Search Results (198)

The deep-sea tunnels at the Sanshan Island Gold Mine are subjected to extreme conditions characterized by high stress and complex erosion resulting from high mineralization. Under these conditions, conventional shotcrete is prone to performance degradation and insufficient durability, posing a threat to the long-term safety of the tunnels. At the same time, mine water is difficult to recycle on-site. To address these engineering challenges, this study utilized fly ash (FA), S105-grade ground granulated blast furnace slag (GGBS), polypropylene coarse fiber (PPCF), and hydroxypropyl methylcellulose (HPMC) as modifying components and employed the response surface method (RSM) to optimize the mix design of mine water-blended shotcrete. The study selected compressive strength, direct shear strength, and chloride ion electrical flux at 6 h as response indicators and constructed a quadratic polynomial regression model. Analysis of variance and goodness-of-fit tests indicated that the model possessed good significance and reliability of fit. Based on this model, the optimal mix design was determined: an FA/GGBS blend ratio of 3:7, a cement replacement rate of 20%, a PPCF content of 3.3%, and an HPMC content of 0.18%. Performance testing showed that the optimal mixture achieved a compressive strength of 25.24 MPa, a direct shear strength of 8.08 MPa, and a chloride ion electrical flux of 778 C after 6 h. Compared to the control group, its peak compressive strength decreased by only 9.98%, while its residual strength increased significantly; direct shear strength increased by 18.1%, and electrical flux decreased by 33.8%. This indicates that the material’s mechanical load-bearing capacity, deformation coordination, and corrosion resistance have been enhanced in a synergistic manner. Field industrial trials have verified that this modified concrete possesses excellent ductile yield characteristics, can effectively suppress water seepage in mine tunnels, is capable of withstanding extreme underground operating conditions, and enables the efficient reuse of mine water resources. Full article

This study investigated the corrosion resistance of laser-cladded AlCoCrFeNi high-entropy alloy coatings with varying TiO₂ content (0 wt.%, 0.5 wt.%, 1.0 wt.%, and 1.5 wt.%) in 3.5 wt.% NaCl solution. Optimal cladding parameters (1500 W, 40 mm/s, 11.9 g/min) were determined via orthogonal experiments. TiO₂ promoted Ti-rich BCC2-phase precipitation, increased corrosion potential (from −1.4185 V to −0.6841 V), decreased corrosion current density (from 2.33 × 10⁻⁴ to 2.28 × 10⁻⁶ A/cm²), and enhanced charge-transfer resistance. XPS analysis demonstrated that TiO₂ promoted the enrichment of FeO, Cr₂O₃, and TiO₂ components in the passive film while reducing the Al₂O₃ fraction, leading to the formation of a dense and stable composite passive film that effectively inhibited chloride ion attack. In summary, an appropriate amount of TiO₂ doping significantly enhances the corrosion resistance of laser-cladded AlCoCrFeNi HEA coatings, with the 1.5 wt.% addition being the best-performing among the investigated compositions. Full article

Seawater electrolysis is emerging as a key alternative strategy for sustainable hydrogen production in water-scarce regions such as the Atacama Desert; however, the high concentration of chloride ions poses significant challenges related to material stability, selectivity, and corrosion resistance. In this context, Prussian Blue Analogues (PBAs) have recently gained attention as multifunctional materials capable of operating in highly saline environments such as seawater. This review provides a critical analysis of PBAs as electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in seawater and brine systems, with a particular emphasis on nickel hexacyanoferrate (NiHCF), cobalt hexacyanoferrate (CoHCF), and copper hexacyanoferrate (CuHCF). In addition, a comparative analysis across different electrochemical applications is presented, highlighting the limited number of studies conducted under real seawater conditions. Furthermore, the limitations of current electrochemical evaluation protocols are discussed, and a framework for realistic benchmarking under saline conditions is proposed. Finally, emerging opportunities in hybrid materials and high-entropy PBAs are addressed, positioning PBAs as a promising platform for next-generation electrochemical technologies for sustainable solar hydrogen production from seawater or highly chloride-concentrated brines. Full article

