites developed based on siloxanes modified with carbon nanoforms are materials with great application potential in the electronics industry, medicine and environmental protection. This follows from the fact that such nanocomposites can be endowed with biocompatibility characteristics, electric conductivity and a high mechanical durability. Moreover, their surface, depending on the type and the amount of carbon nanoparticles, may exhibit antifouling properties, as well as those that limit bacterial adhesion. The paper reports on the properties of polysiloxane (PS) and carbon nanotubes (CNT) nanocomposite coatings on metal surfaces produced by the electrophoretic deposition (EPD). A comparison with coatings made of pure PS or pure CNT on the same substrates using the same deposition method (EPD) is provided. The coatings were examined for morphology and elemental composition (SEM, EDS), structural characteristics (confocal Raman spectroscopy), electrical conductivity and were tested for corrosion (electrochemical impedance spectroscopy-EIS, potentiodynamic polarization-PDP). The results obtained in this study clearly evidenced that such hybrid coatings conduct electricity and protect the metal from corrosion. However, their corrosion resistance differs slightly from that of a pure polymeric coating.

Recycling of Some Water Soluble Drugs for Corrosion Inhibition of Steel Materials: Analytical and Electrochemical Measurements

The accumulation of the expired vitamin B6 drugs is hazards for both our child’s and environment, the present research aimed to reuse the expired water soluble drug in its pharmaceutical form as potential non-toxic corrosion inhibitor for steel alloys used in manufacturer of the petroleum pipe lines in 1.0 M HCl. Atomic absorption spectroscopy(AAS) and electrochemical techniques were used to evaluate the corrosion inhibition efficiency, effect of concentrations and temperature were studied, the data show that the inhibition efficiency was increased with concentrations and decreased with temperature. Potentiodynamic polarization data show that the expired vitamin B6 retard both anodic and cathodic potential meaning it is a mixed inhibitor. The electrochemical impedance spectroscopy EIS, techniques data shows that the expired drug help to increases the polarization resistance by adsorbing on metal/electrolyte interface. This kind of adsorption found to obeying Langmuir adsorption isotherm model. The data obtained from the used techniques exhibit good agreement between them with (± 1) to prove that the used expired vitaminB6 medicinal drugs act as eco-friendly corrosion inhibitor for the steel in acidic environment in its pharmaceutical from

Self-Assembled MoS2/ssDNA Nanostructures for the Capacitive Aptasensing of Acetamiprid Insecticide

The aim of this work is to detect acetamiprid using electrochemical capacitance spectroscopy, which is widely used as a pesticide in agriculture and is harmful to humans. We have designed aptasensing platform based on the adsorption of a DNA aptamer on lipoic acid-modified MoS2 nano-sheets. The biosensor takes advantage of the high affinity of single-stranded DNA sequences to MoS2 nano-sheets. The stability of DNA on MoS2 nano-sheets is assured by covalent attachment to lipoic acid that forms self-assembled layer on MoS2 surface. The biosensor exhibits excellent capacitance performances owing to its large effective surface area making it interesting material for capacitive transduction system. The impedance-derived capacitance varies with the increasing concentrations of acetamiprid that can be attributed to the aptamer desorption from the MoS2 nanosheets facilitating ion diffusion into MoS2 interlayers. The developed device showed high analytical performances for acetamiprid detection on electrochemical impedance spectroscopy EIS- derived capacitance variation and high selectivity toward the target in presence of other pesticides. Real sample analysis of food stuff such as tomatoes is demonstrated which open the way to their use for monitoring of food contaminants by tailoring the aptamer.

Corrosion and Micromorphological Analysis of Temporary Stainless Steel and Titanium Alloy Anchorage Devices

The aim of this study was to compare the surface micromorphology and corrosion resistance of different temporary anchorage devices (TADs) composed of titanium alloy (SIN®) and stainless steel (DAT Steel® and Bio Ray®). Ten samples of each TAD were submitted to qualitative analyses using energy-dispersive and scanning electronic microscopy before and after immersion in artificial saliva (1500 ppm of fluoride) for 30 days. The chemical analysis was done by X-ray fluorescence, and the corrosion tests were performed by electrochemical means (open circuit potential—OCP, potentiostat, and electrochemical impedance spectroscopy—EIS, using anodic potentiodynamic polarization curves). Passive film resistance (PFR) and corrosion current were established. The corrosion rate was determined by the mass loss test. Greater smoothness and fewer machining defects were observed for the stainless steel TAD before artificial saliva immersion. Comparatively, higher corrosion resistance was found for titanium alloy TAD after immersion in saliva. There was no release of ions into the TAD when immersed in artificial saliva. ANOVA and Tukey tests showed that OCP (V) was significantly lower for the titanium alloy TAD (p = 0.030) than the stainless steel brands. Epite (V) and Epite−OCP (V) were significantly higher for the titanium alloy TAD (p = 0.0009 and p = 0.0005, respectively). Stainless steel TADs presented lower roughness surface than titanium alloy TAD, although the latter presented higher corrosion resistance than the former.

