Electrochemical Current Noise Research Articles

Albumin Protein Impact on Early-Stage In Vitro Biodegradation of Magnesium Alloy (WE43).

Mg and its alloys are promising biodegradable materials for orthopedic implants and cardiovascular stents. The first interactions of protein molecules with Mg alloy surfaces have a substantial impact on their biocompatibility and biodegradation. We investigate the early-stage electrochemical, chemical, morphological, and electrical surface potential changes of alloy WE43 in either 154 mM NaCl or Hanks' simulated physiological solutions in the absence or presence of bovine serum albumin (BSA) protein. WE43 had the lowest electrochemical current noise (ECN) fluctuations, the highest noise resistance (Zn = 1774 Ω·cm2), and the highest total impedance (|Z| = 332 Ω·cm2) when immersed for 30 min in Hanks' solution. The highest ECN, lowest Zn (1430 Ω·cm2), and |Z| (49 Ω·cm2) were observed in the NaCl solution. In the solutions containing BSA, a unique dual-mode biodegradation was observed. Adding BSA to a NaCl solution increased |Z| from 49 to 97 Ω·cm2 and decreased the ECN signal of the alloy, i.e., the BSA inhibited corrosion. On the other hand, the presence of BSA in Hanks' solution increased the rate of biodegradation by decreasing both Zn and |Z| while increasing ECN. Finally, using scanning Kelvin probe force microscopy (SKPFM), we observed an adsorbed nanolayer of BSA with aggregated and fibrillar morphology only in Hanks' solution, where the electrical surface potential was 52 mV lower than that of the Mg oxide layer.

Electrochemical and surface characterization studies of winged bean extracts doped TEOS-PDMS sol-gel protective coatings on reinforcing bar in acidic medium

Hybrid sol-gel coatings consisting of tetraethoxysilane (TEOS)-polydimethylsiloxane (PDMS) molecular precursors doped with winged bean extracts were synthesized for the corrosion protection of reinforcing steel in a 0.5 M HCl medium. The incorporation of winged bean extracts doped into hybrid TEOS-PDMS composite coatings on reinforcing steel resulted in a protective system with superior corrosion protection performance, as determined by electrochemical impedance spectroscopy, electrochemical noise measurement and potentiodynamic polarization. When compared to the undoped TEOS-PDMS silanol coating, the corrosion current density and electrochemical current noise resistance values of the winged bean extracts doped hybrid coatings were much lower, whereas charge transfer resistance values were significantly higher. Scanning electron microscopy, Fourier transform infrared spectroscopy, and energy-dispersive X-ray spectroscopy techniques were used to analyse the morphology and structure of developed sol-gel coatings. In addition, atomic force microscopy and wettability analyses were exploited to further understand the characteristics of hybrid silanol coatings. The outcome of this study corroborates that winged bean extracts doped TEOS-PDMS hybrid coatings could be adopted as potential coatings for reinforcing steel.

Imidazoline behavior as corrosion inhibitor in the electrochemical characterization of SCC behavior of an API X70 steel exposed to brine solution

Abstract The effect of concentration of an organic imidazoline as inhibitor on internal stress corrosion cracking (SCC) behavior of an API X70 pipeline steel exposed to a brine solution was studied. The SCC process using simultaneously the slow strain rate stress test (SSRT) and electrochemical measurements was performed. Fracture surface analysis and secondary cracking were observed through a scanning electron microscopy (SEM). According to SEM fractography and SSRT results, the steel showed high SCC susceptibility with a brittle fracture and several secondary cracks without addition of inhibitor, whereas the addition of inhibitor to brine solution was effective to increase the SCC resistance of steel at concentrations of inhibitor of 50 and 100 ppm. A further addition of concentration of inhibitor had a negative effect on the mechanical properties of the steel. Electrochemical measurements results are in accordance with the SCC susceptibility, indicating that corrosion inhibitor film suppressed the anodic and cathodic reactions increasing the resistance to SCC until concentration of 100 ppm. Further addition of inhibitor aggravated the localized corrosion due to local desorption of inhibitor molecules. The Hilbert–Huang transform (HHT) analysis revealed the contribution of different corrosion process contained in the electrochemical current noise (ECN) signals at several inhibitor concentrations.

