Behavior Of Corrosion Products Research Articles

Tribocorrosion of couplings in seawater environment: An investigation on the positive-negative role of synergy

Tribocorrosion is a recent paradigm of tribology defined as the combination of simultaneous mechanical and chemical wear of couplings. To date, this phenomenon is common in several engineering fields, such as the naval sector where marine equipment, offshore platforms and so on are clear examples. In this regard, the synergy between the mechanical and the chemical effects has a notable effect on the behavior of couplings in seawater environment. Nevertheless, the latter can act also as antagonistic factor. Hence, in this manuscript, an investigation was conducted on a tribosystem composed of an alumina sphere and a stainless-steel AISI 316 L flat, immersed in an artificial seawater solution of 3.8 % NaCl and a pH of 8.2. The analysis, carried out by a reciprocating tribometer equipped with a two/three-electrode potentiostat, was performed for different loads and frequency values, and their correlation with synergistic effects was investigated. The open-circuit potential, friction coefficient, tribocorrosive current and total wear were evaluated for different tribological conditions. It was found that the force and sliding velocity had a significant position in the synergistic response, passing from positive to negative mainly due to the protective action of oxide layer and lubrication behavior of corrosion products formed during the motion. Moreover, the current was modeled via two analytical laws discussed in literature, providing a good agreement with experimental data. Lastly, was provided the oxide thickness evolution formed on the samples surface and its relationship with total wear.

Importance of the autoclave testing parameters on the initial stage of corrosion under CO2-containing geothermal environments

Autoclave corrosion testing has been used for many years; however, few have studied the effect of its shortcomings on the formation of corrosion products and corrosion behaviour. In particular, understanding of these effects under high temperature and high pressure (HTHP) is rare. In this study, we highlighted the important parameters such as heating periods, flow rates and volume-to-surface ratios influencing carbon steel corrosion in the early stages. Especially, characterisation and protection behaviour of corrosion products associated with corrosion behaviour in the heating stage under the geothermal CO2-containing environment were systematically studied via mass loss, in-situ electrochemistry and surface analysis techniques. The roles of pCO2, volume-to-surface ratio and flow rate influence the formation of the corrosion products in the early stage are also evaluated.

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.

Cracking in Reinforced Concrete Cross-Sections Due to Non-Uniformly Distributed Corrosion.

Corrosion affecting reinforced concrete (RC) structures generates safety and economical problems. This paper is focused on the simulation of corrosion-induced fractures in concrete, whereby non-uniform corrosion growth is taken into account. In particular, the volumetric expansion of rust accumulated around reinforcement bars causes cracking of the surrounding concrete. This phenomenon is simulated using the finite element (FE) method. In the analyses, concrete is described as a fracturing material by using a damage-plasticity model, steel is assumed to be elastic-plastic and rust is modeled as an interface between concrete and steel. The behavior of corrosion products is simulated as interface opening. Two-dimensional FE models of RC cross-sections with 2, 4 or 6 reinforcing bars are considered. Crack formation and propagation is examined. Moreover, interactions between cracks and patterns of possible failure are predicted. The most developed and complex crack pattern occurs around the side reinforcing bar. Conclusions concerning the comparison of results for uniform and non-uniform corrosion distribution as well as the prediction of concrete spalling are formulated.

Investigation of the filling-overflow behavior of corrosion products in reinforced mortar

The investigation of the filling-overflow behavior of corrosion products in concrete is important for accurately predicting corrosion-induced concrete cover cracking. This paper utilizes the ethylene diamine tetra acetic acid (EDTA) titration method to quantitatively study the iron content in each zone of corroded reinforced mortar specimens. Based on this, the proportion and distribution of corrosion products are analyzed. Results show that approximately 50% of the corrosion products are transported to the mortar and corrosion products show a transport pattern to the surrounding low-concentration area in mortar. The direction of ion invasion on the mortar specimen does not exhibit a significant impact on the transport of corrosion products, while both the geometric size and quality of the mortar specimen affect the transport of corrosion products. Furthermore, the proposed method employs EDTA titration to quantify the filling and overflow of corrosion products, providing a valuable approach for further experimental research.

A two-stage study of steel corrosion and internal cracking revealed by multimodal tomography

Modeling of corrosion-induced cracking is limited by lacking knowledge on the behavior of corrosion products. In this work, the corrosion and cracking processes were experimentally investigated in 3D at two different stages. The processes were measured at micro-structural scale, applying nondestructive neutron and X-ray computed tomography in two scans at different stages in the corrosion process. A method to evaluate the average volumetric strain of the compressed corrosion layer was proposed and displacements in the concrete matrix were measured. Strain localization revealed cracks not directly visible in the images. Multimodal tomography demonstrated to be an effective method for investigating steel corrosion in reinforced concrete.

