Electrochemical Noise Analysis Research Articles

Use of Electrochemical Noise for the Study of Corrosion by Passivated CUSTOM 450 and AM 350 Stainless Steels

Precipitation-hardening stainless steels, like AM 350 and Custom 450, are extensively utilized in various aerospace applications. The latter steel is utilized for applications needing great strength and corrosion resistance. In contrast, the former steel has a good corrosion resistance and moderate strength. The purpose of this study was to analyze transient frequencies in the electrochemical noise of Custom 450 and AM 350 stainless steels that had been passivated for 60 and 90 min at 25 and 49 °C using baths of citric and nitric acid and then immersed in solutions containing 1% sulfuric acid (H2SO4) and 5% sodium chloride (NaCl). The potentiodynamic polychromatic curves employed electrochemical techniques and noise (EN) based on the ASTM-G5 and G199 standards. Two methods of data analysis were applied concerning EN: the domain of frequencies (power spectral density, PSD) and the time–frequency domain (Hilbert-Huang Transform). The PHSS passivated in citric acid indicated current densities in the H2SO4 solution between 10−2 and 10−3 mA/cm2, while those in the NaCl solution were recorded around 10−4 and 10−5 mA/cm2. The citric acid functions as a passivating agent. The results of the electrochemical noise analysis show that the PHSS passivated in nitric acid displayed a greater corrosion resistance. Moreover, there is a tendency for PHSS to be passivated in nitric acid to corrode locally.

Emerging Data Processing Methods for Single‐Entity Electrochemistry

AbstractSingle‐entity electrochemistry is a powerful tool that enables the study of electrochemical processes at interfaces and provides insights into the intrinsic chemical and structural heterogeneities of individual entities. Signal processing is a critical aspect of single‐entity electrochemical measurements and can be used for data recognition, classification, and interpretation. In this review, we summarize the recent five‐year advances in signal processing techniques for single‐entity electrochemistry and highlight their importance in obtaining high‐quality data and extracting effective features from electrochemical signals, which are generally applicable in single‐entity electrochemistry. Moreover, we shed light on electrochemical noise analysis to obtain single‐molecule frequency fingerprint spectra that can provide rich information about the ion networks at the interface. By incorporating advanced data analysis tools and artificial intelligence algorithms, single‐entity electrochemical measurements would revolutionize the field of single‐entity analysis, leading to new fundamental discoveries.

Emerging Data Processing Methods for Single-Entity Electrochemistry.

Single-entity electrochemistry is a powerful tool that enables the study of electrochemical processes at interfaces and provides insights into the intrinsic chemical and structural heterogeneities of individual entities. Signal processing is a critical aspect of single-entity electrochemical measurements and can be used for data recognition, classification, and interpretation. In this review, we summarize the recent five-year advances in signal processing techniques for single-entity electrochemistry and highlight their importance in obtaining high-quality data and extracting effective features from electrochemical signals, which are generally applicable in single-entity electrochemistry. Moreover, we shed light on electrochemical noise analysis to obtain single-molecule frequency fingerprint spectra that can provide rich information about the ion networks at the interface. By incorporating advanced data analysis tools and artificial intelligence algorithms, single-entity electrochemical measurements would revolutionize the field of single-entity analysis, leading to new fundamental discoveries.

Electrochemical Noise Analysis Using Experimental Chaos Theory, Power Spectral Density and Hilbert–Huang Transform in Anodized Aluminum Alloys in Tartaric–Phosphoric–Sulfuric Acid Solutions

