Cathodic Polarization Research Articles

Influence of platinum content on semiconductor and electrochemical properties of materials based on titanium suboxides

The effect of platinum content on the surface morphology, phase composition and electrochemical properties of materials based on titanium suboxides was investigated. Titanium suboxides are formed at the stage of coating reduction under cathodic polarization, which allows the formation of a porous developed surface for electrodeposition of catalytic platinum layers. The main allotropic modification of TiOx in the studied composite materials is anatase, which contains particles of elemental titanium and platinum. The investigated materials are highly doped semiconductors with a high concentration of charge carriers. With an increase in the platinum content, an extreme dependence of the potential of flat zones is observed, which is associated with the formation of a composite material. The electrocatalytic activity was studied in the reactions of oxygen and hydrogen evolution. The overvoltage of oxygen production on platinum-containing materials is much lower than on the TiOx electrode. The slope of the linear dependence of the potential on the current density decreases with an increase in platinum content. The Tafel slope for the studied materials in the hydrogen evolution reaction was 160 mVdec–1 for coatings containing 0.25 mgcm–2 Pt; whereas it was equal to 42 and 43 mVdec–1 for electrodes with 0.5 and 2 mgcm–2 Pt, respectively.

Small Punch Test to Estimate the Threshold Stress in Aggressive Environments by Incremental Step Loading

The present work is a relevant advance in the validation of the incremental step loading technique (ASTM F1624 standard) when applied to Small Punch tests (SPT) for the threshold load determination of medium- and high-strength steels in aggressive environments, as a novel alternative to conventional time-consuming tests under constant load. It completes previous works by the authors on this topic, extending a methodology to estimate the threshold stress from SPT tests in aggressive environments, covering the whole range of hardness marked by ASTM F1624 as the main goal. This is achieved by calibrating a model of the material’s hardness by the use of a coefficient in function of it. For this purpose, four medium- and high-strength steels of 33, 35, 50 and 60 HRC (Hardness Rockwell C) are exposed to three different cathodic polarization hydrogen embrittlement environments of 1, 5 and 10 mA/cm2 in 1N H2SO4 acid electrolyte connected to a platinum anode. Threshold stresses in these circumstances are obtained by uniaxial specimens following ASTM F1624 and compared to their homologous threshold loads obtained by Small Punch tests according to the authors’ original methodology proposal. Finally, the aforementioned model, consisting of a correlation based on composing an elastic and a plastic part, is calibrated for a hardness ranging 33–60 HRC, this being the main original contribution of this work; the elastic part is dependent just on the elastic-to-plastic transition SPT load, while the plastic part is ruled by a material hardness-dependent coefficient. This technique supposes an advance in engineering tools, due to its applicability in situations of material shortage, such as in-service components, welded joints, local areas, complex geometries, small thicknesses, etc., often present in aerospace, automotive or oil–gas, among others.

Oxygen Reduction Reaction Coupled Electro‐Oxidation for Highly‐Efficient and Sustainable Water Treatment

AbstractElectro‐oxidation (EO) technology demonstrates significant potential in wastewater treatment. However, the high energy consumption has become a pivotal constraint hindering its large‐scale implementation. Herein, we design an EO and 4‐electron oxygen reduction reaction coupled system (EO‐4eORR) to replace the traditional EO and hydrogen evolution reaction (HER) coupled system (EO‐HER). The theoretical cathodic potential of the electrolytic reactor is tuned from 0 V (vs. RHE) in HER to 1.23 V (vs. RHE) in 4eORR, which greatly decreases the required operation voltage of the reactor. Moreover, we demonstrate that convection can improve the mass transfer of oxygen and organic pollutants in the reaction system, leading to low cathodic polarization and high pollutant removal rate. Compared with traditional EO‐HER system, the energy consumption of the EO‐4eORR system under air aeration for 95 % total organic carbon (TOC) removal is greatly decreased to 2.61 kWh/kgTOC (only consider the electrolyzer energy consumption), which is superior to previously reported EO‐based water treatment systems. The reported results in this study offer a new technical mode for development of highly efficient and sustainable EO‐based treatment systems to remove organic pollutants in waste water.

