Electrochemical Noise Data Research Articles

Monitoring of silver alloy tarnishing in sulphides by electrochemical noise measurements: Application of statistical and recurrence plot analysis

Silver historical artefacts were manufactured using Ag‒Cu alloys; these can tarnish in environments containing sulphides (H2S, COS), causing changes in their aesthetics and, occasionally, complete loss. This creates problems for their conservation and restoration. In this study, the tarnishing process of Ag-Cu alloys (0.925, 0.800, and 0.720) immersed in (NH4)2S for 48 h was evaluated by electrochemical noise (EN) measurements. To relate the EN to the corrosion process, the EN data were subjected to direct examination and statistical and recurrence analyses. The Cu anodic behaviour controlled the icorr, the process was chaotic at the beginning (localized corrosion), and at longer immersion periods, the process became stochastic (passive condition). Based on the maximum line and the determinism percentage, a localized corrosion stage occurred at the beginning, followed by passivation that controlled the corrosion mechanism of the silver alloys.

Data Mining Applied to the Electrochemical Noise Technique in the Time/Frequency Domain for Stress Corrosion Cracking Recognition

In this paper, time/frequency domain data processing was proposed to analyse the EN signal recorded during stress corrosion cracking on precipitation-hardening martensitic stainless steel in a chloride environment. Continuous Wavelet Transform, albeit with some limitations, showed a suitable support in the discriminatory capacity among transient signals related to the different stress corrosion cracking mechanisms. In particular, the aim is to propose the analysis of electrochemical noise signals under stress corrosion cracking conditions in the time–frequency domain by using the Hilbert–Huang approach. The Hilbert–Huang Transform (performed by the Empirical Mode Decomposition approach) was finally proposed to carry out an identification of the corrosion mechanisms in comparison to conventional data processing methods. By using this approach, a detailed simultaneous decomposition of the original electrochemical noise data in the time and frequency domain was carried out. The method gave useful information about transitions among different corrosion mechanisms, allowing us to (i) identify a specific characteristic response for each corrosion damaging phenomenon induced by stress corrosion cracking, (ii) time each corrosion of the damaging phenomenon, and (iii) provide a topological description of the advancing SCC damaging stages. This characteristic evidences that the Hilbert–Huang Transform is a very powerful technique to potentially recognize and distinguish the different corrosion mechanisms occurring during stress corrosion cracking.

Enhancing pitting corrosion inhibition of AISI 304 stainless steel using a green frankincense-modified ferric chloride solution

Abstract To inhibit pitting corrosion of AISI 304 stainless steel (SS), the effect of different percentages of frankincense addition to a 0.5 M ferric chloride solution was explored in this work for the first time. The samples were investigated for pitting corrosion susceptibility via electrochemical noise (EN) tests, where the current and potential noises were recorded for 10000 seconds, and potentiodynamic polarization. The frequency domain of EN data was analyzed using power spectral density (PSD). Frankincense addition to the ferric chloride solution effectively reduced the pitting corrosion of AISI 304 SS. The pitting inhibition was concluded from the high fluctuations in current noises over the test period, its decreasing amplitude, the greater positive potential, the lower current values, and the lower spectral noise and noise resistances with increasing frankincense additions. Optical microscope images supported pitting inhibition with frankincense addition, where pits decreased in number per mm2 and size. A significant decrease in the pit size and pits mm−2 was observed with the 10 wt.% frankincense addition. It was attributed to the adsorption of the inhibitor on the stainless steel surface, inhibiting the adsorption of chloride ions. Additionally, frankincense addition reduced the corrosion current and increased the corrosion potential positively.

Nonlinear dynamics of ascorbic acid‐KI interaction on carbon steel corrosion in acid medium

AbstractAscorbic acid (AA) has been reported as a corrosion inhibitor of carbon steel. The combined effect of AA and potassium iodide (KI) in the dynamics of the corrosion process of 1018 carbon steel is studied by electrochemical impedance spectroscopy (EIS) and electrochemical noise (EN) in an acid medium. EN data were used for nonlinear analysis by means of recurrence plots and their corresponding parameters, as well as by delay maps. Important information about the corrosion process of carbon steel corrosion in the presence of these two substances was obtained. AA does not behave as an inhibitor in this system, but the influence of KI is significant in inhibitor efficiency. The dynamics is established mainly by the adsorption of the I− ions on the steel surface and confirmed by the information entropy. The action of AA is to increase the degree of chaos when concentration increases. A relevant aspect determined is the relationship between the nonlinear dynamics of a corrosion process and its intensity.

