Corrosion Deposits Research Articles

Effect of pulse electroplating parameters on the morphology and corrosion resistance of Ag plating coating

Pulse electroplating technology has the characteristics of fine grain and good corrosion resistance. In order to ensure the good application of electroplated silver cone cavity in solar radiation detector. The effects of three process parameters, including average current density (0.4–1 A dm−2), pulse on-time (0.2–1.8 ms) and pulse off-time (0.8–4.8 ms), on the deposition rate, appearance and corrosion resistance of silver coating were studied by control variates. The surface morphology and composition of silver coatings were studied by scanning electron microscope (SEM), laser confocal microscopy and energy dispersive x-ray spectrometer (EDX). The corrosion resistance of silver coating in 3.5 wt% NaCl solution (pH=5.5) was studied by polarisation curves and electrochemical impedance spectroscopy. The results show that pulse electroplating takes advantage of the dynamic change of current to influence the size of deposited particles and the degree of densification of the coating by precisely adjusting the pulse plating parameters, and ultimately obtains the coating with excellent morphology. The optimal parameters are: average current density 0.6 A dm−2, pulse on-time 1.2 ms, pulse off-time 1.8 ms. The silver coating prepared under process conditions has excellent corrosion resistance (7059 Ω cm−2). The surface crystal grain is dense, without obvious defects.

Hot Corrosion Damage Modeling in Aeroengines Based on Performance and Flight Mission

Hot corrosion is a form of chemical damage that causes surface degradation, sound material loss, and reduced component life. A lifing analysis in aeroengines without considering hot corrosion can lead to unexpected damage findings and increased scrap rates due to blade thickness loss beyond repair. This paper presents a novel methodology to predict hot corrosion damage based on aeroengine performance and flight mission analysis while taking into account environmental exposure, fuel quality, and material factors. The participating mechanisms, from salt and sulfur ingestion to deposition and hot corrosion attack, are discussed to explain the phenomenon in aeroengine components. In the investigated engine type, the first stage of the low-pressure turbine is the most affected. The application of the new methodology provides insights into the damage progression during the flight, the most affected components and the importance of capturing variations in the fuel quality, environmental exposure at the flight region, and the thrust derate policy. For a representative 1500 n mile mission, the variations in environmental exposure, fuel quality, and derate policy within typical limits can result in up to +350% damage. The outputs of the new framework can inform the decision making for maintenance, repair, and overhaul contract costing and scheduling.

3D scanning of daguerreotypes

Daguerreotypes are historical photographic images made on mirror-like metallic plates. These are heritage objects whose shape cannot be measured with invasive techniques, like contact probes, but the high reflectivity of their surfaces makes the use of non-invasive, 3D-measuring optical techniques challenging. Moreover, the dark areas resulting from their degradation produce a very high contrast, which add extra difficulties to their measurement. In the last few years, several strategies have been developed to overcome the limitations of optical techniques when measuring reflective metallic surfaces. Many of these solutions are not applicable to the study of cultural heritage artifacts, as they are invasive. We attempted the use of conoscopic holography in a 3D-scanning system using a double-exposure strategy. This is a promising option for 3D measuring of daguerreotypes, as we experimentally demonstrated in this work. We present the results obtained from the analyses of two 19th-century daguerreotypes with different superficial conditions. The double-exposure allowed us to obtain high-quality data from the entire object surface. This enabled the measurement of micro-scale details related to the manufacturing process and/or to the corrosion deposits. The proposed methodology can be exploited to monitor the overall health of highly reflective metallic objects but also the outcomes of some conservation treatments, such as cleaning.