Oxygen Reduction Reaction Coupled Electro-Oxidation for Highly-Efficient and Sustainable Water Treatment.

Electro-oxidation (EO) technology demonstrates significant potential in wastewater treatment. However, the high energy consumption has become a pivotal constraint hindering its large-scale implementation. Herein, we design an EO and 4-electron oxygen reduction reaction coupled system (EO-4eORR) to replace the traditional EO and hydrogen evolution reaction (HER) coupled system (EO-HER). The theoretical cathodic potential of the electrolytic reactor is tuned from 0 V (vs. RHE) in HER to 1.23 V (vs. RHE) in 4eORR, which greatly decreases the required operation voltage of the reactor. Moreover, we demonstrate that convection can improve the mass transfer of oxygen and organic pollutants in the reaction system, leading to low cathodic polarization and high pollutant removal rate. Compared with traditional EO-HER system, the energy consumption of the EO-4eORR system under air aeration for 95 % total organic carbon (TOC) removal is greatly decreased to 2.61 kWh/kgTOC (only consider the electrolyzer energy consumption), which is superior to previously reported EO-based water treatment systems. The reported results in this study offer a new technical mode for development of highly efficient and sustainable EO-based treatment systems to remove organic pollutants in waste water.

Degradation of steel 20 during cathodic polarization and hydrogen embrittlement of steam boiler screen pipes during operation

The paper examines the differences in the properties of new pipes, pipes artificially saturated with hydrogen and boiler screen pipes after long-term operation. The embrittlement process was studied by observing changes in the microstructural structure, mechanical properties and identifying the mechanism of hydrogen attack on the objects under study. It was discovered that there was no decarbonization characteristic of natural saturation with hydrogen and a decrease in the ultimate tensile strength of artificially saturated pipes. The nature of cracking was also different — transcrystalline with artificial saturation and intercrystalline with natural saturation. At the same time, the nature of the fractures — with areas of hydrogen fragility — and the average concentrations of accumulated hydrogen in pipes artificially hydrogenated and hydrogenated during operation were identical. Significant differences in the physical and mechanical properties of all three types of pipes have been recorded, which makes it impossible to transfer the results obtained with model samples artificially saturated with hydrogen to actually operated objects.

Effect of Zr addition on the corrosion resistance of Ti-Mo alloy in the H2O2-containing inflammatory environment

Reactive oxygen species (ROS), produced by immune cells during inflammatory reaction, are known to promote corrosion of standard biomedical materials such as CP-Ti and Ti-6Al-4V. Electrochemical corrosion in the ROS environment can be further accelerated in the vicinity of fretting regions, where titanium can be polarized towards negative potentials. This study considers both of these aspects and presents corrosion analysis under complex inflammatory conditions for Ti-Mo and Ti-Mo-Zr alloys, which offer exceptional strain-hardening behavior and ductility. Combining electrochemical impedance spectroscopy (EIS) and atomic emission spectroelectrochemistry (AESEC) allowed us to understand the origin of ROS-induced corrosion. At free corrosion conditions, Zr was found to suppress oxide layer growth without any significant effect on the dissolution process. On the other hand, Zr suppressed dissolution rate under cathodic potentials. Although applying cathodic potential resulted in a rapid increase of dissolution rate, cross-section transmission electron microscopy (TEM) analysis did not reveal significant influence of the short cathodic polarization on the oxide film growth during further prolonged exposure at free corrosion conditions.

Influence of temperature on the cathodic polarization behavior and calcareous deposit properties of X65 steel in sea water

PurposeThis paper aims to investigate how cathodic polarization behavior significantly affects the selection of cathodic protection parameters and the effectiveness of protecting underwater metal structures. Factors such as water depth and operating conditions impact seawater temperature, making it crucial to understand the effects of temperature on cathodic protection parameters for underwater pipelines.Design/methodology/approachIn this paper, potentiostatic polarization was carried out by three-electrode method, and morphology, X-ray diffraction and electrochemical analysis.FindingsIt was determined that the stable current densities at the minimum negative potential (−0.8 VSSC) for pipeline steel varied at different temperatures: 7°C, room temperature and 60°C. The cathodic protection potential corresponding to the lowest stable current density was observed to be −1.0 VSSC at 7°C and −0.95 VSSC at room temperature and 60°C.Originality/valueThis study elucidates the mechanisms by which different temperatures affect the protective performance of calcareous deposits and current densities.

