Analysis of Localized Corrosion Morphology and Microbial Distribution in Duplex Stainless Steel Tubes of Seawater Heat Exchanger

Domain-Constrained Diffusion Framework for Point Cloud–Based Corrosion Morphology Generation and Chained Evolution

A probabilistic-based numerical modeling of natural gas pipelines with random corrosion morphology

This study investigates the effect of nano-TiO₂ (nTiO₂) reinforcement on the corrosion behaviour of cold work aluminium composites in a 0.3M H₂SO₄ environment. Al-nTiO₂ composites were fabricated with 0%, 1%, 2%, 3%, and 5% weight fractions of nano-TiO₂ using stir casting. The corrosion performance was evaluated using potentiodynamic polarization (PDP), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). The results show that increased TiO₂ content enhances corrosion resistance up to 5%, particularly at lower cold-working loads. Sample J (5% TiO₂, 2 kg load) exhibited the lowest corrosion rate (0.09474 mm/yr) and highest polarization resistance (809.58 Ω). SEM/EDX analysis revealed denser passive layers and reduced sulfur compound deposits in higher TiO₂ composites. This work highlights the effectiveness of nano-TiO₂ in improving electrochemical stability and corrosion morphology of aluminium composites in acidic environments.

To address the challenges posed by rock bolt corrosion to engineering safety and service life, this study focuses on corrosion detection through integrated image processing, deep learning, and feature extraction methods. An automatic corrosion identification model was constructed based on computer-vision object-detection algorithms. By incorporating a Feature Pyramid Network, the model's multi-scale object-detection capability was significantly enhanced. The corrosion features were extracted via image binarization and grayscale matrix analysis. The binary image method accurately quantified pitting density, revealing an initial increase followed by a decrease over time. The corrosion morphology was simulated using a Fractional Brownian Motion model, validating the accuracy of fractal feature calculations. The fractal dimension increased significantly with prolonged corrosion time, which not only characterize surface roughness evolution and corrosion rate, but also provide a reliable quantitative indicator for metal corrosion assessment. This research offers a technical framework integrating image processing, deep learning, and fractal theory for rock bolt corrosion monitoring and maintenance.

Cariogenic Streptococcus mutans accelerates the crevice corrosion of 316L stainless steel in simulated oral environment.

Developing efficient green inhibitors from sustainable and cost-effective materials remains a challenge. Nitrogen (N) and sulfur (S) co-doped carbon dots (CDs) were synthesized from dried lycium as carbon, nitrogen, and sulfur sources, using hydrothermal reaction. The corrosion inhibition performance of these CDs on carbon steel in 1 M HCl solution was investigated using electrochemical measurements and surface characterizations techniques. The lycium-derived CDs, were rich in oxygen-, nitrogen-, and sulfur-containing functional groups, had an average size of ~ 20.3 nm and a pyrrole-like N content of 65.3%. These characteristics contributed to their effective inhibition performance, achieving a maximum inhibition efficiency of 88.4% for carbon steel at a concentration of 100 mg/L. Adsorption isotherm and corrosion morphology analyses indicated that the inhibition mechanism of CDs primarily involves the formation of a protective film through both physical and chemical adsorption. Pyrrole-like N species, via π-complex formation, play a significant role in achieving excellent inhibition by promoting parallel adsorption onto the steel surface. This study demonstrates a green approach for synthesizing efficient biomass-derived CDs, promoting the development of sustainable and effective corrosion protection strategies.

The grounding system is a key infrastructure that ensures the stable and safe operation of the power system. The corrosion behavior of earthing materials within soil environments significantly impacts their long‐term reliability. This article studies the corrosion behavior of three typical grounding materials systematically: Cu, carbon steel, and galvanized steel, in acidic soil simulated solutions with varying Cl − concentrations (0.05%, 0.5%, 1%, 2%). The corrosion rate and corrosion resistance of the material were evaluated through electrochemical testing and weight loss method, combined with corrosion morphology observation and product analysis. The results indicate that the impedance arcs and the impedance modulus of the three materials both decrease as the concentration of Cl − increases. The impedance modulus of Cu decreased from 10 5 to 10 3 Ω·cm 2 . The corrosion current density increased significantly from 0.157 to 8.190 μA·cm −2 for Cu and from 9.130 to 19.300 μA·cm −2 for carbon steel, and the corrosion rate rises significantly. Cu exhibits optimal corrosion resistance due to its ability to form a dense corrosion product film. The corrosion rate remained low below 0.008 mm/a across all Cl − concentrations. Galvanized steel has certain protective capabilities when the coating is intact, but its failure accelerates with the increase in the Cl − concentration showing a maximum corrosion rate of 0.0273 mm/a at 1% Cl − and a maximum pitting depth of 6.804 μm at 2% Cl − . The corrosion products of carbon steel are loose and porous, with the worst corrosion resistance. The carbon steel exhibits a maximum pitting depth of 109.56 μm at 2% Cl − . This research can provide a basis for selecting materials for grounding electrodes in acidic environments with high Cl − content.