Analysis of electrochemical current noise data arising from corrosion of Al alloy in a gel electrolyte by wavelet and recurrence methods

Gel electrolytes are preferred to liquid electrolytes due to the slower movement of ions, thereby lower damage. However, the use of gel electrolytes causes an increase in corrosion susceptibility due to the non-flat surfaces of cells. The use of corrosion inhibitors is one of the most practical methods for corrosion protection. The effect of penicillin as an inhibitor in a gel electrolyte containing 3.5% NaCl was investigated on the corrosion of 6061 Al alloy. Both electrochemical impedance spectroscopy (EIS) and electrochemical current noise (ECN) techniques were employed for data collection. The ECN data were analyzed by both the wavelet transform and the recurrence methods. According to EIS data, the inhibition efficiency (IE) increased from 77% to 94% for up to 15 days. The IE values obtained from ECN data increased from 81% to 90% over immersion time. The recurrence plots of the blank sample proved the increase of pit density with increasing the immersion time from 1 day to 15 days. However, the SDPS plots of the blank sample showed an increase of pit size with increasing the immersion time from 1 to 15 days. The recurrence plots proved the inhibition effect of penicillin on the corrosion of Al alloy that is apparent from the significant lowering of vertical black lines.

Using of asymmetric cell to monitor corrosion performance of 304 austenitic stainless steel by electrochemical noise method

In this study, corrosion of 304 Austenitic stainless steel (ASS) with varies oxide layers, developed at two temperatures, is investigated by an asymmetric (Asy) cells in 0.05 M FeCl3 solution with time. Therefore, the Asy electrodes system is introduced to perform valuable data. Electrochemical current noise (ECN) signals resulting from the Asy cells are elucidated using the standard deviation of partial signals (SDPS) plot, the recurrence plot (RP), and the statistical procedure which derived from wavelet transform (WT) along with electrochemical impedance spectroscopy (EIS). The Asy electrodes indicated a high advantage and improved the detection of intergranular corrosion (IGC) on the 304 ASS alloy compared with the symmetric (Sym) ones. The trend of signals is eliminated, and then the disintegration of every signal is also performed into 10 crystals. Afterward, the standard deviation of every crystal is shown with the SDPS plots. Besides, ECN signals related to dissimilar crystal numbers are distinguished by the RP, based on the signals population. According to EIS measurements, the thickness of passive oxide layer of sample heated at 0–700 °C is decreased from 57 to 33 nm with immersion time, while it is increased from 9 to 27 nm for sample heated at 1100-700 °C.

Electrochemical noise analysis to evaluate the localized anti-corrosion properties of PP/graphene oxide nanocomposite coatings

• Electrochemical noise was used to evaluate the localized corrosion of PP-based NCCs. • PP|Graft|GO = 0.1 illustrated the best localized corrosion performance. • PP|Graft|GO = 0.1 was able to re-passive and prevent the growth of large & deep pits. • In the presence of GO, the transients shift to the higher frequencies at all times. Electrochemical noise analysis was applied to evaluate the localized anti-corrosion performance of polypropylene (PP)-based nanocomposite coatings (NCC). In this regard, the NCCs were developed on mild steel from a solution containing PP, MAH-grafted PP, and different percentages of graphene oxide (GO). The coated samples were subjected to thermal tests, salt spray, and electrochemical noise (EN) analysis. Electrochemical potential and current noise (EPN & ECN) signals were evaluated to find information about localized corrosion. First, the raw signals were analyzed based on the empirical mode decomposition (EMD), then the 3D diagrams (intensity, time, and frequency) were plotted using the Hilbert transform. The results showed in the presence of GO, the transients shift to the higher frequencies at all times, which confirms more tendency to uniform corrosion instead of localized. Introducing 3 wt% of GO NPs into the coating leads to the electrochemical noise resistance increasing by 5 times (>10 8 Ω.cm 2 ), pit initiation rate decreasing, and pit radius reduction (by ∼5 times). As a result, MAH-grafted PP and GO in these NCCs can act as effective barriers against corrosive agents, especially the agents that cause pitting corrosion.