Unraveling short-term O2 contamination on under deposit corrosion of X65 pipeline steel in CO2 saturated solution

The impact of short-term O2 contamination on the deposit-covered pipeline steel under a CO2-saturated solution was investigated using steel coupon and wire beam electrode. Results show that the brief exposure to O2 destroyed the FeCO3 film, and converted it into porous iron oxides, weakening its protection property. However, upon CO2 reinjection, the dense FeCO3 film regrew soon underneath the damaged FeCO3 layer on the bare steel, restoring its protective properties. Conversely, the localized corrosion beneath the deposits persisted and worsened, fueled by macro-cell current between the bare steel and the deposit-covered steel.

STUDYING THE INFLUENCE OF NEW COMBINED INHIBITORS ON THE PROCESSES OF CORROSION AND SALT DEPOSITION IN OIL-FIELD EQUIPMENT

Aggressive salts contained in formation waters accelerate the processes of corrosion and salt deposition in oilfield equipment, which leads to unforeseen accidents, contamination of soil and groundwater with harmful substances, as a result of which the ecological balance of the environment is disrupted. Corrosion and scaling that occur during oil production create difficulties during the operation of wells, and, consequently, increase the cost of produced oil.This article covers the results of studies concerning two compositions developed from technical phosphatide - an emulsion obtained by hydration of vegetable oils, as well as sodium hexametaphosphate, ammophos and polypropylene glycol bottoms. When vegetable oils are treated with water and steam (hydration process), the phospholipids contained in the oils combine with water and are released in the form of precipitates called phosphatide emulsions. Such emulsions consist of 45–75 % water, and the rest is phospholipids in the vegetable oil sediment.Technical phosphatides are a group of esters that contain a phosphoric acid residue associated with an amino alcohol. They are natural surfactants and are non-toxic.Preliminary studies have shown that each of the chemical compounds included in the developed reagents has certain inhibitory properties, but when formulated, these compounds provide a synergistic effect.Based on the results of laboratory studies, it was found that at an optimal concentration of reagents of 200 mg/l, the developed compositions provide protection of equipment from corrosion destruction by 94–95 %, and from scaling by 87–88 %. The developed mixed-type inhibitors at optimal concentrations equally effectively inhibit both cathodic and anodic processes on the electrode.The use of these inhibitors leads to the prevention of steel corrosion in the two-phase oil-electrolyte system, as well as to a significant reduction in the rate of scaling.The proposed new compositions can be used in oil wells and in-field transport systems, as well as in reservoir pressure maintenance systems to protect against corrosion and scale deposits.Field tests of the corrosion inhibitor were carried out in deep pumping wells at the Bibieybatneft oil and gas production department. Tests have shown that as a result of using the inhibitor, the protective effect at a concentration of 200 mg/l was 89–90 %, and the effect of salt deposition was 70 %.

Preparation and properties of Ag-containing porous layer on 6061 aluminum alloy surfaces

This study focused on the preparation of Ag-containing porous layers on the surface of a 6061 aluminum alloy using different voltages. The microstructure, Ag deposition form, corrosion resistance, and antibacterial properties of the Ag-containing porous layers on the 6061 aluminum alloy were analyzed using scanning electron microscopy, X-ray photoelectron spectroscopy, electrochemical workstation, and antibacterial tests. The results indicated that the Ag-containing porous layer prepared at 30 V exhibited the highest Ag deposition and antibacterial rate, amounting to 1.78 wt% and 99.73 %, respectively. The deposited Ag mainly existed in the form of Ag+ combined with O2− and SO42− within the Ag-containing porous layers. Compared to that of the 6061 aluminum alloy matrix, the Ag-containing porous layer prepared at 30 V had a wear volume of 0.015 mm3, a reduction of 98.37 %, an increase in the corrosion potential (Ecorr) to −0.485 V, and an increase of 0.848 V. In conclusion, Ag-containing porous layers demonstrated significant antibacterial, wear resistance, and corrosion resistance properties.

Inspirations from Field-Reservoir CO2 Flooding with Different Miscible Degrees under Cross-Scale Oil Reservoir Conditions.

