Electrochemical Frequency Modulation Techniques Research Articles

Corrosion of Steel Rebars in Construction Materials with Reinforced Pervious Concrete

Pervious concrete has great potential for use in many practical applications as a part of urban facilities that can add value through water harvesting and mitigating severe damage from floods. The construction and agricultural industries can take direct advantage of pervious concrete’s characteristics when water is a key factor included in projects as part of the useful life of a facility. Pervious concrete also has applications in vertical constructions, fountains, and pedestrian crossings. This work evidences that pervious concrete’s corrosion current increases with increasing aggregate size. Also, corrosion is a factor to consider only when steel pieces are immersed, aggravated by the presence of chlorine, but it drains water and does not retain moisture. Steel-reinforced pervious concrete was studied, and the grain size of the inert material and the corrosion process parameters were investigated. The electrochemical frequency modulation technique is proposed as a suitable test for a fast, reproducible assessment which, without damaging reinforced cement structures, particularly pervious concrete, indicates a trend of increasing corrosion current density as the size of the aggregate increases or density diminishes.

Development of QSAR based GFA predictive model for the effective design of a new bispyrazole derivative corrosion inhibitor

In this study, seven newly synthesized bispyrazole derivatives (PYR-1 to PYR-7) were investigated as corrosion inhibitors for 304 stainless steel (304 SS) in 1.0 M HCl solutions at different concentrations (10−13 to 10−5 M) using electrochemical frequency modulation technique (EFM). The experimental data were utilized to develop a predictive model for the anticorrosion abilities of bispyrazole ˗ based compounds. The model was developed by using the quantitative structure-activity relationship (QSAR) as a tool to relate essential molecular descriptors of bispyrazol with their experimental inhibition efficiencies. Chemical descriptors associated with frontier molecular orbitals (FMOs) were obtained using density Functional theory (DFT) calculations, while others were obtained from additional calculations performed using Material Studio 7 software. The suggested QSAR model was used to predict the corrosion inhibition efficiency of a newly synthesized bis[3‐(4`‐biphenyl)‐4‐[(4‐acetyl‐2‐(N‐phenylacetamido)‐4,5‐dihydro‐1,3,4‐thiadiazol‐5‐yl]‐1H‐pyrazol‐1‐yl]phosphineoxide,(PYR-8), another inhibitor within the same bispyrazole family. The predicted inhibition efficiency was validated by several electrochemical techniques. The predicted QSAR values for PYR-8 showed good agreement with experimental data, establishing the reliability of the model in predicting the inhibitor's performance.

Use of Polynomial Approximation in the Electrochemical Frequency Modulation Technique for Determination of Corrosion Rates in Activation-Controlled Systems

The electrochemical frequency modulation (EFM) is a promising nondestructive technique that uses a small biharmonic disturbance signal along with the discrete Fourier transform to calculate the corrosion current and Tafel slopes from a set of equations that rely on harmonic components. Significant results have been published mainly on systems exhibiting Tafel behavior. This work presents the use of polynomial approximation as a data analysis alternative for the EFM technique, which has three main advantages over the procedure proposed by the authors of the EFM technique: (a) reduction of the estimation error caused by the capacitance effect, (b) reduction of the estimation error caused by high harmonic components, and (c) the reduction of computational complexity. This analysis was tested experimentally using a traditional three-electrode cell with a carbon steel working electrode and a sodium chloride solution as the electrolyte. Finally, the results were compared to linear polarization tests and weight loss measurements, where a good agreement was found between the proposed analysis and the other techniques.

Copper Corrosion Protection by 4-Hydrocoumarin Derivatives: Insight from Density Functional Theory, Ab Initio, and Monte Carlo Simulation Studies

The corrosion inhibition performance of 4-hydrocoumarin derivatives has been studied using weight loss, electrochemical impedance spectroscopy, potentiodynamic polarization, and electrochemical frequency modulation techniques. However, experimental studies have not explained why the methoxy (OCH3) group contributes more to the increase in corrosion inhibition than the methyl (CH3) and chlorine (Cl) functional groups. In this theoretical study, the electronic aspect of the target corrosion inhibitors will be studied in detail to help strengthen the explanation in the experimental research. Density functional theory, ab initio, and Monte Carlo simulations have been used to analyze the corrosion inhibition performance of 4 curcumin derivatives against copper. The quantum chemistry approach is carried out under gas and aqueous conditions in neutral and protonated inhibitors. The Monte Carlo simulation was used to observe the dynamics and the mechanism of inhibition of the target molecule on the copper surface. The quantum chemistry approach can mimic the geometrical parameters of molecular inhibitors. It can also explain electronically why the OCH3 functional group is superior to other substituents. The adsorption energy of the 4-hydroquinone derivative is linearly correlated with the reported experimental study. The level of corrosion inhibition efficiency is OCH3 > CH3 > H > Cl.