A study on synergistic effect of chloride and sulfate ions on copper corrosion by using electrochemical noise in asymmetric cells

The current study includes a systematic examination of copper corrosion initially in each of NaCl and Na2SO4 solutions separately and then in the mixture solution of Cl− and SO42− ions as aggressive ions. Electrochemical current noise (ECN) signals resulting from asymmetric (Asy) as well as symmetric (Sym) cells have been interpreted using wavelet transform (WT) along with statistical procedures. The signals have been detrended and the decomposition of every signal has been carried out into 8 crystals. Then the standard deviation of every crystal has been illustrated with the standard deviation of partial signal (SDPS) plots. The Asy electrodes increased the pitting detection on copper compared with the Sym ones, indicating higher efficiency of the Asy electrodes. Asymmetric-copper electrodes have been studied using SDPS plots at different temperatures (40, 60, as well as 80 °C). Finally, in order to partly understand the effect of Cl− and SO42− ions on the corrosion of copper, the stabilization of Cu2+ cations by Cl− and SO42− ions in aqueous solutions have been modeled by DFT calculations. The derived results are in accordance with the experimental data.

A novel corrosion inhibitive system comprising Zn-Al LDH and hybrid sol-gel silane nanocomposite coating for AA2024-T3

A novel layered double hydroxide (LDH)/silane bilayer system was introduced as an effective non-hazardous protective coating for AA2024-T3. Also, the loaded corrosion inhibitors' effect on the bilayer coating system's active anticorrosion properties was studied. For this purpose, diethyldithiocarbamate (DEDTC) molecules, as an eco-friendly corrosion inhibitor, were intercalated in the LDH conversion layer. Furthermore, Ce3+ cations were loaded in the sodium montmorillonite and then incorporated in the mixture of tetraethoxysilane and γ-amino propyltriethoxysilane. The grazing incidence X-ray diffraction, Fourier-transform infrared spectroscope, and scanning electron microscope (SEM) equipped with energy dispersive spectroscope were used to analyze the structural, surface functional groups, microstructure, and chemical composition of the coatings. Electrochemical impedance spectroscopy, potentiodynamic polarization, and electrochemical current noise technique were employed to investigate the layers' protection behavior. Based on the obtained results, the presence of corrosion inhibitors in the structure of the coatings resulted in a dramatic enhancement in the protection behavior of the substrate. The polarization results illustrated that the corrosion current density of the bilayer system was reduced from 170 to 6.7 nA/cm2 after employing the corrosion inhibitors into the coating structure. The electrochemical tests and SEM results illustrated the induction of the active anticorrosion properties for the bilayer system containing the DEDTC molecules and Ce3+ cations. The total noise energy for the scratched double-layer coating in the presence and absence of corrosion inhibitors was calculated to be 4.1 and 9.5 pA2, respectively, indicating efficient corrosion inhibition.

Construction of an epoxy coating with excellent protection performance on the AA 2024-T3 using ion-exchange materials loaded with eco-friendly corrosion inhibitors

Ion-exchange materials were used in this study to boost the active/passive anti-corrosive functionality for the epoxy coating applied on the AA2024-T3. For this purpose, a zinc-aluminum layered double hydroxide conversion coating (LDH) loaded with diethyldithiocarbamate molecules was synthesized as the surface pretreatment for the AA2024-T3. Also, sodium montmorillonite was filled with Ce3+ cations and then applied on the LDH layer after being mixed with the hybrid sol-gel silane solution. The surface-modified layer was finally coated with epoxy resin. The three-layer coating system's electrochemical behavior in the absence and presence of the ion-exchange materials and the corrosion inhibitors was examined using electrochemical impedance spectroscopy (EIS), electrochemical current noise, and salt spray testing. The synthesized layers' chemical composition and surface morphology were analyzed using SEM-EDS. Results indicated that the epoxy coating active/barrier anti-corrosive performance significantly improved in the presence of ion-exchange materials loaded with the corrosion inhibitors. Based on the findings, the loading of the corrosion inhibitors into the structure of the ion-exchange material coated on the AA2024-T3 substrate leads to an enhancement in the log|Z|10mHz of the three-layer coating from 6.3 to 8.27 Ω·cm2. Additionally, the incubation of active protection performance for the three-layer coating after being loaded with the corrosion inhibitors was illustrated through the electrochemical testing and surface analysis.