An integrated investigation of the crystalline, rheological and physical properties of corrosion products in cementitious materials

This paper discusses the behaviour of the rheological behaviour of corrosion products (produced in the laboratory) in a high alkaline environment to understand hydraulic-induced fracture by corrosion products in reinforced concrete. A mixture of iron powder, sodium chloride, calcium hydroxide, and water was used to produce corrosion products. The development of corrosion products was studied at 2, 4, 6, and 8-week intervals. Imaging techniques, along with rheological characterization methods, were conducted to understand the viscoelastic flow behaviour of corrosion products. The results show that corrosion products exhibited different rheologic properties throughout the corrosion process. Three iron oxide phases (Magnetite, Goethite, and Lepidocrocite) were detected throughout the initiation and propagation stages of corrosion in the laboratory. The corrosion products obtained for each study period behaved as colloidal materials, demonstrating all the characteristics of shear-thinning materials. As a result of chemical and particle disintegration, the viscosity of corrosion products decreased with the applied shear rate. In addition, the experimental data showed that the density and particle size of corrosion products decreased with time. These results can be used to understand the progress of corrosion's damage in reinforced concrete.

Effect of Ni on the oxidation behavior of corrosion products that form on low alloy steel exposed to a thin electrolyte layer environment

The oxidation behavior of corrosion products that form on Ni-containing low alloy steel was investigated by electrochemical polarization curves, scanning electron microscopy, electron probe micro-analyzer, X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. The corrosion products were oxidized to Green Rust containing Cl- (Green Rust(Cl-)) and an amorphous substance, which were produced in an ordinary- and negative-pressure environment, respectively. The enrichment of Ni in the corrosion product could inhibit two oxidation reactions of the corrosion product, especially inhibiting the formation of amorphous substances. In addition, oxygen reduction could be also suppressed via the enrichment of Ni.

Influence of the Transients and Water Chemistry Parameters on Corrosion Product Behavior in the Primary System of Naval Reactor Plants

This technical note describes the influence of the transients and corrective additives on the distribution of loosely bonded forms of solid-phase corrosion products between the equipment surfaces and the primary coolant of a naval reactor plant. It is shown that the concentration of loosely bonded corrosion products increases by tenfold during the transient, and the feeding of corrective additives allows a several-fold reduction in the rate of their resedimentation on the internal surfaces of equipment, and as a consequence, improvement of corrosion product removal efficiency by cleanup filters. The proposed solutions allow removal of up to 70% of loosely bonded corrosion products from the coolant using standard filters.

Deposition behavior of corrosion products in an Iter water-cooling experimental loop

Abstract The deposition behavior of corrosion products was studied in a water-cooling experimental loop designed according to International Thermonuclear Experimental Reactor (ITER) specification. Using non-destructive on-line magnetic thickness method, the deposition thickness of magnetic oxides (Fe3O4) with temperature ranging from 80 °C to 150 °C, was measured in the experimental loop. This experimental loop made of stainless steel. The pH at 25 °C value of the coolant was set 7.0, 8.0, 9.0, 10.0 and 10.5 respectively, using lithium hydroxide (LiOH) as the alkalinity regulator of the coolant. The experimental results show that temperature plays a vital role in determining the deposition thickness, and the temperature near 140 °C yields the maximum deposition thickness. Besides, alkalinity of the coolant, tube curvature and particle size also have some effect on the deposition thickness. These experimental data provide reference for radiation protection design of fusion reactor.

Influence of the dissolved hydrogen concentration on the radioactive contamination of the primary loops of DOEL-4 PWR using the OSCAR code

Corrosion products are generated in the primary circuit during normal operation and are activated in the core. Those activated corrosion products, mainly 58Co and 60Co (coming respectively from the activation of 58Ni and 59Co), are then transported by the primary fluid and deposited on the out-of-flux surfaces (steam generators, primary coolant pipes…). To minimize this radioactive contamination, one needs to understand the behavior of corrosion products by carrying out measurements in PWRs and test loops combined with a reactor contamination assessment code named OSCAR. The aim of this article is to evaluate the influence of the change in the Dissolved Hydrogen (DH) concentration on the contamination of the primary loops of DOEL-4 PWR, a Belgian unit. After the description of the principle of the OSCAR V1.3 code, its use is illustrated with the simulation of DOEL-4. Finally, those calculations are compared to autoclave experiments called DUPLEX with thermodynamic and chemical conditions closed to those observed in PWRs. OSCAR V1.3 calculations show that an increase in the DH concentration results in a decrease in 58Co surface activities. These results are consistent with those from the DUPLEX experiments. Finally, an increase of the DH concentration is then recommended in operating PWRs to reduce the 58Co surface contamination.