Structural components fabricated from carbon steels such as EN- 8 are widely employed in engineering applications where they are frequently exposed to corrosive environments. The present investigation focuses on evaluating the corrosion behaviour of butt-welded EN-8 steel joints when subjected to different corrosive media. Three representative environments were selected for this study: 1 M hydrochloric acid (HCl) simulating an industrial acidic condition, synthetic seawater representing marine exposure, and distilled water serving as a neutral environment. Arc welding was employed to fabricate butt joints using E7018 electrodes under controlled parameters. The specimens were exposed to the respective corrosive environments for predetermined time intervals, and the corrosion rates were determined using the weight loss method. Microstructural characterization was performed to analyse the corrosion morphology across the weld zone, heat-affected zone (HAZ), and base metal, while microhardness testing was carried out to assess the degradation in mechanical properties. Results revealed that the corrosion rate was highest in 1 M HCl, moderate in seawater, and negligible in distilled water. The HAZ exhibited the most pronounced corrosion attack owing to its heterogeneous microstructure and residual stresses developed during welding. A gradual stabilization of corrosion rate over time was observed, which may be attributed to the formation of a protective oxide film. Overall, the study highlights that acidic environments significantly accelerate the corrosion of welded EN-8 joints, and careful consideration of operating environment is essential for prolonging the service life of welded components. These findings provide valuable insights for the design and maintenance of welded steel structures in industrial and marine conditions.

Incoloy 800H is important structural alloy for heat exchange tubes of Generation IV nuclear power systems. Revealing the key heat treatment effects on the microstructure and corrosion behavior of 800H is a key issue for its performance optimization and safe application in IV nuclear power industries. This work investigated the solid solution heat treatment–microstructure–corrosion resistance relationship using various electrochemical corrosion techniques and morphology characterizations. The results showed that 1120 °C was an insufficient solid solution heat treatment temperature for 800H, at which 800H demonstrated uneven enlargement of grains and undissolved Cr-carbides, which resulted in fast corrosion. 800H demonstrated even growth of grains with best grain uniformity and dissolution of Cr-carbides at 1150 °C, thus showing the best corrosion resistance. However, the further increase in solid solution temperature to 1180 °C resulted in excessive grain growth and severe intergranular corrosion (IGC) attack. This work deepened the understanding of the corrosion mechanism of 800H and provided data for its performance optimization.

The 5083 aluminum alloy is widely used in marine engineering due to its excellent corrosion resistance and weldability. To address microstructural defects that may arise during hot rolling, homogenization annealing is employed as a critical post-processing step to enhance mechanical and processing properties. This study systematically investigates the effects of different homogenization annealing temperatures (held for 1 h) on the microstructure, corrosion behavior, and mechanical properties of hot-rolled 5083 aluminum alloy. The microstructural characteristics, phase composition, and corrosion morphology were characterized using scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), polarized light microscopy (POM), electron backscatter diffraction (EBSD), and electrochemical tests. Microhardness was measured using a Vickers hardness tester. The results indicate that the annealing temperature markedly influences the type, morphology, and distribution of precipitated secondary phases and significantly affects grain refinement. The alloy treated at 350 °C (5083–350 °C) exhibited optimal corrosion resistance, as evidenced by electrochemical impedance spectroscopy showing the highest charge transfer resistance and surface morphology analysis revealing minimal and shallow corrosion pits. Simultaneously, this treatment achieved significant stress relief and secondary phase precipitation strengthening, resulting in a peak microhardness of 78.8 HV. The study demonstrates that 350 °C homogenization annealing synergistically improves both the corrosion resistance and mechanical properties of hot-rolled 5083 aluminum alloy, providing valuable insights for optimizing its heat treatment process.