Shattering the Water Window: Comprehensive Mapping of Faradaic Reactions on Bioelectronics Electrodes.

It is generally accepted that for safe use of neural interface electrodes, irreversible faradaic reactions should be avoided in favor of capacitive charge injection. However, in some cases, faradaic reactions can be desirable for controlling specific (electro)physiological outcomes or for biosensing purposes. This study aims to systematically map the basic faradaic reactions occurring at bioelectronic electrode interfaces. We analyze archetypical platinum-iridium (PtIr), the most commonly used electrode material in biomedical implants. By providing a detailed guide to these reactions and the factors that influence them, we offer a valuable resource for researchers seeking to suppress or exploit faradaic reactions in various electrode materials. We employed a combination of electrochemical techniques and direct quantification methods, including amperometric, potentiometric, and spectrophotometric assays, to measure O2, H2, pH, H2O2, Cl2/OCl-, and soluble platinum and iridium ions. We compared phosphate-buffered saline (PBS) with an unbuffered electrolyte and complex cell culture media containing proteins. Our results reveal that the "water window"─the potential range without significant water electrolysis─varies depending on the electrolyte used. In the culture medium that is rich with redox-active species, a window of potentials where no faradaic process occurs essentially does not exist. Under cathodic polarizations, significant pH increases (alkalization) were observed, while anodic water splitting competes with other processes in media, preventing prevalent acidification. We quantified the oxygen reduction reaction and accumulation of H2O2 as a byproduct. PtIr efficiently deoxygenates the electrolyte under low cathodic polarizations, generating local hypoxia. Under anodic polarizations, chloride oxidation competes with oxygen evolution, producing relatively high and cytotoxic concentrations of hypochlorite (OCl-) under certain conditions. These oxidative processes occur alongside PtIr dissolution through the formation of soluble salts. Our findings indicate that the conventional understanding of the water window is an oversimplification. Important faradaic reactions, such as oxygen reduction and chloride oxidation, occur within or near the edges of the water window. Furthermore, the definition of the water window significantly depends on the electrolyte composition, with PBS yielding different results compared with culture media.

Alkali Metal Cations Induce Structural Evolution on Au(111) During Cathodic Polarization.

The activity of the electrocatalytic CO2 reduction reaction (CO2RR) is substantially affected by alkali metal cations (AM+) in electrolytes, yet the underlying mechanism is still controversial. Here, we employed electrochemical scanning tunneling microscopy and in situ observed Au(111) surface roughening in AM+ electrolytes during cathodic polarization. The roughened surface is highly active for catalyzing the CO2RR due to the formation of surface low-coordinated Au atoms. The critical potential for surface roughening follows the order Cs+ > Rb+ > K+ > Na+ > Li+, and the surface proportion of roughened area decreases in the order of Cs+ > Rb+ > K+ > Na+ > Li+. Electrochemical CO2RR measurements demonstrate that the catalytic activity strongly correlates with the surface roughness. Furthermore, we found that AM+ is critical for surface roughening to occur. The results unveil the unrecognized effect of AM+ on the surface structural evolution and elucidate that the AM+-induced formation of surface high-activity sites contributes to the enhanced CO2RR in large AM+ electrolytes.

Resistance of the welded joint of X70 steel for main gas pipelines against corrosion-mechanical cracking under cathodic polarization in near-neutral pH solutions

ABSTRACT Resistance of welded joint of X70 steel welded using Sv-08G1NMA and OK 10-74 flux wire against stress-corrosion cracking in near-neutral pH solution NS4 was investigated by slow-strain rate method, voltammetry, optical and scanning electron microscopy, electrolytic permeation of hydrogen. It was established that the stress-corrosion cracking of welded joint occurs through the base metal in the range of potentials more positive than −0.921 V by the anodic dissolution mechanism, more negative than −1.050 V is consistent with a hydrogen embrittlement mechanism, and in the potentials' range from −0.921 V to −1.050 V – both by the anodic dissolution and hydrogen embrittlement mechanism. The susceptibility to stress-corrosion cracking coefficient KS increases with the polarization potential shift −0.750 V → −0.950 V → −1.050 V as follows: for the welded joint – 1.1 → 1.16 → 1.35, for X70 steel as 1.0 → 1.12 → 1.0.

