Journal articles: 'Mechanism of cathodic reactions'

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Wang, Shao Qing, Fa Qin Xie, Xiao Fei Yao, and Xiang Qing Wu. "Mechanism of Cathodic Plasma Electrolytic Deposition on Ti6Al4V Alloy in Al(NO₃)₃ Ethanol-Aqueous Solution." Advanced Materials Research 1145 (March 2018): 54–58. http://dx.doi.org/10.4028/www.scientific.net/amr.1145.54.

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Barrier layer was prepared by Micro-arc oxidation(MAO) technique in silicate solution, and cathodic plasma electrolytic deposition (CPED) technique was used to fabricate Al2O3 ceramic coatings on Ti6Al4V alloy in Al(NO3)3(30g/L) and ethanol-aqueous solutions. Surface morphology and elemental of the coatings were investigated by scanning electron microscope (SEM) and energy disperse spectroscopy (EDS). Reaction phenomena were recorded and products of reactions were analyzed by infrared absorption spectrum KBr compression method. Furthermore, mechanisms of different electrolytes were evaluated.

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Kahyarian, Aria, Bruce Brown, and Srdjan Nešić. "Mechanism of Cathodic Reactions in Acetic Acid Corrosion of Iron and Mild Steel." CORROSION 72, no. 12 (December 2016): 1539–46. http://dx.doi.org/10.5006/2177.

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Dang, Trung Dung. "STUDY ON THE PREPARATION OF MANGANESE DIOXIDE VIA CATHODIC ELECTROLYSIS." Vietnam Journal of Science and Technology 55, no. 5B (March 24, 2018): 34. http://dx.doi.org/10.15625/2525-2518/55/5b/12207.

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A novel synthesis method was developed to prepare manganese dioxide via cathodic electrolysis in potassium permanganate solution. The morphology and the composition of the synthesized products were analyzed by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction spectroscopy (XRD). The electrolyzed products include two kinds of materials: amorphous and crystalline manganese dioxide. The manganese dioxides were formed by cathodic reduction via two reaction mechanisms: direct and indirect electrochemical reactions. The electrolysis current performance strongly depends on the electrolyte solution temperature, applied voltage and not clearly depends on electrolyte solution concentration. With high current performance and uniformity products, the cathodic reduction of potassium permanganate is promising method for manganese dioxide fabrication.

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Liu, Chenxu, Jin Zhang, Yedong He, Peng Wang, Shunjie Deng, and Shuguang Zhang. "Al2O3 Microspheres Prepared by Cathode Plasma Electrolysis." Australian Journal of Chemistry 70, no. 1 (2017): 120. http://dx.doi.org/10.1071/ch16214.

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Al2O3 microspheres were prepared by cathode plasma electrolysis (CPE) in an aqueous solution of Al(NO)3·9H2O. Compared with high-temperature calcination methods, the CPE method afforded the preparation of microspheres directly at room temperature. The results showed that regular microspheres formed under relatively high concentrations of Al(NO)3·9H2O. The microspheres, with diameters mostly in the range of 5–30 μm, consisted of γ-Al2O3 and α-Al2O3. The possible formation mechanism included the following processes: (1) Al(OH)3 intermediate was formed during the cathodic reactions; (2) plasma energized the intermediate to Al2O3; and (3) microspheres formed under the effect of the surface tension.

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Asmara, Yuli Panca. "Simulation of CO2 Corrosion of Carbon Steel in High Pressure and High Temperature Environment (HPHT)." Journal of Integrated and Advanced Engineering (JIAE) 2, no. 1 (March 31, 2022): 63–70. http://dx.doi.org/10.51662/jiae.v2i1.41.

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In HPHT environments, the mechanism of CO2 corrosion faces a challenge as an effect of chemical-physical reactions on the metal surface. The presence of other elements in the CO2 system complicates corrosion behavior. To provide a realistic mechanism for corrosion process, some corrosion prediction models have developed software using fundamental theories such as electrochemical reactions and thermodynamics theories. Existing methods to predict corrosion rate models in HPHT environments have shown reasonable results. This paper reviews software of corrosion predictions which calculate corrosion rate based on mechanistic theories that study effects of H2S, acetic acid (HAc) concentrations, shear stress, pH in temperature from 25oC – 100oC and pressure from 1–10 bar. From the simulation, corrosion rate increased significantly in the high pressure CO2 environment. Corrosion rate at pH 4 increased to 30 mm/y at a temperature from 15oC to 90oC. While at pH 8 corrosion rate reached 4 mm/y. This lower corrosion rate indicated a tendency for deposits formation at higher pH. Corrosion rate behaves in a different mechanism at high temperatures. The corrosion rate decreased to 4 mm/y when the temperature increased to more than 90oC. Effects H2S gas and HAc were identified to increase corrosion rate. Both elements provide extra cathodic reaction and create limiting current density in the cathodic reaction process based on polarization sweep models. However, the polarization graph calculated using corrosion models could not display passive behavior in the anodic polarization process. Thus, further, improvement should be considered. From the data calculation, it can be shown that corrosion prediction software can predict corrosion rate in HPHT conditions.

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Altunöz-Erdoğan, Deniz, Nevin Erk, and Esma Kılıç. "Voltammetric methods of reboxetine analysis and the mechanism of its electrode reactions." Open Chemistry 11, no. 5 (May 1, 2013): 706–16. http://dx.doi.org/10.2478/s11532-013-0213-8.

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AbstractReboxetine (RBX) electrochemical redox behavior at hanging mercury drop (HMDE) and glassy carbon electrodes (GCE) was studied in various pH Britton-Robinson universal buffers using cyclic voltammetry and square-wave voltammetry. RBX was reduced at the HMDE and oxidized at the GCE with reversible adsorption controlled and irreversible diffusion controlled processes respectively. The anodic peak is due to the amine and the cathodic peak may correspond to oxygen protonation. An oxidation reaction mechanism is proposed. The linear relation between peak currents and RBX concentration allowed simple, sensitive, precise and inexpensive voltammetric procedures to be developed. The limit of detection was 0.04 µM RBX. The procedures were successfully applied to human urine and RBX tablet assay. Therapeutic RBX concentrations in human serum were not detected due to strong drug-protein binding. Using bovine serum albumin, the methods were used to investigate the effect of serum protein binding on RBX determination.

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Zhuzhel’skii, D. V., V. A. Krylova, V. D. Ivanov, and V. V. Malev. "Mechanism of electrochemical reactions of polyaniline films formed under the conditions of cathodic oxygen reduction." Russian Journal of Electrochemistry 45, no. 2 (February 2009): 145–51. http://dx.doi.org/10.1134/s1023193509020049.

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Sunarya, Yayan. "3-Mercaptopropionic Acid as Corrosion Inhibitor for Carbon Steel in CO2 Aerated 1% NaCl Solution with Buffer Control-pH." Molekul 13, no. 2 (December 8, 2018): 98. http://dx.doi.org/10.20884/1.jm.2018.13.2.340.

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In this research, 3-Mercaptopropionic acid (MPA) as corrosion inhibitor of carbon steel in CO2 aerated 1% NaCl solution with buffer pH adjustment has been studied by means of electrochemical impedance (EIS) and polarization (Tafel plot). MPA was found to be an effective carbon steel inhibitor. Percentage inhibition efficiency (IE %) calculated by both Tafel plot and EIS, ranged from 85% to 90%. MPA was found to affect the cathodic processes and act as cathodic-type inhibitors. Mechanism of inhibit corrosion by adsorption mechanism leads to the formation of a protective chemisorbed film on the metal surface film which suppresses the dissolution reaction and the hydrogen evolution reaction is activation controlled.