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.

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.

Susceptibility of Dissimilar IN600 Welded Joints to Stress Corrosion Cracking Using Slow Strain Rate Test in Sodium Electrolytes

The stress corrosion cracking (SCC) behavior of aged plates of Inconel 600 welded to Inconel 600 plates in the as-received condition was studied using the slow strain rate test (SSRT) in two sodium containing electrolytes at 25 and 80 °C. The aged plate was used to simulate damage by the operation service. Electrochemical noise (EN) was used to monitor the SCC. The plates were gas metal arc welded (GMAW) employing ERNiCrMo-3 and ER310 filler wires along with 95% Ar + 3% N2 + 2% O2 and 97% Ar + 3% N2 as the shielding gas, respectively. The microstructure of the welded joints was characterized using optical and scanning electron microscopy. The results of the SCC revealed that when sodium thiosulfate was used, the loss in plasticity was higher in the NiCrMo-3 joint with around a 20 percent decrease. Conversely, in the 310 welds, the loss in plasticity was higher in the sodium hydroxide, which diminished by 12 percent. A few secondary microcracks were observed in the transversal section in specimens of both welds. The results of the EN showed an increase in the potential and current when the sample reached the tensile strength and then decreased when the neck was formed; these changes indicate that some events occurred during the SSRT. The EN data showed two types of corrosion: general corrosion for NiCrMo-3 and mixed corrosion for the 310 welded joint in both environments. Electrochemical polarization was also employed to understand the mechanism of SCC.

Evaluation of the formation and protectiveness of a lithium-based conversion layer using electrochemical noise

The formation process of a lithium-based conversion layer on AA2024-T3 and its corrosion protective behavior are studied using electrochemical noise (EN). Wavelet transform, as well as noise resistance analysis, have been employed to interpret the EN data. The EN data confirmed five different stages during the conversion layer growth, accompanied by anodic dissolution, increasing corrosion protection of the conversion layer, and adsorption, growth and desorption of hydrogen bubbles simultaneously. The detachment of hydrogen bubbles, localized and uniform corrosion generate different features in the EN signals with energy maxima in high, intermediate and low frequency bands, respectively. In addition, EN results show that the lithium-based conversion layer still provides efficient protection after re-immersion in a corrosive environment, even though localized damage occurs. Moreover, the EN data corresponds well with the morphological layer formation and breakdown observed with microscopy techniques. The results demonstrate that EN is a powerful tool to provide continuous time- and frequency-resolved information about inhibition efficiency.

An integral non-intrusive electrochemical and in-situ optical technique for the study of the effectiveness of corrosion inhibition

This work investigates an integrated analysis of in-situ optical data and time-frequency information from electrochemical potential noise (EPN) data to study the effectiveness and durability of an anodic and cathodic corrosion inhibitor. Two different corrosion inhibiting species, cerium(III) (Ce(III)) and phytic acid (PHA), are tested on aluminum alloy AA2024-T3. Corrosion of AA2024-T3 serves as a negative reference. Time-frequency analysis of EPN data provides a direct insight in the kinetics of the electrochemical processes related to different types of corrosion and/or inhibitor activity over time. The simultaneous, in-situ optical technique allows visualizing and quantifying the surface changes associated with the electrochemical signals. Both Ce(III) and PHA were not capable to inhibit corrosion to a large extent, as re-immersion led to electrochemical (corrosion) activity for both inhibitors. Time-variant changes between corrosion, inhibitor activity, inhibited state and re-activation can effectively be discriminated from each other.

An assessment of intrinsic noise of pseudo-reference electrodes and instrumental noise to enable reliable electrochemical noise measurements in situ on organically coated metal

Electrochemical noise measurement (ENM) is well-established as a standard test procedure for laboratory use to assist in assessing organic coatings. However, its non-destructive nature makes it particularly appealing for field use i.e. the monitoring of actual structures. A fundamental requirement for collecting valid electrochemical noise data in any situation is the use of a stable reference electrode that produces as little noise as possible. This is particularly important for organically coated substrates, where the currents being measured are very small due to attenuation of the signal by the high-impedance coating. Standard electrodes, e.g. the saturated calomel electrode, are not suitable for field measurements. In the present study, a method of assessing candidate electrodes and their noise characteristics is proposed leading to a suggestion for a suitable pseudo-reference electrode (PRE). An important conclusion is that when used as a PRE, the area of the electrode influences the noise characteristics. In general, the smaller the electrode the lower the current noise. But this has to be balanced against small electrodes having higher impedance, the latter being undesirable, so an optimization is needed.

