Deposition Of Corrosion Products Research Articles

Modeling Corrosion Product Deposition Processes in Pipelines of Heat Supply Systems

Modeling Corrosion Product Deposition Processes in Pipelines of Heat Supply Systems

Assessment of nominal and off-nominal parameters of a soluble boron free small modular reactor design

Boric acid is traditionally used for reactivity control in pressurised water reactors. However, it increases the rate at which reactor components corrode. This leads to increased operational radioactive waste produced through neutron-activation of corrosion fragments. During reactor operation, radioactive corrosion product deposits, or so-called crud, accumulate on fuel cladding in regions of high burnup. Boron compounds have been detected in such deposits, and they cause axial-offset anomaly, i.e. deviation in axial power prediction. Accumulation of boron-laden deposits can reduce plant efficiency to about 70 % over time. This work presents the design process and analysis of nominal and off-nominal parameters of a soluble boron-free small modular reactor core. The design, and analyses were carried out using CASMO4e, CMSLINK, and SIMULATE3 codes. In addition, a borated variant of the target boron-free core was designed and used as reference. Equilibrium cycles were achieved for both the reference and the boron-free core. The limiting FΔH during the transition to equilibrium was found to be 1.754 and 1.651 for the reference and boron-free cores. The equilibrium FΔH were found to be 1.624 and 1.57 compared to the design limit of 1.7. The hot zero power MTC for the boron-free core at beginning of cycle was found to be –22.67 pcm/K compared to −3.64 pcm/K for the reference. The removal of boric acid made the MTC coefficients more negative and the FΔH lower compared to the reference. The boron-free core had enough rod-worth for power and isothermal defect counteraction and reactor shut down.

Evolution of the Corrosion Products around MnS Embedded in AISI 304 Stainless Steel in NaCl Solution.

The characterization and evolution of corrosion products deposited on/around MnSs, a typical kind of inclusive particle embedded in AISI 304 stainless steel, was analyzed using a quasi-in-situ method in a 3.5 wt.% NaCl solution. On/around the MnS inclusion, a corrosion product layer with spinel Fe3-xCrxO4 as the main component was formed, with a thickness of several hundred nanometers. Below the layer, there was a cavity layer in which part of the MnS remained, forming secondary pitting along the MnS/matrix boundary. The mechanism of corrosion product deposition and evolution accompanied by MnS dissolution, as well as the characteristics of the corrosion products, are discussed.

Pressurized water reactor fuel corrosion-related unidentified deposit and its related safety issues – I. Corrosion product deposition and heat transfer

CRUD depositions on fuel cladding are the main cause of power shift and localized corrosion in nuclear power plants. This paper is the first of a three-part study concerning the formation mechanism of CRUD depositions and its related heat transfer issues. In this paper, CRUD depositions are obtained under subcooled boiling conditions in 2 × 2 rod array channels via accelerated deposition method to explore corrosion product deposition and its feedback on heat transfer. Imbalance of deposition and erosion at initial stage causes fouling resistance to increase first and then decrease. CRUD growth is proposed as a relatively pure fouling process combining soluble precipitation and particulate aggregation. Through high-resolution characterizations, boiling chimney diameters span from 3 μm to a dozen microns. Principal components are nickel ferrite and nickel elemental with Fe/Ni ratio of 1.9:1. Static contact angle decreases to less than 30°. Effective CRUD thermal conductivity decreases with the increase of heat flux with 1.3866 W/(m × K) on average. The results of this study provide a precise method for understanding corrosion product deposition and its impact on heat transfer to further establish accurate CRUD-related models and predict CRUD-related safety issues.

Laser remelting of high-velocity arc-sprayed Fe-based amorphous coating for improving corrosion resistance in 3.5 % NaCl solution with varying Na2S concentrations