Electrochemical noise analysis of cathodically protected steel reinforcement in concrete using carbon fiber sheet as anode

This paper presents an efficiency and mechanism analysis of impressed current cathodic protection (ICCP) for corroded steel reinforcements in concrete by means of electrochemical noise (EN), which is an advanced technique that allows real-time monitoring without any disturbance. The considered variables include protection method (non-protection, ICCP) and current density of ICCP (30 mA/m2, 90 mA/m2). In the cases of ICCP, carbon fiber sheet is adopted as the anode thanks to its good electrochemical properties and durability. Electrochemical potential noise (EPN) and electrochemical current noise (ECN) of steel reinforcement in concrete are measured every 30 d during the 120-d exposure period and analyzed from the perspectives of time and frequency domains. The results show that ICCP treatment with a current density of 30 mA/m2 leads to slighter fluctuations in ECN signals, an improvement in noise resistance Rn, and decreases in the low frequency plateau WL in power density diagram (PSD) of ECN signals. It indicates that the corrosion of steel is alleviated. However, the results of the specimen protected with a current density of 90 mA/m2 are the opposite, which is overprotected and hydrogen corrosion may happen. Compared to the specimen with no protection, the specimen treated with 30 mA/m2 ICCP shows an evident increase in energy proportion of d1-d3 wavelet crystals. Additionally, with increasing the treatment duration, the energy proportion of d1-d3 wavelet crystals increases. This illustrates that ICCP is more effective in inhibiting general corrosion than pitting corrosion. Extra caution should be paid to EPN signals of specimens subjected to ICCP, namely polarization, because EPN signals may anomalously exhibit severer fluctuations as a result of insufficient depolarization. It is suggested to use ECN signals instead of EPN signals to analyze the corrosion behavior of specimens subjected to ICCP.

Influence of zinc sulfate concentration in baths on the structure, morphology and tribocorrosion properties of Fe-Zn alloy coating

To address the glazing issue of impregnated diamond bit in drilling hard and compact rock formations, Fe-Zn alloys were electrodeposited from acid sulfate baths and the surface morphology , phase composition, microhardness and tribocorrosion property of the deposits were studied. As the ZnSO 4 concentration increased from 0 g/L to 20 g/L, the morphology of deposits changed from fine-grained clusters to triangular based pyramids, and finally to granular grains. α phase, η phase and a mixture of α phase and η phase were identified in Fe-Zn coatings. And the microhardness of the deposits is influenced by the Zn content and grain size of Fe-Zn alloy. Furthermore, tribocorrosion behaviors of the deposits were investigated in NaCl solutions by electrochemical measures (potentiodynamic polarization, electrochemical current noise) with an abrasion-corrosion rig. Results of tribocorrosion tests showed that the primary form of the material loss was pure mechanical wear , except the deposit obtained at 20 g/L ZnSO 4 , whose mass loss due to corrosion-induced abrasion contributed most to its total material loss. The degradation mechanism of Fe-Zn deposits was also detailed in this paper. • Fe-Zn alloy was electrodeposited from an acid bath with improved stability. • The morphology of Fe-Zn deposits changed with the variation of phase structure. • Fe-Zn coating with 20% Zn provided the best combination of hardness and mass loss. • The wear mechanism of Fe-Zn deposits in silica slurry with NaCl was discussed.