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He, Xiang Zhu, Wen Jun Zhang, and Yong Xiu Wang. "Electrodepositon and Properties of Ni-Diamond Composite Coatings." Advanced Materials Research 702 (May 2013): 176–80. http://dx.doi.org/10.4028/www.scientific.net/amr.702.176.

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Ni-diamond composite coatings are conducted by electrodepositon. The crystal structure and surface morphology of the composite coatings were examined with X-ray diffraction (XRD) and scanning electron microscopy (SEM) and the mechanism of Ni-diamond co-deposition is conducted by catholic polarization and cyclic voltammetry method. The result reveals that diamond particles are successfully embed in Ni matrix and the coatings have an amorphous structure. Cyclic voltammetry indicate that nickel deposition process is an irreversible electrode reaction and cathode polarization curve shift towards positive with the increase of scan rates. Cathodic polarization curve shows that reduction potential of nickel to shift to more negatives with the addition of complexing agent and the slope of the polarization curve is decrease; The addition of brightener and dispersant hinder the deposition of Ni2+ and promote the growth of crystal nucleus; The join of wetting agents and diamond particles have no big influence on the deposition of nickel.

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Ju, Hong, and Yan Li. "Coulostatic-Based Research on Corrosion Inhibition Mechanism of Three Inhibitors for Hot Dipped Coating Steels." Applied Mechanics and Materials 229-231 (November 2012): 87–90. http://dx.doi.org/10.4028/www.scientific.net/amm.229-231.87.

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The corrosion inhibition mechanism of three inhibitors for hot dipped coating steels in HCl acid was studied by coulostatic method. The results showed that the anodic Tafel slope ba and cathodic Tafel slope bc significantly increased with increasing of corrosion inhibitor concentration. While the corrosion current density Icorr decreases with the corrosion inhibition concentration increasing. And the inhibition efficiency increased with the inhibitor concentration. The inhibiting action of these compounds were attributed to blocking of the electrode surface by adsorption through its active centers. The three inhibitors were both mixed inhibitors, and reacted as good inhibition by the adsorption of the active sites in the cathodic reaction and the anodic reaction of corrosion process.

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Kahyarian, Aria, Bruce Brown, and Srdjan Nešić. "The Unified Mechanism of Corrosion in Aqueous Weak Acids Solutions: A Review of the Recent Developments in Mechanistic Understandings of Mild Steel Corrosion in the Presence of Carboxylic Acids, Carbon Dioxide, and Hydrogen Sulfide." Corrosion 76, no. 3 (January 20, 2020): 268–78. http://dx.doi.org/10.5006/3474.

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The recent developments in mechanistic understandings of mild steel corrosion in the presence of carboxylic acids, carbon dioxide, and hydrogen sulfide, when place side by side, reveal a simple, universal mechanism despite all the differences conventionally presumed for these corroding systems. These findings are recast into a generic mechanistic view of corrosion in aqueous weak acid solutions herein. In this mechanism, the buffering effect resulting from the chemical dissociation reaction inside the boundary layer, is highlighted as an inherent property of all weak acids. The validity of this mechanism was further examined through mathematical experimentation based on a comprehensive mechanistic model. It is shown that this mechanism is able to account for a wide range of characteristic behavior of cathodic currents, including those previously associated with the direct reduction reactions. The results are ultimately presented as a simple and generic categorization of weak acids based on their pKa values to serve as a basis to assess the detrimental effect of any weak acid on mild steel corrosion in aqueous acidic solutions.

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Ambrosioni, Brice, Anthony Barthelemy, Dorin Bejan, and Nigel J. Bunce. "Electrochemical reduction of aqueous nitrate ion at tin cathodes." Canadian Journal of Chemistry 92, no. 3 (March 2014): 228–33. http://dx.doi.org/10.1139/cjc-2013-0406.

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The remediation of nitrate-contaminated water using electrochemical reduction at a tin cathode has previously been shown to give almost quantitative denitrification (removal of dissolved nitrogen species) under highly cathodic polarization. A particular focus of this project was to identify specific role(s) for tin in the reaction in the context of the previous literature. The current efficiency for denitrification was enhanced in alkaline solution, and the reaction was accelerated by the presence of small concentrations of Sn(II) salts, which are in a dynamic exchange between cathodic deposition and corrosion of the cathode. Literature precedent indicates that Sn(II) salts promote the “dimerization” pathway of NO to hyponitrite in preference to reduction to ammonia. Hyponitrite is a known intermediate in the electrochemical reduction of nitrate, but its spontaneous decomposition gives predominantly N2O, which does not reduce further to N2. We have shown that hyponitrite is reduced electrochemically in competition with its thermal decomposition, which provides a pathway to N2 via the spontaneous dehydration of HO−NH−NH−OH. The possible role of surface-bound Sn−H species in the reduction mechanism is discussed, but further work is needed to substantiate this proposal.

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Ismail, I., and M. K. Harun. "ADHESION FAILURE OF RUBBER/METAL COMPOSITES UNDERGOING CORROSION." Rubber Chemistry and Technology 90, no. 3 (July 1, 2017): 455–66. http://dx.doi.org/10.5254/rct.16.83764.

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ABSTRACT Rubber/metal composites are known to be highly durable in a normal atmospheric condition. However, when they are exposed to an aggressive environment such as the marine environment, they tend to fail prematurely. The failure is usually caused by the loss of adhesion of the rubber to metal substrate. The aim of this work is to elucidate the adhesion failure mechanism by using a commercial bonding system for bonded rubber/metal exposed in a marine environment. A simulation study that was carried out through a salt spray test indicated that corrosion of the exposed metal substrates induced the loss of adhesion through cathodic disbonding. Laboratory exposure in alkaline medium, cathodic disbonding, and anodic undermining tests suggested that the hydroxyl ions generated from corrosion reactions contributed to the adhesion failure.

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Perevezentseva, D. O., and E. V. Gorchakov. "Electrochemical Response of Gold Nanoparticles at a Graphite Electrode." Advanced Materials Research 1040 (September 2014): 297–302. http://dx.doi.org/10.4028/www.scientific.net/amr.1040.297.

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The electrochemical activity of gold nanoparticles at graphite electrodes by the method of cyclic voltammetry is studied. In this article the nature of the supporting electrolyte, modification time of graphite electrode by gold nanoparticles and the potential range on the value of the “inverse” cathodic peak are investigated. The “inverse” cathodic peak of gold nanoparticles formed in the reaction mixture HAuCl4:Na3C6H5O7:NaBH4=1:1:4 is observed on the cathodic branch of cyclic voltamperegram at Ec = 0.05 V at graphite electrode. The mechanism of stepwise electrochemical oxidation and reduction of the phase structure of gold on the surface of the graphite electrode in 0.1 M NaOH is offered. The “inverse” cathodic peak of gold nanoparticles on the cathodic branch of cyclic voltammogram at graphite electrode is caused by oxidation of Au2O to Au2O3.<br /><br />

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Wu, Donghai, Yuexian Li, Guanghua Lu, Qiuhong Lin, Lei Wei, and Pei Zhang. "Removal of Aqueous Para-Aminobenzoic Acid Using a Compartmental Electro-Peroxone Process." Water 13, no. 21 (October 20, 2021): 2961. http://dx.doi.org/10.3390/w13212961.