In this study, high-velocity arc-spraying (HVAS) was employed to produce Fe-based amorphous coatings, and subsequent to that, laser remelting (LR) technology was applied on the as-sprayed coatings (ASC) to prepare laser remelted coatings (LRC). The corrosion resistance of both coatings was tested in 3.5 wt% NaCl solutions containing varying Na2S concentrations (0, 20, 50, 100, and 200 ppm) to accurately simulate the corrosion environment of offshore components. The corrosion behavior was investigated using electrochemical workstation, scanning electron microscopy, energy dispersive spectroscopy and X-ray photoelectron spectroscopy. The experimental results revealed that LR resulted in the elimination of defects in Fe-based amorphous coatings, a substantial reduction in porosity, the disappearance of the laminar structure, and the achievement of a homogeneous composition. The corrosion tendency of ASC and LRC both exhibited a pattern of initially decreasing, then increasing and finally decreasing with increasing sulfide concentration. This was attributed to the deposition of corrosion products on the surface and the dissolution of the corrosion products. When the sulfide concentration exceeded 50 ppm, the corrosion current density of both coatings slowly and was lower than that at 20 ppm, indicating that both coatings possessed strong corrosion resistance at higher sulfide concentrations. Highly polarized anions in solution (e.g. HS−, S2−) occupied vacancies in the passivation film, destabilizing the coating's passivation film and consequently diminishing its corrosion resistance. From the electrochemical analysis, it was evident that LRC exhibited greater corrosion resistance than ASC at all sulfide-containing solution concentrations, which was attributed to its smoother surface, denser structure and more stable passivation film.

A comparative study on the inhibition of microalgae attachment performance between Cu-based alloy laser cladding layer containing submicron Cr-rich precipitated phases and copper in simulated seawater

Copper alloys are prominent materials in ships and marine engineering structures due to their effective antifouling performance. However, the deposition of insoluble corrosion products dramatically deteriorates their antifouling performance during long-term immersion. To solve this conundrum, we have developed a novel Cu-based alloy cladding layer containing submicron Cr-rich precipitates, which aims to promote the corrosion products flaking through the effect of precipitates, thus effectively inhibiting microalgae attachment. After being immersed for 180 days, the coverage rates of microalgae on the cladding layer were below 2%, while those on the copper exceeded 40%. The remarkable inhibition of microalgae attachment achieved by the cladding layer is mainly due to the Cr-rich precipitates embedded in the unique and loose multi-layer structure corrosion product as Cr2O3-rich particles, which promotes the corrosion product cracking and flaking. Thereby, the cladding layer kills attached microalgae by increasing their reactive oxygen species (ROS) levels.

CRUD deposition induced multi-physics effects analysis in PWR

In PWR, the deposition of corrosion products from the steam generator leads to the formation of Chalk River Unidentified Deposits (CRUD) on the surface of fuel rods. CRUD deposition can cause issues such as CRUD induced localized corrosion, axial power anomaly and deterioration of cladding heat transfer. A new multi-physics program named CIFF (CRUD Induced eFFects analysis) is developed to analyze the effects caused by CRUD deposits. CIFF is a 1.5D model and can be used to simulate the variations in surface temperature, cladding corrosion and fuel deformation caused by CRUD deposition. A three-node CRUD deposition model is developed based on mass transfer theory and chemical equilibrium. The calculations of heat transfer, mechanical deformation, oxide layer growth, CRUD deposition and fission gas behavior are fully coupled based on finite element analysis and numerical solution technology. Axisymmetric element is used to solve the deformation of fuel rod under thermal expansion, gas pressure, creep and radiation swelling. The performance of CIFF is validated through IFA-513, ANO-2, Oconee and PCCL cases. The DBN-1 case is used to explore the influence of CRUD. The results indicate that CRUD deposition and CRUD induced local corrosion deteriorate the heat transfer of cladding, resulting in a three-stage increase of cladding temperature and accelerated growth of the oxide layer. CRUD deposition also leads to a relative increase in the gap pressure exceeding the coolant pressure by 8.4 %, a relative increase in the fuel rod strain by 10 % and a relative decrease in the gap size by 11 %, which indirectly leads a premature pellet-cladding mechanical interaction by 90 days.

Process Optimization Using Box‐Behnken Design for the Solvent Extraction and Separation of Iron, Cobalt, and Nickel from Simulated Crud Solution

AbstractThe corrosion product deposit (crud) found on the surface of the fuel rod of the pressurized water reactors (PWRs) chiefly made up of nickel ferrite. Fe, Co, Ni and Cr are the major elements exist in PWR crud. Ascribable to the simplicity in execution, handling, and option for recyclability, solvent extraction technique has been broadly used in nuclear energy sector. In the present investigation, the recovery of iron, cobalt, and nickel has been studied from simulated crud solution in nitrate medium using a novel hydrophobic menthol‐decanoic acid‐based deep eutectic solvent. Process parameters such as pH, DES concentration and shaking time were considered as input variables, and concentration of Fe, Co, and Ni as response variables for the design of experiments. Response surface methodology via Box‐Behnken design using polynomial quadratic model was selected for optimization of solvent extraction experiments. A total of 17 runs were conducted and the results were used for optimization purpose. Complete separation of Co/Fe and Co/Ni is achievable under various extraction conditions. As per the BBD analysis, the optimization conditions obtained were pH=1.9, [DES]=2.99 mol/L and shaking duration=18.27 min. Under these conditions,the amount of Fe, Co and Ni extracted were found as 32.29 g/L, 0.2111 g/L, and 19.83 g/L, respectively.