Grouting materials used in water-rich and chloride-exposed environments require adequate workability, mechanical performance, and durability. To optimize the formulation, a series of orthogonal tests was conducted to assess how fly ash (10–30%), rust inhibitor (1–3%), and anti-corrosion agent (2–6%) affect the fresh and hardened properties of cement grouts at a constant water-to-binder ratio of 0.5. Setting behaviour, mechanical properties, chloride ion penetration resistance, pore structure, and hydration products were investigated. Fly ash and the anti-corrosion admixture prolonged the setting time. The highest 28-day compressive and flexural strengths were obtained at 20% fly ash. At 30%, the dilution effect outweighed the later-age pozzolanic contribution and slowed strength development. Within the investigated range, 6% anti-corrosion admixture provided the greatest improvement in strength and chloride ion penetration resistance, whereas the rust inhibitor had a smaller effect on the charge passed. Mixtures containing 20% fly ash and 4–6% anti-corrosion admixture exhibited lower porosity and a refined pore-size distribution. By contrast, 30% fly ash resulted in a less favourable pore structure. SEM and XRD results indicated a denser matrix at 28 days, consistent with continued cement hydration and the later-age pozzolanic reaction of fly ash. Previous studies have mainly focused on individual mineral or chemical admixtures, whereas the combined effects of fly ash, rust inhibitors, and anti-corrosion admixtures under fixed workability conditions remain insufficiently understood. This study reveals their distinct and complementary roles, providing a basis for the multi-objective optimisation of grouting materials in chloride-rich and water-saturated environments. Overall, 20% fly ash, 4–6% anti-corrosion admixture, and 1–2% rust inhibitor provided the best performance balance under the investigated conditions. Full article

The corrosion mechanism and corrosion behavior of a monolithic Zr-based (Zr₄₈Cu₃₆Al₈Ag₈)Si_0.75 bulk metallic glass (BMG) and a Zr-based (Zr₄₄Cu₃₆Al₈Ag₈Ta₄)Si_0.75 BMG matrix composite (BMGMC) in 3.5 wt.% NaCl solution were investigated. Potentiodynamic polarization tests were conducted to evaluate the corrosion and passive behavior of BMGs. Both monolithic BMG and BMGMC exhibited distinct pitting corrosion in sodium chloride solution. The monolithic BMG exhibited a higher value of pitting overpotential, η_pit, and a wider passive region, when compared to that of BMGMC, indicating that the monolithic BMG has a better pitting resistance than the BMGMC. The worse corrosion resistance of BMGMC can be attributed to the weak passive film of the interface area between the precipitates and the glassy matrix, where it can be more easily broken through by halide ions, Cl⁻, preferentially. Furthermore, galvanic corrosion can occur due to the potential difference between Ta precipitates and the matrix of BMGMC, leading to an even more severe corrosion of the BMGMC. Full article

Electrochemical corrosion is one of the main causes of degradation of substation grounding devices and directly impacts the operational reliability of electric power facilities. Despite numerous studies on individual corrosion factors, comprehensive models considering the combined effects of soil physical and chemical properties and electrical operating conditions remain limited. This study analyzes emergency situations associated with grounding system failures and examines the effect of the main factors of electrochemical corrosion, including chloride ion concentration, soil moisture, environmental acidity, seasonal temperature changes, and leakage currents. Based on Faraday’s law, a mathematical model of electrochemical corrosion rate is proposed that combines the influence of the factors considered through correction factors. For practical implementation, an algorithm for the dynamic assessment of degradation of grounding system elements has been developed. The proposed model predicts changes in the cross-sectional area of grounding device elements, changes in grounding resistance, and the occurrence of potentially hazardous operating conditions. The developed algorithm assesses the risk of exceeding the permissible grounding potential, violating thermal withstand, the occurrence of hazardous step voltages, insulating breakdown, and disrupting the selectivity of relay protection devices. Full article

