Steel Corrosion Products Research Articles

Multispectral Imaging and Spectral Unmixing for Characterization of Relative Phase Composition of Steel Corrosion Products

Multispectral Imaging and Spectral Unmixing for Characterization of Relative Phase Composition of Steel Corrosion Products

Study on microstructure and mechanical properties of steel corrosion products in marine environment

The microstructure and mechanical properties of steel corrosion products in marine environment are key parameters for developing the concrete corrosion-induced model. In this study, steel corrosion products from steel plates, concrete specimens with 10 mm and 20 mm covers, and cracked beams in Zhejiang province were sampled and analyzed. Initially, the microstructure of the steel corrosion products were determined by X-ray diffractometry (XRD), thermogravimetric analysis (TG), scanning electron microscopy (SEM), and energy-dispersive spectrometry (EDS). Subsequently, the mechanical properties of steel corrosion products including nanoindentation elastic modulus, hardness and instantaneous elastic modulus were measured by nanoindentation and consolidation experiments. This study holds potential for establishing the concrete corrosion-induced model and assessment of the concrete structure durability in marine environment.

Bioinduced corrosion of carbon and alloyed steel by thermophilic microorganisms in the presence of uranyl ions under anaerobic conditions

Intensification of corrosion in short-term experiments on carbon (СS) and stainless (SS) steel as materials for underground radioactive waste disposal by thermophilic microbial communities isolated from neutral (Tuva region) and alkaline thermal radionuclide-enriched environments (Tau Tona mine) in the presence of uranium under anaerobic conditions was studied. The corrosion rate of carbon and stainless steel in the presence of the Tau Tona culture increased up to 14 and 3.7 times, respectively. The increase correlated with the predominance of metal-reducing bacteria in the culture. The culture from Tuva, dominated by fermentative bacteria, increased the corrosion rate 6 to 4 times, depending on the type of steel and organic substrate. The main mechanism of microbial corrosion of both types of steel was the dissolution of passivating corrosion products, mainly magnetite, due to their reduction by iron-reducing bacteria or chelation by metabolic products of fermenting bacteria. Surface corrosion was observed on carbon steel and pitting on stainless steel. In the presence of uranyl ions, the corrosion rate of both types of steel increased up to 19 `. Uranyl ions can be reduced to UO2 by microorganisms and will not further affect steel oxidation, furthermore, accumulation of reduced forms of uranium in corrosion products may passivate steel corrosion. It was found that in the presence of organic substances in the environment it can intensify chemical corrosion processes of both types of steel due to the complexation of steel corrosion products, preventing the formation of a passivating corrosion layer. Thus, in the presence of acetate, the corrosion rate of black and stainless steel was 12–36 % higher, in the presence of trehalose it increased the corrosion rate by 1–24 %.

Study on the corrosion and damage behaviours of P110 tubing of deep shale gas wells

This study conducts weight loss corrosion experiments by a high-temperature autoclave to investigate the corrosion behaviours and the damage rules of mechanical properties of P110 tubing under coupling working conditions of multiple factors (temperature 50–155 °C, CO2 content 1%–2%, Cl− content 10,000–20,000 mg/L). It analyses the characteristics of corrosion products of P110 steel using X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy (EDS). In addition, the 3D morphology and size of local corrosion pits are measured microscopically. The mechanical properties’ damage behaviours at different tubing positions are analysed by constant-load tensile stress corrosion tests. The results showed that the average corrosion rate of the tubing reaches the maximum value of 1.627 mm/a at the middle section of the shale gas well. With an increase in temperature and CO2 partial pressure, the depth of the local corrosion pits on the tubing rises from 3.8 to 25.0 μm. The yield strength and tensile strength of the tubing at the bottom-hole section reduced by less than 8%, and the coupling damage effect of stress and corrosive mediums is serious. The tubing shows a sensitivity to stress corrosion cracking at the bottom-hole section. It was recommended that corrosion inhibitors should be cyclically added to inhibit CO2 corrosion to control the corrosion rate of the tubing within the range of medium-degree corrosion, thus ensuring that the strength reduction of P110 tubing under the corrosion working conditions containing CO2 and sulphate-reducing bacteria coupled with tensile stress is within the controllable range of safety factor.