Zn-Al layered double hydroxide as an inhibitive conversion coating developed on AA2024-T3 by one-step hydrothermal crystallization: Crystal structure evolution and corrosion protection performance

In the present work, a ZnAl layered double hydroxide (LDH) conversion coating was synthesized on 2024-T3 aluminum alloy by a one-step hydrothermal method. For this purpose, the effect of synthesis parameters, including the amount of Zn2+ cations and hexamethylenetetramine molecules, on the structural changes were evaluated by using the scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS) analysis and X-ray diffraction (XRD) spectroscopy. Also, benzimidazole (BI), as corrosion inhibitor of the AA2024-T3, was intercalated into the LDH film structure by an anion-exchange process. The intercalation of BI molecules into the LHD structure was studied using the SEM-EDS and XRD analysis. Furthermore, electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PD), and electrochemical current noise measurements were employed in 3.5 wt% NaCl solution to assess the protection performance of the LDH coating. The PD test results showed that the LDH conversion coating's polarization resistance increases from 24.05 to 131.1 kΩ/cm2 after the intercalation of the BI molecules into the structure of the ZnAl LDH layer. The induction of active protection performance for the LDH film modified with BI molecules was demonstrated through the EIS test results.

Use of electrochemical current noise method to monitor carbon steel corrosion under mineral wool insulation

Corrosion of carbon steel under mineral wool insulation was studied using the electrochemical current noise (ECN) method. Intensities of corrosion were validated using gravimetry, and the form of corrosion confirmed using optical microscopy. The standard deviation of the current noise signal agreed with weight loss results and was demonstrated as a reliable indicator of the degree of corrosion under mineral wool insulation. Recurrence quantification analysis was used to extract feature variables from ECN signals, which were later used to develop a random forest model to identify the type of corrosion, i.e., uniform or localised corrosion. The trained model was successfully applied to predict the extent of localised corrosion associated with mineral wool insulation.

In-situ monitoring of pitting corrosion of Q235 carbon steel by electrochemical noise: Wavelet and recurrence quantification analysis

Abstract Pitting corrosion of Q235 carbon steel in 0.25 M NaHCO3 with different concentrations of chloride ions was in-situ monitored by electrochemical noise (EN) technique, and the EN signals were analyzed by transient shape analysis, wavelet analysis and recurrence quantification analysis (RQA). Four typical electrochemical current noise (ECN) transients corresponding to different pitting stages including passivation, random metastable pitting, transition stage and stable pitting stage were observed. It was found that the RQA parameters, recurrence rate (R) and determinism (D), show the ability to separate the four ECN transients, while wavelet parameter show poor ability to distinguish the ECN transients arising from random metastable pitting and transition stage. Furthermore, the ratio of D and R (η) was proposed to monitor the pitting corrosion. The average value of η for the passivation and random metastable pitting is 1.88 and 1.63, and it gradually increases to around 6 during the transition stage and early stable pitting stage, the value slightly decreased to 4.16 at the late stable pitting stage. The detailed relationship between the EN characteristic parameters and dynamic process of pitting corrosion is discussed.

Evaluation of the localized corrosion on Mg electrode surface by electrochemical noise technique

AbstractThe symmetrical and asymmetrical electrodes made of Mg were studied in 0.1‐M NaCl electrolyte adjusted at pH 12. The statistical and wavelet methods were employed for analyzing the electrochemical current noise (ECN) signals. The asymmetric configuration was used for electrochemical detection of filiform corrosion on Mg electrode. The real time scale of the dominant transients of the asymmetric electrodes was detected on the basis of the maximum peak in the SDPS plots. The SDPS values of the real time scale crystals of the ECN signals resulting from asymmetrical electrodes increased with the increase in immersion time due to the onset of filiform corrosion.