Aluminum and its alloys find widespread applications across diverse industries such as the automotive, construction, and aeronautics industries. When these alloys come into contact with ambient air, an Al2O3 thin oxide layer is naturally formed, typically measuring 2 to 4 nm and exhibiting remarkable hardness and protective qualities, rendering the alloys corrosion-resistant in specific atmospheric and chemical environments. This study aimed to characterize the electrochemical behaviors of anodized AA2024 and AA7075 alloys within a complex three-component electrolyte composed of tartaric–phosphoric–sulfuric acid (TPSA) solutions. The anodized specimens were subsequently exposed to 3.5 wt.% NaCl solution at room temperature, and their electrochemical performances were meticulously evaluated using an electrochemical noise (EN) analysis in accordance with ASTM G-199, respectively. In the EN, three methods of data analysis were used: the time domain analysis (chaos analysis: application of Lyapunov exponent and dimension correlation), the frequency domain analysis (power spectral density, PSD), and the time–frequency domains analysis (Hilbert–Huang transform, HHT). Scanning electron microscopy (SEM) was used to observe the morphologies of the anodized surfaces. The results indicated that the AA2024-0, AA2024-1, and AA2024-2 alloys and the AA7075-2 and AA7075-3 samples exhibited mixed corrosion according to the Lyapunov constant, with a notable inclination towards localized corrosion when analyzed using the PSD and HHT methods. The surface was not homogenous, and the corrosion process was predominately localized in specific zones.

Effect of refrigerant absorbent combinations in the corrosion resistance of copper as structural material in absorption refrigeration systems (ARS)

ABSTRACT The present research was focused on analyzing the corrosion resistance of copper in the presence of refrigerant-absorbent combinations such as lithium bromide (LiBr), lithium nitrate (LiNO3) and calcium chloride (CaCl2), used in Adsorption Refrigeration Systems (ARS). Electrochemical techniques such as open circuit potential, electrochemical impedance spectroscopy, electrochemical noise analyses and potentiodynamic polarisation curves were applied to study the test solution combination effect on the corrosion rate of copper as a structural material in ARS. OCP analyses reveal that the E corr shifted based on the temperature and test solution. Meanwhile, when the copper was immersed in LiBr/H2O + CaCl2 at 80°C, the corrosion current density (I corr) was lower (0.003 mA/cm2). Also, The R p estimated from EIS shows an increase at 80°C. Micrographs of the copper surface immersed in LiBr/H2O and LiBr + CaCl2 observed cracks and pits. But also, when the corrosion product layer was removed, a less heterogeneous surface was revealed.

Effect of pH and applied stress on hydrogen sulfide stress corrosion behavior of HSLA steel based on electrochemical noise analysis

Effect of pH and applied stress on hydrogen sulfide stress corrosion behavior of HSLA steel based on electrochemical noise analysis

Effect of zirconia in the corrosion behavior of intermetallic Mo3Si alloy in molten salts mixture of NaNO3 and KNO3

AbstractThe corrosion effect of zirconia addition, 1, 2, and 5 atomic percent (at.%), on the hot corrosion behavior of Mo3Si intermetallic alloy in 60 wt.% NaNO3 + 40 wt.% KNO3 at 600°C, has been evaluated by using electrochemical methods. Electrochemical techniques included electrochemical noise analyses (ENA), polarization curves (PC), and linear polarization resistance (LPR). The average grain size decreased when the specimen was alloyed with Zr from 90 μm for as‐cast Mo3Si, down to 25 and 10 μm for alloys containing 1, 2, and 5 at.% Zr, respectively. All specimens showed a passive behavior, with the corrosion current density values decreasing for adding either 1 or 2 at.% Zr but increasing for specimens containing 5 at.% Zr. The corrosion process was under charge transfer control for the as‐cast alloy or when 1 or 2 at.% Zr was added, but it was diffusion controlled when 5 at.% Zr was added. The noise resistance value (Rn) increased for specimens containing 1 or 2 at.% Zr but decreased when 5 at.% Zr was added. X‐ray diffraction showed the presence of SiO2, MoO4, Mo4O11, and ZrO2 in the passive layer.