CO2 Corrosion of Mild Steel Exposed to CaCO3-Saturated Aqueous Solutions

The behavior of CO2 corrosion of mild steel was studied in a CaCO3 saturated aqueous solution. The bulk water chemistry ([Fe2+], [Ca2+], and pH) was controlled and the mass transfer characteristics inherent to the experimental setup were well defined. A combination of weight loss and electrochemical techniques, as well as surface characterization tools, were used to assess the behavior of corrosion products over long-term experiments. Three corrosion periods were identified based on the analysis of the corrosion rates and Nyquist response values versus exposure time. Residual Fe3C was the early corrosion product; however, FexCayCO3 (x + y = 1) precipitated within its pores over the course of experiments where a favorable local water chemistry was achieved, regardless of the bulk solution. Results show that the presence of Ca2+ did not jeopardize the final protectiveness of corrosion products.

Study of flow-assisted corrosion (FAC) in a API 5L X-70 steel in a brine-H2S–CO2 system using the rotating cylindrical electrode

Corrosion caused by the mixture CO2/H2S in the transport of hydrocarbons is one of the most important research areas in the energy industry due to the severe problems it produces during the wear and tear of the pipes. Based in previous studies, in the present investigation the corrosion of API 5L X-70 steel in media with CO2 and H2S is studied as well as mixtures of both media, by means of a rotating cylindrical electrode due to the need to know the behavior of corrosion products in metals. The corrosion rate is evaluated at different pressures of H2S and CO2 and at 30 and 60 °C using the potentiodynamic polarization resistance measurements. From the results, it is observed that steel at the conditions of 0.8 bar H2S + 0.2 bar CO2 at 30 °C, yielded the lowest corrosion rate. This behavior is attributed to the fact that when H2S predominates it allows the formation of a greater number of protective layers comprised by a mixture of oxides, sulfides, sulfates and carbonates as corrosion products.

WITHDRAWN: A study on the prediction of corrosion product behavior for PWR primary system by using CRUDTRAN

WITHDRAWN: A study on the prediction of corrosion product behavior for PWR primary system by using CRUDTRAN

PWR circuit contamination assessment tool. Use of OSCAR code for engineering studies at EDF

Normal operation of PWR generates corrosion and wear products in the primary circuit which are activated in the core and constitute the major source of the radiation field. In addition, cases of fuel failure and alpha emitter dissemination in the coolant system could represent a significant radiological risk. Radiation field and alpha risks are the main constraints to carry out maintenance and to handle effluents. To minimize these risks and constraints, it is essential to understand the behavior of corrosion products and actinides and to carry out the appropriate measurements in PWR circuits and loop experiments. As a matter of fact, it is more than necessary to develop and use a reactor contamination assessment code in order to take into account the chemical and physical mechanisms in different situations in operating reactors or at design stage. OSCAR code has actually been developed and used for this aim. It is presented in this paper, as well as its use in the engineering studies at EDF. To begin with, the code structure is described, including the physical, chemical and transport phenomena considered for the simulation of the mechanisms regarding PWR contamination. Then, the use of OSCAR is illustrated with two examples from our engineering studies. The first example of OSCAR engineering studies is linked to the behavior of the activated corrosion products. The selected example carefully explores the impact of the restart conditions following a reactor mid-cycle shutdown on circuit contamination. The second example of OSCAR use concerns fission products and disseminated fissile material behavior in the primary coolant. This example is a parametric study of the correlation between the quantity of disseminated fuel and the variation of Iodine 134 in the primary coolant.

A Study on Corrosion Product Behavior Prediction for Domestic PWR Primary System by using CRUDTRAN

Radionuclide deposited on the surface of several internal and external systems in a nuclear power plant is created by the activation of corrosion products from nuclear reactor structural materials and fission products. Especially, the constant contact between water and the surface corrodes the inside where primary system makes coolants and corrosion products mixed. Also, these are circulated along the systems. For comparing models, CRUDTRAN, DISER, MIGA-RT and CPAIR codes are analyzed to predict the quantity of radionuclide and corrosion product of primary reactor that are used at the stage of designing. The corrosion products behavior of domestic PWR primary system was predicted by using CRUDTRAN. This study aims to increase the reliability of corrosion product evaluation model by comparing the actual values and calculated values with the data of a Westing House-type Nuclear Power Plant.