Sinteza dva supramolekularna koordinaciona polimera i elektrohemijska procena njihovog učinka inhibicije korozije na koroziju ugljeničnog čelika u kiseloj sredini

The effect of the SCPs-[CuII(en)2] [CuI (CN)2]2. H2O] (SCP1) and {[H2DAB] [Cu4(CN)6].2H2O} (SCP2) as corrosion inhibitors for carbon steel (CS) was studied in 1.0M HCl solution. As the synthesized inhibitor dose increases, the inhibition productivity (%e) increases reaching to 90.3% and 89.9% at 21x10-6M dose for SCP2 and SCP1, respectively. This result evidenced by mass loss (ML) investigated at three different temperatures 25-35-45oC, while potentiodynamic polarization (PP), electrochemical impedance spectroscopy (EIS), and electrochemical frequency modulation technique (EFM) were tested at 25°C. The synthesized inhibitors adsorbed on the CS surface physically allowing Henry isotherm. The results displayed that the synthesized inhibitors are excellent and their (%e) was significantly increased by raising the dose and decreased by raising the temperature. Polarization curves revealed that the synthesized inhibitors act as mixed type. The thermodynamic parameters were calculated and discussed. The protection was confirmed by the creation of the thin film of inhibitors precipitated on the surface of CS.

Electrochemical behavior of two dyes as corrosion inhibitors for carbon steel in acid medium and studying their biological activities by practical and theoretical aspects

The inhibitive action of azo dye aminophenol derivatives, namely 6-(4-benzenesulfonic acid azo)-3-aminophenol (compound (1)) and 4-(2,3-dimethyl-1-phenylpyrazol-5-one azo)-3-aminophenol (compound (2)) against the corrosion of C-steel in 2 M HCl solution using Tafel polarisation, surface morphology, electrochemical impedance spectroscopy and electrochemical frequency modulation techniques. The inhibition efficiency increased with increasing inhibitor concentrations and decreased with increasing temperature. Tafel polarization curves showed that the corrosion rate was decreased with increasing compounds concentration into HCl solution. Inhibition efficiency values obtained from various methods employed were in reasonable agreement. It was found that the order of % IE of these investigated compounds obey the following order: compound (2) > compound (1). Also, the antimicrobial and antifungal activities of the aminophenol derivatives compounds (1 and 2) and comparing them with the standard antibacterial and antifungal drugs were described. The results showed that the compound (2) is very good antibacterial agents against Bacillus subtilis and Staphylococcus aureus. The compound (2) is more active than the compound (1) and penicillin G against Bacillus subtilis and Staphylococcus aureus. It was found that the compound (2) is more active than penicillin G which is used as the antibacterial standard drug against Enterobacter sp. and Klebsiella pneumoniae. Molecular docking was used to predict the binding between aminophenol derivatives compounds (1 and 2) and the receptors of the crystal structure of Staphylococcus aureus (3q8u) and the crystal structure of Escherichia coli (3t88). The compound (2) showed best interaction with receptor of Staphylococcus aureus (3q8u) than the compound (1).

A Revised Model for Electrochemical Frequency Modulation for Corrosion Estimation

Electrochemical frequency modulation technique allows for evaluation of corrosion rate without prior information of the Tafel parameters. The basic premise of this approach is that since the material degradation can be described by a nonlinear model, the application of an AC perturbation signal will result in the generation of higher harmonics corresponding to the multiples of the original signal frequency. However, the previous research has ignored the following: (i) the effect of the double layer capacitance (Cd) at the surface of the corroding electrode, and (ii) the solution resistance (Rs) on the output signal, which makes the estimation of faradaic current impossible. Thus, the true corrosion rate cannot be calculated.Our research has shown that when these two effects are taken into account, the output signal displays shift in the higher order harmonics, which is a function of not only the order of the harmonics but also of the Tafel parameters Cd, and Rs. Thus, it becomes possible to calculate the faradaic current and accurately estimate the corrosion rate.

