Electrochemical Corrosion Processes Research Articles

Corrosion behavior of X65 steel in gaseous and liquid CO2 transport environments containing multiple impurities and different H2O content

The mechanism of H2O content in different CO2 phase states on the corrosion of pipeline steel was studied by using high-pressure corrosion simulation tests, scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and water chemistry simulation calculations. The results show that the corrosion mechanism of X65 steel did not change significantly under different CO2 phase state systems, and the corrosion products were similar. As the H2O content of the system increased, the sulfur-containing products in the corrosion products increased and the degree of corrosion worsened. Additionally, because the aqueous phase formed by the liquid CO2 system contained more corrosive substances, which promote the electrochemical corrosion process of X65 steel, the corrosion degree of X65 steel in a liquid CO2 system was significantly higher than that of X65 steel in a gaseous CO2 system.

Preparation and characterization of groove-shaped Ti/Cu layered electrode with superior hydrogen evolution performance

In this study, a comprehensive investigation on the performance of laminated electrodes for hydrogen evolution reaction (HER) is conducted using experiments and numerical simulation. A laminated composite electrode with superior catalytic activity is designed, synthesized and tested, which is comparably researched with traditional homogeneous electrodes. A Ti/Cu laminated electrode with a slot width of 250 µm is fabricated by explosive welding and an electrochemical corrosion process is applied to create groove-shaped interface. The results show that the grooved laminated electrode has superior hydrogen precipitation performance and conductivity, exceptional stability, and minimal potential fluctuation. Hydrogen production efficiency of laminated electrode is 120% higher than that of Cu electrode, which is verified in our self-made hydrogen-making device. COMSOL simulation results were found to be consistent with the experimental findings. Overall, this study provides valuable insight into enhancing electrode performance, with broad engineering implications.

Experimental Study on the Effect of Carbon Graphitization Degree and Pore Structure on the Electrochemical Durability of Gas Diffusion Layers

Gas diffusion layers (GDLs) in high-temperature, high-humidity, and high-electric-potential environments can be affected by the carbon corrosion and degradation of Polytetrafluoroethylene (PTFE) network structures, resulting in reduced reliability and hydrophobicity. By using cyclic voltammetry and offline characterization, a high-potential scanning of 1–1.5 V is applied to the GDL in the three-electrode system, considering the role of gradient graphitization degree and pore size structure in corrosion. Accelerating the electrochemical corrosion process of carbon and PTFE allows the identification of corrosion location, extent, and determinants. The results indicate that after 800 cycles of high-potential triangulation scanning, the graphitization of gas diffusion base has the most significant impact on the GDL’s durability. On the other hand, the durability of the GDL’s microporous layer is influenced by its small pore size structure rather than its graphitization degree. Furthermore, the corrosion process of GDLs with a small pore size structure tends to be relatively slow, providing a basis for GDL selection and durability prediction.

Numerical simulation of oil and gas pipeline corrosion based on single- or coupled-factor modeling: A critical review

Numerical simulation is an effective research approach to assess the condition and predict the remaining service life of process pipelines suffering corrosion hazards. This work comprises a critical review of 182 academic articles to analyze environmental factors affecting the pipeline corrosion process, basic numerical methods for corrosion simulation, and single- and coupled-factor numerical investigations. Numerical simulation of corroded pipelines could combine the electrochemical corrosion processes and structural characteristics of pipelines to obtain more accurate results. Multiphysics-based techniques have been successfully applied to simulate the evolution process of corroded pipelines affected by two or more coupled factors under stray current interference. Through integration with learning-based algorithms, predictive studies are conducted to assess the development of corrosion. The challenge for current research is that the remaining types of corrosion are difficult to describe by numerical methods. Opportunities are proposed to improve the pipeline corrosion simulation model to describe more corrosion types and realistic corrosion morphologies, including time-varying corrosion simulation, random field in the simulation, and microelectrochemical corrosion simulation.

Corrosion engineering towards NiFe-layered double hydroxide macroporous arrays with enhanced activity and stability for oxygen evolution reaction.