Ti-6Al-4Zr-3Nb-1.1Mo-1Sn-1V (Ti90) alloy is widely used in marine engineering and oil and gas extraction due to its excellent strength, impact toughness, and corrosion resistance. The corrosion behavior of Ti90 alloy after solution treatment at 750 °C, 900 °C, 940 °C, and 960 °C in 5 M hydrochloric acid (HCl) solution was investigated using open-circuit potential (OCP), potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), static immersion tests, and surface characterization. The results of electrochemical tests indicate that the corrosion resistance of Ti90 alloy increases with rising solid solution temperature. The static immersion tests show that the variation trend of the annual corrosion rate at different solid solution temperatures in 5 M HCl solution is consistent with the electrochemical test results. The corrosion morphology of Ti90 alloy reveals that the α phase is more prone to decomposition than the β phase. The corrosion behavior of Ti90 alloy in 5 M HCl solution is mainly influenced by the volume fraction of the β phase and the size of the α phase.

Purpose The purpose of this study to characterize the erosion–corrosion characteristics of a 90° horizontal elbow under different sand content conditions. This study aims to reveal the effect of sand content in liquid–solid two-phase flow on the erosion–corrosion of the elbow and to provide theoretical guidance for the protection against erosion–corrosion of elbows under such conditions. Design/methodology/approach A pipe flow test device was used to study the effect of sand content on the erosion–corrosion of a 90° horizontal elbow. The weight loss method was used to quantify the erosion–corrosion rates at different locations of the elbow under different sand content conditions. Electrochemical tests were used to characterize the electrochemical properties of different locations on the elbow, and surface analysis techniques were used to examine the erosion–corrosion morphology of the elbow. Findings This study reveals that the erosion–corrosion rates, electrochemical characteristics and surface morphologies on the inner surface of the 90° horizontal elbow are significantly influenced by sand content. As the sand content increases from 0% to 1.25%, the arc radius of the electrochemical impedance spectrum noticeably decreases, while the erosion–corrosion rates and maximum pit depths increase substantially. The surface morphology transitions from sheet-like structures to more severe pit and groove formations. When the sand content increases from 1.25% to 2.5%, the reduction in the arc radius is minor, and the changes in erosion–corrosion rates and maximum pit depths are less pronounced, though still present. Surface morphologies continue to develop in greater depth, with an increase in the number of pits and grooves. In liquid–solid two-phase flow, the areas of severe erosion–corrosion are mainly at the bottom of the horizontal elbow and on the outside of the elbow outlet. Overall, this study highlights that sand content is a significant factor in accelerating erosion–corrosion, with higher sand concentrations leading to more extensive damage on the elbow surface. Originality/value This study investigates how sand content affects the erosion–corrosion of a 90° horizontal elbow. It characterizes the erosion–corrosion rates, electrochemical properties and surface morphologies at various locations of the elbow, revealing the underlying mechanisms by which sand content influences its erosion–corrosion behavior.

Low-carbon microalloyed bainitic ferrite steels are highly sought for their excellent combination of strength, toughness, and weldability, making them suitable for applications like pipelines, pressure vessels, and structural components. In this study, a quenching and partitioning (Q&P) heat treatment was applied to an API 5L X65 pipeline steel to develop a bainitic ferrite microstructure containing film and block-type retained austenite. The effect of this transformation on mechanical properties and corrosion resistance was systematically investigated. Mechanical testing revealed a significant improvement in yield and tensile strength (630 and 950 MPa, respectively), while preserving reasonable toughness. The transformation also led to continuous yielding behavior and high strain hardening due to suppressed Cottrell atmospheres and the presence of retained austenite. Electrochemical analysis demonstrated superior corrosion resistance compared to the traditional ferrite-pearlite microstructure, characterized by a 78% reduction in corrosion current density and improved passivation behavior. Immersion testing and surface analysis further confirmed the stability of retained austenite and the uniform corrosion morphology. These findings demonstrate that the Q&P process is an effective and novel route for enhancing both mechanical and corrosion performance of low-carbon pipeline steels, particularly for applications in harsh and corrosive environments such as oil and gas transmission.