Numerical modeling of non-uniform corrosion of concrete reinforcement considering calcium leaching and chloride diffusion coupling effect

A novel numerical model is proposed for characterizing the nonuniform corrosion of steel bars. The proposed model corrects the anodic Tafel slope through the concentration of chloride and accounts for the adsorption-binding impact of chloride. The viability of the presented model is confirmed with regard to chloride diffusion and the distribution of steel corrosion products. The rebar-concrete interface's non-uniform distribution of oxygen and chloride concentrations along the circumferential direction influences the corrosion current density. Calcium leaching influences the migration of oxygen and chloride, and speeds up the electrochemical corrosion of the rebar.

Humic acid as eco‐friendly corrosion inhibitor for EH40 ship plate steel

In this study, a new type of green corrosion inhibitor, namely, sodium humate (SH), was extracted from humus soil, which is a natural humus plant, by dissolution‐neutralization, and then used for corrosion inhibition of low carbon steel in seawater. The corrosion inhibition performance of SH on low carbon steel EH40 in seawater was tested by weight loss method and electrochemical technology. The surface and corrosion products of low carbon steel were observed and analyzed by scanning electron microscope (SEM), atomic force microscope (AFM), contact angle and X‐ray photoelectron spectroscopy (XPS). The results show that SH is a mixed corrosion inhibitor, and the optimum concentration is 2 g L−1. At this concentration, the inhibition rate can reach 93.6%. It mainly affects the semi‐reaction of cathodic corrosion. By forming a corrosion protection layer with uniform adsorption on the surface of EH40 steel, EH40 steel becomes more resistant to seawater corrosion.

Effect of Doping Trace Rare Earth Elements on Corrosion Behavior of EH36 Offshore Platform Steel

EH36 offshore platform steel, La (0.0031%) steel, Ce (0.0027%) steel, and Pr (0.0001%) steel were selected as the research objects. The corrosion of four groups of steel was simulated by immersion experiments. In the presence of Cl− the effect of rare earth elements (La, Ce, Pr) on corrosion was investigated by the weight loss method. The morphology of the corrosion products and the apparent morphology after the removal of the corrosion products were observed by scanning electron microscopy (SEM); the main components of four steel corrosion products were analyzed by X-ray diffraction (XRD). The electrochemical behavior and the influence of temperature and Cl− concentration on the corrosion of the four kinds of steel were analyzed by an electrochemical polarization curve and Nyquist diagram. The results showed that the addition of trace rare earth elements, La, Ce, and Pr, to EH36 offshore platform steel can reduce the corrosion rate and the corrosion current density (Icorr), and increase the charge transfer resistance during the corrosion process. The Icorr of La steel, Ce steel, and Pr steel is 6.59 × 10−5 A·cm−2, 7.57 × 10−5 A·cm−2, and 9.53 × 10−5 A·cm−2, respectively, which is lower than that of EH36 steel (Icorr = 1.82 × 10−4 A·cm−2). The influence of Cl− concentration and temperature on the four steels showed the same trend; that is, with the increase in Cl− concentration, the corrosion rate first rises and then slows down, and with the increase in temperature, the corrosion rate gradually accelerates. Rare earth elements promote the production of more α-FeOOH in the rust layer, and the compactness of this product plays a certain role in protecting the steel matrix. The addition of trace rare earth elements, La, Ce, and Pr (less than 0.004%), improves the corrosion resistance of EH36 steel.