The Influence of H<sub>2</sub>SO<sub>4</sub>- NaCl Electrolyte Composition to the Electrochemical Noise Behaviour of a High-Alloy Cast Steel

In this study, the influence of varying sulphuric acid – sodium chloride electrolyte composition to the electrochemical noise behaviour of a high-alloy cast steel was analysed. The noise analysis was carried out in a bare 0.1 M sulphuric acid solution, in a pure 5 wt.% sodium chloride solution and three solutions with defined ratios of both. The electrochemical current noise signal was recorded with a sampling rate of 100 Hz for 1 hour in each test solution. For the identification of the frequency content of notified characteristic transients, the current-time records were analysed by the continuous wavelet transform (CWT). The characteristic transients were extracted from the noise signal for a further analysis of their frequency and amplitude characteristics. The results show high-frequency transients in the bare sulphuric acid and low-frequency transients in the pure sodium chloride solution. In the combined electrolyte solutions the portion of low-frequency components increases when the NaCl content increases and indicates the enhancing influence of localised damage evolution processes at the steel surface.

Electrochemical noise analysis of corrosion behaviour of asymmetric electrodes made of mild steel in NaHCO3 solutions at different NaCl concentrations

In this paper, the corrosion of asymmetrical electrodes made of mild steel was studied in 0.5 M NaHCO3 solutions with the addition of NaCl both before and after the immersion of electrodes. The statistical and wavelet methods were used for analysing the electrochemical current noise (ECN) signals. The ECN signals arising from asymmetric electrodes in 0.5 M NaHCO3 solution (pH 9) in the absence and presence of three different NaCl concentrations were unidirectional. This can pertain to the presence of the oxide layer. The thickness of the passive oxide layer and noise detection decreased on increasing the NaCl concentration from 0.3 to 0.7 M. The predominant transients of ECN signals and their SDPS values were lower in the case of 2 h delaying compared with simultaneous NaCl increase to 0.5 M NaHCO3 solution.

Identifying defect size in organic coatings by electrochemical noise, galvanostatic step and potentiostatic step techniques

Organic coating effectively protects metal from corrosion in atmospheric environment. As the coating undergoes degradation in harsh environment enriched with Cl− and at high temperature, there is a need to develop in-situ electrochemical methods to in-field detect the defect size in organic coatings that exposed to atmospheric conditions. This work aims to develop several electrochemical methods including open circuit potential (OCP), electrochemical current noise (ECN), electrochemical impedance spectroscopy (EIS), galvanostatic step and potentiostatic step, and the parameters obtained from each method are compared. Experimental results indicate that, apart from corrosion potential, the other four techniques can effectively detect the defect size in organic coatings by using polarization resistance or charge transfer resistance. Galvanostatic step and potentiostatic step can be used in field corrosion detection due to its concise instrumentation and short measurement time.

Advantages of asymmetric over symmetric electrodes made of mild steel for measurements of electrochemical current noise

The symmetric and asymmetric electrodes made of mild steel were investigated in 4000 ppm NaCl + 1000 ppm NaNO2 solution at different pH values (4, 6, 8 and 10). The obtained electrochemical current noise (ECN) signals were analyzed by statistical and wavelet techniques. The results indicated that the asymmetric electrodes were more suitable than symmetric electrodes for the ECN measurements in near-neutral and alkaline solutions. The asymmetric configuration led to increase the ECN detection and to determine the actual time scale of the predominant transients directly from the maximum peak in their SDPS plot.

Electrochemical noise signals evaluation to classify the type of corrosion using Synchrosqueezing transform

In this research, the corrosion type evaluation on the 6061-T6 aluminum alloy exposed to three different solutions using the Electrochemical Noise (EN) technique evaluated by the Synchrosqueezing Transform (SST), and the Shannon energy (SSE) methods is presented. The solutions used for the tests were Sulfuric Acid (15% H2SO4), Sodium Chloride (3.5% NaCl), and demineralized Water (diH2O), these solutions were chosen to evaluate the type of corrosion because of each one of them produces a different corrosion type on the Aluminum alloy. To carry out the evaluation, firstly, the EN signals (Electrochemical Potential Noise (EPN) and Electrochemical Current Noise (ECN)) are obtained from probes. After, these signals are evaluated by the SST-SSE method without removing the DC drift. Finally, the EPN and ECN are evaluated using only the SST method. To show the effectiveness of the SST-SSE and SST methods, a comparison with the Wavelet Transform and the Localization Index is carried out.