Electrochemical Noise Measurements Research Articles

Electrochemical noise measurements on stainless steel using a gelled electrolyte

The present paper presents pioneering results about the use of the electrochemical noise (EN) technique to study corrosion of metal surfaces of complex geometry in a gel electrolyte based on agar-glycerol, the composition of which was previously optimized for electrochemical measurements on stainless steel (SS) surfaces. EN results obtained with AISI 304 SS electrodes in both gelled and liquid electrolytes using three different modes (zero-resistance ammeter, potentiostatic, galvanostatic) of measurements have been compared and discussed. Tests carried out in gel allow the possibilities and limitations of using portable gel cells for monitoring corrosion of SS complex surfaces to be determined.

Electrochemical Noise Measurements with Dummy Cells: Evaluation of a Round-Robin Test Series

Round-robin (RR) tests on electrochemical noise (EN) measurements with dummy cells have been performed in the European Cooperative Group on Corrosion Monitoring of Nuclear Materials since 2006. Dum...

Detrending and Other Features of Data Processing in the Measurements of Electrochemical Noise

Measurements of electrochemical noise in solid-state electrochemical cells with a heteropolycompound- based electrolyte are carried out. The noise power spectral density is calculated using various detrending methods. The impedance real component is calculated by means of the Nyquist formula. The results of the calculations are compared with the data obtained by the electrochemical impedance classical method.

Effect of neutral salt spray (NSS) exposure on the lap-shear strength of adhesive-bonded 5052 aluminum alloy (AA5052) joints

This work explores the mechanisms for the non-linear degradation of the lap-shear strength of adhesive-bonded 5052 aluminum alloy (AA5052) joints exposed to neutral salt spray (NSS) environment up to 1200 hours. The lap-shear testing results show that a mixed failure dominated by adhesive failure occurred in both unexposed and exposed adhesive-bonded AA5052 joints. The lap-shear strength of adhesive-bonded AA5052 joints declined sharply in the preliminary stage of NSS exposure (e.g. shorter than 240 hours), then it decreased moderately as the NSS exposure time increased. Differential scanning calorimetry (DSC), scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and electrochemical noise measurement were applied to exploring the degradation mechanisms of the lap-shear strength of adhesive-bonded AA5052 joints. The adhesive properties remained nearly unchanged after exposure in the NSS environment. The decreased hydrogen bond at the AA5052/adhesive interface was responsible for the sharp degradation of the lap-shear strength of adhesive-bonded AA5052 joints in the preliminary stage of NSS exposure. In the later stage of NSS exposure (e.g. more than 240 hours), the surface oxidation of AA5052 substrates dominated the lap-shear strength degradation of adhesive-bonded AA5052 joints.

Wide frequency band electrochemical noise measurement and analysis of a Li/SOCl2 primary battery

Electrochemical noise of a primary LiSOCl2 battery was measured in a wide frequency band during discharge at a constant value resistor. Power spectral density calculation method was used as the first stage of data analysis. Measurements with two analog to digital converter speed rates made it possible to carry out precision analysis in more than five order wide frequency bands starting from 2.5 kHz down to 17 mHz. It was shown that each power spectral density spectrum consists of two regions. Each of them possesses linear frequency dependence with its own slope. They intercept in the frequency band from 10 Hz down to 0.1 Hz depending on the state of charge value. Dispersion and high-order moments such as kurtosis and skewness calculation methods were applied to analyze electrochemical noise data as alternate analysis techniques. It was found that dispersion calculation can give useful information about electrochemical noise evolution during discharge process for the investigated battery type.

Electrochemical noise measurement methodologies of chemical power sources

The electrochemical noise of a primary lithium battery was measured at an open circuit by two experimental approaches: with a filtering capacitor and with the same battery to eliminate open circuit voltage of the system under test. Both methodologies give the same results if they are applied correctly but they can sometimes cause experimental problems. Two experiments were carried out with battery discharge at resistive load. It was shown that it is very difficult to provide the conditions for properly operation of the two battery method to avoid saturation of measurement device when the amplifier uses high gain values.