In recent years, CO2 flooding has become one of the main enhanced oil recovery (EOR) methods, especially for tight formations in different oilfields around the world. Most of the CO2 flooding projects carried out in the world are based on miscible flooding, however, this technique is less effective in China because of the depth of the reservoirs and the heavy components of the crude oil. Near-miscible flooding and immiscible flooding have also been gradually applied to China's domestic oil fields, and have achieved certain oil increase effects, but there are still some challenges such as gas channeling, corrosion, and solid phase deposition in the process of CO2 flooding. In this paper, through a detailed review of recent domestic and foreign cases of enhanced oil recovery, the effects of development methods of low permeability and ultralow permeability reservoirs under different miscible degrees are analyzed, and the solutions to some of the existing problems in field tests and experience are systematically summarized. According to the results of field tests, both miscible flooding and near-miscible flooding have similar effects and can achieve better recovery increment, with a long effect period and slow gas breakthrough speed. In addition, the problems of gas channeling, corrosion, and solid phase deposition occurring in the process of CO2 flooding are analyzed, and solutions such as a change in injection methods and coatings are put forward, which effectively promote the development of CO2 flooding technology. Those suggestions are of great significance for improving the oil recovery rate of unconventional oil reservoirs, ensuring the national energy supply, and low-carbon emissions reduction in China.

Corrosion deposition in deforming anodes of in-ground cathodic protection systems: A three-dimensional transient study

Cathodic protection as a complementary technique is widely considered in the industry along with the selection of suitable materials as well as efficient coating considerations. In cathodic protection (CP), anode produces a current output to protect the structure (cathode) and part of the current output is wasted by the grounding system. We developed a 3D, and time-dependent numerical model to simulate the anode corrosion (using arbitrary Lagrangian-Eulerian method), find the deposit formation (by interface tracking level set method), anode mass loss and current wasted by the grounding system. We also defined a CP efficiency as anode mass loss times the current percentage received by the structure. The CP efficiency can be utilized for anode quantity and placement pattern. The results showed when the conductivity of corrosion products (deposit) is lower than that of soil, the current output from the anode decreases over time. When the deposit conductivity is higher than that of soil, the current output from the anode increases in time, reaches a peak, then decreases. This is due to the competition among three factors: anode surface increase, medium conductivity change, and inhibition effect of the deposition layer. For the studied case, almost 54% of the current from the anode is wasted by the grounding system. To illustrate the significance of CP efficiency, this study compares three alternative anode configurations with the original design. It is observed that for a 14.5 kg anode, burying the anodes 2 m deeper enhances the mean potential distribution on the structure by 4%. Additionally, the configuration featuring the 7.7 kg anode, owing to its superior dimensional design, demonstrates improved performance compared to other configurations.

A Bayesian network‐based susceptibility assessment model for oil and gas pipelines suffering under‐deposit corrosion

AbstractOil and gas pipelines are exposed to harsh operating conditions that facilitate their susceptibility to complex corrosion mechanisms. This affects their integrity and results in failure with associated consequences. Capturing these complex corrosion phenomena requires a robust approach. This study proposes the application of a dynamic probabilistic model to capture the key influential factors that contribute to the complex under‐deposit corrosion (UDC) mechanism in oil and gas pipelines. The Bayesian network model assesses the pipeline's susceptibility (degradation rate) to the UDC, capturing parametric dependencies. The predicted corrosion rates are input data for the corrosion propagation prediction. Three semi‐empirical corrosion propagation models are used for a comparative assessment to establish the degree of susceptibility given the prevalent influential factors and model parameters. The proposed approach is tested on an offshore pipeline, and the degree of impact of the key influential parameters is predicted. The result shows a percentage increase in the degradation rate by 18.7%, 33.2%, 35.8%, and 63.4%, respectively, for the various interaction scenarios. The present approach offers an adaptive and robust technique that would provide an early warning guide on the rate of pipeline degradation to aid integrity management for offshore assets suffering from deposit corrosion.