Assessment of the inhibition performance of ZIF-8 on corrosion Mitigation of API 5L X65 steel in 3.5 wt% NaCl: Experimental and theoretical insight

The synthesis and application of ZIF-8 as an effective corrosion inhibitor for the corrosion of API 5L X65 steel in 3.5 wt% NaCl have been studied. The synthesized ZIF-8 was characterized using some surface probe approaches, which include field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR TEM), and X-ray photoelectron spectroscopy (XPS), respectively. The results showed that ZIF-8 exhibited regular hexagonal and orthorhombic-shaped nanoparticles. An approximately 62% yield was achieved. Electrochemical studies such as open circuit potential (OCP), potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS) were performed. The polarization results show that ZIF-8 is a mixed-type inhibitor, revealing a strong impact on both the anodic and cathodic polarization current values. The EIS studies reveal an increase in the charge transfer resistance upon the introduction of ZIF-8. The existence of a strong protective film adsorbed on X65 steel was recognized via XPS and FT-IR analysis. The highest inhibition efficiency value of 98.1% was recorded at a concentration of 0.120 wt% ZIF-8. Quantum chemical computations in the framework of DFT and molecular dynamic simulation were used to determine the reaction sites on the inhibitor, and as such, in-depth insight into the reaction mechanism was revealed.

Catalytic Effect of Titanium Ions on the Cathodic Reduction of Selenium (VI), Copper (II), Uranium (VI) Ions and Other Metals in an Aqueous Solutions

It is known that catalytic processes are widely applied in the field of organic chemistry; however they also play a significant role in inorganic chemistry. Nonetheless, numerous unresolved issues persist in the technology of inorganic substances and the extraction of metals and nonmetals in their elemental states. This publication aims to consolidate the results of our pioneering research utilizing the redox Ti (IV)–Ti (III) system, which demonstrates a catalytic action on the cathodic reduction of selenium (VI), copper (II), platinum (IV), palladium (IV), bismuth, arsenic (V) ions, uranium (VI), as well as manganese dioxide suspension. It has been demonstrated that in the presence of the redox Ti (IV)–Ti (III) system, hard-to-reduce selenate ions can be reduced at room temperature. The catalytic action of the redox Ti (IV)–Ti (III) system has been reliably demonstrated, and the reaction mechanism has been established. In the electrochemical production of metal powders (Cu, Pt, Pd, Bi) at cathode current densities exceeding the limiting value, a portion of the current is irreversibly lost to the discharge of hydrogen ions. Consequently, the current efficiency (CE) for powder production does not exceed 80 %. We have established that in the presence of titanium (IV) ions, due to their catalytic action, the CE increases by more than 15 %. It has also been shown that during the cathodic polarization of hexavalent uranium its reduction to uranium (IV) in the presence of the catalyst increases by more than 50 %. The reduction of hard-to-reduce arsenate ions in the presence of titanium (IV) ions proceeds with high CE to the active trivalent state, and further reduction can proceed electrochemically. The cathodic reduction of a manganese dioxide suspension was investigated. In the presence of a catalyst — titanium (IV) ions, manganese in this dioxide is reduced to the divalent state with a current efficiency exceeding 90 %.

On the Impact of Cathodic Polarization on the Chloride Threshold of Carbon Steel in Alkaline Solutions

On the Impact of Cathodic Polarization on the Chloride Threshold of Carbon Steel in Alkaline Solutions