Corrosion mechanism of advanced high strength dual-phase steels by electrochemical noise analysis in chloride solutions

The corrosion behavior of ferrite-martensite and ferrite-bainite dual-phase steels in NaCl, CaCl2, and MgCl2 solutions was studied by cyclic potentiodynamic polarization (CPP) and electrochemical noise (EN) techniques. The results showed a trend for mixed corrosion due to no passivation by a protective oxide layer. For the ferrite-martensite dual-phase steels, the ferrite phase was preferentially corroded compared with the martensite phase in test solutions. Bainite-microstructure in ferrite-bainite dual-phase steels was preferentially corroded compared with ferrite-phase in CaCl2 and MgCl2 solutions. The corrosion behavior in test solutions in dual-phase steels could be divided into three steps: dissolution in anodic-phase/microstructure, non-uniform corrosion, and localized corrosion. The results indicated that factors such as galvanic coupling between ferrite/martensite, ferrite/bainite, metallic-matrix/inclusion-phases, metallic-matrix/secondary phases, and self-corrosion of each phase and microstructure contributed to the non-uniform and localized corrosion in dual-phase steels.

A novel method for identifying corrosion types and transitions based on Adaboost and electrochemical noise

PurposeThe purpose of this paper is to identify corrosion types and corrosion transitions by a novel electrochemical noise analysis method based on Adaboost.Design/methodology/approachThe corrosion behavior of Q235 steel was investigated in typical passivation, uniform corrosion and pitting solution by electrochemical noise. Nine feature parameters were extracted from the electrochemical noise data based on statistical analysis and shot noise theory. The feature parameters were analysis by Adaboost to train model and identify corrosion types. The trained Adaboost model was used to identify corrosion type transitions.FindingsAdaboost algorithm can accurately identify the corrosion type, and the accuracy rate is 99.25%. The identification results of Adaboost for the corrosion type are consistent with corroded morphology analysis. Compared with other machine learning, Adaboost can identify corrosion types more accurately. For corrosion type transition, Adaboost can effectively identify the transition from passivation to uniform corrosion and from passivation to pitting corrosion consistent with corroded morphology analysis.Originality/valueAdaboost is a suitable method for prediction of corrosion type and transitions. Adaboost can establish the classification model of metal corrosion, which can more conveniently and accurately explore the corrosion types. Adaboost provides important reference for corrosion prediction and protection.

Microbe-induced pitting of Fe-based amorphous coating

It is well known that Fe-based amorphous coatings demonstrate excellent performance against marine corrosion, but the corrosion resistance is significantly reduced in the presence of ocean-microbes. However, the mechanism of microbe-induced corrosion, named as microbiologically influenced corrosion (MIC), has yet to be understood. In this paper, the MIC mechanism of an Fe-based amorphous coating (with the composition of Fe43.7Co7.3Cr14.7Mo12.6C15.5B4.3Y1.9) in the presence of Pseudomonas aeruginosa (one of the typical ocean-microbes) was elaborately investigated by electrochemical impedance spectroscopy (EIS), electrochemical noise analysis (EN), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The electrochemical results show that P. aeruginosa reduced the corrosion resistance of the amorphous coating, manifested by the lower impedance values and higher metastable pitting initiation rate compared to those in a sterile medium. XPS analysis indicates the enrichment of soluble high-valent metal oxides in the passive film formed in the P. aeruginosa medium. In addition, TEM observation reveals pitting initiated exactly beneath P. aeruginosa cells, rather than defect regions (i.e., intersplat) as expected. In the pitting region, a thick biofilm was formed, which resulted in thinning of the underlying passive film. Based on these results, an MIC mechanism based on the inward extracellular electron transfer (EET) effect was proposed, and a potential strategy to relieve MIC was examined.

Identifying the cavitation erosion stages of AA5083 by electrochemical noise analyses

PurposeThe purpose of this paper is to study the cavitation erosion stages of AA5083 by electrochemical noise (EN).Design/methodology/approachEN technology including noise resistance and fast Fourier transform were used to characterize the electrochemical process during the cavitation erosion process.FindingsAA5083 suffers from uniform corrosion during the cavitation erosion process. The whole cavitation erosion process can be divided into three stages: incubation stage, acceleration stage and steady-state stage. EN signals showed obvious differences in different stages of cavitation erosion.Originality/valueEN technique is a suitable method that can be used to study cavitation erosion mechanism and identify cavitation erosion stages.