NiFe-layered double hydroxide (NiFe-LDH) is the benchmark catalyst for the oxygen evolution reaction (OER) in alkaline medium, however, it is still challenging to improve its activity and stability. Herein, NiFe-LDH macroporous array electrodes are demonstrated to significantly enhance the activity and stability for oxygen evolution reaction. The electrodes are fabricated by the chemical and electrochemical corrosion process of Ni foam induced by ferric nitrate, hydrochloric acid and oxygen. are prepared by a controllable corrosion strategy for oxygen evolution reaction. By optimizing the amount of iron salt and acid and selecting the appropriate reaction temperature and time, The NiFe-LDH electrodes only need the overpotential of 180 mV and 248 mV to reach the current density of 10 mA cm-2 and 500 mA cm-2, respectively, and remain highly stable for 1000 h at 500 mA cm-2. The unique macroporous array not only significantly increases the active area of NiFe-LDH catalyst, but also creates a stable nanostructure that avoids severe reconstruction.

Enhanced protection of manganese-doped zinc molybdate with synergistic corrosion resistance effects

Zinc molybdate (ZM) materials modified with different elements have a variety of properties, and therefore the study of metal elements modification for improvement in corrosion protection of ZM can be meaningful in practical applications. Herein, the manganese-doped zinc molybdate (Mn-ZM) material with synergistic anticorrosion effects was prepared through a one-step hydrothermal method. The total impedance value of Mn-ZM coating has increased by 341.6 % and 415.2 % in comparison with that of the ZM coating and pure epoxy coating after immersion in 3.5 wt% NaCl solution for 72 h, showing the best corrosion protection performance. The synergistic corrosion protection effects of Mn-ZM material were based on the multiplayer passive films, the permeation retarding effect and the improvement of hydrophobic and dispersion properties, which could cooperate with each other to delay the electrochemical corrosion processes. Herein, this work provides a new reference for the further study in elemental doping modification of other inorganic anticorrosion materials in applications.

Corrosion-Fatigue Analysis of Wires in Bridge Cables Considering Time-Dependent Electrochemical Corrosion Process

Environmental corrosion and cyclic dynamic loadings are the main causes of cable failures. In the degradation process of cables, the effects of corrosion and cyclic loading are coupled and the corrosion rate is time dependent. To consider the time-variant properties of the electrochemical corrosion process, the evolution curve of corrosion current density was proposed and introduced into a corrosion-fatigue model. Based on the model, we extracted in situ wires from a tied-arch bridge for the corrosion-fatigue analysis. The surface profiles of the wires from midregion and the anchored region were measured. We found that the corrosions in the anchored region of the wires distribute more uniformly than those in the midregion due to the different contact patterns among wires. And the corrosion characteristics of salt spray–corroded wires are close to those of wires from the anchored region. The corrosion-fatigue simulations considering the effect of environments, loadings, and contact patterns of wires show that the failure modes of wires are greatly affected by loadings; the lifetimes of wires and cables are particularly sensitive to environmental corrosivity; and due to different contact patterns, the lifetimes of cables from the midregion are shorter than those from the anchored region by 30%. The research on corrosion fatigue of cables provides a rational basis for the operation and maintenance of cable-supported bridges.

A Comparison of the Microstructure, Mechanical Properties, and Corrosion Resistance of the K213 Superalloy after Conventional Casting and Selective Laser Melting

K213 superalloy was fabricated by conventional casting and selective laser melting (SLM). The microstructures of the two samples were examined, and the mechanical properties and corrosion resistance of these two kinds of K213 alloy were comparatively studied. The results show that segregation of Ti occurs at the grain boundaries of the as-cast alloy, resulting in the formation of MC carbide. Many microcracks were formed in the SLM sample. Premature fracture of the as-cast alloy is caused by the precipitation of the harmful phase (Ti, Mo, Nb)C (MC). The MC carbides and microcracks in the as-cast and SLM alloys, respectively, induce tensile fracture. In comparison, the strength of the SLM sample is greater, while the elongation of the as-cast sample is greater. The oxidation resistance of the SLM sample is better at a high temperature of 800 °C. This is due to the relatively uniform composition and microstructure of the SLM alloy. However, the corrosion rate of the SLM alloy is accelerated during the electrochemical immersion corrosion process due to the existence of microcracks.