Reinforced concrete structures in marine environments are subjected to severe deterioration, particularly in tidal zones. The development of intrinsically hydrophobic concrete through internal modification provides a promising strategy to mitigate this challenge. This study employed sodium methyl silicate (SMS) as a hydrophobic agent to prepare recycled fine aggregate concrete (RFAC), which was subsequently subjected to accelerated indoor chloride dry–wet cycling. The deterioration behavior of RFAC and the degradation mechanism of the SMS-induced hydrophobic film during dry–wet cycling were investigated through evaluations of mechanical performance, hydrophobicity, chloride resistance, microstructure, phase composition, pore structure, chemical bonding, and functional groups. The results show that SMS improves the hydrophobicity of RFAC but inhibits its hydration process. The optimal SMS dosage for RFAC under dry–wet cycling is 9‰, which achieves a balance between hydrophobicity enhancement and pore structure optimization. Compared with ordinary RFAC, the specimen exhibits 12.9‰ and 17.6% increases in compressive strength and RDEM, respectively, after 30 cycles, accompanied by reductions of 25.8%, 52.7%, and 80.0% in peak free chloride content, chloride erosion depth, and convection zone depth, respectively. RFAC with 9‰ SMS exhibits a denser matrix with lower porosity and fewer corrosion products. SMS enhances chloride resistance mainly by reducing water transport and chloride ion ingress through hydrophobic modification. Dry–wet cycling gradually deteriorates the SMS-induced hydrophobic film through the weakening of Si-C-related structures, while the Si-O-Si framework remains relatively stable. A quantitative correlation between the contact angle and free chloride ion content is established, and the modified Lucas–Washburn equation provides a reasonable description of chloride ion penetration depth. Full article

The premature deterioration of reinforced concrete structures caused by steel reinforcement corrosion remains a major challenge to long-term structural durability. This study systematically investigates the effects of corrosion inhibitor dosage on the fresh properties, mechanical performance, chloride ion penetration resistance, and capillary water absorption of self-compacting concrete (SCC). The evolution of the pore structure is characterized using low-field nuclear magnetic resonance (LF-NMR) and X-ray computed tomography (X-CT), and the proportions of pores within different equivalent spherical diameter ranges are quantified. In addition, the microstructural characteristics are examined by scanning electron microscopy (SEM). The results show that the incorporation of the corrosion inhibitor increases the viscosity of fresh SCC, resulting in reductions in slump. In general, the corrosion inhibitor reduces both the compressive strength and splitting tensile strength of SCC, with the smallest strength reduction observed at a corrosion inhibitor dosage of 2 wt%. All mixtures containing the corrosion inhibitor exhibit lower electric flux and water absorption than the control mixture, indicating improved resistance to chloride ion penetration and capillary water ingress. The combined LF-NMR, X-CT, and SEM results indicate that an appropriate corrosion inhibitor dosage may optimize the spatial distribution of hydration products, refine the pore structure, reduce total porosity, and suppress the formation of macropores. Overall, a dosage of 2 wt% provides the most favorable balance among workability, mechanical properties, durability, and microstructural compactness. These findings provide experimental support and technical guidance for the mixture design of durable SCC used in aggressive environments, including marine and salt-lake regions. Full article

A bond interface between new and old concrete is inherently present in bridge widening and rehabilitation projects. Under marine environmental conditions, this interface provides a preferential pathway for chloride ion transport, thereby accelerating chloride-induced corrosion of the bridge structure. Although the mechanical bonding performance of such interfaces has been extensively investigated, the durability of new-to-old concrete systems remains significantly inferior to that of monolithic concrete, particularly in terms of resistance to chloride penetration. In this study, chloride erosion tests on new-to-old concrete specimens were conducted under drying–wetting cycle conditions to investigate the influence of the bond interface on the spatial distribution and temporal evolution of chloride concentration. The results indicate that the chloride concentration at the bond interface is significantly higher than that in other regions. This leads to a dual transport mechanism, where chloride ions not only diffuse inward perpendicular to the exposed surface but also migrate laterally from the interface into the adjacent concrete driven by concentration gradients. Based on these findings, an interface influence coefficient is proposed to quantify the effect of the bond interface on chloride transport capacity. This coefficient exhibits a strong fit with the GaussAmp function. Furthermore, a diffusion coefficient model for new-to-old concrete incorporating the effect of the bond interface is established. Full article