INNOVATIVE INSULATING MATERIAL IN THE ASPECT OF ENSURING THE SAFETY OF HYDROCARBON TRANSPORTATION

Ensuring continuous and safe operation of the main oil and gas pipelines is a critical aspect for preserving the environment and efficient use of hydrocarbon resources. More than half of accidents on trunk gas pipelines occur due to corrosion wear of the metal caused by insufficient protection of the insulation coating. The consequences of such incidents have a devastating impact on the environment and human lives: spilled oil and oil products pollute the soil, and leaking gas can lead to explosions and forest fires.Corrosion processes hiding under the coating due to poor adhesion and due to non-fulfillment of their functions by the coating lead to increased peeling of insulation and the formation of new corrosion foci, including stress-corrosion processes. Consequently, imperfect insulation coating and insufficient adhesion to metal are one of the main causes of accidents on main pipelines.The purpose of this work was to study and prove the chemical interaction of the functional groups of asmol insulation compositions with the metal surface. In the course of work, the following tasks were solved:- assessment of the ratio of initial adhesion parameters obtained in laboratory and route conditions and their values after 1.5 and 6 years of operation;- study of the IR spectrum in order to prove the presence of functional groups in the asmol material;- study of the protective capacity of the asmol coating structure in an aggressive corrosive environment at different temperatures.Methods were used to measure the quantitative adhesion of the anti-corrosion coating and the peel area during cathode polarization, in accordance with State Standard R 51164-98. The composition of the asmol material was studied by IR spectroscopy.It has been shown that functional groups, the presence of which has been confirmed by spectral analysis, of asmol material in the insulation coating make it possible to chemically adhere to steel. Indirect proof of this is the stability of the adhesion strength over time, the cohesive separation of the asmol coating in determining adhesion indicators under trace conditions and the relatively small area of coating detachment during cathode polarization.

Hydrogen states and contents in superelastic TiNi alloy after cathodic polarization

The superelastic TiNi alloy sometimes undergo failure under wet environments owing to hydrogen absorption and/or hydride formation; however, the effects of electrochemical conditions such as potential and pH and the hydrogen state and content on the susceptibility of the material to such degradation processes remain unveiled. In this study, the hydrogen content in the solid-solution state and hydride state in superelastic TiNi alloy were determined upon applying a constant cathodic potential in sulfate solution, and the dependence of the contents on the potential and solution pH was investigated. The formation of hydride was detected via X-ray diffraction (XRD), and the hydrogen content in each state was determined by means of thermal gas desorption spectroscopy (TDS). The specimen receiving a smaller cathodic charge density showed no hydride in the XRD pattern and one obvious peak in hydrogen desorption rate at higher temperature in the TDS profile. In contrast, larger charge density induced hydride formation and two peaks in the hydrogen desorption rate at two different temperatures. The peaks at higher and lower temperatures in the TDS profile can be attributed to hydrogen in solid-solution and hydride states, respectively. The logarithmic content of hydrogen in each state increased almost linearly with increasing logarithmic charge density. Linear relationships were obtained irrespective of potential and pH, with slopes of 0.57 and 0.99 for the solid-solution and hydride states, respectively. The susceptibility to environment-assisted cracking suddenly increased at a charge density of 0.025 MC·m−2, at which the hydrogen contents in the solid-solution state and hydride states were determined to be 30 and 5 mass ppm, respectively.

13C-Labelled Glucose Reveals Shifts in Fermentation Pathway During Cathodic Electro-Fermentation with Mixed Microbial Culture.

Cathodic Electro-Fermentation (CEF) is an innovative approach to manage the spectrum of products deriving from anaerobic fermentation. Herein, mixed microbial culture fermentation using a ternary mixture containing labelled 13C glucose and non-labelled acetate and ethanol was studied to identify the role of polarization on the metabolic pathways of glucose fermentation. CEF at an applied potential of -700 mV (vs. SHE, Standard Hydrogen Electrode) enhanced the production yield of acetate, propionate, and butyrate (0.90±0.10, 0.22±0.03, and 0.34±0.05 mol/mol; respectively) compared to control tests performed at open circuit potential (OCP) (0.54±0.09, 0.15±0.04, and 0.20±0.001 mol/mol, respectively). Results indicate that CEF affected the 13C labelled fermented product levels and their fractional 13C enrichments, allowing to establish metabolic pathway models. This work demonstrates that, under cathodic polarization, the abundance of both fully 13C labelled propionate and butyrate isotopomers increased compared to control tests. The effect of CEF is mainly due to intermediates initially produced from the glucose metabolic transformation in the presence of non-labelled acetate and ethanol as external substrates. These findings represent a significant advancement in current knowledge of CEF, which offers a promising tool to control mixed cultures bioprocesses.