Effect of meat extract as an eco-friendly inhibitor on corrosion behavior of mild steel: Electrochemical noise analysis based on shot noise and stochastic theory

The present work aimed to investigate the corrosion behavior of mild steel in hydrochloric acid solution in the presence of meat extract as an eco-friendly inhibitor using weight-loss, potentiodynamic polarization, electrochemical impedance spectroscopy, and scanning electron microscope. Besides, in order to evaluate the inhibitive performance of meat extract for pitting corrosion of mild steel, electrochemical noise (EN) analysis was used. It was revealed that about 94% of the mild steel surface was covered by meat extract molecules, and the corrosion rate was reduced around 6-fold (from 65 to 11 mpy) comparing to the sample exposed to blank solution. A good trend was observed between the EN data and the results obtained from the other techniques. Based on shot noise theory, introducing meat extract up to 500 ppm into the solution shifts the cumulative probability of the corrosion events on the steel surface to higher frequencies, which is a sign of less localized corrosion. Stochastic modeling indicated that the presence of meat extract inhibitor leads to both a fall in the pit initiation rate and a decrease in the propagation probabilities of the metastable pits. Combining these with the SEM/EDS results revealed that the meat extract by the formation of an adsorption film on the steel surface results in the enhancement of the pitting corrosion resistance.

Electrochemical noise analysis of cavitation erosion corrosion resistance of NbC nanocrystalline coating in a 3.5 wt% NaCl solution

To combat cavitation erosion-corrosion damage inflicted upon mechanical components in marine applications, NbC nanocrystalline coatings were synthesized by a double cathode glow discharge assisted reactive sputtering method. The coating comprised equiaxed B1-NaCl-type NbC grains with an average grain size of ~10 nm and a strong NbC (200)-oriented texture by TEM observation. The electrochemical response of the coating exposed to a 3.5 wt% NaCl solution with and without the influence of cavitation was monitored by electrochemical noise (EN) measurements, in addition to open circuit potential and cyclic polarization. To differentiate the cavitation erosion-corrosion resistance between the NbC coating and a reference Ti-6Al-4V alloy substrate, the EN data were further evaluated, based on a series of analyses, including frequency domain, time-domain, shot noise and wavelet transform. For the Ti-6Al-4V alloy, with increasing output power, the noise resistance (Rn) and slope (k values) of potential and current power spectral density (PSD) decreased, and the average charge in each corrosion event (q) and the total energy of d series crystals increased markedly at the output power levels above 400 W, indicative of a high propensity of pitting corrosion for this alloy. Conversely, the Rn and k values for the NbC coating were found to be almost independent of the output power, and the charge of the corrosion event and the total energy of the d series crystals were much lower than that of the Ti-6Al-4V alloy. The findings garnered from analyzing the EN signals is in accord with what were uncovered from examining the eroded surface morphologies, suggesting that the EN method might offer a reliable and effective tool to probe the cavitation erosion-corrosion behavior in developing durable material.

Performance Study of Aluminium–Zinc Anode using Noise Resistance, Pitting Index and Recurrence Plots from Electrochemical Noise Data

Electrochemical noise technique allows the simultaneous measurement of voltage and current on a material in a process stream. Useful information regarding the state of the sample, initiation, type and growth of corrosion can be obtained. To this end, time domain and recurrence plots have been used to study the electrochemical noise data obtained for an Al–Zn sacrificial anode immersed in NaCl solution over 7 days to understand various corrosion mechanisms occurring on the anode surface. The noise resistance, pitting index and recurrence plots were correlated with scanning electron microscopy (SEM). The results revealed that PI and Rn for the non-heat-treated and heat-treated aluminium–zinc anodes decreased progressively with immersion time. This can be attributed to increasing dissolution activity on the anode surfaces. The obtained Rn for non-heat-treated anodes were greater than 105 Ω cm2 and the Rn for heat-treated anodes were less than 105 Ω cm2. Heat treating the Al–Zn anodes helped to reduce the noise resistance values to a maximum of 12,000 Ω cm2. The recurrence plots showed distinct butterfly-like structures that indicated progressive dissolution activity on the anode surfaces. Lower noise resistance and pitting index as immersion time progressed signified improved electrochemical performance of the anodes.