The long-term operation of plane steel gates under cyclic dry–wet conditions results in complex corrosion behaviour and significant mechanical degradation, particularly under static hydraulic pressure. However, current studies are limited by insufficient field data and the inability of laboratory tests to fully replicate in-service environments. To better understand the dynamic corrosion processes of steel gates, a cellular automata model was employed to simulate the time-dependent evolution of corrosion morphology. The model's accuracy was validated through comparison with experimental results. Furthermore, a finite element model incorporating corrosion-induced damage was established to evaluate the effects of corrosion on structural performance. Results show that the uniform corrosion rate exhibits an initial exponential increase before stabilising due to surface blockage by corrosion products. In contrast, pitting corrosion accelerates in the depth direction, driven by localised autocatalytic reactions. Uniform corrosion gradually reduces global structural integrity, while localised corrosion poses a higher risk of through-thickness penetration and early failure. These findings contribute to a more reliable basis for assessing the durability and maintenance needs of hydraulic steel structures operating in aggressive service conditions.

The alternating magnetic field (MF) environment of coastal substations and magnetic levitation systems generates strong electromagnetic interference, which may affect the corrosion behavior of rebars in concrete structures. To clarify the influence law of rebar corrosion when exposed to an alternating MF, an alternating MF simulation test device was designed and manufactured according to the principle of alternating electromagnetic induction. The macroscopic corrosion morphology and electrochemical corrosion characteristics of rebars under alternating MF of different intensities were investigated by accelerated corrosion tests, electrochemical tests and natural corrosion electrochemical tests. The corrosion behavior mechanism of rebars under alternating MF was revealed. The results show that: 1) The diffusion rate and concentration of corrosion products in the solution are proportional to the magnetic induction strength. The alternating MF accelerates rebar corrosion. 2) The Ecorr of rebar shifts negatively with the magnetic induction strength increases, with a more pronounced shift in the early stage of corrosion than in the later stage. 3) Under the natural corrosion state, the 5 mT MF makes the open circuit potential (OCP) shift 12 mV negatively compared with that without MF. When the potential reaches 8mV, the passivation film begins to be destroyed. 4) The R1 of rebar is inversely proportional to the magnetic induction strength.

Substation equipment operating in harsh environments is highly susceptible to corrosion, yet conventional image segmentation methods often fail to achieve precise delineation of corroded regions. Here, we propose an enhanced TransU-Net-based approach for corrosion segmentation. Deformable convolution is incorporated into the encoder to strengthen the model’s capacity to represent irregular corrosion morphologies. A composite color–texture fusion module is developed to jointly exploit color information from HSV and Lab spaces together with multi-scale texture features. In addition, a Shape-IoU loss function is introduced to refine boundary fitting and improve contour accuracy. Experimental evaluations demonstrate that the proposed method consistently outperforms state-of-the-art models across multiple metrics, achieving an Intersection over Union (IoU) of 75.42% and a Recall (PA) of 83.14%. These results confirm that the model substantially enhances corrosion recognition accuracy and edge integrity under complex background conditions, offering a promising strategy for intelligent maintenance of substation infrastructure.

In recent years, the automotive industry has increasingly adopted multi-material structures to reduce vehicle weight and, consequently, lower CO₂ emissions. In the development of materials technology for multi-material vehicle bodies, effective measures must be implemented to prevent galvanic corrosion at material interfaces. However, there are many parts in a vehicle that are concerns about corrosion, and it is known that the corrosion environment differs greatly depending on the part. Numerical simulations utilizing computational science provide a highly effective approach for investigating corrosion behavior under a wide range of environmental conditions. In this study, galvanic corrosion between carbon steel and aluminum alloy was analyzed through quantitative numerical simulations based on the electrochemical properties of each material.The numerical simulation model was constructed under the assumption that corrosion would occur at the butt joint of carbon steel and aluminum alloy in a NaCl aqueous solution. COMSOL Multiphysics was utilized for the simulations. Electrochemical measurements were conducted to validate the numerical simulation model. The test electrodes were prepared by arranging carbon steel and aluminum alloy in parallel and embedding them in epoxy resin. NaCl solutions of varying concentrations were used as the test solution. Changes in galvanic current and potential over time were measured in a non-degassed environment at room temperature. After three hours of measurement, the surface corrosion morphology of the aluminum alloy and carbon steel was observed using a microscope.Galvanic current measurements revealed that the aluminum alloy acted as the anode, while carbon steel functioned as the cathode in the NaCl solution. The galvanic current increased with rising NaCl concentration, and the galvanic potential exhibited a tendency to shift toward more negative values. Surface observations after the corrosion test indicated the occurrence of pitting corrosion on the aluminum alloy, with the number of pits increasing in proportion to the NaCl concentration. In contrast, no significant corrosion was observed on carbon steel in high-concentration NaCl solutions, however, the amount of corrosion on carbon steel increased as the NaCl concentration decreased. A computational simulation was conducted, considering the expansion of the pitting corrosion area on the aluminum alloy with increasing NaCl concentration. The results demonstrated that the anode current on the aluminum alloy almost matched the cathode current generated on the carbon steel in highly concentrated NaCl solutions, but as the NaCl concentration decreased, the anode current on the aluminum alloy diminished, leading to anode dissolution (self-corrosion) on the carbon steel.