Mikania micrantha extract/KI blend as a novel synergistic inhibitor for steel corrosion in concentrated H3PO4 solution

Mikania micrantha extract (MME) was prepared by reflux extraction from the exotic invasive weed of Mikania micrantha using ethanol water solution as the solvent. The synergistic inhibition effect and mechanism of MME and potassium iodide (KI) on the corrosion of cold rolled steel (CRS) in 4.0 M H3PO4 solution was investigated by gravimetric, electrochemical and surface analysis techniques for the first time. The results show that either MME or KI has moderate inhibitive action, and the maximum inhibition efficiency is below 65 % at 20 ℃. However, incorporation MME with KI can produce a synergism (s > 1), and obtain a pleasant inhibition of 92.9%. The adsorption of MME on CRS surface obeys Freundlich isotherm, while KI and MME/KI complex follow Langmuir isotherm. They are all mixed-type inhibitors, and MME/KI mixture significantly retards the electrochemical corrosion comparing with individual MME or KI. The process of electrochemical corrosion is controlled by charge transfer, and the charge transfer resistance follows the order of MME/KI > KI > MME. SEM and AFM demonstrate that the corrosion of CRS surface is efficiently retarded by the blend of MME and KI. From FTIR and XPS analysis, the formed layer of the synergistic inhibited CRS surface is mainly composed of the organic compounds with polar groups in MME. There is also a synergistic inhibition of the major components (rutin, quercetin, chlorogenic acid and ferulic acid) with KI. MME/KI can be deemed as a novel efficient inhibitor for steel in concentrated phosphoric acid, which develops an original path for the utilization of Mikania micrantha in the field of metallic corrosion and protection.

Role of second phases in the corrosion resistance and cerium conversion coating treatment of as-extruded Mg–8Al–4Ca magnesium alloy

The presence of a second phase in the Mg–8Al–4Ca (at. %) alloy plays a significant role on both its corrosion behavior and the chemical conversion coating processes. Using scanning Kelvin probe force microscopy (SKPFM), a lower Volta-potential of the second phase present on the surface has been measured. The β-Al-Ca phase has a higher electrochemical activity than the α-Mg matrix and may act as the micro-galvanic anode in a local electrochemical corrosion process. Transmission electron microscopy (TEM) examinations reveal that the β-Al-Ca phase is more susceptible to corrosion than the α-Mg matrix in an aqueous solution, and its higher activity and higher corrosion rate accelerate the hydrogen evolution rate on the α-Mg matrix in the cerium (Ce) conversion coating process. It's also been discovered that by immersing the bare Mg–Al–Ca alloy in deionized (DI) water, the β-Al-Ca phase, exposed on the surface, can be dissolved and converted in situ into aluminum hydroxide (Al(OH)3), and the Ce conversion coating can be deposited via replacement reactions in the subsequent conversion coating process. A thicker Ce coating with smaller blisters has then been produced on the DI-treated Ce-coated Mg specimen; it indeed improves the corrosion resistance.

Interstitial Compound Fe3C-Doped Fe(0) Nanoparticles Embedded in Mesoporous Carbon Efficiently Boosting Cr(VI) Removal

The high reactivity of Fe(0) with Cr(VI) makes it the best choice for Cr(VI) removal. Interstitial compound Fe3C was produced during the carbothermic reduction of mesoporous phenolic resin/ferric ions to form Fe(0)/Fe3C nanoparticles embedded in mesoporous carbon (Fe(0)/Fe3C@MesoC). Fe3C accelerates the electrochemical corrosion process of α-Fe(0) in solution, and the positive/negative equipotential interface that is formed by iron–carbon (Fe–C) microelectrolysis of Fe(0)/Fe3C@MesoC induces the capture of Cr(VI) anions and Cr(III) cations as a result of this process. Cr(VI) was completely reduced to Cr(III) by the Fe(0)/Fe3C@MesoC catalyst with a high electron efficiency (40.5%) relative to nanosized zero-valent iron (1.9%) and Fe@MesoC (32.7%). Surface ferrous ions are the principal reactive species responsible for Cr(VI) reduction (at least 64%); Fe(0)/Fe3C and undetectable surface ferrous ions account for a small part of Cr(VI) reduction (around 28%), and only 8% of Cr(VI) ions are reduced by active hydrogen (H*). The proposed structure of Fe(0)/Fe3C@MesoC provides new insight into iron–carbon material preparation and application in in situ chemical reduction.