Persian Liquorice extract as a highly efficient sustainable corrosion inhibitor for mild steel in sodium chloride solution

The Persian Liquorice was introduced as a sustainable corrosion inhibitor with excellent inhibition action for mild steel in sodium chloride solution. Persian Liquorice is a root of Glycyrrhiza glabra including many active compounds like Glycyrrhizin (GL), 18β- Glycyrrhetinic acid (GA), Liquritigenin (LTG), Licochalcone A (LCA), Licochalcone E (LCE), and Glabridin (GLD). The Fourier transform infrared (FT-IR) spectroscopy was utilized to track various active components exist in the Persian Liquorice extract. Electrochemical impedance spectroscopy, potentiodynamic polarization and electrochemical current noise measurements were conducted to investigate the corrosion inhibition role of various concentrations of Persian Liquorice extract toward mild steel corrosion in sodium chloride solutions. Surface analysis, molecular dynamics and quantum mechanics simulation methods were combined to get insights of inhibitor molecules adsorption on the mild steel surface. The electrochemical investigations revealed that in the presence of 600 ppm Persian Liquorice extract the maximum inhibition efficiency of 98.8% was obtained, which is connected to the build-up of a protecting layer over the mild steel surface, blocking the pathway of harsh ions diffusion. There is no report on use of any sustainable corrosion inhibitor for mild steel in chloride solution with this high level of inhibition power even after long immersion time (72 h). The formation of protecting layer on the mild steel surface was proved by scanning electron microscope and atomic force microscope results. The results derived from MD simulations and QM calculations revealed the adsorption of Persian Liquorice components on the steel substrate via donor-acceptor interactions.

Software and Instrumentational Methods of Enhancing the Resolution in Electrochemical Noise Measurements

Several methods of enhancing the signal-to-noise ratio for instrumentation designed to measure electrochemical noise are practically tested. The experiments are carried out using model RC-circuits and lielectrolyte electrochemical cells. Strong limitations in the tested objects’ impedance values are found due to the input current noise of the instrumentation, especially during the parallel connection of several channels. The advantages of a two-channel scheme for automatically compensating the instrument’s self noise are demonstrated. Different methods of lowering the dispersion of the frequency dependences of the spectral power density of electrochemical noise are compared. It is shown that averaging over segments with an overlap is the most effective method but averaging over frequencies can lead to large distortions when investigating electrochemical systems.

Comparing the Method and Hardware for Electrochemical Impedance with the Method of Measuring and Analyzing Electrochemical Noise

The experimental techniques of the methods of impedance with an ac current and electrochemical noise are considered in detail. The main features, disadvantages, and limitations of the application of both methods are underlined and compared. The theoretical possibility of using a new method of electrochemical noise measurement to study electrochemical objects is shown. This method combines the method of impedance and traditional potentiometric and amperometric methods of electrochemical noise measurements.

Measurement of electrochemical noise of a Li/MnO2 primary lithium battery

Electrochemical noise of a Li/MnO2 primary lithium battery was measured and analyzed during discharge process for the first time. The amplitude of the noise is shown to increase during battery discharge. The power spectral density frequency dependences of the noise are calculated for various stages of the battery discharge. The amplitudes of power spectral densities of the current noise nearly linear depend on the discharge voltage for frequencies below 1 Hz. The slope of the spectral power density frequency dependence of voltage noise changes from − 1 to − 2 during the battery discharge. It was found that the magnitude and slope of the power spectral density frequency dependence of the noise can be considered as a discharge criterion for a primary lithium battery.

Electrochemical noise measurement of a Li/SOCl2 primary battery

Electrochemical noise of a Li/SOCl2 primary battery was measured during discharge at a constant value resistor. The amplitude of the noise was found to be razing during discharge process. Power spectral density calculation method was used to analyze electrochemical noise. It was found that the slope of power spectral density frequency dependences increases with the battery discharging. The electrochemical impedance of the battery was measured during galvanostatic discharge and investigated using equivalent circuit analysis method. The correlations and some interactions between impedance components and electrochemical noise characteristics during battery discharge process were found and analyzed.

Online Monitoring of the Atmospheric Corrosion of Aluminium Alloys Using Electrochemical Noise Technique

In this work, an electrochemical system based on electrochemical noise (EN) technique for online detection and monitoring of atmospheric corrosion of LY12CZ aluminium alloys has been established. A detecting probe and a monitoring instrument with a software have been developed to perform the electrochemical noise measurements with zero resistance ammeter (ZRA) mode. Experimental results show that the atmospheric corrosion behaviour of aluminium could be effectively detected and monitored by the analysis of the electrochemical potential and current noise, also by the noise resistance variation.