Spatially Resolved Assessment and Analysis of Al-Zn, Mg, and Mg/Al-Zn Metal-Rich Primers Applied to AA 7075-T651 in Full Immersion

The scanning vibrating electrode technique (SVET) was utilized to monitor localized corrosion and substrate protection of three metal-rich primers (MRP). The ability to suppress localized corrosion and provide widespread cathodic polarization to enable sacrificial anode-based cathodic protection of a AA 7075-T651 substrate with either an aluminum-rich primer (AlRP), magnesium-rich primer (MgRP), or a composite magnesium + aluminum-rich primer (MgAlRP) in a polyamide-based epoxy primer coatings fully immersed in 1 mM NaCl was investigated. Pigments did not activate uniformly in each MRP. The notion of throwing power polarizing the bare substrate and uniform current and potential distributions at scratch sites does not describe the behavior observed. In cases where activation occurred, protection was noticed in the form of suppression of local anodes on bare AA 7075-T651. Local corrosion was suppressed on heterogeneously corroding AA 7075-T651 with strong local anodes and cathodes. Widespread cathodic polarization was absent. The MgRP and MgAlRP were shown to provide superior local corrosion suppression associated with pitting on AA 7075-T651 compared to the AlRP.

Regularities of Obtaining Electrochromic WO3 Films at the Cathode Polarization of the Electrode

Regularities of Obtaining Electrochromic WO3 Films at the Cathode Polarization of the Electrode

Cathodic Protection of Carbon Steel in Soil: A Study of Induced Passivation

Two-month experiments were carried out with carbon steel electrodes buried in an artificial sand wetted at 50–55% of saturation with a 0.07 mol L−1 Na2SO4·10H2O solution. Various protection potentials (corrected from the ohmic drop) were applied from −0.60 to −1.13 V/Cu-CuSO4. In each case, the behavior of the electrode protected by cathodic polarization was compared with that of an unprotected electrode. The electrochemical study was performed using voltammetry, linear polarization resistance measurements, and EIS. Surface characterization of the coupons was carried out using optical microscopy and X-ray diffraction. First, cathodic protection was observed to induce a spreading of the electrolyte on the metal surface because of electrocapillary effects. The active area, or more precisely the wet area, of the electrode increased, leading to a decrease in soil electrolyte resistance Rs measured using EIS. This phenomenon was experimentally confirmed via visual observations of the surface of the coupons at the end of the experiments. Secondly, cathodic protection induced a passivation of the steel surface. The passive state persisted for 35 to 85 h after cathodic protection was stopped and could be studied during various periods of interruption of the protection. In each case, the OCP of the previously polarized coupons reached high values, actually 200–250 mV higher than those measured for the unprotected coupons, and was associated with high polarization resistance Rp values (~40 kΩ cm2). Depassivation of the metal finally occurred, a phenomenon revealed by simultaneous important drops of both OCP and Rp.

Boosting the performance of La0.5Sr0.5Fe0.9Mo0.1O3-δ oxygen electrode via surface-decoration with Pr6O11 nano-catalysts

Cobalt-free La0.5Sr0.5Fe0.9Mo0.1O3-δ (LSFM) oxide is particularly investigated as a durable and efficient oxygen electrode material for the reversible solid oxide cells (RSOCs) in this study. Pr6O11 nano-catalysts are introduced into LSFM oxygen electrode as synergistic catalysts to enhance and optimize the electrode reactions. Results demonstrate an effectively promoted oxygen reduction and evolution reaction kinetics of the Pr6O11 decorated LSFM electrode. Polarization resistances (Rp) of LSFM electrode are dramatically reduced with the increasing Pr6O11 nano-catalysts and the lowest Rp of 0.039 Ω cm2 is obtained at 800 °C, which is ∼97% lower than that of the LSFM electrode. The Pr6O11 decorated LSFM oxygen electrode also displays a superior durability under cyclic anodic and cathodic polarizations. Furthermore, both the maximum power density and electrolytic current density of the Pr6O11 decorated cell are more than 2 times that of the LSFM cell. Results make clear reliability of the Pr6O11 decorated LSFM to be a promising oxygen electrode for RSOCs.