The Corrosion Resistance of Aluminum Alloy Modified by Laser Radiation

This study presents an analysis of the impact of the oxide layers, prepared utilizing fiber laser radiation (1062 nm) in ambient air with different process parameters, on the corrosion resistance of EN 5754 aluminum alloy. Due to both high corrosion resistance and high fatigue strength, a 5754 alloy is used, among others, in the marine, aerospace, automotive, and chemical industries. Nevertheless, it corrodes in aggressive environments (with high chloride ions concentration). The controlled delivery of laser radiation energy in the oxygen environment allows the formation of the oxide layer on the surface of the material. We have determined that it significantly affects the resistance of these materials to corrosion. As a result of laser irradiation, changes in the chemical structure of the surface layer (chemical composition as well as surface development) can be observed. It may exert both a positive and a negative consequence on the corrosion resistance. The electrochemical corrosion tests (potentiodynamic polarization and electrochemical impedance spectroscopy EIS) have been carried out in an aggressive environment (3% NaCl). Moreover, microscopic examination, chemical tests, and roughness were also performed. The study revealed that appropriate control of the laser process can significantly increase the original corrosion resistance of the 5754 aluminum alloy.

Heterocyclic Schiff bases as corrosion inhibitors for carbon steel in 1 M HCl solution: hydrodynamic and synergetic effect

{(1Z)-2-oxo-N′-phenyl-N-quinolin-8-ylpropanehydrazonamide (H2L-H) and (1Z)-N′-(4-bromophenyl)-2-oxo-N-quinolin-8-ylpropanehydrazonamide (H2L-Br)} have been studied as corrosion inhibitors of carbon steel in 1 M HCl medium by the weight loss method, potentiodynamic polarization, electrochemical impedance spectroscopy EIS, scanning electron microscopy SEM coupled with Energy Dispersion X-Ray Spectroscopy EDS, Atomic Force Microscopy AFM, IR and UV-visible spectroscopy. The inhibition efficacy has been shown to increase with increasing inhibitor concentration. The corrosion of the carbon steel is mainly controlled by a charge transfer process. The temperature effect was evidenced and the thermodynamic parameters were calculated. The adsorption of the inhibitors on the metal surface obeyed the Langmuir adsorption isotherm. The hydrodynamic effect and the synergetic effect have been implemented. Inhibitory efficiency decreases with increasing rotation speed and the used additives adsorb cooperatively to form a protective layer on the metal surface. The results obtained by the experimental measurements and those of the theoretical calculations (DFT and MD simulation) are in good correlation.

A family of chiral ionic liquids from the natural pool: Relationships between structure and functional properties and electrochemical enantiodiscrimination tests

In spite of the increasing fundamental and practical interest of electrochemistry in ionic liquids (ILs), exploration of chiral ionic liquids (CILs) in view of enantioselective electrochemistry and electroanalysis is surprisingly overdue. In this study a family of chiral ionic liquids (CILs) based on natural chiral building blocks, of easy synthesis, is detailedly characterized in terms of thermal and electrochemical properties, achieving valuable information about structure−property relationships on account of the systematicity of available family terms. Moreover, they are submitted to a series of chiral electroanalysis tests. Cyclic voltammetry in bulk CILs or with CIL as additives in a bulk achiral ionic liquid IL, shows small but statistically significant potential differences for the enantiomers of two quite different chiral probes, an interesting result since enantiodiscrimination in terms of potential differences in chiral voltammetry (more desirable respect to current differences) has been only seldom obtained so far. The present first example of enantioselective voltammetry in CIL media with stereocenters as localized chirality sources also offers an important and so far missing confirmation of the intrinsically superior level of the inherent chirality strategy, recently resulting in larger potential differences with the same protocols implemented in "inherently chiral" ionic liquid media. Furthermore, an alternative transduction mode, based on electrochemical impedance spectroscopy EIS, is proposed to effectively highlight the enantiodiscrimination ability of CIL media in analytical experiments.