Aluminium Corrosion in Bioethanol/Gasoline Blends

In this work, the corrosion behavior of aluminum in different types of bioethanol/gasoline blends has been evaluated by using electrochemical techniques. Evaluated bioethanols included bioethanol from Apple, mango, orange and sugar cane in concentrations of 10 and 20%, whereas employed techniques included electrochemical impedance spectroscopy (EIS), electrochemical noise (EN) and linear polarization resistance (LPR) during 90 days. Corroded samples were analyzed in a scanning electronic microscope (SEM). Obtained results have shown that orange, apple and mango bioethanols/gasoline, in both concentrations, there is a decrease in the impedance value as compared to that for pure gasoline, with the highest corrosion rate exhibited by the sugar cane bioethanol. LPR results indicate that the mango bioethanol/gasolina blends exhibited similar corrosion rates to that exhibited by gasoline. On the other hand, EN measurements showed that in both pure gasoline and the 10% concentration noise reading showed indicating a high susceptibility towards localized type of corrosion, whereas those exhibited by th 20% concentration indicated a susceptibility towards uniform type of corrosion or passivation, which was corroborated by the SEM micrographs.

Analysis of electrochemical noise in NiCd batteries throughout their lifetime

Electrochemical noise measurements have been applied to electrochemical systems that show stochastic behavior. The standard area of study that benefits from this stochastic analysis is localized corrosion modes like pitting and crevice corrosion. Application of electrochemical noise measurements to battery systems, though rare, is recently becoming more popular. The present contribution first establishes a method of analyzing electrochemical voltage noise data for NiCd batteries, then follows four samples of batteries in terms of voltage noise throughout their lifetimes. The noises exhibited by battery systems are small, but finite. This noise is expected to be due to variations in the electrochemistry on the electrode surfaces of the battery. After careful analysis, the voltage noise behavior of NiCd batteries does not appear to show a statistically significant variation of electrochemical voltage noise throughout their lifetimes

Study on adsorption behavior of ketoconazole on Q235 mild steel in 1.0 M HCl solution with electrochemical measurement

The inhibition effect of ketoconazole (KCZ) on Q235 mild steel corrosion in 1.0 M HCl solution was studied using weight loss, electrochemical impedance spectroscopy (EIS), electrochemical noise (EN), scanning electron microscope (SEM) and energy dispersive X-ray detector (EDX). Results reveal that the inhibition efficiency increases with increasing the KCZ inhibitor concentration and the adsorption behavior of ketoconazole onto Q235 mild steel follows the Langmuir adsorption isotherm with negative value of ΔGads0, suggesting a spontaneous adsorption process. It is also found that the type of adsorption of KCZ on the mild steel surface belongs to chemisorption. New parameter of corrosion active energy CAE proposed from EN measurements which representing the electrode reaction speed exhibited the same variation trend with the corrosion rate.

Microstructural and Electrochemical Characterization of Friction Stir Welded Aluminum Alloys

Aluminum alloys of 2000 and 7000 series containing cooper and zinc, respectively, as the main alloying element are extensively used in aircraft structures. However, these classes of aluminum alloys are difficult to join by conventional fusion welding techniques because the dendritic structure formed in the fusion zone can seriously compromise the mechanical and corrosion resistance properties of the joint. Friction Stir Welding (FSW) is attractive for joining high strength aluminum alloys since there is far lower heat input during the process compared with conventional welding methods. FSW is produced by rotating and plunging a specially-designed cylindrical, shouldered tool with a small diameter pin into the joint line between two butted plates. Frictional heat causes the metal to soften and allows the tool to traverse along the joint line [1]. The FSW process generates three distinct microstructural zones: the nugget, the thermomechanically affected zone (TMAZ) and the heat-affected zone (HAZ). These microstructural modifications generally interfere in the performance of the corrosion resistance of welded alloys. In the present study, FSW was used to join two dissimilar aluminum alloys, AA2024-T3 (Al-Cu-Mg) and AA7475-T651 (Al-Cu-Mg-Zn) and the effect of this process on the corrosion resistance of the welded joints and on the microstructure of the alloys was evaluated. Microstructural characterization was carried out by optical microscopy, scanning electron microscopy and atomic force microscopy. The weld zone regions showed significant microstructural changes. Electrochemical impedance spectroscopy (EIS) and Electrochemical noise measurements (ENM) were used to evaluate the corrosion resistance of the different zones of the weld in NaCl solution. Local electrochemical measurements using an electrochemical microcell were carried out across the transverse cross section of the welds. The cell containing the solution, counter and reference electrodes is attached to the carousel of an optical microscope. The electrochemical results showed that the corrosion behavior of the AA2024-T3 / AA7475-T651 alloy is dominated by the electrochemical activity within the intermetallics (IMs). The weld zone regions containing copper IMs have a more noble character than the regions containing Zn and Mg IMs. Therefore, the results showed an increased susceptibility of welded joints to these forms of corrosion in comparison to the unaffected base metal by a more severe attack related to AA7475-T651 alloy. Reference [1] M. Jariyaboon et al. Corrosion Science 49 (2007) 877–909. [2] J.-Q. Su et al. Acta Materialia 51 (2003) 713–729 Acknowledgement: Fapesp 2013/132356