A recently developed high-strength nickel-based corrosion-resistant alloy has attracted increasing interest for drilling and production operations in unconventional oil and gas fields. Owing to its high resistance to media containing H₂S, CO₂ and chloride ions, together with its ultra-high strength and favorable strength–toughness balance, this alloy is suitable for demanding service conditions. During hot working, dynamic recrystallization (DRX) governs deformation softening, grain refinement and the subsequent microstructural state, and thus has a direct influence on final properties. In this work, isothermal compression experiments were conducted on this ultra-high-strength nickel-based corrosion-resistant alloy using a Gleeble thermal simulator at 1000–1150 °C and strain rates of 0.01–10 s⁻¹. Electron backscatter diffraction (EBSD) was used to quantify grain size, grain-boundary misorientation, kernel average misorientation (KAM) and the DRX volume fraction. The results indicate that higher deformation temperature generally accelerates DRX, lowers the KAM value and increases the recrystallized-grain fraction. Under a constant deformation temperature, the DRX volume fraction changes non-monotonically with strain rate, showing an initial increase followed by a decrease. Based on the EBSD-derived DRX fractions, linear and quadratic single-parameter models using the Zener–Hollomon parameter were examined first, but neither provided satisfactory fitting accuracy. A two-variable empirical model was therefore formulated for a fixed true strain of ε = 0.92 by considering deformation temperature and strain rate separately. The predicted values agree well with the experimental data, giving R² = 0.91278 and an average relative error of 8.53%. The proposed model captures the main variation tendency of the DRX volume fraction within the studied processing window and provides a useful basis for microstructure control and hot-working parameter design for ultra-high-strength nickel-based corrosion-resistant alloys. Full article

To lower the water absorption capacity and enhance the anti-corrosion performance of geopolymer coatings, methyltrimethoxysilane (MTOS) was adopted as a hydrophobic modifier to synthesize hydrophobic geopolymer coatings, and their anti-corrosion behaviors were systematically investigated. The results reveal that increasing MTOS content gradually improves the fluidity and setting time of fresh coatings while reducing their bonding strength. MTOS effectively strengthens the surface hydrophobicity of the coatings, decreases the water absorption of coated concrete substrates, and remarkably boosts chloride ion penetration resistance. The modified coatings achieve the optimal anti-corrosion performance at an MTOS dosage of 8 wt.%. Under this optimal condition, the surface water contact angle reaches 135.1°. After 28 days of chloride ion erosion, the chloride ion concentration is 45.0% lower than that of the unmodified counterpart. Meanwhile, the coating exhibits the minimum water absorption rate of 2.06% and the lowest average chloride penetration rate of 0.41 × 10⁻³ mg/(cm²·d), which accounts for only 41% of the standard threshold value. This study demonstrates that MTOS-based hydrophobic modification can significantly upgrade the anti-corrosion capability of geopolymer coatings, which provides a valuable theoretical basis and practical guidance for improving the durability of concrete structures. Full article

Self-compacting concrete (SCC) is widely adopted in complex structural engineering due to its excellent flowability and filling capacity. However, in harsh corrosive environments, its complex internal pore structure can easily serve as a preferential pathway for the transport of aggressive media, leading to durability deterioration. This study systematically investigates the effects of chemical attack inhibitor (CAI) on the workability, mechanical properties, sulfate attack resistance, and chloride ion penetration resistance of SCC. The micro-mechanisms governing pore structure evolution are elucidated using low-field nuclear magnetic resonance (LF-NMR) and X-ray computed tomography (X-CT). At a CAI dosage of 2%, the fresh SCC exhibits a slump of 260 mm and slump flow of 720 mm, indicating excellent filling and gap-passing abilities. Meanwhile, the compressive strengths at 3 d, 7 d, and 28 d remain at a high level. After 120 sulfate wet-dry cycles, the strength loss rate is only 8.4%, with an erosion resistance coefficient exceeding 90%. In addition, the resistance to chloride ion penetration is significantly improved, with an electric flux of only 1331 C, which is considerably lower than that of the control group (1637 C). At the optimal dosage of CAI, the concrete exhibits a dense and uniform internal structure devoid of macroscopic defects or cracks, with minimized porosity, thus synergistically enhancing the resistance to sulfate attack and chloride attack. On the contrary, further increasing the CAI dosage markedly intensifies the inhibitory effect of organic components on cement hydration, leading to increased early-age defects and enhanced pore connectivity. Thus, an appropriate amount of CAI can effectively improve the overall performance of SCC, providing a solid experimental basis and theoretical support for its engineering application in harsh corrosive environments. Full article

