ABSTRACT Sulfate saline soil in cold and arid regions accelerates the deterioration of buried pipelines, but the roles of salt crystallization and ice formation in steel corrosion remain unclear. In this study, the corrosion behavior of X80 steel in sulfate saline soil was investigated under different temperatures, salt contents, and corrosion times using potentiodynamic polarization tests, electrochemical impedance spectroscopy tests, polarized optical microscopy, SEM, XRD, and XPS. The corrosion rate first increased and then decreased with increasing salt content at 20°C and 10°C. Decreasing temperature sharply reduced the corrosion rate, and corrosion was strongly inhibited under frozen conditions. Steel surface corrosion changed from mainly uniform corrosion at 20°C and 10°C to local pitting corrosion at subzero temperatures. The results indicate that dissolved sodium sulfate promotes corrosion before crystallization, whereas mirabilite precipitation and ice formation inhibit corrosion by consuming liquid pore water and restricting ion transfer and oxygen diffusion.
ABSTRACT The current Swiss concept for the disposal of high‐level waste involves the emplacement of carbon steel disposal canisters in a deep geological repository in Opalinus Clay. The development of canister designs able to provide complete containment of radionuclides for at least 10 000 years follows a design‐by‐analysis approach that involves advanced analysis to evaluate the response and performance of a design under various conditions. The preliminary canister design is made of carbon steel, and the closure is completed by electron beam welding. Assessment of the canister lifetime is done by evaluating the degradation mechanisms that can take place in the repository and bounding the possible damage to the canister under conservative assumptions. Structural assessments and fracture mechanics are then employed to demonstrate that the degraded canister remains unbreached.
ABSTRACT Andra (French National Agency for Radioactive Waste Management) is responsible for identifying, implementing and guaranteeing safe management solutions for all French radioactive waste. The Cigéo project is the underground facility located in a geological layer, designed to dispose of high and intermediate‐level long‐lived radioactive waste produced by French facilities. The Cigéo disposal will be in operation for around 100 years. For over 30 years, Andra has been carrying out research and development work to support the design of a safe facility over this exploitation period and far beyond it, confining radioactivity to protect man and environment. In the context of the high‐level waste cells, R&D work is among others studying the evolution of the main metallic components, the casing and the overpack, under the combined effect of corrosion and mechanical processes. The aim is to identify the most robust and durable materials. Andra performed using several measurement techniques corrosion tests in laboratories and in a deep geological laboratory in various environments (temperature, oxygen…) representative of the future Cigéo disposal.
ABSTRACT The corrosion performance of Inconel X750 was systematically investigated in aggressive chloride‐containing environments representative of service conditions encountered in aerospace and offshore systems. Electrochemical techniques, including open circuit potential (OCP) monitoring, linear and potentiodynamic polarization, cyclic polarization, and galvanic coupling, were employed in combination with long‐term immersion and crevice corrosion testing. The results show that Inconel X750 exhibits excellent corrosion resistance in both acidic and brine solutions, maintaining stable electrochemical behavior over exposure periods of up to 12 months. Potentiodynamic polarization measurements showed corrosion current densities on the order of 10 nA, corresponding to a corrosion rate of approximately 0.054 mil/year. Cyclic polarization tests showed no significant susceptibility to pitting or localized corrosion. In addition, crevice corrosion evaluations confirmed the absence of measurable attack under both parallel and angled crevice configurations. Galvanic coupling experiments further indicated that Inconel X750 demonstrated excellent corrosion resistance with minimal degradation risk. Although Inconel X750 behaved anodically relative to Hastelloy C276 during galvanic coupling, the measured galvanic current remained very low, indicating negligible galvanic corrosion. The superior corrosion resistance is attributed to the formation of a stable, chromium‐rich passive oxide layer with strong repassivation capability, which effectively limits metal dissolution and suppresses localized corrosion processes. These findings highlight the robustness of Inconel X750 in chloride‐rich environments and demonstrate its suitability for critical applications requiring long‐term corrosion resistance, including components such as offshore valve springs and related mechanical systems.