Numerical study on surface corrosion deposition of fuel elements and its influence on flow heat transfer

Corrosion of pressurized water reactors (PWR) in nuclear power plants can lead to serious safety hazards. This study aims to analyze the deposition of corrosion products using FLUENT software. Deposition models and thermal resistance models were developed, and the effects of deposits on the reactor’s thermal–hydraulic characteristics were evaluated. Additionally, the impact of various parameters on deposition and thermal–hydraulic characteristics was examined. Results show that deposits accumulate extensively in the inlet section of the fuel cladding, while appearing as spot deposits in the outlet section. For deposit thicknesses below 30 μm, the surface temperature of the cladding gradually increases. However, when the thickness exceeds 30 μm, the surface temperature rapidly rises. Furthermore, the study reveals that the deposition amount decreases with increasing inlet flow velocity, exhibits an upward trend with higher inlet temperature, and increases with a higher wall heat flux density. This research provides important insights for understanding core deposition and thermal–hydraulic characteristics in nuclear reactor systems. It offers valuable guidance for enhancing safety and operational efficiency in nuclear power plants.

Effect of hydrogen on steels in hydrogen sulfide-containing and other environments at gas facilities

The impact of hydrogen sulfide raw materials on steel equipment and pipelines is known and is associated not only with internal corrosion processes, but also with the hydrogenation of carbon and low-alloy steels used. Penetration of hydrogen into steel can lead to the loss of its strength properties and subsequent destruction of gas pipelines operated under high pressure conditions. The manifestations of cracking characteristic of hydrogen sulfide environments, which are a consequence of the penetration of hydrogen into steel, are the most dangerous from the point of view of the safety and reliability of the operation of facilities for the production and transportation of corrosive gas. The effect of H2S on the decrease in ductility of the main types of structural steels was studied based on the results of simulation tests. The formation of blisters (bloatings) and cracks on the surface of steels due to the effect of hydrogen on steel was recorded. The study of the phase composition and properties of corrosion products was carried out in order to assess their possible influence on the processes of steel hydrogenation. The formation of evenly distributed on the surface and the densest corrosion deposits will hinder both the corrosion processes and the penetration of hydrogen into steel. A decrease in the plastic properties of steel is also observed when exposed to hydrogen, which can be transported both separately and together with methane through the main gas pipelines. The main possible means of protecting steels that are unstable to hydrogenation is the use of corrosion inhibitors. It was established that the most effective corrosion inhibitors with rational technologies of application and dosage can protect steels from penetration of hydrogen into them and their destructive effect.

Green Hydrogen Production Directly from Seawater with No Corrosion Using a Nonmetallic Electrode: A Novel Solution and a Proof of Concept