Seawater zinc–air batteries (SZABs) stand out as promising candidates for marine and offshore energy supply. However, their practical implementation is greatly restricted by tardy oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) kinetics at the air cathode, severe chloride ion-induced catalyst corrosion, and structural deterioration of traditional binder-containing electrodes in seawater media. Herein, we design and fabricate a binder-free integrated electrode consisting of carbon-supported iron phthalocyanine- modified star-like cobalt sulfide arrays directly grown on nickel foam. The optimal catalyst (0.3FePc-C/CoS) integrates the respective advantages of Fe single atoms and cobalt sulfide, exhibiting excellent ORR and OER activity, delivering a prominent half-wave potential of 0.89 V versus RHE, and exhibiting a low OER overpotential of 160 mV at 50 mA cm⁻² and robust stability in seawater. As a self-supported air cathode, the 0.3FePc-C/CoS-based battery attains a favorable open-circuit voltage reaching 1.48 V, prominent peak power density (126.4 mW cm⁻²), small charge–discharge potential polarization (0.52 V), excellent energy efficiency (68.8%) and extraordinary long-term cycling durability (>360 h). This work not only discloses a feasible synergistic modulation strategy for constructing high-performance bifunctional electrocatalysts but also provides a valuable reference for developing corrosion-resistant integrated air electrodes toward practical marine energy storage applications. Full article

Chloride and sulfate ion attacks are among the leading causes of deterioration in reinforced concrete structures, leading to the corrosion of steel reinforcement, expansion, cracking, and premature structural failure. Early detection of these ion-induced deteriorations is essential not only for maintaining safety but also for supporting sustainability objectives by extending service life, reducing material consumption, and minimizing carbon-intensive repairs. This review synthesizes current advances in non-destructive testing (NDT) techniques used to identify and quantify the impacts of chloride and sulfate ions in reinforced concrete. The mechanisms of ion ingress and their associated degradation processes are examined together with the operating principles, strengths, and limitations of key NDT methods, including electrical resistivity, acoustic emission, infrared thermography, ground penetrating radar, and ultrasonic pulse velocity. By enabling timely maintenance decisions and reducing unnecessary demolition or intrusive testing, these NDT methods contribute directly to sustainable infrastructure management. Through comparative analysis and real-world case studies, the paper highlights the most effective NDT applications for deterioration scenarios and outlines emerging innovations that enhance accuracy, data interpretation, and long-term monitoring capabilities. The findings demonstrate how advancements in NDT support the development and preservation of durable and sustainable concrete structures. Full article

Electrochemical water splitting stands as a feasible approach for sustainable hydrogen production, but its industrial implementation is restricted by sluggish oxygen evolution reaction (OER) kinetics and excessive dependence on freshwater resources. As a widely existing alternative, seawater contains a high concentration of chloride ions (Cl⁻), which give rise to serious electrode corrosion and catalyst deactivation, bringing great challenges to actual electrolysis applications. Herein, we report a facile room-temperature two-step soaking strategy to fabricate sulfur-modified NiFe layered double hydroxide (S-NiFe-LDH) catalysts for efficient OER in both alkaline freshwater and seawater electrolytes. The introduction of sulfur not only optimizes the electronic structure of NiFe-LDH to strengthen intrinsic catalytic activity and speed up charge transfer, but also promotes the formation of a Cl⁻-resistant layer, thus significantly improving corrosion resistance. In addition, DFT calculations show sulfur modification in NiFe layered double hydroxide upshifts the O 2p-band center to activate lattice oxygen, switches the oxygen evolution reaction pathway to the lattice oxygen mechanism with reduced thermodynamic barriers, and realizes the selective adsorption of OH⁻ over Cl⁻. As a result, the as-prepared S-NiFe-LDH catalyst exhibits exceptional OER performance, requiring overpotentials (η) of 250, 270, and 290 mV to reach current densities of 50, 100, and 200 mA·cm⁻² in 1 M KOH, respectively, with a Tafel slope of 22.3 mV·dec⁻¹. Moreover, it maintains remarkable stability for more than 200 h in alkaline seawater electrolytes and achieves nearly 100% Faradaic efficiency for water splitting, effectively avoiding the parasitic chlorine evolution reaction (CER). This work provides a scalable and energy-efficient synthetic route for designing advanced non-noble metal catalysts, paving the way for industrial-scale hydrogen production from seawater. Full article