Предотвращение вторичного загрязнения питьевой воды в металлических сетях водоснабжения

Introduction. The requirements of current regulatory documents guarantee the quality of drinking water leaving water treatment facilities (WTF). Hence, the water, coming into water supply networks, made of steel and cast iron pipes, made of gray-cast iron, is transported to consumers. Its quality must meet the standards of GOST R (Russian National Standard) 51232-98 “Drinking water” and SanPiN (Sanitary Regulations and Norms) 1.2.3685-21 “Hygienic standards and requirements to ensure the safety and (or) harmlessness of habitat factors for people”. The aim of the study is to analyze methods of preventing secondary pollution of drinking water in water supply networks, made of metal, and to identify the most effective and practically grounded method. Materials and methods. The concepts of electrochemical corrosion and microbiological corrosion of the inner surface of pipes were used to perform the analysis. Three methods of preventing the formation of a layer of deposits on the inner surface of steel and gray cast-iron pipes are used in the practice of water treatment and disinfection of drinking water: the method of using strong oxidants, such as chlorine and sodium hypochlorite, for the disinfection of drinking water; the method of increasing the pH level of drinking water; the method of using chemicals to ensure the formation of a microscopic film on the surface of layers of deposits to “slow down” electrochemical and microbiological corrosion processes on the inner surface of pipes. Results. The authors have identified a method for preventing the secondary pollution of drinking water, time-tested by the twelve years of practical use by the operator of WTF and drinking water supply and distribution networks made of metal. Conclusions. The effectiveness of the method of preventing the secondary pollution of drinking water through the use of new generation reagents, made of polyhexamethyleneguanidine hydrochloride, has been proven in practice.

Development and Evaluation of Lamella Settlers Combined with Electrocoagulation for Treating Suspended Sediment

Stormwater quality has become an increasingly important issue in agricultural, urban, and construction sectors. Soil, nutrient, and pollutant discharge caused during rainfall events is one of the greatest sources of stormwater quality degradation. Enhanced stormwater treatment mechanisms are needed to economically and efficiently remove suspended pollutants in runoff. In this research, the performance of electrocoagulation (EC) combined with lamella settlers (LS) was investigated. EC is a highly effective and proven water-treatment technology that uses an electrochemical anode corrosion process to destabilize and remove contaminants and that has been shown to have widespread applications for treating a variety of wastes. LSs have been shown to enhance soil-particle capture by increasing the surface area and reducing the settling distance. This research demonstrated that the combination of EC and LS can enhance the sedimentation process while simultaneously decreasing the required detention time and size of traditional sediment control practices (i.e., detention basins, sediment basins). Combining EC with a LS is a novel approach for treating suspended particles in stormwater. In this project, bench-scale experiments were conducted using EC as pretreatment upstream of a LS reactor. Synthetic silica filler at concentrations of 500 mg/L, 1,000 mg/L, and 5,000 mg/L were used to evaluate treatment efficiency at 0.5-h, 1.0-h, and 1.5-h residence times. Collected data, including turbidity, total suspended solids, and particle size distribution, were used to statistically characterize the system’s sediment removal performance. Through a series of experiments and statistical analyses of the results, an optimized EC+LS reactor with 1.27-cm (0.5-in.) LS plate spacing and 1.5-h residence time reduced turbidity by up to 98% and total suspended solids by 99% in effluent when compared with a base case reactor with a 31.8 cm (12.5 in.) settling distance (no LS plates installed) and 0.5-h residence time without EC pretreatment. In addition, particle size distribution analyses resulted in a decrease in the D90 value by 84%, indicating that the optimized reactor was effective in capturing larger-diameter soil particles. To validate the laboratory results with synthetic sediment-laden influent, stormwater samples were collected from a construction site and treated through the optimized system, resulting in a turbidity reduction of 50% and TSS reduction of 69%.