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.

Corrosion mechanisms of Al‐alloyed hot‐dipped zinc coatings in wet supercritical carbon dioxide

AbstractCommercial hot‐dip galvanized zinc (Zn‐0.2% Al), galfan (Zn‐5% Al), and galvalume (Zn‐55% Al) coatings were exposed to wet scCO2, followed by an assessment of microstructural changes in the coating structure. Zinc and galfan coatings showed similar surface activity with abundant zinc dissolution and uniform corrosion product deposition. The Al‐rich phases of the galfan coating were intact in the studied atmosphere and eventually became embedded within the deposits. The zinc dissolution ended for zinc and galfan coatings when the free metal surface was blocked from the surrounding medium by a uniform corrosion product layer. Galvalume showed scarce reactivity: dissolution of zinc in the Zn‐rich interdendritic areas proceeded slowly compared to zinc and galfan, and the Al‐rich dendrites (with nm‐scale Zn inclusions) remained intact. The ion beam milling technique combined with modern nm‐resolution energy‐dispersive spectroscopy analysis enabled previously unseen visualization of the discussed corrosion processes.

The coupling mechanism of shrinkage defects and graphite on the corrosion resistance of ductile iron

This study investigated the coupling mechanism of shrinkage defects and graphite on the corrosion resistance of ductile iron by electrochemical measurements, quasi-in-situ immersion tests and numerical simulations. The detrimental impact of shrinkage defects was confirmed by elevated corrosion current density and the formation of a porous corrosion product layer. Multiple-galvanic coupling effect among the matrix, graphite, and shrinkage defects serves as corrosion triggers, which is verified by scanning Kelvin probe force microscopy (SKPFM) and numerical simulations. Additionally, quasi-in-situ observations corroborate the deposition of corrosion products and Cl enrichment at defect bottoms, expediting occluded cell formation and corrosion propagation.

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.

(Invited) Contribution of Oxygen Reduction to Mg Corrosion: Computational Modelling

The magnesium corrosion mechanisms are still a matter of discussions. Independent from that there is agreement that the cathodic behaviour is based on the superposition of water and oxygen reduction reactions [1]. Accessing the amount of cathodic reaction contributions to the entire corrosion current density via experiment is challenging [2,3]. In a recent work of Wang et al. [4] a combined experimental and computational approach was utilized to explore the superposition of cathodic reactions during Mg corrosion in aqueous electrolytes for different iron impurity situations. The study shows significant variation of percentual contribution of oxygen reduction to the cathodic current for the studied purity levels.In this work a computational modelling approach is presented accordingly. It is based on the numerical model developed by Höche [5] and enables virtual local electrochemical testing and computational assessment of (electro-)chemical system and transport descriptors. Respective simulation results show, how corrosion and testing system parameters change the measured oxygen approach curves. Subsequently a multi-parameter calibration enabled the quantification of oxygen reduction reaction to the entire corrosion process. The reproduction of experimental results and strategies for model improvement are discussed. REFERENCES: [1] Höche, D., Blawert, C., Lamaka, S. V., Scharnagl, N., Mendis, C., & Zheludkevich, M. L., The effect of iron re-deposition on the corrosion of impurity-containing magnesium. Physical Chemistry Chemical Physics, 18-2 (2016), 1279-1291.[2] Yasakau, K. A., Höche, D., Lamaka, S. L., Ferreira, M. G., & Zheludkevich, M. L., Kelvin microprobe analytics on iron-enriched corroded magnesium surface. Corrosion, 73-55 (2017), 583-595.[3] E.L. Silva, S.V. Lamaka, D. Mei, M.L. Zheludkevich, The Reduction of Dissolved Oxygen During Magnesium Corrosion, ChemistryOpen, 7 (2018) 664-668.[4] C. Wang, W. Xu, D. Höche, M.L. Zheludkevich, S.V. Lamaka, Exploring the contribution of oxygen reduction reaction to Mg corrosion by modeling assisted local analysis, Journal of Magnesium and Alloys, 11 (2023) 100-109.[5] Höche D., Simulation of corrosion product deposit layer growth on bare magnesium galvanically coupled to aluminum. Journal of the electrochemical society, 162-1 (2014), C1. ACKNOWLEDGEMENTS: C. Wang, W. Xu, thank China Scholarship Council for the funding, grants no. 201806310128 and 201908510177