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The presence of emerging contaminant para-aminobenzoic acid (PABA) in the aquatic environment or drinking water has the potential to harm the aquatic ecosystem and human health. In this work, the removal of aqueous PABA by a compartmental electro-peroxone (E-peroxone) process was systematically investigated from the kinetic and mechanism viewpoints. The results suggest that single electrolysis or ozonation was inefficient in PABA elimination, and the combined E-peroxone yielded synergistic target pollutant degradation. Compared to the conventional E-peroxone oxidation, the sequential cathodic reactions, followed by anodic oxidations, improved the PABA removal efficiency from ~63.6% to ~89.5% at a 10-min treatment, and the corresponding pseudo first-order kinetic reaction rate constant increased from ~1.6 × 10−3 to ~3.6 × 10−3 s−1. Moreover, the response surface methodology (RSM) analysis indicated that the appropriate increase of inlet ozone concentration, applied current density, initial solution pH value, and solution temperature could accelerate the PABA degradation, while the excess of these operational parameters would have a negative effect on the treatment efficiency. The comparation tests revealed that the coupling of electrolysis and ozonation could synergistically produce hydroxyl radicals (HO•) and the separation of cathodic reactions and anodic oxidations further promoted the HO• generation, which was responsible for the enhancement of PABA elimination in the compartmental E-peroxone process. These observations imply that the compartmental E-peroxone process has the potential for aqueous micropollutants elimination, and the reaction conditions that favor the reactive oxygen species generation are critical for the treatment efficiency.

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Hu, Jun, Yun Wang, Lijun Yu, Yongqiang Zou, and Yuqi Wang. "An Investigation of a Combined Thiourea and Hexamethylenetetramine as Inhibitors for Corrosion of N80 in 15% HCl Solution: Electrochemical Experiments and Quantum Chemical Calculation." International Journal of Corrosion 2015 (2015): 1–12. http://dx.doi.org/10.1155/2015/548031.

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The inhibition mechanism of thiourea (TU) and hexamethylenetetramine (HMTA) mixed in 15% HCl solution on N80 surface was investigated by potentiodynamic polarization, electrochemical impedance spectroscopy measurements, and surface morphology analysis. Quantum chemical calculations and molecular dynamics simulations were performed to study the properties of TU and HMTA. The results showed that the inhibitors can form strong bonds and stable films on the surface, which inhibits the cathodic and anodic reactions in HCl solution and reduces the diffusion coefficients of corrosive particles.

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Kuzminykh, Maria M., Victoria V. Panteleeva, and Anatoliy B. Shein. "CATHODIC HYDROGEN EVOLUTION ON IRON DISILICIDE. I. ALKALINE SOLUTION." IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENIY KHIMIYA KHIMICHESKAYA TEKHNOLOGIYA 62, no. 1 (December 30, 2018): 38–45. http://dx.doi.org/10.6060/ivkkt.20196201.5745.

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The kinetics of hydrogen evolution reaction on FeSi2-electrode in 1.0 M NaOH solution has been studied using methods of polarization and impedance measurements. With the help of diagnostic criteria for the hydrogen evolution reaction mechanisms based on the analysis of the dependence of the parameters of the equivalent electric circuit on overvoltage, it was established that the reaction of hydrogen evolution on iron disilicide in the alkaline electrolyte proceeds along the discharge - electrochemical desorption route, where desorption is the rate-determining stage. Both stages are irreversible, the transfer coefficients of the stages are equal (α1 = α2 = α), simultaneously the hydrogen absorption reaction by the electrode material proceeds in the diffusion mode (in the whole investigated range of potentials). It was found that the adsorption of atomic hydrogen is described by the equation of the Langmuir isotherm. The influence of various methods of modifying of the surface of FeSi2-electrode on the kinetics and mechanism of the cathodic process has been studied. It was found that the modification of the disilicide surface by hydrogenation at a current density of i = 30 mA/cm2, an anodic etching in 0.5 M H2SO4 at the potential E = 0.4 V relative to the standard hydrogen electrode, an anodic etching in 1.0 M NaOH at the potential E = 0.1 V, chemical etching in 5.0 M NaOH at 70 °C reduce the overvoltage of hydrogen evolution, but the mechanism of the cathodic process does not change as a result of the modification. Reduction of the overvoltage of hydrogen evolution on iron disilicide is due to the action of two factors: the development of the surface and the change in the composition of the surface layer of the electrode. It has been concluded that FeSi2 in the alkaline electrolyte is a promising electrode material that exhibits activity in the electrolytic hydrogen evolution reaction.

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Arukalam, I. O. "Inhibiting potential of hydroxypropyl methylcellulose on acid corrosion of mild steel and aluminium." Pigment & Resin Technology 43, no. 6 (November 3, 2014): 394–404. http://dx.doi.org/10.1108/prt-07-2013-0059.

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Purpose The aim of this paper is to appraise the inhibiting potential of hydroxypropyl methylcellulose (HPMC) on the corrosion of mild steel and aluminium in sulphuric and hydrochloric acid solutions. Design/methodology/approach The effects of two different corrodents on the dissolution of mild steel and aluminium were examined. Corrosion rates were determined using the weight loss technique. Inhibition efficiency was estimated by comparing the corrosion rates in absence and presence of the additive. The kinetics and mechanism of HPMC adsorption were investigated by impedance study while the anodic and cathodic partial reactions were studied by polarization measurements. Findings The results reveal that corrosion rate of mild steel and aluminium decreased with addition of HPMC. The corrosion rate and inhibition efficiency were found to depend on the concentration of the inhibitor. The polarization data indicated that the inhibitor was of mixed-type, with predominant effect on the cathodic partial reaction. electrochemical impedance spectroscopy confirms that corrosion inhibition was by adsorption on the metal surface following Freundlich adsorption isotherm via physisorption mechanism. Originality/value Hydroxypropyl methylcellulose has been studied for the first time as an inhibitor of mild steel and aluminium corrosion and the results suggest that the inhibitor could find practical applications in corrosion control in HCl and H2SO4 acid media. The findings are particularly useful, considering the fact that HPMC is a good film former and viscosity enhancer which could also be used in paint formulation.

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Hwang, Ye Yeong, Ji Hyun Han, Sol Hui Park, Ji Eun Jung, Nam Kyeong Lee, and Yun Jung Lee. "Understanding anion-redox reactions in cathode materials of lithium-ion batteries through in situ characterization techniques: a review." Nanotechnology 33, no. 18 (February 10, 2022): 182003. http://dx.doi.org/10.1088/1361-6528/ac4c60.

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Abstract As the demand for rechargeable lithium-ion batteries (LIBs) with higher energy density increases, the interest in lithium-rich oxide (LRO) with extraordinarily high capacities is surging. The capacity of LRO cathodes exceeds that of conventional layered oxides. This has been attributed to the redox contribution from both cations and anions, either sequentially or simultaneously. However, LROs with notable anion redox suffer from capacity loss and voltage decay during cycling. Therefore, a fundamental understanding of their electrochemical behaviors and related structural evolution is a prerequisite for the successful development of high-capacity LRO cathodes with anion redox activity. However, there is still controversy over their electrochemical behavior and principles of operation. In addition, complicated redox mechanisms and the lack of sufficient analytical tools render the basic study difficult. In this review, we aim to introduce theoretical insights into the anion redox mechanism and in situ analytical instruments that can be used to prove the mechanism and behavior of cathodes with anion redox activity. We summarized the anion redox phenomenon, suggested mechanisms, and discussed the history of development for anion redox in cathode materials of LIBs. Finally, we review the recent progress in identification of reaction mechanisms in LROs and validation of engineering strategies to improve cathode performance based on anion redox through various analytical tools, particularly, in situ characterization techniques. Because unexpected phenomena may occur during cycling, it is crucial to study the kinetic properties of materials in situ under operating conditions, especially for this newly investigated anion redox phenomenon. This review provides a comprehensive perspective on the future direction of studies on materials with anion redox activity.

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Muster, Tim H., and Johannes Jermakka. "Electrochemically-assisted ammonia recovery from wastewater using a floating electrode." Water Science and Technology 75, no. 8 (January 31, 2017): 1804–11. http://dx.doi.org/10.2166/wst.2017.060.