Probing Interfacial Co‐Crystallisation using Simultaneous Potential and Current Measurements at Liquid‐Liquid Interfaces Polarised by Common Ion Approach

AbstractThe simultaneous measurement of potential and current variations at the interface between two immiscible electrolyte solutions, which was polarised using tetraalkylammonium cations as a common ion, is reported here. Various concentration ratios of tetramethyl‐, tetraethyl‐, or tetrapropylammonium were dissolved in each phase. Such biphasic systems were then used to verify that the measured interfacial potential difference agreed with theory. This experimental set‐up was then used to probe the interfacial cocrystallisation process of hydrophilic, cationic caffeine with lipophilic 1‐hydroxy‐2‐naphtoic acid (1H2N). The presence of caffeine in the aqueous phase led to higher current values, caused by interfacial charge transfer. Electrochemical noise analysis suggested that a two‐step process was occurring at the ITIES (i) a potential‐driven nucleation with the transfer of caffeine from the aqueous to the organic phase; (ii) a growth stage where the interfacial potential no longer plays a role.

Corrosion behavior of 316L SS under cavitation condition in simulated seawater

PurposeThe purpose of this paper is to study the corrosion behavior of 316L stainless steel under cavitation condition in simulated seawater.Design/methodology/approachElectrochemical impedance spectroscopy and electrochemical noise analyses are used to characterize the electrochemical process during the cavitation erosion process.FindingsBecause of good corrosion resistance of this material, mechanical damage is the main cause of cavitation erosion. The alloy surface is in active dissolution state during the cavitation erosion process, and the corrosion rate is accelerated as time prolongs which is verified by electrochemical results.Originality/valueElectrochemical noise is an effective way to study the corrosion under cavitation erosion process.

Effect of heat treatments on metastable pitting of 316L stainless steel fabricated by selective laser melting

Effect of heat treatments on metastable pitting of 316L stainless steel fabricated by selective laser melting (SLM) was studied by scanning electron microscopy, potentiodynamic polarization, electrochemical noise (EN) and transient analysis techniques. The results show that the selective laser melted (SLMed) 316L stainless steel was composed of honeycomb cells with different orientations, and a small number of lack-of-fusion (LOF) pores were randomly distributed. After heat treatment, the honeycomb-like cellular structure transformed into austenite structure, and the non-metallic inclusions coarsened and grew. Non-metallic inclusions can be divided into two types according to the composition difference, one was manganese silicate enriched by Mn, Si and O and the other was MnS coexisted with the manganese silicate. The potentiodynamic polarization results show that the pitting potential of SLMed 316L stainless steel decreased after heat treatment. During the EN tests, three kinds of current transient were found, which corresponded to the metastable pitting initiated by the manganese silicate oxide inclusions, MnS coexisted with the manganese silicate and pore defects, respectively. Statistical analysis results of the transient signals show that the heat treatment reduced the nucleation rate of metastable pitting, and increased the transient amplitude, pit radius and pit stability product. The decreased pitting performance after heat treatment can be attributed to the low pit growth resistance.

Electrochemical Noise Analysis of the X70 Pipeline Steel under Stress Conditions Using Symmetrical and Asymmetrical Electrode Systems

In this work, electrochemical monitoring of stress corrosion cracking (SCC) behavior of a X70 steel in acidic synthetic soil solution during the slow strain rate test (SSRT) was performed by electrochemical noise (EN) using the conventional arrangement of symmetrical electrodes and electrochemical emission spectroscopy (EES) using the asymmetrical arrangement replacing the second working electrode for a platinum micro-cathode. The statistical method, fast Fourier transform, and discrete wavelet transform were used for analyzing the potential and current signals recorded by both arrangements. The results showed that EN arrangement was more effective to detect the crack initiation at a point close to yield strength despite stress-induced asymmetry in one of the electrodes. For the EES arrangement, the micro-cathode had a strong influence on the electrochemical noise of the current and potential under stress conditions. From the transient features, statistical parameters, and wavelet analysis, a discontinuous transgranular SCC mechanism was found. The resistance values obtained by EN measurements had better correlation with the electrochemical impedance spectroscopy results (EIS) than EES measurements.