Why Hydrogen. Nowadays, the energy industry and research laboratories are heavily working on developing ideas and methods to reduce and/or eliminate the carbon dioxide emission to control the problem of global warming. The solution relies on finding alternative green energy resources to reduce the world’s dependence on conventional fossil hydrocarbon energy. Green hydrogen gas from water stands on the top of the alternative resources since it does not produce carbon dioxide when burned and in return does not add to global warming. Since seawater is the largest resource on earth, this makes the hydrogen production from seawater the most economically attractive solution. It is very important to avoid using fresh water as a source of hydrogen energy due to the dependence of all living creatures, humans, animals, plants, etc., on such very limited resources. In this paper, the applications of the proposed novel solution of green hydrogen production directly from seawater relies on solving one of the major problems, electrode corrosion. Generating Hydrogen. The direct method to produce green hydrogen from seawater is the electrolysis technique. This technique requires a direct current power supply for the positive and the negative electrodes. The outcome of the electrolysis is decomposing the saltwater to its positively charged hydrogen and sodium ions at the negative electrode and its negatively charged oxygen and chlorine ions at the positive electrode. The Real Challenge. Traditionally in the electrolysis analysis of water, both electrodes are made of metals. At the positive electrode, both the oxygen and the chlorine cause a high rate of corrosion to that electrode. This results in the interruption of the electrolysis process, bad water condition due to the corrosion deposits, and cost burden due to the need to periodically replace the corroded electrodes and/or use high-cost corrosion-resistant alloys. The Novel Solution. A low-cost but powerful solution to the corrosion problem is introduced, tested, and experimentally proved. The novelty of the solution relies on replacing the classic special high-cost metallic positive electrode with a nonmetallic, no-cost, one. The nonmetallic electrode is made of surface rock portions that have high porosity and pore volume and high permeability and pore connectivity and is saturated with saline water. Surface rocks with the above properties exhibit very low resistivity and hence conduct electricity like metallic electrodes. The voltage and the current conducted by such electrode are controlled by the electrode geometry, connectivity, and physical properties. Results and Discussions. Multiple experiments using the proposed nonmetallic high-porosity and high-permeability positive electrode are conducted and presented in this paper. The experimental work is based on testing multiple rock electrodes with different rock properties, sizes, and connectivity in comparison to the metallic ones. The comparison showed that the novel solution solved the corrosion challenges of the metallic electrodes with excellent efficiency.

Understanding Flow Fouling Deposition and Solute Hideout-Return Behavior at the Phase Change Interface.

Nuclear energy is a competitive green energy, yet corrosion deposition and boron hideout on pressurized water reactor fuel cladding surfaces could cause localized corrosion and power shift, resulting in huge safety and economic risks. Alleviation of these problems requires the understanding of the corrosion deposition mechanism and related boron behavior. In this study, we explore corrosion product deposition in typical fuel assembly channels under subcooled boiling conditions and propose a boron hideout and return mechanism to explain the reason for the failure of the power reduction inhibiting a power shift. Porous corrosion depositions with the same morphology and thickness as the real depositions in a fuel cycle are obtained in a week via the accelerated deposition method simulating a real subcooled boiling and water chemical environment. Stronger subcooled boiling generates more bubbles, resulting in higher supersaturation of corrosion products at the gas-liquid interface. The corresponding precipitated stable crystals are smaller, and the formed deposition layer is looser and thicker with smaller particles. On the basis of the above characterizations, the effect of subcooled boiling, solute concentration, and water chemistry on the corrosion deposition mechanism is revealed. High-resolution characterization methods indicate that boron hides within the depositions mainly in the form of H3BO3 and Li2B4O7. The boron coolant concentration increases by 307.9 ppm after power reduction, confirming the return behavior of porous hidden boron. Hidden boron return behavior brings potential challenges for estimating critical conditions and plant response operations. The results of this study provide a precise method for understanding the corrosion product deposition and boron hideout-return behavior to further develop mitigation strategies for power shift and localized corrosion security issues.

Corrosion prevention of storage tank bottom using impressed current cathodic protection – Experimental and simulation study

Underside failure of storage tank bottoms is a serious industrial problem which is induced by various corrosion phenomena such as under deposit, microbial and stray current corrosion and can lead to leakage of hazardous materials and explosion. Impressed current cathodic protection (ICCP) is a widely used technique to hinder these types of corrosion. However, undue design of the ICCP system can accelerate the corrosion. Therefore, it is necessary to make sure that the tank bottom is totally and properly under protection before implementation. For this aim, a FEM model is designed in this study for validating this presumption. The model is based on the potential and current density distribution of the tank bottom and is designed using the data of a real storage tank being protected in practice. Simulation results showed that the tank bottom's potential with the ICCP applied (considering voltage drop) and its polarized potential at the very first instant of current interruption both are at least −0.850 V vs Cu/CuSO4. Furthermore, based on the calculations, 0.260 to 0.280 V polarization is experienced by the tank bottom. These results confirm full protection of the tank bottom. Effects of anode arrangement, coating application and soil resistance on the system performance are also investigated and the most optimal design is proposed based on the potential distribution. Conducting such a simulation in advance can significantly increase the life time of the structure.