Corrosion behavior of steel exposed to "zero" pollution atmosphere environment for 20 years

In this study, the corrosion behavior of Q235 carbon steel, 09CuPTiRE weathering steel and X60 pipeline steel after 20 years exposure in "zero" pollution atmosphere environment was investigated by corrosion rate analysis, macroscopic observation, scanning electron microscopy, X-ray diffraction, white light interferometers and electrochemical analysis were conducted to analyze. The results showed that the corrosion rate of the three kinds of steels increases first and then decreases with time, and the results indicated that the empirical formula D=Atn was suitable for corrosion kinetics of three materials, and the three kinds of steels all form a relatively dense rust layer, which can effectively protect the metal matrix, inhibit the corrosion process and reduce the rate of corrosion. Under the same exposure time and the same corrosion conditions, the corrosion degree of the three materials is: X60 pipeline steel > Q235 Carbon steel >09CuPTiRE Weathering steel, three kinds of steel corrosion products are the same, only α-FeOOH and γ-FeOOH exist in the rust layer, and the relative content of α-FeOOH is more than γ-FeOOH of each steel in both skyward side and fieldward sides. X60 Pipeline steel has the worst corrosion resistance, and 09CuPTiRE weathering steel has the best corrosion resistance, so 09CuPTiRE weathering steel has better adaptability to this environment.

Effect of post-weld heat treatment on corrosion resistance of X90 pipeline steel joints

Abstract In order to improve the corrosion resistance of welded joints, X90 pipeline steel joints were subjected to post-weld heat treatment at 610 °C, 640 °C, and 670 °C (holding time was 1 h). Through electrochemical corrosion and full immersion corrosion experiments, the corrosion resistance of welded joints under various conditions was tested, and the surface morphology and corrosion products of the corroded samples were analyzed by scanning electron microscopy and X-ray diffraction analysis. The experimental results show that the corrosion products of X90 pipeline steel welded joints in simulated soil solution mainly include Fe(OH)3, γ-FeOOH, α-Fe2O3, γ-Fe2O3, and a small amount of Fe3O4, FeCl3 and Fe. After heat treatment at 610 °C, the corrosion current density of the parent metal, heat-affected zone, and weld metal of the joint changes from 1.081, 2.889, 2.079 (×10−5 A cm−2) to 0.977, 2.211, 1.810 (×10−5 A cm−2), respectively, the corrosion resistance is improved.

Characteristics of corrosion products of steel bars in modified magnesium oxysulfide cement containing chloride salts

The effects of chlorides on the corrosion of steel bars within a matrix comprising modified magnesium oxysulfide (MMOS) cementitious materials was investigated. The phase composition, morphology and distribution of steel corrosion products (SCPs) were studied. There was basically no corrosion of the steel bars in the MMOS cement without chlorides. A high chloride content and a high water/cement (w/c) ratio in the MMOS matrix had adverse effects on the steel bar corrosion. The primary SCPs in the MMOS mixes were iron oxyhydroxides (FeOOH) and ferric oxide (Fe2O3), while ferrous oxide (FeO) was only observed at low w/c ratios, indicating a lower degree of oxidation. The presence of di-iron nonacarbonyl (Fe2(CO)9) at high w/c ratios suggested a higher degree of oxidation. At lower w/c ratios, rust products readily diffused. Conversely, at higher w/c ratios, these products accumulated close to the steel bars, resulting in a compact structure.

Study on scale formation and corrosion behavior of heat exchanger steel 20 at different temperatures

This study investigates the scaling and corrosion behavior of steel 20 of cooling water in two locations: oil depot working area and living quarters. Furthermore, it explores the effect of temperature on scaling rate and corrosion rate. Through static scaling test and dynamic scaling prediction, the scaling effect of water quality is analyzed. The results show that the scaling degree of two water quality conditions is different with the change of temperature. The water scaling initiates at 60 °C in the living quarters, while a slight amount of scaling occurs when the temperature reaches 75 °C at working area. Through the utilization of open circuit potential, polarization curve analysis, scanning electron microscope (SEM) imaging and X-ray diffraction, the corrosion potential, corrosion rate, macroscopic and microscopic corrosion samples, as well as corrosion products of steel 20 were comprehensively examined. It was found that, in the temperature range of 30 −50 °C, the corrosion rate of steel 20 in the working area showed a linear trend with water temperature, while the corrosion rate in the living quarters exhibited an exponential function trend with temperature. Considering the combined impact of scaling and corrosion on heat exchanger performance, if the operating conditions can exceed 40 °C, the water quality within the working area poses minimal risks and operational pressure to the heat exchanger. Therefore, it is more suitable as a cooling water source compared to that in living quarters.