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.

Frequency-Time Domain Analysis of Electrochemical Noise of Passivated AM350 Stainless Steel for Aeronautical Applications

Frequency-Time Domain Analysis of Electrochemical Noise of Passivated AM350 Stainless Steel for Aeronautical Applications

Failure mode diagnosis in proton exchange membrane fuel cells using local electrochemical noise

Early diagnosis of fuel cell failure modes is a very active research topic, as it improves robustness and durability of fuel cells used in commercial applications. The diagnosis method should be suited for being applied in real time, without interfering with the fuel cell operation, and it should be implemented using inexpensive hardware and light equipment. A novel method of failure diagnosis in PEM fuel cells, based on the analysis of local electrochemical noise, is proposed. Seven electrochemical noise signals are acquired in different parts of the cell, significantly increasing the information for an effective diagnosis, since previous studies have only analyzed a single signal from the electrochemical noise in the cell.Each electrochemical noise signal is frequency decomposed using wavelet transform to create a characteristic pattern. These patterns are used in a deep learning neural network to perform the cell state classification. The proposed method has been successfully applied to the classification of 26 different states achieved in experiments where the following factors have been varied: (1) average current density; (2) airflow; (3) drying; and (4) air pressure. The mean successful identification rate of the 26 states is above 85%. The proposed diagnosis method is well-suited for real-time diagnosis, and it can be implemented using lightweight and inexpensive hardware.

Improving the localized corrosion resistance of 304 stainless steel in HCl solution by adsorption of molybdate ions: Interaction mechanisms at the interface using molecular dynamics simulation and electrochemical noise analysis

The present study aimed to investigate the effect of molybdate ions to modify the 304 Austenitic Stainless Steel (ASS) surface against localized corrosion in hydrochloric acid medium. In this regard, surface characterization, such as Scanning Electron Microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS) coupled with Electrochemical Noise (EN) measurements, were conducted. Furthermore, molecular simulations were used to study the interactions of molybdate ions in the steel and solution interface. EN analysis showed that by adding 0.10 mM molybdate ions to 0.5 M HCl solution, the current and potential oscillations were drastically reduced compared to the molybdate ion-free medium, and the value of noise resistance has increased from ⁓3–8 kΩ cm2. SEM observations, XPS analysis, as well as Molecular Dynamic (MD) results showed a considerable reduction in localized corrosion owing to the formation of molybdenum-contained compounds, which were chemically absorbed on the passive film and placed at 4.533 Å over the metal surface. Although 304 ASSs are inhibited by various inhibitors, molybdate ions are efficient species for inhibition of the surface against both general and localized corrosion. Investigation of what happens on the 304 ASS surface from both macroscopic and microscopic points of view through electrochemical measurements and molecular simulations is the focus of this work.

Titanium bipolar plates augmented by nanocrystalline TiZrHfMoW coatings for application in proton exchange membrane fuel cells

A TiZrHfMoW refractory high entropy alloy (RHEA) nanocrystalline coating was engineered onto a commercially pure Ti (CP-Ti) substrate to enhance its corrosion resistance for potential application as bipolar plates for use in proton exchange membrane fuel cells (PEMFCs). The as-prepared RHEA coating possesses a single-phase BCC structure with an average grain size of ∼12 nm. The electrochemical corrosion behavior of the RHEA coating in simulated PEMFC environment, with varying HF concentrations, was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS), in conjunction with detection and analysis of electrochemical noise (EN). The potentiodynamic polarization and EIS measurements of the RHEA coating indicated that, at a given HF concentration, the RHEA coating exhibits a higher Ecorr, a lower icorr and a larger resistance value compared to uncoated CP-Ti. The analysis of the EN signals indicated that the RHEA coating has low correlation dimensions (below 1.4) and small instantaneous amplitudes in the Hilbert spectra, confirming that the RHEA coating was capable of maintaining a stable passive state, regardless of the HF concentrations. Furthermore, the electron work function of TiZrHfMoW RHEA was derived by first-principles calculations to unravel the physics origin of the corrosion resistance of the RHEA coating.