ABSTRACT The oxidation behavior of Ti‐Gd based alloys was systematically investigated at 900°C for up to 100 h. The results show that the oxidation kinetics of all alloys follow a parabolic law. Gd addition accelerates oxidation and degrades oxidation resistance. Fe further exacerbates this effect by stabilizing the β‐Ti phase, in which oxygen diffuses faster than in α‐Ti. In contrast, Al addition significantly improves oxidation resistance by forming an Al 2 O 3 ‐rich barrier layer in the inner oxide scale. Ti‐7.5Fe‐5Gd‐5Al exhibits the best oxidation resistance. These findings provide a theoretical basis for understanding the high‐temperature oxidation behavior of Ti‐Gd based alloys and offer valuable reference for their engineering application as neutron‐absorbing structural materials at elevated temperatures.
ABSTRACT The effects of Y, Si and Mo additions on the oxidation resistance and high‐temperature tensile properties of 5Cr steel were investigated in this study. Si and Y improved oxidation resistance by reducing scale stress and enhancing adherence, whereas Mo exacerbated scale spallation due to stress accumulation and vaporization effects. Y, Si and Mo all contributed to refining and spheroidizing the Cr 23 C 6 precipitates, among which Mo demonstrated a more significant effect than Y and Si. Correspondingly, these alloying elements generally increased the yield strength of 5Cr, with Mo again showing a more pronounced strengthening effect.
ABSTRACT This article examines the impact of externally introduced chromium compounds on the localized corrosion of 316 L stainless steel in acidic chloride environments such as hydrochloric acid. While the corrosion resistance of 316 L relies on the formation of a chromium‐rich passive oxide layer, industrial conditions may expose the steel to various chromium species. Due to their hygroscopic nature, chromium salts can absorb moisture and form persistent thin electrolyte films on metal surfaces, creating aggressive microenvironments that promote localized corrosion. Despite their potential impact, the formation, stability, and corrosive effects of such deposits remain poorly documented. This review highlights the role of hygroscopic chromium salts in destabilizing the passive film of 316 L and increasing susceptibility to pitting and stress corrosion cracking in chloride media, emphasizing the need for further investigation to better assess corrosion risks in industrial environments.
To address the trade-off between high-temperature oxidation resistance and chloride corrosion resistance of CoCrFeNi high-entropy alloys (HEAs), CoCrFeNiTax (x = 0.5, 1.0, 1.5, 2.0) alloys were fabricated via vacuum hot-pressing sintering. The bidirectional regulation of Ta content on oxidation at 800 degrees C and corrosion in 3.5 wt% NaCl solution was systematically investigated. Increasing Ta degrades oxidation resistance with higher mass gain, parabolic rate constant K p, and thicker oxide layers, owing to the deteriorated oxide structure, diluted Cr-based protective film, and accelerated ionic diffusion through the Laves phase. Conversely, Ta markedly improves corrosion resistance by raising the corrosion potential and reducing the corrosion current density, due to the formation of a dense Ta2O5 passive film, which repairs structural defects and resists the attack of chloride ions. This work clarifies the underlying bidirectional regulation mechanisms and provides guidance for the composition design of HEAs applied in extreme environments.
The corrosion behavior of galvanically coupled copper-AISI 304 stainless-steel welds (Cu-Fe immiscible system) fabricated using the novel cold gas tungsten arc welding (CGTAW) process was investigated. The controlling factors and mechanisms governing corrosion in three types of anode-dominated weld microstructures were discussed. In a contaminated circulating water environment, corrosion rates were associated with the degree of mixing between the Cu-matrix and Fe-based phases (uniform or over-mixed distributions) and with the presence of defects. A hierarchical Random Forest (RF)-based machine learning framework was developed to model the process-structure-property relationship, in which process parameters influence corrosion rate through intermediate microstructural evolution and defect formation.
In this investigative study, a fresh amalgamated composite coating BTA@MBCENT (benzotriazole or BTA-loaded mango kernel biochar or MB incorporated CeO2 nanotubes, abbreviated as CENT) with varying weight percentages in epoxy resin is prepared and applied to cherish the environment for industries using mild steel, specifically using saline water (3.5% sodium chloride) circulation systems. The novel coating MBCENT was then employed to examine its life-lengthening and self-healing properties against corrosion, a priori and a posteriori incorporating BTA. After completing the necessary characterization, the coating formulations applied over mild steel surfaces exhibited a water-repellent property. The release kinetics of self-healing BTA inhibitor were evaluated using ultraviolet spectroscopy. Protection efficacy for the coated steel samples immersed is investigated through electrochemical methods. BTA@MBCENT (1.0%) demonstrated an exceptional protection efficiency of 88.63% within 42 days of immersion, suggesting the self-healing coating may serve as a viable alternative to conventional anticorrosive coatings for mild steel against aggressive chloride ions of saline industrial water.