Effect of B. subtilis in simulated acid red soil on the corrosion behavior of X80 pipeline steel

The eastern section of China's West-east gas transmission project is laid in acidic red soil. NRB are widespread in soils and play an important role in metal corrosion. In this article, the corrosion failure behavior and mechanism of X80 pipeline steel under the action of NRB in simulated acidic soil were studied. It was found that the biofilm of B. subtilis had significant inhibitory on the overall corrosion of X80 steel. Electrochemical results prove that the corrosion rate of the sterile group after 14 days of immersion was about 4.5 times that of the bacterial group. However, the biofilm promotes the formation of local corrosion pits. Confocal laser scanning microscopy images indicate that that the corrosion pit depth of the bacterial group (46.1 μm) was three times that of the bacterial-free group (15.7 μm) after 14 days. The pH of the acidic environment was slightly improved by B. subtilis. XPS results proved that B. subtilis complicates the corrosion products of X80 steel through its nitrate reduction ability and metabolism.

Influence of Cr(III) on the formation and transformation of corrosion products of steel in marine environments

A fundamental approach is used to better understand the influence of Cr on the resistance of low alloy steel to marine corrosion. It focuses on the formation and transformation of corrosion products of steel in seawater-like electrolytes. Fe(OH)2 precipitates are then prepared by mixing a solution of NaCl, Na2SO4·10H2O, FeCl2·4H2O or FeCl2·4H2O + CrCl3·6H2O (so that Cr = 8% and Fe = 92%), with a solution of NaOH. The initial concentration ratio of reactants, Q=frac{2[{{{rm{Fe}}}}^{2+}]+3[{{{rm{Cr}}}}^{3+}]}{[{{{rm{OH}}}}^{-}]}, is set at Q = 0.88, 1, and 1.136. In a first approach, the obtained aqueous suspension is stirred, at a controlled temperature of 25 ± 0.5 °C, to be oxidized by air. The resulting oxidation product is characterized by XRD and Raman spectroscopy. In a second approach, the Fe(OH)2 precipitates are aged one week in suspension in anoxic conditions, filtered, mixed as a wet paste with glycerol and set as a thin compact layer on the sample holder of a X-ray diffraction system. The oxidation process of Fe(OH)2 is then monitored in situ during the acquisition of the X-ray diffractogram. The obtained results demonstrate that Cr(III) hinders the formation of green rust compounds, hence hindering the formation of γ-FeOOH, i.e., the main oxidation product of green rust compounds. The other oxidation pathways of Fe(OH)2, which lead to Fe3O4 or α-FeOOH, are thus favored. Nevertheless, Cr(III) favors mainly the solid state transformation pathway of Fe(OH)2, thus promoting α-FeOOH via the formation of poorly ordered Fe(III) oxyhydroxides, namely feroxyhyte and ferrihydrite.

Влияние сорбции на выход иода-129 из ближней зоны ПГЗРО

In terms of potential long-term radiation hazard, 129I is seen as a most problematic radionuclide, which is explained by its high mobility and long half-life. The paper explores its forms that may occur in VHLW from SNF reprocessing. It also overviews the studies focused on 129I sorption by engineered barrier materials considered typical for DGR sited in crystalline rocks, namely, bentonite and steel containers for vitrified high-level waste. The paper shows that when considered, the realistic coefficients for the interphase 129I distribution on bentonite and carbon steel corrosion products have little effect on its release beyond the DGR’s near field However, 129I release into the DGR’s near field is expected to be retarded in a quite considerable way if the empty space inside the insulating containers is filled with selective sorbents.