Electrochemical noise analysis to obtain the Rsn value via FFT using Excel

Electrochemical noise (EN) measurements are based on the fluctuations of the electrochemical potential and the current that occur during, for example, a corrosion process without an external signal perturbation. EN analysis (ENA) allows assessment of the type of corrosion and rapid determination of the corrosion rate. Microsoft Excel®, an inexpensive and readily available software package, is an excellent tool for performing repetitive calculations, with automation that saves time for the users. It is a useful tool for the analysis of EN data using fast Fourier transform (FFT), a process that is often made repeatedly and, if not automated, is quite laborious. This work presents a step-by-step procedure using Excel to perform these calculations, automating the process of obtaining the spectral electrochemical noise resistance, . This routine was used to analyze experimental potential and current noise data recorded for chalcopyrite. The results were comparable to those obtained for the same set of experimental data using Origin® software.

Sequential co-precipitation as a convenient preparation method of anticorrosive hybrid calcium phosphate/calcium silicate powder pigments

Hybrid powder pigments based on calcium phosphates and Ca-exchange silicates (CPS) were prepared via a sequential co-precipitation method. Chemical composition of CPS and reference pigments (calcium phosphates (CP) and calcium silicates (CS)) was investigated in relation to molar ratio of substrates and pH value of reaction medium. Steel corrosion inhibition efficiency (η) for the pigments was evaluated using electrochemical noise (EN), polarization resistance (POL) and Tafel (TAF) techniques. XRD and FT-IR data indicated that CPS are mixtures of the relevant CP and CS pigments. The EN, POL and TAF data revealed a sinusoidal relation between η and P:Si molar ratio in the substrates (at pH = 8.5 or 11). The best anticorrosive features were observed for CPS prepared at Si molar excess (pH = 8.5) (ηEN = 99%, ηPOL = 73% and ηTAF = 85%). Probably, the synergistic effect was resulted by a specific content and molar ratio of Ca, P2O5 and Si in the CPS-based electrolytes.

Quantification of the Atmospheric Corrosion of 304 and 2205 Stainless Steels Using Electrochemical Probes Based on Thevenin Electrochemical Equivalent Circuit Model

Stainless steel (SS) is one of the most widely used engineering materials in marine engineering. However, its corrosion in the marine atmospheric environment due to the high concentration of Cl− is a problem. The SS corrosion is a threat to the development and security of marine industry; therefore, evaluating the corrosion resistance of SSs is necessary. In this work, atmospheric corrosion detection probes based on a symmetrical electrode system were used to study the corrosion behaviors of 304 SS and 2205 duplex stainless steel (DSS) in a simulated marine atmosphere. A theoretical model for electrochemical noise (EN) data analysis based on the Thevenin electrochemical equivalent circuit (EEC) model was established. The relationship between the EN characteristic parameters and the corrosion rate was obtained. The Thevenin EEC model analysis showed that the relationship between the noise resistance (Rn), the noise impedance [Rsn(f)], and the impedance modulus (|Z(f)|) was R_{{text{n}}} approx R_{{{text{sn}}}} = {}^{sqrt 3 }left| {Z(f)} right|. Thus, Rn and Rsn can be used as indicators for quantitative corrosion evaluation. The results of EN detection for the 304 SS and 2205 DSS showed that in a simulated marine atmospheric environment, the passive films on the two SSs were relatively intact at the initial exposure stage, and their dissolution rates were slow. The corrosion resistance of the 2205 DSS was higher than that of the 304 SS. With the deposition of Cl− on the SS surface, pitting was initiated and the dissolution rate increased. The pitting initiation process on the SS surface was random, and part of the active pores could be repassivated.

APPLICATION OF QUANTUM CHEMICAL, NOISE AND THE ELECTROCHEMICAL FREQUENCY MODULATION TO INVESTIGATE THE ADSORPTION AND CORROSION INHIBITION BEHAVIOR OF 2-AMINO-6-HYDROXYBENZOTHIAZOLE FOR STEEL API X80 IN ACIDIC SOLUTION

Different theoretical, electrochemical and surface techniques were applied to study the corrosion inhibition effects of 2-Amino-6-hydroxybenzothiazole in 5% HCl solution. The density functional theory was carried out and quantum chemical factors like the energy gap, energy of highest occupied molecular orbital, the energy of lowest unoccupied molecular orbital, the fraction of electron transferred, and Mulliken charges have been calculated. In addition, according to quantum calculation, S atom in 2-Amino-6-hydroxybenzothiazole indicated more tendency for electrophilic attack in adsorption. The main reason for high inhibition efficiencies in very low concentrations is the planar and simplicity of inhibitor structure which leads to increasing the efficiency of adsorption by functional group especially sulfur. Electrochemical frequency modulation and potentiodynamic polarization indicated that this material has excellent inhibiting features in very low concentrations. The influence of DC trend on the explanation of electrochemical noise data was evaluated by polynomial fitting and the optimum polynomial order m=4 was obtained. Noise resistance and the inhibition efficiency was calculated and compared in different methods. The theory of shot noise in frequency domain was used to obtain the electrochemical event charge. The corroded surface of steel in the absence and existence of thiazole compound was studied by Atomic force microscopy.