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This work presents and explores a novel methodology for the removal and recovery of ammonia from wastewater based upon two mechanisms: electrochemical oxidation and a previously unreported electrochemically-assisted surface transfer mechanism. Recovery of ammonia is enabled by placing a porous cathodic electrode at the wastewater-air interface. In this configuration, the cathode creates local alkalinity and an electric field that draws ammonium ions towards the wastewater-air interface, resulting in near-linear reductions of dissolved ammonium irrespective of concentration. This approach leads to significant ammonia recovery without the need for ion-exchange membranes. In addition, anodic reactions that simultaneously occur at depth in the wastewater induce ammonia oxidation in accordance with proven mechanisms. The floating electrode approach offers improved ammonia removal efficiency in comparison to electrooxidation. Trials conducted on synthetic wastewater (900 mg NH4+-N l−1) and filtered anaerobic centrate (560 mg NH4+-N l−1) demonstrated ammonia concentration decreases up to 216 mg l−1 hr−1 and 110 mg l−1 hr−1, respectively, under the application of 5 mA cm−2 current density. The technology would be best used to treat municipal and industrial wastewaters possessing high ammonia concentration, including anaerobic digester centrate and urine, and offers potential to assist in removing ammonia from environmental waters.

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Kuzminykh, Maria М., Viktoria V. Panteleeva, and Anatoliy B. Shein. "CATHODIC HYDROGEN EVOLUTION ON IRON DISILICIDE. II. ACIDIC SOLUTION." IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENII KHIMIYA KHIMICHESKAYA TEKHNOLOGIYA 62, no. 2 (February 7, 2019): 59–64. http://dx.doi.org/10.6060/ivkkt.20196202.5750.

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The kinetics of hydrogen evolution reaction on FeSi2-electrode in 0.5 M H2SO4 solution has been studied using methods of polarization and impedance measurements. With the help of diagnostic criteria for the hydrogen evolution reaction mechanisms based on the analysis of the dependence of the parameters of the equivalent electric circuit on overvoltage, it was established that the reaction of hydrogen evolution on iron disilicide in the sulfuric acid solution proceeds along the discharge - electrochemical desorption route, where desorption is the rate-determining stage. Both stages are irreversible, the transfer coefficients α of the stages are equal, simultaneously the hydrogen absorption reaction by the electrode material proceeds in the kinetic mode (in the whole investigated range of potentials). It was found that the adsorption of atomic hydrogen is described by the equation of the Langmuir isotherm. The influence of thin oxide film on the hydrogen evolution kinetics is noted. The influence of various methods of modifying of the surface of FeSi2-electrode on the kinetics and mechanism of the cathodic process has been studied. It was found that the modification of the disilicide surface by hydrogenation at a current density of i = 30 mA/cm2, an anodic etching in 0.5 M H2SO4 at the potential E = 0.4 V relative to the standard hydrogen electrode, an anodic etching in 1.0 M NaOH at the potential E = 0.1 V, chemical etching in 5.0 M NaOH at 70 °C reduce the overvoltage of hydrogen evolution, but the mechanism of the cathodic process does not change as a result of the electrode modification. Reduction of the overvoltage of hydrogen evolution on iron disilicide is due to the action of two factors: the development of the surface and the change in the composition of the surface layer of the electrode. It has been concluded that FeSi2 in the sulfuric acid solution is a promising electrode material that exhibits activity in the electrolytic hydrogen evolution reaction.

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Garcia-Costa, Alicia L., Andre Savall, Juan A. Zazo, Jose A. Casas, and Karine Groenen Serrano. "On the Role of the Cathode for the Electro-Oxidation of Perfluorooctanoic Acid." Catalysts 10, no. 8 (August 8, 2020): 902. http://dx.doi.org/10.3390/catal10080902.

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Perfluorooctanoic acid (PFOA), C7F15COOH, has been widely employed over the past fifty years, causing an environmental problem because of its dispersion and low biodegradability. Furthermore, the high stability of this molecule, conferred by the high strength of the C-F bond makes it very difficult to remove. In this work, electrochemical techniques are applied for PFOA degradation in order to study the influence of the cathode on defluorination. For this purpose, boron-doped diamond (BDD), Pt, Zr, and stainless steel have been tested as cathodes working with BDD anode at low electrolyte concentration (3.5 mM) to degrade PFOA at 100 mg/L. Among these cathodic materials, Pt improves the defluorination reaction. The electro-degradation of a PFOA molecule starts by a direct exchange of one electron at the anode and then follows a complex mechanism involving reaction with hydroxyl radicals and adsorbed hydrogen on the cathode. It is assumed that Pt acts as an electrocatalyst, enhancing PFOA defluorination by the reduction reaction of perfluorinated carbonyl intermediates on the cathode. The defluorinated intermediates are then more easily oxidized by HO• radicals. Hence, high mineralization (xTOC: 76.1%) and defluorination degrees (xF−: 58.6%) were reached with Pt working at current density j = 7.9 mA/cm2. This BDD-Pt system reaches a higher efficiency in terms of defluorination for a given electrical charge than previous works reported in literature. Influence of the electrolyte composition and initial pH are also explored.

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Qiu, Na, Chanchan Shen, Yongxia Liu, Xiuqing Li, Guangyin Jia, Jingping Qin, and Xinglei Wang. "Degradation of Ibuprofen by the Electro/Fe3+/Peroxydisulfate Process: Reactive Kinetics, Degradation Products and Mechanism." Catalysts 12, no. 3 (March 13, 2022): 329. http://dx.doi.org/10.3390/catal12030329.

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Ibuprofen (IBU), a nonsteroidal anti-inflammatory drug, is one of the most widely used and frequently detected pharmaceuticals and personal care products in water bodies. This study examined the IBU degradation in aquatic solutions via ferric ion activated peroxydisulfate (PDS) coupled with electro-oxidation (EC/Fe3+/PDS). The degradation mechanisms involved three synergistic reactions in the EC/Fe3+/PDS system, including: (1) the electro-oxidation; (2) SO4•− generated from the activation of PDS by ferrous ions formed via cathodic reduction; (3) SO4•− generated from the electron transfer reaction. The radical scavenging experiments indicated that SO4•− and •OH dominated the oxidation process. The effects of the applied current density, PDS concentration, Fe3+ dosage, initial IBU concentration and initial pH as well as inorganic anions and humic acid on the degradation efficiency, were studied, and the degradation process of IBU followed the pseudo-first-order kinetic model. About 99.37% of IBU was removed in 60 min ((Fe3+ concentration) = 2.0 mM, (PDS concentration) = 12 mM, (initial IBU concentration) = 30 mg/L, current density = 15 mA/cm2, initial pH = 3). Finally, seven intermediate compounds were identified and probable IBU degradation pathways in the EC/Fe3+/PDS system were speculated.

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Bergel, Alain. "Recent Advances in Electron Transfer Between Biofilms and Metals." Advanced Materials Research 20-21 (July 2007): 329–34. http://dx.doi.org/10.4028/www.scientific.net/amr.20-21.329.

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Microbial biofilms produce electrochemical interactions with metal surfaces by following a wide variety of different electron exchange pathways. Reviewing the mechanisms identified in the biocorrosion of steels leads us to distinguish direct and indirect mechanisms for biofilm-catalysed cathodic reactions. Indirect mechanisms are due to the production of metal oxides or hydrogen peroxide (aerobic corrosion) or metal sulphides (anaerobic corrosion), which further react with the metal surface. Direct mechanisms involve adsorbed biocompounds, generally enzymes or their active sites, which catalyse the cathodic reduction of oxygen for aerobic biocorrosion or the proton/water reduction in anaerobic processes. Recent studies dealing with the role of hydrogenases in anaerobic corrosion have shed light on the important role of phosphate species via so-called cathodic deprotonation. Advances in the development of microbial fuel cells have also resulted in new concepts, mainly for oxidation processes. Some microbial cells have been shown to be able to produce their own electron mediators. Others can transfer electrons directly to electrodes through membrane-bound electron shuttles or achieve long-range transfer through conductive pili.