Effect of Doping of Nanoparticles on the Properties of Zn-Ni Composite Coatings

The purpose of this paper was to investigate the effect of Al2O3 and TiO2 nanoparticles contents on structural proporties, microhardness and corrosion resistance of Zn-Ni alloy coationg. Zn-Ni, Zn-Ni-Al2O3 and Zn-Ni-TiO2 composite coatings were electrodeposited on steel substrate by direct current in sulphate bath.The structure of the coatings was studied by X-ray diffration and by scaning electron miroscopy. The results showed the appearance of Ni5Zn21 phases and that the incrorporation of Al2O3 and TiO2 in the Zn-Ni coating refined the crystal grain size.The corrosion performance of coating in the 0.6M NaCl as a corrisive solution was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy EIS methods. It was found that the incorporation of nanoparticules in Zn-Ni alloy coating have better corrosion resistance and the values of Rct and Zw increase, while the values of Cdl decrease with increasing of nanoparticules.

Improved Performance of LiFePO4 Cathode through Use of Single Lithium Ion Conducting Polymer Binders Based on Sp 3 Boron Atoms

Active materials and electrolytes are widely explored to improve the energy and power density of the batteries. However, polymer binder is the key component for the control of the electrode (composite) interfaces, which include the conductive agent/active materials interface, the conductive agent/current collector interface, and the initial active materials/electrolyte interface, facilitating electron and ion conductivity, retaining the physical structure of electrode and stable cycling improving the performance of the LIB. According to Sugita et al. [1] and the approach based on the thermodynamic work of adhesion, polar binders improve the composite electrode wettability, increasing the ionic conductivity in conventional composites; these showed highest capacity, suggesting that Li+ conduction inside the polymeric binder contributes to the enhancement of electrochemical performance. In this work, we report a serie of binders based on sp3 boron atoms and poly(ethylene glycol) PEG400 bridges and other alcohols. These binders were obtained by polymerization in-situ with lithium tetrametoxyborate (LTMB), on the LiFePO4 and SP-carbon surfaces (120°C, 12h), after homogenized in methanol by magnetic stirring. The electrodes based on polyborates as binders were processed and compared with electrodes with PVDF as binder, according to the methodology used by G. Guzman et al. [2] In addition, the effect of charge delocalization present in BO4 - groups, associated to strong electron-withdrawing substituents and their effect on the ionic conductivity in polyborates binders, was studied by electrochemical impedance spectroscopy EIS. The results suggest that increased in ionic conductivity of the SLICB relative to the PVDF, decreases the charge transfer resistance in LiFePO4 cathodes. During the process of stabilization of the cell at C-rate of C/10, the cathodes based on PVDF as binder have better capacity, however, it is easily degraded with the increase of the C-rate. In general, the use of SLICB allows improving the load capacity of LiFePO4 cathodes, mainly at high C-rate values. Besides, they allow for a lower degree of degradation, which is possible to observe in the reversibility tests at low C-rate values, see figure 1. Figure 1. Rate capabilities collected during 40 cycles for a Li-ion cell at subsequent C-rates of 0.1, 1, 10 and 0.1C. Cell contains a cathode composite comprised: LiFePO4: SP-Carbon and different polymer binders 86-07-07 %w) and electrolyte of 1 M LiPF6 in a mixture of PC:EC:DMC (1:1:1 V%). Acknowledgements This work was supported, GR thanks (project seciti/080/2017) IG thanks CONACYT (proyect 237343) for financial support. G. Guzman is grateful to CONACYT for the scholarship granted to pursue his doctoral studies. Reference s : [1] M. Sugita, H. Nakamura, M. Yoshio, IMLB-2006, No. 486. [2] G. Guzmán, J. Vazquez, G. Ramos, M. Bautista, I. González, Electrochimica Acta 247 (2017) 451–459 Figure 1

A New Polymeric Nanocomposite Coating for Corrosion Protection of Carbon Steel in HCl Solution

In the present work, four polymeric nanocomposite PNC coatings were prepared with different concentrations of yttrium aluminum garnet nanoparticles YAG-NPs in polyvinyl butyral PVB matrix. The corrosion protection of the PNC coatings applied on the carbon steel surface was investigated in 1.0 M HCl solution by electrochemical impedance spectroscopy EIS. The YAG-NPs were synthesized by pulse electrochemical method. The formation of YAG-NPs was confirmed through XRD and SEM analysis. The EIS data obtained from the coated samples both without and with YAG-NPs samples were fitted with an equivalent circuit containing two time constants. The protection efficiency values of the PNC coatings were calculated from EIS data. The PNC coating containing 0.025 wt YAG-NPs as the efficient coating showed the best corrosion protection in HCl solution for immersion times up to 28 days.

A Novel Application for Low Frequency Electrochemical Impedance Spectroscopy as an Online Process Monitoring Tool for Viable Cell Concentrations.