ABSTRACT The corrosion behavior and mechanism of typical steels in the novel proportion NaNO 3 ‐KNO 3 ‐Ca(NO 3 ) 2 (16‐48‐36 wt%, NKC) molten salt have been reported. Static corrosion tests of 347H stainless steel (347H), 321 stainless steel (321SS) and 20# carbon steel (20#CS) were conducted in NKC salt at 480°C for 360 h. Their annual corrosion rates are 10.5, 12.9, and 31.4 µm/year separately, and the corrosion resistance ranks as 347H > 321SS > 20#CS. Corrosion is primarily driven by selective oxidation and elemental dissolution. 347H forms a dense (Fe,Cr) 2 O 3 layer with a flat surface and minor granular products. 321SS undergoes chromium depletion and precipitation, resulting in the formation of Fe 2 O 3 and Fe‐Ni phases, which lead to uneven local corrosion. 20#CS develops a porous Fe 2 O 3 /Fe 3 O 4 mixed layer characterized by distinct pits and general corrosion. These findings provide new insights into steel corrosion and key data for material selection.
A Fe47.0Cr24.1Mo6.0Nb2.9Ni15.0Al5.0 high-entropy alloy (HEA) coating containing Laves and B2-NiAl phases was fabricated on 304 stainless steel substrates by laser cladding. Compared with the substrate, the coating exhibited increases of 88% in hardness and 75% in wear resistance by dry sliding tests in air at room temperature, 350 degrees C, and 550 degrees C for 30 min, mainly owing to the synergistic effects of dispersion strengthening and second-phase strengthening. The corrosion behavior was investigated by exposure in lead-bismuth eutectic (LBE) at 550 degrees C with dissolved oxygen concentration of 1 & times; 10-6 wt.% for 500, 1000, 1500, and 2000 h. After exposure, the coating formed a compact Fe3O4-FeCr2O4-Al2O3 triple-layer oxide scale with a thickness of less than 1 mu m, which was approximately one-tenth of that formed on the substrate under the same conditions. The B2-NiAl phase promoted the formation of the protective oxide scale, whereas the Laves phase suppressed its excessive growth. These results provide a mechanistic understanding and technical guidance for the design of protective materials for key moving parts in lead-cooled fast reactors (LFRs).
Liquid lead (Pb) is an attractive heat transfer fluid for advanced thermal energy storage (TES) systems. In the search for adequate structural materials that withstand the corrosive nature of liquid Pb at high temperature, Al-containing materials might offer excellent corrosion resistance due to their ability to form protective alumina scales. This study investigates the corrosion behavior of two commercial ferritic FeCrAl alloys, Kanthal APM and Kanthal APMT, and two titanium aluminides, TNM-B1 and GE 48-2-2, in liquid Pb under conditions relevant for TES systems. Exposure tests are performed in liquid Pb with 2E-7 wt.% dissolved oxygen at 600 degrees C and 700 degrees C for up to 5000 h. Examination of the specimens after exposure shows the formation of stable and protective oxide scales at 600 degrees C on all materials, while exposure at 700 degrees C leads to various failure mechanisms, ranging from internal oxidation for APM to severe Pb penetration for TNM-B1 and GE 48-2-2.
In this study, Premature leakage of a stainless-steel pipeline used to transfer a 4% potassium permanganate (KMnO4) solution was investigated to identify the degradation mechanism responsible for the failure after a short service period. Visual inspection revealed tubercle formation and deposit accumulation on the inner pipe surface, while scanning electron microscopy (SEM) analysis showed localized corrosion features, including micro-pitting and tunnel-like cavities beneath biofilm layers. SEM-EDS analysis detected sulfur-rich corrosion products within the deposits and pit interiors, suggesting sulfide formation possibly associated with microbiologically influenced corrosion. The observed corrosion mechanism is consistent with microbial sulfate reduction coupled with electrochemical iron dissolution, leading to iron sulfide deposition and localized under-deposit corrosion. The study demonstrates that biofilm formation can create localized anaerobic microenvironments that enable microbiologically influenced corrosion (MIC), even in oxidizing KMnO4 transfer systems, providing new insights into MIC risks in chemical-handling pipelines.