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Zhao, Bin, and Li Ke Zou. "Corrosion Inhibition of Chloroacetic-Acid Modified Imidazoline for Q235 Steel in H₂SO₄ Solution." Advanced Materials Research 710 (June 2013): 41–44. http://dx.doi.org/10.4028/www.scientific.net/amr.710.41.

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A new chloroacetic-acid modified imidazoline (CAMI) was synthesized via the quaternization of imidazoline intermediate, obtained from the amidation and cyclization reactions of benzoic acid and diethylene triamine, with chloroacetic-acid. The performance of the synthesized compound CAMI as corrosion inhibitor for Q235 carbon steel in 5% sulfuric acid solution was investigated by weight loss measurement and potentiodynamic polarization technique. The results show that CAMI possesses strong inhibitive effect on the corrosion of Q235 carbon steel in acid medium and restrains the corrosion without changing the cathodic and anodic corrosion mechanism as a mixed-type inhibitor.

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Liu, Pingli, Yanhua Zhu, and Liqiang Zhao. "New corrosion inhibitor for 13Cr stainless steel in 20% HCl solution." Anti-Corrosion Methods and Materials 67, no. 6 (September 23, 2020): 557–64. http://dx.doi.org/10.1108/acmm-12-2019-2228.

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Purpose A novel compound was synthesized by cyclohexylamine, acetophenone and cinnamaldehyde through Mannich reaction in laboratory to use as corrosion inhibitor for steel in acidification process. Design/methodology/approach The corrosion and inhibition of 13Cr stainless steel in conventional acidification solution were investigated by electrochemical measurements and soaking experiments. The corrosion appearance was observed with scanning electron microscope on the whole surface of 13Cr stainless steel in 20% HCl solution, and the protection film was confirmed on the surface in presence with inhibitor. Findings Results manifested that the inhibitor C23H27NO can effectively inhibit the corrosion reaction by forming an adsorption layer function as a barrier. Polarization curves indicated that the mixed inhibitor can reduce anodic dissolution and cathodic hydrogen evolution reactions simultaneously. The results of impedance measurements indicated that this inhibitor cannot change the corrosion mechanism of 13Cr stainless steel in 20% HCl solution. The results of the study can provide a theoretical basis for the application of 13Cr stainless steel in conventional acidification solutions during oil well acidification construction process. Originality/value A novel compound was synthesized by cyclohexylamine, acetophenone and cinnamaldehyde through Mannich reaction in laboratory to use as corrosion inhibitor for steel in acidification process. The corrosion and anti-corrosion mechanism of 13Cr steel in acid solution was proposed.

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Newman, R. C., and K. Sieradzki. "Corrosion Science." MRS Bulletin 24, no. 7 (July 1999): 12–15. http://dx.doi.org/10.1557/s0883769400052647.

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Corrosion is a branch of materials research that is, by its nature, “schmutzy” (dirty). It has a reputation as an unglamorous subject and certainly suffers from an image problem in the materials community: the guest editors would like to have a dollar for every time we sat down and discussed “How can we make corrosion sound positive?” Solving corrosion problems requires an understanding of corrosion mechanisms, and corrosion mechanisms are infinitely subtle and interesting. Corrosion processes can often encompass concepts from a variety of disciplines, including thermodynamics, surface science, electrochemistry, physical metallurgy, and solid-state and statistical physics. While corrosion of metals is the subject of this issue of MRS Bulletin, ceramics, polymers, and geological materials are all greatly affected by corrosion.Corrosion of metals is an electrochemical process, composed of anodic (metal oxidation) and cathodic (reduction) reactions occurring on a surface. The rates of these reactions are measured as current densities (in units of A m−2). On a single piece of metal, the anodic and cathodic current densities can vary arbitrarily from point to point, as long as the total anodic and cathodic currents are equal. This variation, which is associated with local differences in pH, surface composition, or defects in a surface film, leads to various localized phenomena, such as pitting and stress-corrosion cracking, and also to intriguing oscillatory dynamics.

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Miskovic-Stankovic, Vesna. "The mechanism of cathodic electrodeposition of epoxy coatings and the corrosion behaviour of the electrodeposited coatings." Journal of the Serbian Chemical Society 67, no. 5 (2002): 305–24. http://dx.doi.org/10.2298/jsc0205305m.

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The model of organic film growth on a cathode during electrodeposition process proposes the current density-time and film thickness-time relationships and enables the evaluation of the rate contents for the electrochemical reaction of OH? ion evolution and for the chemical reaction of organic film deposition. The dependencies of film thickness and rate constants on the applied voltage, bath temperature and resin concentration in the electrodeposition bath have also been obtained. The deposition parameters have a great effect on the cathodic electrodeposition process and on the protective properties of the obtained electrodeposited coatings. From the time dependencies of the pore resistance, coating capacitance and relative permittivity, obtained from impedance measurements, the effect of applied voltage, bath temperature and resin concentration on the protective properties of electrodeposited coatings has been shown. Using electrochemical impedance spectroscopy, thermogravimetric analysis gravimetric liquid sorption experiments, differential scanning calorimetry and optical miscroscopy, the corrosion stability of epoxy coatings was investigated. A mechanism for the penetration of electrolyte through an organic coating has been suggested and the shape and dimensions of the conducting macropores have been determined. It was shown that conduction through a coating depends only on the conduction through the macropores although the quantity of electrolyte in the micropores of the polymer net is about one order of magnitude greater than that inside the conducting macropores.

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De Matteis, Cristina I., and James H. P. Utley. "Electroorganic reactions. Part 37. The stereochemistry and mechanism of the cathodic hydrogenation of methyl 4-tert-butylcyclohex-1-enecarboxylate." Journal of the Chemical Society, Perkin Transactions 2, no. 6 (1992): 879. http://dx.doi.org/10.1039/p29920000879.

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Zhao, Di, Jiali Fu, Yan Liu, Fenghua Guo, and Aichang Li. "Photoelectrocatalytic activity and reaction mechanism of Ag2S/Ag3PO4/Ni nanothin films for rhodamine B." Functional Materials Letters 10, no. 02 (April 2017): 1750005. http://dx.doi.org/10.1142/s1793604717500059.

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Ag2S/Ag3PO4/Ni thin films were prepared using an electrochemical method. The surface morphology, phase structure, optical characteristics and band structure of the thin films were analyzed using scanning electron microscopy (SEM), X-ray diffraction (XRD) and ultraviolet-visible diffuse reflectance spectroscopy (UV–Vis DRS), respectively. Additionally, the films photoelectrocatalytic (PEC) activity and stability were evaluated using rhodamine B (RhB) as a model compound. Ag2S/Ag3PO4/Ni thin films that were prepared under optimum conditions contained nanoparticles that were approximately 25[Formula: see text]nm in size and exhibited high PEC activity. At an optimum cathodic bias of [Formula: see text]0.60[Formula: see text]V, the PEC degradation rate of RhB was 1.93 times greater than that of Ag3PO4/Ni thin film. Especially, the film displayed excellent PEC stability, even after being reused eight times. The possible PEC reactions between the film and RhB under visible-light irradiation are discussed in this paper.

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Paul, Subir, and Bikash Kar. "Mitigation of Mild Steel Corrosion in Acid by Green Inhibitors: Yeast, Pepper, Garlic, and Coffee." ISRN Corrosion 2012 (December 2, 2012): 1–8. http://dx.doi.org/10.5402/2012/641386.