The impact of deposits in cylindrical pipes on hydrodynamics and heat transfer

The paper deals with the problems of shell-and-tube heat exchangers operation taking into account the influence of scale and corrosion deposits on heat transfer efficiency. On the basis of numerical modeling performed in the ANSYS CFX program complex, research of various geometrical characteristics of heat exchangers, as well as deposit thicknesses on the heat transfer efficiency was carried out. The simulation results showed that the increase in fouling thickness worsens heat transfer in heat exchangers with large tube diameters, while in heat exchangers with small diameters the heat transfer fluid velocity increases, compensating for the additional thermal resistance. The influence of various parameters on the operation of heat exchanger equipment is evaluated and recommendations on optimization of its operation and frequency of cleaning are offered.

Предремонтная подготовка резервуаров, осложненная пирофорными отложениями

Purpose. One of the most important measures to reduce fire and explosion safety of hot and repair work at oil and oil products storage tanks is premaintenance works. Most oil tank fires occur during this stage. Premaintenance works are significantly complicated by corrosion deposits on tank inner surface. When conducting premaintenance works, there is a risk of spontaneous combustion of pyrophoric sediments. The most frequent cases of catching fires occur at high-sulfur oil tanks with pyrophoric sediments, and that requires a new approach to conducting this technological operation. Methods. Methods of comparison, description and generalization were used in the study. The information basis for the study was scientific sources, regulatory documents and reports of fire analyses at tank farms. Findings. Analysis of practice of operating tanks for storing high-sulfur oil, as well as data on tank fires shows that current approach to premaintenance works is ineffective. It is necessary to adjust current regulatory documentation in the field of improving fire and explosion safety at petrochemical industry facilities and develop new, more effective means of anti-corrosion protection for tanks with high-sulfur oil. Research application field. Analysis and development of regulatory- technical base will allow finding a new approach to methods of premaintenance works and hot works to improve fire and explosion safety at tank farms for storing high-sulfur oil. Conclusions. In-depth studying the problem of storing high-sulfur oil in tanks and the issue of its purification will allow us to find more modern and high-quality methods for conducting premaintenance works to ensure fire and explosion safety at tank farms.

Deposition Mechanism, Structure and Corrosion Protection of ZrO2-Based Conversion Coatings on AA6060 Primary and Recycled Aluminum Alloys

Chemical conversion coatings (CC) are amongst the most common surface pretreatments for aluminium alloys before further organic coating steps. The presence of a conversion layer can increase the resistance towards underpaint corrosion such as filiform corrosion (FFC). Here we explore the deposition mechanism, structure and protective properties against FFC of a ZrO2-based CC on AA6060 aluminium alloy by means of electrochemical techniques as open circuit potential measurements, potentiodynamic polarization and dynamic electrochemical impedance spectroscopy (dEIS). Surface composition and elemental distribution are characterized by X-ray photoelectron spectroscopy (XPS), Glow Discharge Optical Emission Spectroscopy (GD-OES) and Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS). The variation of important parameters such as charge transfer resistance and capacitance during the conversion layer deposition gives insight into the deposition mechanism. GD-OES and XPS shed light into the structure and composition of the formed CC layer constituted of a mixture of Zr (hydr)oxides based products, redistribution of alloy elements and the nature of deposited additives. Finally, FFC tests reveal a comparable performance between primary and recycled alloys.