Passivation Characterization of Nickel-Based Glassy Alloys in Artificial Sea Water

The effect of different pH values of artificial sea water on the passivation behavior and the pitting corrosion resistance of Ni70Cr21Si0.5B0.5P8C≤0.1Co≤1Fe≤1 (VZ1) and Ni72.65Cr7.3Si6.7B2.15C≤0.06Fe8.2Mo3 (VZ2) glassy alloys were studied using impedance spectroscopy measurements (EIS), cyclic polarization, and electrochemical frequency modulation techniques. The results showed that the alloys undergo a general corrosion process and tend to form an oxide film on the alloy surface, developing a stable protective layer in the artificial seawater solution. In both alloys, the lower corrosion current density was observed at a pH of 8.5 but had less pitting corrosion resistance. The VZ1 alloy had a relatively lower passive current density value, having a smaller anodic hysteresis loop area compared to the VZ2 alloy. The effect of the medium’s pH on corrosion potential, corrosion current density, pitting potential, and repassivation potential was investigated and discussed, as was surface morphology.

Study Pitting Corrosion of P110 Steel by Electrochemical Frequency Modulation Technique and Coupled Multielectrode Array Sensor

By using the electrochemical frequency modulation (EFM) technique, coupled multielectrode array sensor (CMAS), and other corrosion research techniques, the pitting corrosion behavior of P110 steel in oilfield formation water was studied. The results showed that serious pitting corrosion was observed on P110 steel at 90°C in oilfield formation water. The EFM and CMAS techniques could be used for monitoring or detecting pitting corrosion effectively. The average corrosion rates obtained by EFM and CMAS both decreased with time. At the first 12 h of the test the average corrosion rate was quite high and general corrosion occurred, and then the average corrosion rate decreased and the pitting corrosion was observed from the EFM results. The CMAS result showed that when the pitting corrosion happened, there were obvious localized anode and cathode pots on the metal surface that directly caused the pitting corrosion and might be related to the structure of the protective layer.

Corrosion Inhibition of Aluminum in 1 M H2SO4 by Tecoma Non-aqueous Extract

Tecoma extract was investigated as a green corrosion inhibitor for aluminum in 1 M H2SO4 solution using weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy and electrochemical frequency modulation techniques. It was found that this extract presented excellent corrosion inhibition performance for aluminum and show the maximum 90.2% inhibition efficiency at 300 ppm. Polarization curves revealed that the used extract represents mixed-type inhibitor. Adsorption of used extract led to a reduction in the double-layer capacitance and an increase in the charge transfer resistance. The inhibition efficiency was improved with concentration of the extract, while decreased with improvement of corrosion temperature of the medium. The adsorption isotherm of the extract on aluminum surface conformed to the Langmuir adsorption model. Surface analysis was tested using scanning electron microscope. The results obtained from all investigated techniques are in good agreement.

Dynamic tafel factor adaption for the evaluation of instantaneous corrosion rates on zinc by using gel-type electrolytes

Electrochemical corrosion measurements allow calculation of the instantaneous zinc corrosion rate via polarization resistances by using tafel factors. However, the determination of the actual tafel factor is problematic since it depends on the state of the formed zinc layers and the corrosion reactions taking place. Therefore, valid tafel factors are either determined in additional experiments via dynamic polarization or estimated by calculation. In most cases a constant value for tafel factors is assumed for simplification, without regard to the real conditions of the corroding system. Since naturally formed zinc layers are unstable using conventional test electrolyte solutions determination of tafel factors is hindered additionally and inaccurate interpretations can result. For some time now, the use of gel-type electrolytes in corrosion research has enabled minimally invasive investigation of zinc surface layers and thus offers new approaches to a scientifically proven determination of tafel factors. The paper presents a new method for the determination and evaluation of tafel factors using gel-type electrolytes and electrochemical frequency modulation technique (EFM). This relatively new electrochemical method offers the possibility to determine both polarization resistances and tafel factors within one measurement and in short measuring intervals. Starting from a comprehensive parameter study it is shown that a direct relationship between the two values exists that can be described mathematically. This contribution presents the determined tafel factors for the system gel-type electrolyte/zinc and discusses their applicability and their limits.