Corrosion products deposition and its effects on conjugate heat transfer for helical cruciform fuel assembly

The corrosion products in the primary loop of the nuclear reactor can be deposited on the surface of the fuel rod, forming a deposition layer called CRUD layer, introducing the heat transfer resistance. The CRUD layer will result in an increase in the temperature of the cladding and accelerating the corrosion of the cladding. In this work, the corrosion product deposition and thermal resistance models of the deposition layer were established. The deposition behavior of corrosion products on the surface of a novel Helical-Cruciform Fuel (HCF) assembly and its influence on fluid-solid conjugate heat transfer were studied by coupling the deposition models with the flow and heat transfer models for fuel rods and coolant. The results show that the deposition rate of particles is affected by the wall shear force; the deposition rate of impurity ions is affected by the wall shear force and the temperature of the coolant in the viscous layer. The erosion rate of the deposited layer is related to the wall shear force and the sum of the particle and ion deposition rates. The thickness of CRUD layer on the surface of HCF assembly increases with the decrease of coolant flow rate and the increase of fuel power. Furthermore, the CRUD layer thickness varies in a period of 90° along the circumference of the fuel and reaches a peak at the root of the fuel ribs.

Time-Dependent Corrosion Behavior of Aluminum Using Advanced Electrochemical and Characterization Techniques

The time-dependent corrosion behavior of pure aluminum (Al) in a chloride-containing environment was investigated using various electrochemical and characterization techniques for up to 336 h. Transmission electron microscopic and secondary ion mass spectroscopic analysis revealed the continuous dissolution of the surface film over the immersion time. In the meantime, the increasing passive oxide thickness resulted in the surface film resistance enhancement over the immersion time, as indicated by the electrochemical impedance spectroscopic analysis. The electrochemical noise measurements showed an increase in the corrosion kinetics with immersion time until 60 h because of the accelerated localized corrosion in the early stage of immersion. However, an inhibition in corrosion kinetics occurred after longer immersion times due to corrosion product deposition inside the pit.

Non-Linear Evaluation of Coatings Performance: Evaluation of Polyester/Melamine Coil Coating Hydrolysis in NSS Test

Coating is one of the most common and effective ways to protect metallic elements from corrosion. The evaluation of a coating’s performance is related to its quality and durability. Neutral salt spray (NSS) is a common accelerated test used for coatings. Commercial polyester/melamine coil coatings applied on aluminum specimens were exposed to NSS and recorded at 0, 200,400, 600 and 1000 h of exposure. Coating performance changed with time of exposure. The main degradation process is due to the hydrolysis of the coating. A decrease in corrosion rate was observed due to the sealing of the coating, probably due to the deposition of corrosion products, salts, or a mixture of both. EN (electrochemical noise) was a more sensitive technique comapred to EIS (electrochemical impedance spectroscopy). The first changes in the coating were detected after 400 h of exposure by EIS and after 200 h by EN. EIS and EN showed equivalent results in studying the corrosion evolution of coated aluminum. Non-linear analysis using recursive plots (RP) showed the chaotic dynamics occurring with time and the interaction of micro electrochemical cells that formed on the metallic surface; it offered information similar tothe traditional EIS technique and adds complementary data to understand the corrosion phenomenon.

An FFT-based framework for predicting corrosion-driven damage in fractal porous media

Understanding fracture in cementitious materials caused by the deposition and growth of corrosion products requires scale-bridging approaches due to the large length-scale difference between the micro-pores, where deposition occurs, and the structure, where deterioration manifests. Cementitious materials bear a highly heterogeneous micro-structure owing to the fractal nature of micro-pores. Simultaneously, a corrosion-driven fracture is a multi-physics problem involving ionic diffusion, chemical reactions, and stress development. This multi-scale and multi-physical character makes scale-bridging studies computationally costly, often leading to the use of simplified fractal porous media, which has important consequences for the quantitative interpretation of the results. Recent advances in homogenization approaches using Fast-Fourier-Transform (FFT) based methods have raised interest due to their ease of implementation and low computational cost. This paper presents an FFT-based framework for solving corrosion-driven fractures within fractal porous media. We demonstrate the effectiveness of the Fourier-based spectral method in resolving the multiple corrosion-driven mechanisms such as ionic diffusion, stress development, and damage within a fractal porous microstructure. Based on the presented methodology, we analyse the impact of simplifying fractal porous media with simple Euclidean geometry on corrosion-driven fracture. Our results demonstrate the importance of preserving both the porosity and fractal nature of pores for precise and reliable modelling of corrosion-driven failure mechanisms.