Assessing underdeposit corrosion inhibitor performance for carbon steel in CO2/Sulfide environment

Under deposit corrosion (UDC) that occurs due to the deposition of solid particles, like iron sulfide or organic solids, and CO2 corrosion, cause disasters for pipelines and fluid-handling apparatus. This research investigated the impact of mineral deposits, like iron disulfide, iron sulfide, and sand, on the inhibition performance of the commercial UDC inhibitor in sulfated CO2-saturated brine solution at 60 °C and 1000 rpm flow rates for different immersion times. The deposit characteristics, type, and coverage technique on the steel (full/partial) were explored. The surface morphology, elemental analysis, and particle size of deposits in the absence and presence of the inhibitor were analyzed. The inhibitive effect at different inhibitor concentrations and the corrosion rates of steel in the absence and presence of the deposits were calculated from the fitting process of the electrochemical impedance spectroscopy (EIS) results. The utilized UDC inhibitor has the highest efficiency (about 95 %) at a concentration of 400 ppm. The FeS, FeS2 and SiO2 deposits in the presence of the inhibitor offered a 77.5 %, 94.5 % and 94.6 % inhibition efficiency after 6h of immersion time, resulting in about 77.5 %, 25.6 % and 60.1 % increase in their efficiencies before the addition of the inhibitor. Therefore, the inhibitor can effectively inhibit the UDC triggered by FeS and SiO2 deposits in an aqueous environment containing sulfated CO2. However, it is unavailable in the steel underneath the FeS2 deposit to inhibit corrosion. EDX and XPS analyses confirm the success of the inhibitor movement through deposits and its adsorption on steels.

Обследование скрытых участков стальных труб малого диаметра с применением ультразвуковой дефектоскопии

According to the current regulatory documents, as the established service life of gas pipelines for various purposes expires, they must be inspected in order to assess the current technical condition, make a decision on the residual life and the possibility of further operation at hazardous production facilities, as well as other buildings and structures. The possibility is considered related to using ultrasonic testing for detecting damage of corrosion origin in the sections of such pipelines hidden from the direct observation in interfloor ceilings and passages through the walls of buildings at the facilities in various branches of industries, as well as in gas distribution and gas consumption systems, and water pipelines. In addition, the possibility of identifying layered deposits of various origins in the cavity of small-diameter steel pipes is considered. At energy facilities, as well as in water supply pipelines, such deposits can lead to a significant reduction in the flow area of the pipeline, up to its complete blocking. Deposits inside the pipelines form an anisotropic layered medium, and the passage of ultrasonic waves through it has a number of features that prevent the use of traditional ultrasonic echo testing. For small-diameter pipes, the criterion is given under which it is possible to perform «remote» (waveguide) ultrasonic testing of the hidden sections of pipes at a distance of up to 600 mm. It is illustrated how, from such a distance, it is possible to detect corrosion deposits in pipes by ultrasonic testing methods using phased array antennas. At the same time, it is possible to assess the thickness («power») of layered deposits and their structure even when the passage section of the pipeline is filled with such deposits up to 100 %. Use of the methods presented in the article allows to increase the accuracy of calculating the residual life of the pipeline and reduce the uncertainty in setting safety factors in such calculations.

Electrochemical Study on the Macro-Cell Corrosion of Pipeline Steel Partially Covered by Different Kinds of Mineral Deposits.

This study presents the impact of mineral deposits (SiO2, Al2O3, and CaCO3) on the corrosion behavior of X65 pipeline steel in CO2-containing brine solution with low pH. The study investigates the initiation and propagation of under deposit corrosion (UDC) using a wire beam electrode (WBE) partially covered by different mineral deposit layers, in conjunction with electrochemical measurements and surface characterization. The results indicate that the corrosion behavior varies, depending on the characteristics of the deposit. During the test period, the Al2O3-covered steel acted as the main anode with more negative potential, while the bare steel acted as the cathode. The SiO2-covered steel acted as the cathode with more positive potential and a localized FeCO3 layer formed beneath the silica mineral. The CaCO3-covered steel initially acted as an anode with a more negative potential but transformed into the cathode at the end of the test. Additionally, shallow and small pits were observed beneath the deposits with the depth in the sequence Al2O3 > SiO2 > CaCO3.