Effect of deep cryogenic treatment on corrosion resistance of AA7075-RRA

7075 alloy was treated with deep cryogenic treatment (DCT) and retrogression and re-aging treatment (RRA). The corrosion behavior of the alloy was investigated by potentiodynamic polarization measurement, electrochemical impedance spectroscopy and intergranular corrosion test. The microstructure and corrosion morphology of the alloy were observed by transmission electron microscope and scanning electron microscope, respectively. The results showed that DCT could change the electrochemical corrosion process of the alloy. DCT applied to different stages of RRA treatment had a great influence on the number, size and distribution of the matrix and grain boundary precipitates. When DCT was applied after retrogression treatment, Icorr and corrosion rate of the alloy on electrochemical test was 0.006 mA cm−2 and 0.197 mm/a, respectively, and IGC depth was 25 μm. Moreover, the discontinuous grain boundary precipitates showed a better distribution state, thus corrosion resistance was remarkably improved.

Effect of macropores at the steel-concrete interface on localized corrosion behaviour of steel reinforcement

The steel-concrete interface determines the steel corrosion and the durability of concrete structures. In this paper, the relationship between macropores and localized corrosion is quantified, based on the natural deterioration of 5 wt% Cr steel reinforced mortar and laboratory tests of 5 wt% Cr steel in the saturated calcium hydroxide solution. The results show that, considering environmental factors with the same chloride content and water saturation, large interfacial macropores are always the weakest zones at which both corrosion initiation and propagation preferentially take place. The localized rate of steel corrosion (mm/year) increases linearly with the logarithm of the macropore volume (μL), and the slopes are in the range of 0.05–0.11 depending on the chloride level. The weakened pH buffering effect of solid Ca(OH)2 at interfacial macropores is not the only reason for this phenomenon; the impacts of macropores and their volume on the electrochemical corrosion process are also significant. In small macropores, both cathodic and anodic polarizations are strengthened, and the thermodynamic driving force of the iron dissolution reaction is reduced.

Dynamics of Brittle Cracks under the Influence of Low Temperatures

The article contains an investigation methodology of underwater pipelines for transporting hydrocarbons under working loading cycles. The process of hydrogenation of steels occurs with development of brittle cracks under working pressure. The brittle cracks are also caused by the processes of electrochemical corrosion. These transgranular processes lead to an increase in crack formation processes.Controlling the dynamics of brittle cracks allows to control working processes in the underwater main pipelines for transporting hydrocarbons, as well as define measures to maintain stability of underwater pipelines including measures for cathodic protection.

ФИЗИЧЕСКАЯ МОДЕЛЬ МАССОПЕРЕНОСА КОРРОЗИОННОГО ВОДОРОДА В ПАРОГЕНЕРАТОРАХ ТИПА НАТРИЙ-ВОДА БЫСТРЫХ РЕАКТОРОВ

For timely and prompt detection of the inter-circuit depressurization of the steam generator of the “sodium-water” type in the 2nd circuit, continuous monitoring of the content of hydrogen, as a product of the interaction of sodium with water, is carried out in all operating modes. However, in reality, the main source of hydrogen in the sodium of the 2nd circuit is the process of electrochemical corrosion of 10X2M steam generator steel in a steam-water medium, the speed of which is never zero and is controlled at the minimum achievable level by means of the water-chemical regime of the 3rd circuit. At the same time, during the operation of the steam generator, deposits of corrosion products accumulate on the surface of the structural steel from the side of the 3rd circuit. The removal of deposits is carried out with the help of operational chemical flushes (ECPs). However, during the ECP, the corrosion rate of steel inevitably increases significantly (by about three orders of magnitude), which leads to an increase in the concentration of hydrogen in water and in sodium. This phenomenon has previously caused concern to the operational services of nuclear power plants due to the likely through-corrosion during regular ECP (every year, one of the three steam generators is washed). However, it is unacceptable to operate a steam generator without ECP, and to reduce the corrosion rate of steel of steam generator pipes in a steam-water environment, after ECP, a chemical passivation stage is carried out with different formulations, the effectiveness of which is different. This article presents a physical model of the mass transfer of corrosive hydrogen in a steam generator during chemical washing, passivation and start-up of the steam generator. An operational criterion for evaluating the effectiveness of passivation by the rate of increase in the concentration of hydrogen in the sodium of the second circuit during the subsequent start-up of BN-600 steam generators is proposed: if the rate of increase in the concentration of hydrogen in the 2nd circuit is less than 0.05 ppm/h, then passivation is effective, if more than the passivation formula requires revision. For BN-800 steam generators, the technology of passivation after ECP has not yet been determined, the article proposes a calculated criterion for its efficiency of 0.015 ppm/h.