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Synthesized organic chemicals, used as inhibitors in mitigating the corrosion of huge quantities of steel articles, pose a major threat to the global environmental problems and health hazards. Naturally occurring products which had been used for natural medication purposes, since the human civilization, are found to inhibit corrosion of steel. Electrochemical studies of the effects of black pepper, garlic, yeast, and coffee on acid corrosion of steel have shown that the corrosion current decreases by manyfold with increase in concentration of the inhibitors. These green inhibitors have been found to get adsorbed maximum up to 70–90%. The polarizing effect is more on cathodic reactions than on anodic reactions, acting as cathodic inhibitor, while a few behaves as anodic to mixed inhibitor. Mechanisms of adsorption are investigated by Frumkin, Temkin, and Langmuir isotherms. The free energy of adsorption is found to be between −15 and −40 kJ/m for most inhibitors, indicating the phenomena of physical adsorption.

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Chahul, Habibat F., Elijah Maji, and Tanko B. Danat. "Adsorptive, inhibitive and thermodynamics studies on the corrosion of mild steel in the presence of Mangifera indica gums." Ovidius University Annals of Chemistry 30, no. 2 (January 1, 2019): 75–80. http://dx.doi.org/10.2478/auoc-2019-0014.

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Abstract The adsorption and inhibitive behavior of gums obtained from Mangifera indica tree was investigated at 303-333 K using weight loss and linear polarization measurements. The results obtained from both measurements showed that Mangifera indica gums inhibited the corrosion of mild steel in 1.0 M HCl. Linear polarization measurements revealed Mangifera indica gums to inhibit both the anodic and cathodic reactions on the surface of the mild steel thereby functioning as a mixed-type inhibitor. Adsorption behavior of the gums were approximated by the isotherm models of Langmuir, Freundlich and Temkin. The adsorption mechanism derived from the trend in inhibition efficiency as a function of temperature as well as kinetic and activation parameters signified Mangifera indica gums adsorbed on the surface of the mild steel through the mechanism of physisorption and that the adsorption process was exothermic and spontaneous.

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Kadapparambil, Sumithra, Kavita Yadav, Manivannan Ramachandran, and Noyel Victoria Selvam. "Electrochemical investigation of the corrosion inhibition mechanism of Tectona grandis leaf extract for SS304 stainless steel in hydrochloric acid." Corrosion Reviews 35, no. 2 (July 26, 2017): 111–21. http://dx.doi.org/10.1515/corrrev-2016-0074.

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AbstractThe use of Tectona grandis leaf extract as a green corrosion inhibitor for stainless steel 304 (SS304) in 2 m hydrochloric acid was investigated using electrochemical techniques. Potentiodynamic polarization studies with different inhibitor concentrations showed that the inhibitor is of mixed type, which works by affecting both cathodic and anodic reactions. Adsorption analysis using the potentiodynamic polarization and electrochemical impedance spectroscopy runs result in standard free energy of adsorption values between −20 kJ mol−1 and −40 kJ mol−1, indicating a comprehensive adsorption, which is a mixture of both physisorption and chemisorptions processes. Fourier transform infrared spectroscopy studies show the appearance of new peaks and shift in peak positions at some locations with the use of an inhibitor, which indicates the interaction between the inhibitor molecules and metal surface. Contact angle analysis indicates the formation of hydrophobic film on the metal surface.

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Fang, Xiao Jun, Li Liu, Zhi Gang Yang, and Yong Qiang Zhang. "Corrosion Behavior and Mechanism of Oil Casing Steel in CO₂ Salt Solution." Materials Science Forum 1035 (June 22, 2021): 534–38. http://dx.doi.org/10.4028/www.scientific.net/msf.1035.534.

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The influence of temperature, flow rate, PH value, and oxygen content on the corrosion law in the carbon dioxide salt solution of J55 oil casing was investigated by the corrosion weight loss method. The results showed that with the increase of temperature, the corrosion rate of J55 steel first increased and then decreased and the corrosion rate reached the maximum at 100°C. The corrosion rate was closely related to the formation of corrosion products. The increase of the flow rate speeded up the transfer rate of the corrosive medium to the metal surface and hindered the formation of FeCO3 on the metal surface. The corrosion rate was significantly higher than the corrosion rate under static conditions, and as the flow rate increased, the corrosion rate of J55 steel increased accordingly. The increase of the pH value gradually reduced the concentration of hydrogen ions, and cathodic reaction of hydrogen ion depolarization during metal corrosion process was inhibited, and the tendency to form an oxidizing protective film on the surface of carbon steel increased, thereby reducing the corrosion rate of metals. With the increase of oxygen content, there were both hydrogen evolution reaction of CO2 and oxygen absorption reaction caused by O2 in the cathode process. The corrosion rate of J55 steel gradually increased, and at the same oxygen content, the higher the carbon dioxide content, the greater the corrosion rate is.

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Sainis, Salil, and Caterina Zanella. "A Study of the Localized Ceria Coating Deposition on Fe-Rich Intermetallics in an AlSiFe Cast Alloy." Materials 14, no. 11 (June 3, 2021): 3058. http://dx.doi.org/10.3390/ma14113058.

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Corrosion inhibiting conversion coating formation is triggered by the activity of micro-galvanic couples in the microstructure and subsequent local increase in pH at cathodic sites, which in the case of aluminium alloys are usually intermetallics. Ceria coatings are formed spontaneously upon immersion of aluminium alloys in a cerium conversion coating solution, the high pH gradient in the vicinity of intermetallics drives the local precipitation of ceria conversion compounds. Cu-rich intermetallics demonstrate a highly cathodic nature and have shown the local precipitation reaction to occur readily. Fe-rich intermetallics are, however, weaker cathodes and have shown varied extents of localized deposits and are in focus in the current work. Model cast Al-7wt.%Si alloys have been designed with 1 wt.% Fe, solidified at different cooling rates to achieve two different microstructures, with big and small intermetallics, respectively. Upon subjecting the two microstructures to the same conversion coating treatment (immersion in a 0.1 M CeCl3 solution) for a short period of 2 h, preferential heavy deposition on the boundaries of the big intermetallics and light deposition on the small intermetallics was observed. Based on these observations, a mechanism of localized coating initiation at these Fe-rich intermetallic particles (IM) is proposed.

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Jai, Junaidah, and Wan Shabuddin Wan Ali. "Palm Olein Corrosion Inhibitor for Aluminium in HCl Solution." Scientific Research Journal 8, no. 2 (December 31, 2011): 49. http://dx.doi.org/10.24191/srj.v8i2.5050.

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Aluminium (Al) is a low cost, lightweight and corrosion resistant material, which corrodes when exposed to pitting agents. Palm olein exhibits characteristics, which indicate its suitability as a corrosion inhibitor. Tween 20, hexane and diethyl triamine were used as additives to Palm olein to form the inhibitor formulation POT20HA. The inhibition efficiency (IE) and behaviour of the POT20HA were determined using potentiodynamic polarization in which Al 6061 samples were immersed in a 1 M HCl solution at 26, 50 and 70 o C in the presence of different POT20HA concentrations: 0, 0.03, 0.07, 0.10, 0.13 and 0.17 M. The IE increased with increasing POT20HA concentration, but decreased with increasing temperature. The work presented indicates that POT20HA is a mixed-type inhibitor capable of inhibiting both corrosive anodic and cathodic reactions. According to the Langmuir isotherm results POT20HA adsorbs on the Al 6061 surface through semiphysiosorption and/or semi-chemisorption. The POT20HA adsorption mechanism on Al 6061 takes through the protonation of micelles by the HCl solution, whereby protonated micelles in the presence of chloride ions adsorb on both cathodic and anodic surface corrosion sites.