The selection of alloys for Gen IV molten salt nuclear reactors (MSR) involves several considerations, including corrosion resistance. Gen IV reactors aim to improve safety, sustainability, and efficiency compared to previous generations. In addition to selecting corrosion-resistant materials, there has been consideration by the community for the implementation of corrosion mitigation strategies, such as controlled salt chemistry, maintenance of appropriate temperature and pressure conditions, and application of protective coatings or surface treatments to reactor components. Nevertheless, up until recently, the majority of material development was done by trial and error, and any corrosion studies were forensic post-test investigations. Flow loop corrosion tests with controlled impurities simulate reactor physical conditions but lack coupon-level understandings of governing electrochemical parameters and corrosion processes coupled to metallurgy that dictate corrosion morphology development.Molten salt environments present several challenges to nuclear reactor structural materials, such as selective dealloying (Cr, Fe, etc.)1,2 coupled with the presence of lattice strain, grain boundaries and dislocation substructures3 that accelerate molten salt corrosion. In this work, the corrosion dealloying behavior of Ni-Cr alloy (5-20wt.%) was studied in molten LiF-NaF-KF (or FLiNaK) salts at 600°C. To simulate irradiation conditions, alloys were cold-rolled to achieve reductions of thickness of 10%, 30%, and 50%, introducing a high density of dislocations and their substructures. Separately, model Ni-Cr alloys between 5 and 20 wt.% were subjected to heavy Ni ion radiation up to a peak damage of 2.2 μm and 60 dpa.All samples were subjected to potentiostatic holds in carefully selected electrochemical potential regimes where only Cr dealloying occurs in FLiNaK at 600oC 4. A porous Ni-rich ligament was formed under certain conditions that undergo coarsening and densification. The post-dealloying samples were characterized by scanning electron microscopy, electron backscatter diffraction, and scanning transmission electron microscopy techniques to characterize micro and nanoscale changes in structure and composition. A significant difference in the dealloying behavior of pristine, cold-rolled, and irradiated materials dealloying behavior was observed. Insights on the irradiation and cold-rolling effects on the rate process and parting limit of Ni-Cr under dealloying will be discussed. Acknowledgment Research is primarily supported as part of the fundamental understanding of transport under reactor extremes (FUTURE), an Energy Frontier Research Center (EFRC) funded by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES). This work was performed in the Department of Materials Science and Engineering (DMSE) in the Center for Electrochemical Science and Engineering (CESE) at the University of Virginia. Utilization of the Malvern-Panalytical Empyrean diffractometer was supported by Nanoscale Materials Characterization Facility (NMCF) with National Science Foundation (NSF) under award CHE-2102156. H.C. acknowledges the National Science Foundation Graduate Research Fellowship (GRFP), GRANT#: 1842490.

To accurately simulate the progression of pipeline corrosion, this paper proposes a three-dimensional corrosion modeling method for curved random surfaces based on spatial frequency composition. It applies this method to the inner surface of layered pipelines to emulate both the morphological characteristics and the evolution of internal corrosion. Combined with ultrasonic guided wave technology, the approach enables quantitative assessment of internal corrosion in layered pipelines. First, trigonometric series expansion and nonlinear polynomial superposition are used to characterize the roughness and curvature of the corroded surface, respectively, establishing a mathematical model capable of accurately representing complex corrosion morphologies. Next, a COMSOL–ABAQUS co-modeling approach is employed to build a finite element model of a three-layer composite pipeline consisting of a steel pipe, an insulating layer, and an anti-corrosion layer, with curved random-surface corrosion on the inner surface of the steel pipe. Finally, a wavelet packet decomposition algorithm is applied to extract features from the guided wave echo signals, creating a damage index matrix to correlate the corrosion area with the damage index quantitatively. The results show that the damage index increases steadily with the corrosion area, confirming the effectiveness of the proposed method. This study provides an alternative technical approach for high-fidelity modeling and precise assessment of pipeline corrosion detection.