Corrosion failure analysis of engineering structural steels in tropical marine atmospheres: A comparative study of ordinary and new weathering steels

Reliable applications for weathering steels face challenges in harsh tropical marine atmospheric environments. The development of new weather steel suitable for tropical marine atmospheric environments is of great significance. In the paper, the corrosion failure behavior of ordinary and newly designed weathering steels exposed to tropical marine environments for two years was studied by employing various analytical methods. The results indicate that the extensive formation of akaganeite and lepidocrocite occurs deep inside the abnormally thick corrosion products of ordinary weathering steel with the accumulation of Cl−, which is laborious to be affected by the rinsing effect of rainfall. Based on the study of the composition, phase, and structure of abnormally thick corrosion products, a chain evolution mechanism of corrosion failure is proposed. By optimizing the content of Cu, Mo, and Ni, the newly designed weathering steel can effectively suppress the chain failure process and increase the corrosion resistance by approximately doubling. On the whole, the newly designed weathering steel can be well applied to tropical marine atmospheric environments.

Correlating X-ray computed tomography observations with respirometric measurement of aluminium alloy 6063 corrosion under FeCl3 droplets

Corrosion of aluminium alloy 6063-T6 with exposure to simulated steel corrosion products using ferric chloride droplets was investigated. Focus of these experiments was to understand the role of oxygen in the redox process; therefore, samples were exposed to standard atmospheric conditions as well as to oxygen-derived conditions. Respirometric measurements indicate that the hydrogen evolution reaction (HER) is the dominant cathodic reaction. Especially in the initial stages when the corrosion rates are the highest, the HER occurs almost exclusively. At the later stages the oxygen reduction reaction (ORR) barely takes over as the main cathodic reaction. The dissolved volumes and maximum corrosion depths determined with X-ray Computed Tomography (XCT) were more significant for those samples deprived of oxygen. The composition of iron-rich deposits formed consisted of magnetite and maghemite, supporting exposure conditions where reactions were deprived of oxygen.

Evolution of corrosion degradation in galvanised steel bolts exposed to a tropical marine environment

The time-dependent degradation of galvanised steel bolts subjected to marine atmospheric exposure for a maximum period of 2 years in the Wenchang marine environment of Hainan province, South China, was investigated. The results showed that the zinc coating used as a protective surface finish deteriorated quickly due to the harsh environmental conditions. The deterioration of the zinc coating resulted in premature corrosion of the underlying steel substrate as early as 6 months. The main Zn corrosion products found at the initial exposure time were simonkollite (Zn5(OH)8Cl2·H2O), hydrozincite (Zn5(OH)6(CO3)2), and zincite (ZnO). At subsequent exposure times, major steel corrosion products such as lepidocrocite (γ-FeOOH), akaganeite (β-FeOOH), goethite (α-FeOOH), magnetite (Fe3O4), and maghemite (γ-Fe2O3) were detected. Fe3O4/γ-Fe2O3 was consistently found in the rust formed at both the exposed and crevice thread regions between 6 and 24 months of exposure. Based on the geometry of the bolt fastener, the corrosion rate and phase composition distribution varied between the two regions. Differences in oxygen exposure levels, corrosion kinetics, and electrochemical stability of the corrosion products were primary factors in these distinctive corrosion behaviours.

Characteristic identification of steel corrosion products based on terahertz transmission spectroscopy