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Li, Chen, Xian Zhu, Shanshan Yang, Senlin Tian, Yingjie Li, Bo Li, Zonglin Pan, and Huaibei Li. "Novel strategy for the efficient degradation of organic contaminants using porous graphite electrodes: Synergistic mechanism of anodic and cathodic reactions." Chemical Engineering Journal 429 (February 2022): 132340. http://dx.doi.org/10.1016/j.cej.2021.132340.

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38

Jaksic, Jelena, Ljiljana Vracar, Stylianos Neophytides, and Nedeljko Krstajic. "Structural effects on kinetic properties for hydrogen electrode reactions and CO tolerance along Mo-Pt phase diagram." Chemical Industry and Chemical Engineering Quarterly 11, no. 3 (2005): 129–36. http://dx.doi.org/10.2298/ciceq0503129j.

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The effect of structural and surface versus bulk properties of Mo-Pt alloys and intermetallic phases taken along their phase diagram upon kinetic and electrocatalytic features for the cathodic hydrogen evolution (HER) has been thoroughly investigated and displayed. All specimens along Mo-Pt phase diagram in broader reversible potential range feature Volmer-Tafel mechanism with the catalytic recombination of Tafel as the rate-determining step (RDS), while further polarization plot in semi logarithmic (vs. log) system shows Volmer-Heyrowski mechanism with the electrochemical desorption of Heyrowski reaction being the RDS; the extension of the former depends on the degree of MoO3 coverage and blocking active centers of electrode surface. XPS, UPS, XRD and work function characterization of all specimens revealed congenial volcano plots relative to the same dependence in electrocatalysis. As the main observation the most stable and prevailing Pt content specimens feature the best electrocatalytic and kinetic properties. Activated (MoO3 free) MoPt3 and MoPt4 catalysts feature all along the Tafel plot reversible Tafel catalytic reaction as the RDS, and create properties of super-activity within a broader current density range. It has been pointed out that an intermetallic phase with prevailing Mo atomic percentage (MoPt3) features pronounced electrocatalytic properties for the HER.

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Sarkar, N. K., and J. R. Park. "Mechanism of Improved Corrosion Resistance of Zn-containing Dental Amalgams." Journal of Dental Research 67, no. 10 (October 1988): 1312–15. http://dx.doi.org/10.1177/00220345880670101301.

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The aim of this study was to determine the mechanism of improved corrosion resistance of Zn-containing dental amalgams. Two Zn-containing conventional amalgams, their Zn-free counterparts, and three experimental amalgams (SnHg, ZnHg, and SnZnHg) were evaluated by the potentiodynamic polarization technique in 1% NaCl solution. The main difference between the two types of amalgams was found in their respective breakdown potentials at which passivity was destroyed. The breakdown potential of Zn-containing amalgams was about 200 mV more positive than that of the Zn-free amalgams. The improved stability of the Zn-containing amalgams has been attributed to the formation of a previously reported Zn stannate passive film which, according to the polarization data, is more resistant to the aggressive chloride ion than tin hydroxide that forms on Zn-free amalgams. The formation of Zn stannate was not found to affect the oxygen reduction reaction, the major cathodic reaction involved in the corrosion of dental amalgams.

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McEvoy, Todd M., and Keith J. Stevenson. "Elucidation of the electrodeposition mechanism of molybdenum oxide from iso- and peroxo-polymolybdate solutions." Journal of Materials Research 19, no. 2 (February 2004): 429–38. http://dx.doi.org/10.1557/jmr.2004.19.2.429.

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The cathodic electrodeposition of molybdenum oxide thin films prepared from aqueous solutions containing iso-polymolybdates and peroxo-polymolybdates is described. Chronocoulometry, x-ray photoelectron spectroscopy, spectroelectrochemistry, and electrochemical quartz crystal microgravimetry were used to establish corresponding reaction mechanisms for films grown at different deposition potentials. Electrodeposition from acidified iso-polymolybdate solutions proceeds by the reduction of molybdic acid, whereas deposition from aqueous peroxo-based solutions involves the graded reduction of several solution components, primarily comprising molybdic acid and peroxo-polymolybdates. Careful regulation of the deposition potential allows for controlled growth of distinct molybdenum oxide compositions producing films with varied water content and valency.

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41

Ruszaj, Adam. "Electrochemical machining – state of the art and direction of development." Mechanik 90, no. 12 (December 11, 2017): 1102–9. http://dx.doi.org/10.17814/mechanik.2017.12.188.

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Electrochemical machining process (ECM) can be applied for efficient shaping advanced materials conducting electrical current, which are difficult or impossible for machining using conventional methods. In electrochemical machining, the workpiece is an anode and material is removed as a result of electrochemical reactions “atom by atom” without mechanical forces. This mechanism of material removal make it possible to obtain high quality of machined surface layer with uniform properties. The very important advantage of ECM process is also the fact that there is not a tool wear (working electrode – cathode), because the equivalent reaction to anodic dissolution is hydrogen generation on cathode surface and hydrogen can be easily removed from, the inter-electrode gap by electrolyte flow. Because of this advantages, the ECM process is widely applied in space, aircraft, car and electromechanical industry and research stimulating ECM development are carried out.

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Singh, Meenesh R., Jason D. Goodpaster, Adam Z. Weber, Martin Head-Gordon, and Alexis T. Bell. "Mechanistic insights into electrochemical reduction of CO2 over Ag using density functional theory and transport models." Proceedings of the National Academy of Sciences 114, no. 42 (October 2, 2017): E8812—E8821. http://dx.doi.org/10.1073/pnas.1713164114.

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Electrochemical reduction of CO2 using renewable sources of electrical energy holds promise for converting CO2 to fuels and chemicals. Since this process is complex and involves a large number of species and physical phenomena, a comprehensive understanding of the factors controlling product distribution is required. While the most plausible reaction pathway is usually identified from quantum-chemical calculation of the lowest free-energy pathway, this approach can be misleading when coverages of adsorbed species determined for alternative mechanism differ significantly, since elementary reaction rates depend on the product of the rate coefficient and the coverage of species involved in the reaction. Moreover, cathode polarization can influence the kinetics of CO2 reduction. Here, we present a multiscale framework for ab initio simulation of the electrochemical reduction of CO2 over an Ag(110) surface. A continuum model for species transport is combined with a microkinetic model for the cathode reaction dynamics. Free energies of activation for all elementary reactions are determined from density functional theory calculations. Using this approach, three alternative mechanisms for CO2 reduction were examined. The rate-limiting step in each mechanism is **COOH formation at higher negative potentials. However, only via the multiscale simulation was it possible to identify the mechanism that leads to a dependence of the rate of CO formation on the partial pressure of CO2 that is consistent with experiments. Simulations based on this mechanism also describe the dependence of the H2 and CO current densities on cathode voltage that are in strikingly good agreement with experimental observation.

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Kotok, Valerii, Vadym Kovalenko, Rovil Nafeev, Volodymyr Verbitskiy, Olena Melnyk, Iryna Plaksiienko, Igor Kovalenko, Viktoriia Stoliarenko, Valerii Plaksiienko, and Iryna Zamrii. "Efficiency definition of the deposition process of electrochromic Ni(OH)2-PVA films formed on a metal substrate from concentrated solutions." Eastern-European Journal of Enterprise Technologies 6, no. 12 (114) (December 22, 2021): 27–33. http://dx.doi.org/10.15587/1729-4061.2021.246511.