New approaches in process monitoring during industrial fermentations are not only limited to classical pH, dO2 and offgas analysis, but use different in situ and online sensors based on different physical principles to determine biomass, product quality, lysis and far more. One of the very important approaches is the in situ accessibility of viable cell concentration (VCC). This knowledge provides increased efficiency in monitoring and controlling strategies during cultivations. Electrochemical impedance spectroscopy—EIS—is used to monitor biomass in a fermentation of E. coli BL21(DE3), producing a recombinant protein using a fed batch-based approach. Increases in the double layer capacitance (Cdl), determined at frequencies below 1 kHz, are proportional to the increase of biomass in the batch and fed batch phase, monitored in offline and online modes for different cultivations. A good correlation of Cdl with cell density is found and in order to get an appropriate verification of this method, different state-of-the-art biomass measurements are performed and compared. Since measurements in this frequency range are largely determined by the double layer region between the electrode and media, rather minor interferences with process parameters (aeration, stirring) are to be expected. It is shown that impedance spectroscopy at low frequencies is a powerful tool for cultivation monitoring.

Corrosion Inhibition of Mild Steel in Acidic Solution by Apricot Gum as a Green Inhibitor

The inhibitive effect of apricot gum AG on mild steel in 0.5 M phosphoric acid solution was investigated by potentiodynamic polarization, electrochemical impedance spectroscopy EIS, linear polarization resistance and electrochemical noise EN techniques. The inhibition efficiency increased with increasing AG concentration up to a certain value and decreased with increasing temperature. Polarization curves indicated that AG acts as a mixed type inhibitor. The EN data were analyzed by statistical and wavelet methods. The results obtained from analysis of EN data was in good agreement with those arising from the polarization and EIS measurements. The adsorption of the inhibitor on the alloy surface in 0.5 M H3PO4 followed the Langmuir isotherm. According to the calculated values of free energy and enthalpy adsorption it was revealed that the adsorption of inhibitor on the steel surface was a combination of physical and chemical adsorption. The morphologies of the uninhibited and inhibited mild steel surfaces in 0.5 M H3PO4 were analyzed by scanning electron microscope SEM. SEM images showed that the alloy surface damage is significantly decreased in presence of the inhibitor.

Au-Based Catalysts: Electrochemical Characterization for Structural Insights.

Au-based catalysts are widely used in important processes because of their peculiar characteristics. The catalyst performance depends strongly on the nature and structure of the metal nanoparticles, especially in the case of bimetallic catalysts where synergistic effects between the two metals can be occasionally seen. In this paper, it is shown that electrochemical characterisation (cyclovoltammetry CV and electrochemical impedance spectroscopy EIS) of AuPd systems can be used to determine the presence of an electronic interaction between the two metals, thus providing a strong support in the determination of the nature of the synergy between Au and Pd in the liquid phase oxidation of alcohols. However, it seems likely that the strong difference in the catalytic behavior between the single metals and the bimetallic system is connected not only to the redox behaviour, but also to the energetic balance between the different elementary steps of the reaction.

Electrochemical comportment of Ni-Ti alloys immersed in two types of artificial saliva.

The main objective of this work was to study the electrochemical behavior of Ni-Ti alloy immersed in two types of artificial saliva: neutral saliva (Ringer's solution, pH = 7.4) and acidic saliva (Fusayama solution pH ∼ 2.3). This study was conducted by the application of various electrochemical methods [monitoring of the corrosion potential over time; E = f(t), polarization curves; j = f(E), and electrochemical impedance spectroscopy EIS]. The overall results showed that the acidification of the saliva and/or the increase of its temperature causes the ignition of the corrosion phenomena of the Ni-Ti alloy. Indeed, the corrosion rate increases significantly with increasing temperature and the decreasing of the pH medium. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 778-784, 2017.

Quantum chemical studies on adsorption of imidazole derivatives as corrosion inhibitors for mild steel in 3.5 NaCl solution

Adsorption of benzimidazole, 2-methylbenzimidazole and 2-aminobenzimidazole on mild steel in 3.5 NaCl solution was studied using density function theory DFT calculations. In this regard, charge transfer resistance Rct and double layer capacitance Cdl obtained by electrochemical impedance spectroscopy EIS were used to calculate surface coverage and to build prediction models. When prediction models were only based on quantum chemical parameters of imidazoles, the most effective parameters were frontier orbital energies meaning that dominant mechanism of adsorption was chemisorption. However, models based on imidazoles and iron quantum chemical parameters revealed that the most effective parameter is dipole moment meaning that dominant mechanism of adsorption is physisorption. Prediction models based on inhibitor-FeOH2H2O4 and inhibitor-FeOH3H2O3 systems presented dipole moment and electron donating power as the most effective parameters for θR and θC based calculations, respectively. Such a behavior could be attributed to chemical interaction of inhibitors with FeOH2H2O4 and FeOH3H2O3 on the mild steel surface resulting in a porous thick layer which could not effectively block the surface but could decrease double layer capacitance.