Elucidating the electrochemical mechanism for enhanced corrosion of Ti3C2Tx-coated mild steel

Two-dimensional (2D) transition metal carbides, carbonitrides and nitrides (MXenes) represent a burgeoning group of 2D layered materials with widespread applications due to unique performance characteristics, in which titanium carbide (Ti3C2Tx) as corrosion inhibitor provides good physical barrier effect. Given that, as-prepared Ti3C2Tx MXene via chemical etching of titanium aluminium carbide (MAX) phase using HF/oxidants have good corrosion resistance of their own, but it is of inevitable importance to understand the effect of their hydrophilic surfaces and high electrical conductivities on corrosion of alloy substrate. Herein Ti3C2Tx MXene coating was prepared on mild steel substrate (Q345) to explore its corrosion behaviors in different conditions. The corrosion current density (i corr) of MXene-coated Q345 was 6.39 × 10–6 A · cm−2, which was higher than that of uncoated Q345 sample (5.66 × 10–6 A · cm−2). After 3 days of storage in wet environment of 40% and 90% relative humidity (RH) at 30 °C, MXene-coated Q345 had suffered from a higher degree of spatially inhomogeneous corrosion, while the surface of uncoated substrate was still neat and glossy in spite of undergoing 1 month of storage under the same condition. The results demonstrate that Ti3C2Tx MXene accelerates the corrosion of Q345. Conductive and hydrophilic Ti3C2Tx could act as an electrode to propagate the charge generated by the oxidation of Fe, which forms a micro corrosion cell with substrate. Thus, the electrochemical corrosion process of substrate is accelerated.

The Effect of Immersion Corrosion Time on Electrochemical Corrosion Behavior and the Corrosion Mechanism of EH47 Ship Steel in Seawater

In this paper, electrochemical corrosion tests and full immersion corrosion experiments were conducted in seawater at room temperature to investigate the electrochemical corrosion behavior and the corrosion mechanism of high-strength EH47. The polarization curve, EIS (electrochemical impedance spectroscopy), SEM (scanning electron microscope), and EDS analyses were employed to analyze the results of the electrochemical corrosion process. The electrochemical corrosion experiments showed that the open circuit potential of EH47 decreases and then increases with an increase in total immersion time, with the minimum value obtained at 28 days. With an increase in immersion time, the corrosion current density (Icorr) of EH47 steel first decreases and then increases, with the minimum at about 28 days. This 28-day sample also showed the maximum capacitance arc radius, the maximum impedance and the minimum corrosion rate. In the seawater immersion test in the laboratory, the corrosion mechanism of EH47 steel in the initial stage of corrosion is mainly pitting corrosion, accompanied by a small amount of crevice corrosion with increased corrosion time. The corrosion products of EH47 steel after immersion in seawater for 30 days are mainly composed of FeOOH, Fe3O4 and Fe2O3.

Electrochemical process of early-stage corrosion detection based on N-doped carbon dots with superior Fe3+ responsiveness

Iron corrosion is a subject of great technological importance and extensive public concern. However, the highly efficient detection of iron corrosion at early stage is still a challenging task. Herein, bright fluorescent carbon dots (CDs) with superior response to Fe3+ were prepared by simple solvothermal process based on citric acid and ammonia. The obtained CDs are able to rapidly, sensitively and selectively respond to Fe3+. The quantitative analysis showed that the CDs exhibited a linear response to Fe3+ in the range of 10 to 300 µM, with a detection limit of 0.9 μM. And the fluorescence quenching of CDs was obvious enough to be detected by the naked eyes. Such promising responsiveness of CDs offers a great opportunity for real-time and visual detection of Fe3+ during electrochemical corrosion process. In addition, due to the excellent stability and solubility of CDs, patterned papers and hydrogels have been fabricated utilizing cellulose and PVA as matrices. The as-prepared biocompatible, environmental-friendly and disposable CDs based fluorescent materials were successfully used for detecting the degree of iron corrosion. This could provide a simple and visual strategy for monitoring the safety of structural metal materials.