Corrosion Inhibition and Adsorption Behavior of Some Cationic Surfactants on Carbon Steel in Hydrochloric Acid Solution

The corrosion protection of Cetylpyridinium bromide (CPB) and Cetyltrimethylammonium bromide (CTAB) as cationic surfactant on the corrosion of C-steel in 1 M hydrochloric acid has been studied by weight loss, Tafel polarization, electrochemical impedance spectroscopy, and electrochemical frequency modulation techniques. The carbon steel samples were also analyzed by scanning electron microscopy. The % protection efficiency increases with increasing concentration of the surfactants and decreases with temperature rise. The % protection efficiency reached to 94 % at a concentration of 150 ppm. The protection of C-steel by these surfactants was attributed to the synergistic effect between bromide anions and positive quaternary ammonium ions. The charge transfer resistance increased and double layer capacitance decreased. Surfactant molecules adsorbed on the surface of steel obeys Langmuir adsorption isotherm.

Corrosion Inhibition of Carbon Steel in 1 M Hydrochloric Acid Solution by Aqueous Extract of Thevetia peruviana

The inhibitive effect of Thevetia peruviana on the corrosion behavior of carbon steel in 1 M HCl was studied using the weight loss method, polarization, AC electrochemical impedance spectroscopy and electrochemical frequency modulation techniques. The inhibition efficiency was found to depend on the concentration of the extract and the temperature of the medium. Results showed that this extract acts as a mixed-type inhibitor. The charge transfer resistance increases but the double layer capacitance decreases by increasing the extract concentration. It was found that the investigated extract acts via adsorption on the carbon steel surface and obeys the Temkin adsorption isotherm. The effect of temperature on the corrosion rate in the absence and presence of the extract was investigated, some activated, and the adsorption parameters were calculated. The results of the electrochemical methods were in good agreement with the weight loss measurement results.

Oxazole derivatives as corrosion inhibitors for 316L stainless steel in sulfamic acid solutions

AbstractOxazole derivatives were investigated as corrosion inhibitors for 316L stainless steel (SS) in sulfamic acid (NH2HSO3) solutions by potentiodynamic polarization, electrochemical impedance spectroscopy, and electrochemical frequency modulation techniques. The results showed the variation in inhibition performance of the inhibitors with varying concentrations and temperatures. The maximum efficiency was found to be 91% at 2 × 10−4 M concentration of the inhibitors for the immersion period of 3 h. Langmuir was tested to describe the adsorption behavior of inhibitor on 316LSS surface. Potentiodynamic polarization study clearly revealed that these compounds act as mixed-type inhibitors. The results of the electrochemical impedance study showed a decrease in double layer capacitance and increase in charge transfer resistance. The results of various electrochemical techniques show good agreements with each other.

Hydroxyethylcellulose used as an eco-friendly inhibitor for 1018 c-steel corrosion in 3.5% NaCl solution

The inhibition effect of hydroxyethylcellulose (HEC) on 1018 c-steel corrosion in 3.5% NaCl solution was investigated by using potentiodynamic polarization, electrochemical frequency modulation (EFM) and electrochemical impedance spectroscopy (EIS) techniques. The potentiodynamic polarization studies suggested that HEC acts as a mixed-type inhibitor. Data obtained from EIS were analyzed to model the corrosion inhibition process through equivalent circuit. Results obtained from EFM technique were shown to be in agreement with potentiodynamic and EIS techniques. The adsorption behavior of HEC on steel surface follows the Langmuir adsorption isotherm. Thermodynamic parameter (ΔG°ads) and activation parameters (Ea*, ΔH* and ΔS*) were calculated to investigate mechanism of inhibition. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis system were performed to characterize the film formed on the metal surface. DMol3 quantum chemical calculations were performed to support the adsorption mechanism with the structure of HEC molecule.

Corrosion inhibition of carbon steel by Roselle extract in hydrochloric acid solution: electrochemical and surface study

The inhibiting effect of Roselle extract (Krd) on carbon steel in 0.5 M HCl solution was investigated by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), electrochemical frequency modulation (EFM), scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) methods. It was found that Krd extract acts as a good inhibitor for carbon steel corrosion in the acid solution. The results showed that Krd extract simultaneously retarded the hydrogen evolution on the cathode and the metal dissolution on the anode, which indicated that this inhibitor is an excellent mixed-type (cathodic/anodic) inhibitor. The dissolution rate decreases with increasing Krd extract concentration and increases with increasing the temperature. The adsorption of Krd extract on the active cathodic sites was found to follow the Langmuir adsorption isotherm. The maximum inhibition approached 91.0 % in the presence of 500 ppm Krd using the EFM technique. The formation of a protective film on the carbon steel surface in the presence of Krd was shown and confirmed by SEM results. There are good agreements between EIS, EFM, the potentiodynamic polarization data, and SEM/EDX results.