Computational and Experimental Study onthe Adsorption and Inhibition Effects of 1,3-Benzothiazol-6-ol on the Corrosion ofSteel X80 in Acidic Solution

Abstract In this work, the adsorption and inhibition behavior of 1,3-benzothiazol-6-ol were investigated by computational and experimental techniques for steel X80 corrosion in acidic solution. The density functional theory was carried out and quantum chemical factors like the energy gap, energy of highest occupied molecular orbital, the energy of lowest unoccupied molecular orbital, the fraction of electron transferred, and Mulliken charges have been calculated. In addition, according to quantum calculation, S atom in 1,3-benzothiazol-6-ol indicated more tendency for electrophilic attack in adsorption. The main reason for high inhibition efficiencies in very low concentrations is the planar and simplicity of inhibitor structure which leads to increasing the efficiency of adsorption by functional group especially sulfur. Electrochemical frequency modulation and potentiodynamic polarization indicated that this material has excellent inhibiting features in very low concentrations. The influence of DC trend on the explanation of electrochemical noise data was evaluated by polynomial fitting and the optimum polynomial order m = 5 was obtained. Noise resistance and the inhibition efficiency was calculated and compared in different methods. The theory of shot noise in frequency domain was used to obtain the electrochemical event charge. The corroded surface of steel in the absence and existence of thiazole compound was studied by Atomic force microscopy.

Density Functional Theory and Electrochemical Noise Analysis of Corrosion Inhibition Behavior of N,N '-bis(1-(3,5-dihydroxyphenyl)ethylidene)propane-1,3-diamine on Steel in HCl Solution

The inhibition effect of N,N ′-bis(1-(3,5-dihydroxyphenyl)ethylidene)propane-1,3-diamine was studied on steel corrosion in 1 M hydrochloric acid solutions. The density functional theory was applied to calculate quantum chemical parameters such as the highest occupied molecular orbital energy, the lowest unoccupied molecular orbital energy, electron affinity, global electrophilicity index, the fraction of electron transferred, global nucleophilicity index, and Mulliken charges. According to quantum calculation, the diamine compound showed high interaction and effective adsorption on steel surface and high inhibition efficiencies and therefore nitrogen atoms of inhibitor indicated more tendencies for the electrophilic effect in the adsorption. Electrochemical impedance and potentiodynamic polarization indicated that this material has excellent inhibiting features in very low concentrations. The influence of DC trend on the explanation of electrochemical noise data was evaluated by polynomial fitting and the optimum polynomial order m = 4 was obtained. Noise resistance and the inhibition efficiency was calculated and compared in different methods. The theory of shot noise in frequency domain was used to obtain the electrochemical event charge. The corroded surface of steel in the absence and existence of thiazole compound was studied by Atomic force microscopy.

Electrochemical Frequency Modulation, Electrochemical Noise, and Atomic Force Microscopy Studies on Corrosion Inhibition Behavior of Benzothiazolone for Steel API X100 in 10% HCl Solution

In this work, electrochemical and surface techniques were applied to study the corrosion inhibition effects of benzothiazolone. 10% HCl was used to simulate the oil and gas well-acidizing fluid. Electrochemical frequency modulation and potentiodynamic polarization indicated that this material has excellent inhibiting features in very low concentrations. The influence of DC trend on electrochemical noise data was evaluated by polynomial fitting, and the optimum polynomial order m = 4 was obtained. After detrending, the charge of corrosion reaction obtained by electrochemical noise decreased with increasing inhibitor concentrations. In addition, the inhibition efficiencies from electrochemical noise were in agreement with data obtained by other electrochemical methods. Surface studies illustrated that the corroded surface was smoother in the presence of benzothiazolone. Electrochemical impedance and noise showed that benzothiazolone blocked the electrode surface by adsorption obeying Langmuir isotherm. According to quantum calculation, S atom in benzothiazolone indicated more tendencies for electrophilic attack in adsorption process. The main reason for high inhibition efficiencies in very low concentrations was the planar and simplicity of inhibitor structure which led to increasing the efficiency of adsorption by functional group especially sulfur.