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Electrochemical devices based on nickel hydroxide electrodes are used in different areas. The main ones are chemical current sources, variable transparency “smart” windows, devices for carrying out electrocatalytic reactions, sensors for determining various substances. In this regard, methods of nickel hydroxide synthesis are of great interest, especially those that allow forming nickel hydroxide directly on the surface of electrodes. One of these methods is electrochemical deposition with cathodic current polarization. The available information on nickel hydroxide synthesis from nickel solutions was considered. It was shown that the available data mainly covered information on dilute solutions from 0.01 to 0.25 mol/L Ni(NO3)2. In addition, no comparison was found in the literature for the efficiency of the cathodic formation of Ni(OH)2 at different concentrations of nickel nitrate. To eliminate the lack of information, the dependence of the current efficiency on the concentration of nickel nitrate in the electrodeposition solution was determined at a constant cathode current density of 0.625 mA/cm2. The resulting dependence decreased nonlinearly with increasing concentration. The nickel hydroxide deposit formed in this case had an X-ray amorphous structure, and it depended little on the Ni(NO3)2 concentration. In addition, the current efficiency reached zero at concentrations of 1.5 mol/L Ni(NO3)2 and higher. However, with polyvinyl alcohol in the solution and at Ni(NO3)2 concentrations of 1.5 and 2 mol/L, electrochemically and electrochromically active Ni(OH)2 films were deposited. The current efficiency calculated indirectly for 1.5 and 2 mol/L Ni(NO3)2 solutions was 3.2 and 2.3 %, respectively. Thus, it was concluded that polyvinyl alcohol affected the mechanism of nickel hydroxide electrodeposition from aqueous solutions of nickel nitrate.

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DE MATTEIS, C. I., and J. H. P. UTLEY. "ChemInform Abstract: Electroorganic Reactions. Part 37. The Stereochemistry and Mechanism of the Cathodic Hydrogenation of Methyl 4-tert-Butylcyclohex-1- enecarboxylate." ChemInform 23, no. 35 (August 21, 2010): no. http://dx.doi.org/10.1002/chin.199235099.

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Han, Yu Mei, and X. Grant Chen. "Corrosion Characteristics of Al-B₄C Metal Matrix Composites in Boric Acid Solution." Materials Science Forum 877 (November 2016): 530–36. http://dx.doi.org/10.4028/www.scientific.net/msf.877.530.

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The corrosion behavior of Al-B4C metal matrix composites in H3BO3 solutions with different Cl- contents was investigated using potentiodynamic polarization and zero resistance ammetry techniques. Results show that the corrosion of Al-B4C composites in H3BO3 solution increases with increasing B4C volume fraction in the composites. The main corrosion characteristic of Al-B4C composites in H3BO3 solution is the galvanic corrosion between Al matrix and B4C particles. In the galvanic couple, B4C particle acts as cathode and Al matrix acts as anode. The cathodic reaction is hydrogen revolution reaction, which controls the corrosion mechanism of Al-B4C composites. Pitting is not observed on the composite surface in the H3BO3 solution with zero Cl-. However, with addition of Cl- in H3BO3 solution, pitting occurs and the corrosion resistance remarkably decreases with increasing Cl- content. The corrosion resistance of Al-B4C composites in H3BO3 solutions is compared with that in the standard 3.5% NaCl solution.

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Hamade, R. F., A. Tarhini, S. Salhab, and M. Al-Ghoul. "Modeling Cathodic Weakening of Rubber/Steel Adhesive Bonds as Liquid–Solid Reactions." Journal of Adhesion Science and Technology 26, no. 6 (March 1, 2012): 745–65. http://dx.doi.org/10.1163/016942411x579984.

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Zhou, JiaYu, Zili Li, JianGuo Liu, Xiao Xing, Gan Cui, ShouXin Zhang, Ran Cheng, and YiShu Wang. "Effect of AC interference on hydrogen evolution reaction of x80 steel." Anti-Corrosion Methods and Materials 67, no. 2 (January 20, 2020): 197–204. http://dx.doi.org/10.1108/acmm-11-2019-2216.

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Purpose The purpose of this paper is to quantify the influence of alternating current (AC) interference on hydrogen evolution reaction of X80 steel. Design/methodology/approach The hydrogen evolution potential was obtained by cathodic potentiodynamic polarization curve. The instantaneous potential under AC interference was obtained by high-frequency acquisition with three-electrode system. Electrochemical impedance spectroscopy and Tafel polarization curves were used to study the influence mechanism of AC interference on instantaneous potential. Findings It was concluded that the hydrogen evolution reaction could occur on X80 steel under AC interference. There were critical AC current densities of about 100 to 200 A/m2, beyond which the cathode reaction of X80 steel changed from oxygen absorption to hydrogen evolution. Besides the pH value, the initial polarization potential EZ and impedance module of the steel/electrolyte interface under AC interference were also the factors that affected the critical AC densities in different solutions. Originality/value This research quantified the hydrogen evolution capacity of X80 steel under AC interference, which could be applied to clear the effect of AC interference on hydrogen evolution reaction.

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Stankovic, Zvonimir, Vladimir Cvetkovski, and Vesna Grekulovic. "The effect of bi presence as impurities in anodic copper on kinetics and mechanism of anodic dissolution and cathodic deposition of copper." Chemical Industry 64, no. 4 (2010): 337–42. http://dx.doi.org/10.2298/hemind100329021s.

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The influence of Bi, as foreign metal atoms in anode copper, on kinetics and mechanism of anodic dissolution and cathodic deposition of copper in acidic sulfate solution was investigated using the galvanostatic single-pulse method. Results indicate that presence of Bi atoms in anode copper increases the exchange current density, as determined from the Tafel analysis of the electrode reaction, which is attributed to the increase of the crystal lattice parameter determined from XRD analysis of the electrode material.

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Crolet, J. L. "Detailed mechanisms of hydrogen charging and hydrogen stress cracking of steel in liquid ammonia storage." Matériaux & Techniques 107, no. 4 (2019): 401. http://dx.doi.org/10.1051/mattech/2019022.

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When the unprecedented environmental cracking of steel in liquid ammonia was collectively studied, its undisputable “anodic character” was taken as the signature of a stress corrosion cracking mechanism, which is effectively the case in aqueous corrosion. Conversely, when the metallurgical precautions proved to be the same as in sour service, this strongly suggested a hydrogen stress cracking mechanism. In aqueous corrosion, however, this can only occur by cathodic hydrogen charging at low potential, and for 50 years, this basic contradiction could never be overcome. Actually, it occurs that the liquid ammonia solvent (NH3) is 50% richer in hydrogen than the water solvent (OH2), so that hydrogen gas can also be produced by a partial oxidisation into ½ N2 + H2. This therefore induces a theoretical possibility of an “anodic” hydrogen charging, or more exactly a protonic cathodic reaction only running at high potential on passive iron in oxygen contaminated ammonia. And once the detrimental potential is achieved through appropriate combinations of oxygen and water traces, the charging process becomes an autonomous oxidation-reduction at the steel surface NH3 → ½ N2 + H2 + (H+ + e−)steel. In Part II (Jean-Louis Crolet, Matériaux & Techniques 107, 402, 2019), this new assumption will be successfully confronted to all the factual data from both field and laboratory experience.

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Stankovic, Z. D., V. Cvetkovski, and M. Vukovic. "The effect of antimony presence in anodic copper on kinetics and mechanism of anodic dissolution and cathodic deposition of copper." Journal of Mining and Metallurgy, Section B: Metallurgy 44, no. 1 (2008): 107–14. http://dx.doi.org/10.2298/jmmb0801107s.

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The influence of the presence of Sb atoms, as foreign metal atoms in anode copper, on kinetics, and, on the mechanism of anodic dissolution and cathodic deposition of copper in acidic sulfate solution has been investigated. The galvanostatic single-pulse method has been used. Results indicate that presence of Sb atoms in anode copper increase the exchange current density as determined from the Tafel analysis of the electrode reaction. It is attributed to the increase of the crystal lattice parameter determined from XRD analysis of the electrode material.

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Journal articles on the topic 'Mechanism of cathodic reactions'

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