Adsorption and Corrosion Inhibition Behavior of Carbon Steel by Cefoperazone as Eco-Friendly Inhibitor in HCl

The inhibition effect of cefoperazone (CP) on the corrosion behavior of carbon steel in 0.5 M HCl solution was studied using potentiodynamic polarization, electrochemical impedance spectroscopy, and electrochemical frequency modulation techniques along with scanning electron microscopy (SEM). Results showed that the inhibition efficiency increases with increasing inhibitor concentration and decreases with increasing the temperature. The results indicated that the inhibitive action of CP can be attributed to its adsorption. The results show that CP possesses excellent inhibiting effect for the corrosion of carbon steel and the inhibitor acts as mixed-type inhibitor. The adsorption process is spontaneous and follows Langmuir adsorption isotherm model. The surface adsorption of the inhibitor molecules decreases the double-layer capacitance and increases the polarization resistance. SEM results indicate the formation of an adsorbed protective film on the metal surface. The results obtained from the different techniques were in good agreement which prove the validity of these tools in the measurements of the tested inhibitor.

Cephalosporin antibiotics as new corrosion inhibitors for nickel in HCl solution

Inhibition of nickel corrosion in 1 M HCl solution in the absence and presence of some Cephalosporin antibiotics derivatives was investigated using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and electrochemical frequency modulation (EFM) techniques. The results obtained show that the inhibition efficiency of these compounds depends on their concentrations and chemical structures. The inhibitive action of these compounds was discussed in terms of blocking the electrode surface by adsorption of the molecules through the active centers contained in their structures following the Langmuir adsorption isotherm. The polarization measurement showed that these inhibitors are acting as mixed inhibitors for both anodic and cathodic reactions. The effect of temperature on the rate of corrosion in the absence and presence of these compounds was also studied. The efficiencies obtained from the potentiodynamic polarization technique were in good agreement with those obtained from EIS and EFM techniques. This proves the validity of these tools in the measurements of the investigated inhibitors.

Inhibition Performance and Adsorptive Behavior of Three Amino Acids on Cold-Rolled Steel in 1.0 M HCl—Chemical, Electrochemical, and Morphological Studies

Three selected amino acids, namely, serine (Ser), threonine (Thr), and glutamine (Glu), were tested as corrosion inhibitors for cold-rolled steel (CRS) in 1.0 M hydrochloric acid (HCl) solutions at different temperatures (283 K to 333 K). Chemical (weight loss) and electrochemical (Tafel polarization) methods were used in this study. Electrochemical frequency modulation (EFM), a non-destructive corrosion measurement technique that can directly give values of corrosion current without prior knowledge of Tafel constants, was also used. Experimental corrosion rates determined by the Tafel extrapolation method were compared with those obtained using the EFM technique and the weight-loss method. Morphologies of the corroded and the inhibited surfaces were studied by means of atomic force microscopy (AFM) and scanning electron microscopy (SEM). Tafel plots showed that the three tested amino acids act as mixed-type inhibitors. The three tested amino acids appeared to function through adsorption following the Temkin adsorption isotherm model. Glu was found to inhibit corrosion of steel more effectively than Ser and Thr.

Corrosion inhibition of nickel in H2SO4 solution by alanine

The effect of alanine, as a safe inhibitor, was studied by measuring the corrosion of Ni in aerated and stagnant 1 M H2SO4 solution (pH ∼0.2). Measurements were performed under various conditions using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and the new electrochemical frequency modulation (EFM) methods. The obtained results showed that the addition of alanine alone gives a moderate inhibition and acts as an anodic-type inhibitor. The inhibition is due to physical adsorption of alanine on the metal surface. The inhibition efficiency enhances with increasing alanine concentration and immersion time but decreases with rise in temperature. The apparent activation energy, Ea, is higher in the presence than in the absence of alanine. Addition of I− ions greatly improves the inhibition efficiency of alanine. The synergistic effect is due to enhanced adsorption of alanine cations by chemisorbed I− anions on the metal surface. The results obtained from polarization, EIS and EFM techniques are in good agreement indicating that EFM method can be used successfully for monitoring corrosion rate of Ni in H2SO4 solution with and without alanine.