In vitro corrosion resistance and dual antibacterial ability of curcumin loaded composite coatings on AZ31 alloy: Effect of amorphous calcium carbonate

Rapid corrosion and bacterial infection are obstacles to put into use biodegradable magnesium (Mg) alloy as biomedical materials. In this research, an amorphous calcium carbonate (ACC)@curcumin (Cur) loaded poly-methyltrimethoxysilane (PMTMS) coating prepared by self-assembly method on micro-arc oxidation (MAO) coated Mg alloy has been proposed. Scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy are adopted to analyze the morphology and composition of the obtained coatings. The corrosion behaviour of the coatings is estimated by hydrogen evolution and electrochemical tests. The spread plate method without or with 808 nm near-infrared irradiation is applied to evaluate the antimicrobial and photothermal antimicrobial ability of the coatings. Cytotoxicity of the samples is tested by 3-(4,5)-dimethylthiahiazo(-z-y1)-2,5-di- phenytetrazoliumromide (MTT) and live/dead assay culturing with MC3T3-E1 cells. Results show that the MAO/ACC@Cur-PMTMS coating exhibited favourable corrosion resistance, dual antibacterial ability, and good biocompatibility. Cur was employed as an antibacterial agent and photosensitizer for photothermal therapy. The core of ACC significantly improved the loading of Cur and the deposition of hydroxyapatite corrosion products during degradation, which greatly promoted the long-term corrosion resistance and antibacterial activity of Mg alloys as biomedical materials.

Water Chemistry Impact on Activated Corrosion Products: An Assessment on Tokamak Reactors

Activated Corrosion Product (ACP) formation and deposition pose a critical safety issue for nuclear fusion reactors. The working fluid transports the ACPs towards regions accessible by worker personnel, i.e., the steam generator. The code OSCAR-Fusion has been developed by the CEA (France) to evaluate the ACP generation and transport in closed water-cooled loops for fusion application. This work preliminary assesses the impact of water chemistry on the transport, precipitation, and deposition of corrosion products for the EU-DEMO divertor Plasma Facing Unit Primary Heat Transfer System. Sensitivity analyses and uncertainty quantification are needed due to the multi-physics phenomena involved in ACP formation and transport. The OSCAR-Fusion/RAVEN code coupling developed by the Sapienza University of Rome and ENEA are used. This work presents the perturbation results of different parameters chosen for a closed water-cooled loop considering a continuous scenario of 1888 days. The aim of this work is to preliminarily assess the variation of build-up of ACPs, perturbing the alkalizing agent concentration into the coolant, and the corrosion and release rates of different materials. The assessment of ACP formation deposition and transport is fundamental for source term identification, reduction of radiation exposure assessment, maintenance plan definition, design optimization, and waste management.

Study on the deposition migration and heat transfer characteristics in the reactor core based on OpenFOAM

Corrosion deposition in heat exchangers may lead to a reduction in heat transfer efficiency, and even can affect equipment operational safety. Traditional CFD deposition heat transfer analysis methods are limited by model size, making it difficult to obtain global, long-term deposition heat transfer characteristics for complex heat exchange equipment. In this paper, a corrosion product deposition prediction and heat transfer model based on sub-channel analysis is proposed. By integrating it into the nuclear reactor core thermal–hydraulic characteristics analysis code CorTAF, which is developed on the OpenFOAM platform, the corrosion deposition and heat transfer calculation for the entire reactor is achieved. A numerical simulation of the deposition and heat transfer of the AP1000 reactor core during a 300-day operation is conducted. The calculation results clearly show the distribution of corrosion products in the reactor core and the temperature changes of the fuel cladding with the deposition days: the maximum deposition thickness on the core cladding surface is 38.3 μm, and the highest temperature increase is 11.0 K. The deposition and cladding temperature rise distribution is not linear with operation time but is closely related to the core power distribution. The modeling method successfully obtains the corrosion deposition and heat transfer characteristics of the entire reactor core, and has potential implications for the prediction of corrosion deposition distribution and thermal effect calculations in other large-scale heat exchange equipment.