Mitigation of Corrosion on Magnesium Alloy by Predesigned Surface Corrosion.

Rapid corrosion of magnesium alloys is undesirable in structural and biomedical applications and a general way to control corrosion is to form a surface barrier layer isolating the bulk materials from the external environment. Herein, based on the insights gained from the anticorrosion behavior of corrosion products, a special way to mitigate aqueous corrosion is described. The concept is based on pre-corrosion by a hydrothermal treatment of Al-enriched Mg alloys in water. A uniform surface composed of an inner compact layer and top Mg-Al layered double hydroxide (LDH) microsheet is produced on a large area using a one-step process and excellent corrosion resistance is achieved in saline solutions. Moreover, inspired by the super-hydrophobic phenomenon in nature such as the lotus leaves effect, the orientation of the top microsheet layer is tailored by adjusting the hydrothermal temperature, time, and pH to produce a water-repellent surface after modification with fluorinated silane. As a result of the trapped air pockets in the microstructure, the super-hydrophobic surface with the Cassie state shows better corrosion resistance in the immersion tests. The results reveal an economical and environmentally friendly means to control and use the pre-corrosion products on magnesium alloys.

Prediction of cover crack propagation in RC structures caused by corrosion

The paper proposes a model relating the level of reinforcement corrosion (in terms of loss of rebar radius) with the width of corrosion-induced cracks. The model is developed using a simulation of the process of corrosion-induced crack opening by means of finite-element (FE) modelling. Concrete is treated as a linear elastic material, a vertical crack is introduced above a reinforcing bar and expansive behaviour of corrosion products is modelled using a thermal analogy. Corrosion products are divided into those that penetrate (dissipate) into cracks (no crack propagation) and those that cause crack opening. The amount of corrosion products penetrating into cracks at a specified crack width is evaluated using FE modelling and analyses of experimental results. It was found that a corrosion loss of 0·1–0·4 mm dissipated into the cracks when the crack width was 1·0 mm. The influence of geometric parameters such as rebar diameter, spacing and location, and thickness of top and edge concrete covers were investigated. The limits of applicability of the proposed relationships were established using non-linear FE modelling.

Sorption of nickel and cobalt ions onto cobalt and nickel ferrites

The corrosion of the metal parts in the primary circuit of pressurized water reactors leads to the release of colloidal particles (NiFe2O4, CoFe2O4, NiO, Ni…) and ionic species (Co, Ni, Cr…). Particles can interact with ionic species in the primary medium, contributing to their transport and to their deposition onto surfaces outside the neutron flux generating radioactive contamination. Sorption and zetametry experiments at 25°C were performed on the Ni2+/CoFe2O4 and Co2+/NiFe2O4 systems in order to determine the behaviour of corrosion products in the fluid of the primary circuit. Sorption appears as surface complexation starting from pH 6 and is followed by precipitation of hydroxide above pH 7.5. Complexation and solubility constants were obtained from the modelling of sorption curves. The two oxide systems present a very similar sorption behaviour, but some differences, due to their different isoelectric points, could be observed on zetametric measurements.

A model for the evolution of concrete deterioration due to reinforcement corrosion

One of the most crucial factors affecting the service life of reinforced concrete (RC) structures attacked by aggressive ions is reinforcement corrosion. As the steel corrosion progresses, crack propagation in concrete medium endangers the serviceability and the strength of RC structural members. In this study, a nonlinear mathematical model for determining the displacement and stress fields in RC structures subjected to reinforcement corrosion is introduced. For corrosion products, a nonlinear stress–strain relation which has been previously confirmed by experimental data is incorporated in the present analysis. In formulation of the governing equations for steel–rust–concrete composite, the rational behavior of corrosion products and penetration of rust into the microcracks are considered. An analytical approach as well as an innovative meshless method, gradient reproducing kernel particle method (GRKPM), are employed for solving the nonlinear boundary value problem. A reasonably good agreement between the results of the two methods is achieved. The performance of the proposed model is then investigated through various comparisons of predicted values with experimentally observed data, and again good agreement is obtained. Moreover, the effects of the crucial parameters associated with the mechanical behavior of rust and concrete on time to cover cracking and some measures of deterioration are studied for different values of rust penetration into the microcracks.