Corrosion of steel materials (such as rebars and steel plates) usually occurs under coating materials. It is, with the existing non-destructive testing (NDT) technologies, difficult to accurately determine the corrosion of steel materials. The terahertz (THz) electromagnetic waves can penetrate the non-polar materials, and theoretically experience an absorption resonance with some corrosion products crystals (i.e., iron oxides). The THz spectroscopy has, therefore, a great application potential to characteristically identify the corrosion of steel materials. In the present study, the optical parameters and, especially, the positions of the characteristic absorption peaks of the corrosion products were systematically investigated and identified using the THz system. The experimental results showed that the refractive index of the different corrosion product samples was in the range of 2.7–3.4 in the effective frequency range of 0 THz - 1.2 THz, and the content of Fe3O4 had a large influence on the optical parameters in the corrosion product mixtures. To measure the characteristic absorption peaks of the corrosion products, the effective frequency range was extended to 0 THz - 10 THz by an assembled broadband THz system. Within this range, the positions of the characteristic absorption peaks were identified as 3.4 THz, 4.2 THz, 4.85 THz, and 5.8 THz for Fe2O3, and as 3.6 THz, 4.05 THz, 5 THz, and 5.45 THz for α-FeOOH. For Fe2O3 and α-FeOOH, the intensities of the absorption peaks at 4.85 THz and 3.6 THz, respectively, showed a linear relationship with the mass content. Furthermore, the THz spectroscopy could accurately identify Fe2O3 and α-FeOOH in the corrosion product mixtures by comparing with the results from IR spectroscopy and Raman spectroscopy. This means that the occurrence of steel corrosion could be detected according to the characteristic absorption peaks of Fe2O3 and α-FeOOH. The experimental results provide a basis for the application of THz spectroscopy in the NDT of the corrosion of steel materials.

Actual Xisha marine atmospheric corrosion behavior of 30CrMnSiA steel in different parts of the aircraft

The corrosion behavior of 30CrMnSiA steel on the surface, inside, and belly of the aircraft was investigated by exposing it in Xisha outdoor, shelter and storehouse. The results show that the corrosion degrees of 30CrMnSiA steel are in the order of outdoor > shelter > storehouse in the same cycle. Based on the polarization curve, the corrosion current density of 30CrMnSiA steel is in the order of outdoor > shelter > storehouse after 1 month of exposure. The corrosion current density shows a decreased tendency with exposure time, which is related to the dense corrosion products on the surface. The corrosion products of 30CrMnSiA steel had the highest number and became gradually dense in outdoor conditions. The shelter had a few corrosion products in an unstable phase. It covered the full surface of the specimen at the late stage. The storehouse had the least corrosion products in an unstable phase. The products partially covered the full surface of the specimen at the late stage. The difference in the corrosion of 30CrMnSiA steel in environments is related to the humidity and Cl- in the exposure environment.

Effects of cathodic protection potential on microbiologically induced corrosion behavior of X70 steel in a near-neutral pH solution

Sulfate reducing bacteria (SRB) are considered as one of the main causes for the failures of buried metal pipes. Although many researchers reported that more negative cathodic protection potential was required in environments containing SRB, SRB would increase the concentration of hydrogen adsorbed on steel surface and thus lead to hydrogen embrittlement. In the study, the optimum cathodic protection (CP) potentials of X70 steel in bacterial and sterile media were evaluated with electrochemical impedance spectroscopy. The morphology and composition of corrosion products were characterized by a scanning electron microscope (SEM), an energy dispersion x-ray spectrometer (EDS), and an x-ray photoelectron spectrometer (XPS). The corrosion morphology of X70 steel in NS4 medium was pits and the corrosion in the bacterial medium was more serious than that in the sterile medium. The corrosion products of X70 steel were FeOOH and Fe2O3 in the sterile medium, whereas its corrosion products in the bacterial medium were FeOOH and FeS. When CP potential was −775 mV, SRB growth was promoted and the optimal protection effect on X70 steel was achieved in the bacterial NS4 medium. Pits were still observed under the biofilm and the corresponding corrosion mechanism was extracellular electron transfer (EET). When CP potential was −875 mV, X70 steel realized the optimal protection in the sterile NS4 solution. However, CO2 hydrolysis and SRB metabolism in the bacterial medium resulted in hydrogen-induced pits. When CP potential was −1025 mV, the growth of SRB was inhibited and severe hydrogen evolution corrosion occurred on X70 steel in bacterial and sterile NS4 media. The optimal CP potential for pipeline steel in the sterile medium may lead to hydrogen corrosion in the bacterial medium when H+ concentration was high.