Typhoons, as frequent extreme convective weather events, significantly affect regional environmental conditions and thus influence the atmospheric corrosion behavior of metallic materials. Yet, few studies examine corrosion mechanisms under typhoon conditions. This study focuses on the typhoon-prone southeastern coast of China, using minute-level Atmospheric Corrosion Monitor (ACM) sensor data to build a unified prediction framework for galvanized steel corrosion rates under both typhoon and normal conditions. We introduce five typhoon-related variables: typhoon translation speed (Moving_ty), maximum wind speed near the typhoon center (Wind_ty), typhoon occurrence (Occur_ty), relative bearing between the typhoon direction and the corrosion site (Bearing_ty), and distance between the typhoon center and corrosion location (Distance_ty). We developed PCFE-Net, a neural network combining feature enhancement and physical monotonic constraints, which significantly outperformed traditional machine learning methods. Predicted corrosion maps matched observed spatial patterns, and interpretability analyses confirmed the model aligns with established physical principles.
ABSTRACT In this paper, the effects of surfactants such as PEG, CTAB and their combination (PEG: CTAB) on the microstructure and corrosion resistance of Ni‐P‐Si 3 N 4 composite coating were systematically studied. The electrochemical test shows that adding PEG or CTAB can reduce the coating defects and improve the corrosion resistance. When PEG and CTAB are used in combination, they show synergistic effect, which further enhances the compactness and corrosion protection of the coating. Among them, when the composite ratio is 3:1 (CTAB: PEG), the corrosion current density is significantly reduced, and the stability of the coating in corrosive medium is improved.
Corrosion in CO2 capture units significantly impacts safety and costs. This study evaluates S275 carbon steel in CO2-loaded monoethanolamine (MEA) as a cost-effective alternative to 316 L stainless steel, testing various inhibitors: methionine, imidazole, sodium sulfite, sodium metavanadate (NaVO3), and copper(II) sulfate (CuSO4). Corrosion performance is assessed using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS), while SEM and confocal microscopy analyze surface mechanisms. Results show that NaVO3 and CuSO4 provide the highest protection, reaching inhibition efficiencies of 94% (750 ppm) and 98% (1000 ppm), respectively. Polarization curves indicate that both inhibitors act as anodic inhibitors by forming protective layers. SEM confirm iron-based oxides in NaVO3-treated samples and mixed copper-iron oxides in CuSO4-treated ones. Overall, S275 steel shows high potential for CO2 capture systems when paired with effective inhibitors.
ABSTRACT This study develops a mechanistic model to predict top‐of‐the‐line corrosion (TLC) in wet natural gas pipelines under sweet (CO₂) and sour (CO₂/H₂S) conditions. The framework incorporates water condensation, CO₂–H₂S–organic acid aqueous speciation, electrochemical kinetics, and corrosion product film formation, emphasizing rapid FeS precipitation in sour service. The proposed sour model reproduced published laboratory data with a mean absolute deviation < 45% across gas compositions (:2‐10 bar, :0‐2 bar), wall temperatures (15°C–75°C), condensation rates (0.002–0.25 ml/m²·s), and organic acid concentrations (0–1300 ppm), while the deviation for sweet service was < 16%. The sour TLC model applied to two offshore sour natural gas transmission pipelines showed strong agreement with in‐line inspection data. Field simulations indicate that the highest sour TLC rates occur at steel surface temperatures of 20°C–35°C, with a maximum corrosion rate of 0.9 mm/year. High condensation rates alone do not cause TLC; significant corrosion can occur even at low condensation rates (0.00002–0.15 g/m²·s). This work establishes one of the first unified mechanistic framework for predicting sour TLC.
ABSTRACT Thin films of alumina processed by atomic layer deposition (ALD) were electrochemically investigated by impedance spectroscopy (EIS) and linear sweep voltammetry (LSV) as well as material analysis (SEM, FTIR). The resulting films are almost free of water and organic residues originated from the ALD process. Nevertheless, the electrochemical results show significant deviation from the expected properties and behavior. The ALD films show a significant reactivity in aqueous electrolytes, indicating electron conductivity under cathodic and corrosion under anodic polarization. The thinner the film thickness the higher the electrochemical activity. In the thicker layers, no defects were detected microscopically; however, the incorporation of copper into the alumina oxide layer was confirmed.