Detection of under deposit corrosion in a CO2 environment by using electrochemical noise and recurrence quantification analysis

In this study, the corrosion of carbon steel immersed in CO2 saturated aqueous solutions, in the presence and absence of sand deposits, were investigated by electrochemical noise measurement and recurrence quantification analysis. Uniform corrosion occurred at samples without sand deposit, while localized corrosion took place at the sand-covered steel samples. These two different corrosion types can be accurately predicted by random forest and principal component models based on recurrence quantification analysis of either electrochemical potential or current noise data, regardless of threshold values. The study provides a potential automated online corrosion monitoring scheme to ensure the integrity of pipelines.

Corrosion of mild steel in hydrochloric acid solution in the presence of two cationic gemini surfactants with and without hydroxyl substituted spacers

The corrosion inhibition mechanism of mild steel in acidic solution and in the presence of two cationic gemini surfactants have been studied. These are two surfactants having 12-carbon hydrophobic tails: one with a tetramethylene spacer and the other one with the same spacer containing two hydroxyl groups. EIS and polarization and electrochemical noise measurements revealed superior corrosion inhibition of hydroxyl functional surfactant compared with its counterpart with no hydroxyl group. Surface analysis including AFM, and SEM confirmed less corrosion attacks on the sample exposed to hydroxyl functional surfactant solution. Quantum chemical parameters revealed a good correlation with electrochemical results.

Characterization of Surface-Treated NiTi Alloy by Various Electrochemical Techniques in Phosphate-Buffered Saline

Sol–gel titania thin film coating was prepared on NiTi surfaces, modified with acidified ferric chloride solution. Nanogrids formed on chemical treatment were uniformly covered with titania coating. Cyclic voltammetry studies in phosphate-buffered saline solution revealed that sol–gel titania-coated surface displayed electrochemical properties which were similar to those observed for pure titanium. During polarization, the passive layer formed on modified NiTi was stable for potentials greater than 0.9 V. The overall resistance measured by electrochemical impedance spectroscopy for sol–gel titania surface was in the order of 105 Ω, which was approximately two orders higher than bare NiTi surface. The current noise analyzed using electrochemical noise measurements was minimum after sol–gel coating, which emphasizes the better protection power of the surface from the attack of corrosive species. Dynamic impedance studies carried out on bare and titania-coated NiTi also supports the results obtained from cyclic polarization.

Corrosion behavior of Fe-Mo and Fe-Mo-P cathodic coatings in the simulated electrolyte for sodium chlorate production

The corrosion behavior of electrodeposited binary Fe-Mo and ternary Fe-Mo-P coatings on mild steel substrates as cathodes was investigated in the simulated electrolyte for chlorate production, containing 300 g L−1 of NaCl and 4 g L−1 of K2Cr2O7 at 80 °C. Electrochemical noise measurements (ENM), linear polarization resistance (LPR), electrochemical impedance spectroscopy (EIS) and scanning reference electrode technique (SRET) were used in this investigation under open circuit potential (OCP) in the simulated shutdown conditions of the chlorate production industry (decay). A filiform corrosion was observed on the surface of all electrodes and in the case of mild steel, a number of pitting sites were also detected. The ternary cathode (Fe54Mo30P16) containing the highest phosphorous content showed the best resistance to corrosion compared to other coatings and mild steel. Using the ENM technique, a decrease of 67% of the corrosion rate was measured for the Fe54Mo30P16 coating compared to Fe53Mo47 after 72 h of decay, whereas mild steel showed 6 times more corrosion compared to the Fe54Mo30P16 electrode. The addition of phosphorous to the Fe53Mo47 alloy promoted resistance to corrosion. The corrosion resistance of ternary alloys of Fe-Mo-P were improved with the increase of phosphorous content from 9 to 16 at.%. According to LPR and EIS measurements, the Fe54Mo30P16 showed 56%–60% less corrosion compared to the binary Fe53Mo47 electrode.