Search Results (169)

Weathering steel (WS) is widely used in bridge construction due to its high corrosion resistance, durability, and low maintenance requirements. This paper reviews the performance of WS bridges in Canadian climates, focusing on the formation of protective patina, influencing factors, and long-term maintenance strategies. The protective patina, composed of stable iron oxyhydroxides, develops over time under favorable wet–dry cycles but can be disrupted by environmental aggressors such as chlorides, sulfur dioxide, and prolonged moisture exposure. Key alloying elements like Cu, Cr, Ni, and Nb enhance corrosion resistance, while design considerations—such as drainage optimization and avoidance of crevices—are critical for performance. The study highlights the vulnerability of WS bridges to microenvironments, including de-icing salt exposure, coastal humidity, and debris accumulation. Regular inspections and maintenance, such as debris removal, drainage system upkeep, and targeted cleaning, are essential to mitigate corrosion risks. Climate change exacerbates challenges, with rising temperatures, altered precipitation patterns, and ocean acidification accelerating corrosion in coastal regions. Future research directions include optimizing WS compositions with advanced alloys (e.g., rare earth elements) and integrating climate-resilient design practices. This review highlights the need for a holistic approach combining material science, proactive maintenance, and adaptive design to ensure the longevity of WS bridges in evolving environmental conditions. Full article

The suitability of 347H stainless steel (SS347H) for chloride salt environments is critical in selecting materials for next-generation concentrated solar power (CSP) systems. This study investigated the corrosion behavior of SS347H in a ton-scale purification system with continuously flowing chloride salt under three conditions: exposure to NaCl-KCl-MgCl₂ molten salt vapor, immersion in molten salt, and at the molten salt surface interface. Results revealed that corrosion was most severe in the molten salt vapor, where HCl steam facilitated Cl⁻ reactions with Fe and Cr in the metal, causing dissolution and forming deep corrosion pits. At the interface, liquid Mg triggered displacement reactions with Fe²⁺/Cr²⁺ ions in the salt, depositing Fe and Cr onto the surface, which reduced corrosion intensity. Within the molten salt, Mg’s purification effect minimized impurity-induced corrosion, resulting in the least damage. In all cases, the primary corrosion mechanism involves the dissolution of Fe and Cr, with the formation of minor MgO. These insights provide valuable guidance for applying 347H stainless steel in chloride salt environments. Full article

Eco-friendly mortars have been manufactured with hybrid binders made of blast furnace slag and a reduced amount of clinker. The objective is to explore new formulations suitable for reinforced structures. Previous studies are mainly focused on activation with sulfates, a salt that is corrosive to reinforcing steel. Sodium nitrate and sodium carbonate, easily implementable in construction, have been used as activators in two different concentrations that involve similar Na content. A Type II PC mortar is used as reference. The dimensional stability of the mortars during curing (at 99% RH) and subsequent drying at 40% RH, has been evaluated, as well as their porosity and mechanical properties. Böhme tests revealed that studied hybrid binders have lower wear resistance than PC mortar. Activation with Na₂CO₃ allows the obtention of mortars with reduced porosity and good compression resistance, but generates microcracking that favors chloride diffusion. Activation with nitrates favors precipitation of AFm phases identified through differential thermal analysis. Nitrates in moderate amounts (4% w/w) allow manufacturing hybrid mortars with good resistance to chloride penetration and reasonably good mechanical properties. Hence, this binder can be a promising option for reinforced structures. Higher amounts of nitrates (8%) for activation give rise to more porous mortars. Full article

The slurry aluminizing process is widely employed to enhance the oxidation and corrosion resistance of nickel-based superalloys used in high-temperature environments such as gas turbines and aerospace engines. This study investigates the effects of the concentration of Al vapors in the reactor chamber and the initial slurry layer thickness on the microstructure, chemical composition, and phase composition of aluminide coatings. Coatings were manufactured on Ni-based superalloy substrates using CrAl powders as an aluminum source and chloride- and fluoride-based activator salts. The effect of the initial thickness of the slurry layer was studied by varying the amount of deposited slurry in terms of mg_slurry/cm²_sample (with constant mg_slurry/cm³_chamber). The microstructure and phase composition of the produced aluminide coatings were evaluated by SEM, EDS, and XRD analysis. Slurry thickness can affect concentration gradients during diffusion, and the best results were obtained with an initial slurry amount of 100 mg_slurry/cm²_sample. The effect of the Al vapor phase in the reaction chamber was then investigated by varying the mg_slurry/cm³_chamber ratio while keeping the slurry layer thickness constant at 100 mg_slurry/cm²_sample. This parameter influences the amount of Al at the substrate surface before the onset of solid-state diffusion, and the best results were obtained for a 6.50 mg_slurry/cm³_chamber ratio with the formation of 80 µm coatings (excluding the interdiffusion zone) with a β-NiAl phase throughout the thickness. To validate process flexibility, the same parameters were successfully applied to produce platinum-modified aluminides with a bi-phasic ζ-PtAl2 and β-(Ni,Pt)Al microstructure. Full article

The preparation of low-cost and high-durability cement-based material systems using seawater mixing has become an urgent task in marine engineering construction. The requirements have addressed key challenges, including high transportation costs for fresh water and raw materials, poor structural durability, and difficulty in meeting actual construction schedules. Sulfatealuminate cement (CSA) has become an ideal material for marine engineering due to its high corrosion resistance, rapid early strength, which is 35–40 MPa of 3-day compressive strength and is 1.5–2 times compared ordinary Portland cement (OPC), and low-carbon characteristics, reduced production energy consumption by 35–50%, and CO₂ emissions of 0.35–0.45 tons/ton. The Cl⁻ and SO₄²⁻ in seawater can accelerate the hydration of CSA, promote the formation of ettringite (AFt), and generate Friedel’s salt fixed chloride ions, significantly enhancing its resistance to chloride corrosion. Its low alkalinity (pH ≈ 10.6) and dense structure further optimize its resistance to sulfate corrosion. In terms of environmental benefits, CSA-mixed seawater can save 15–20% fresh water. And the use of solid waste preparation can reduce environmental burden by 38.62%. In the future, it is necessary to combine multi-scale simulation to predict long-term performance, develop self-healing materials and intelligent control technologies, and promote their large-scale application in sustainable marine infrastructure. Full article

Cement-based materials used in China’s coastal and salt lake areas in the northwest are exposed to long-term chloride corrosion, which deteriorates the materials and substantially reduces the durability of the structures. This study investigates the chlorine ion erosion resistance in salt spray environments of cement-based materials made with iron ore tailings (IOTs) as an aggregate (namely, IOTCs). The compressive strength, mass loss, and relative dynamic elastic modulus (RDEM) macroscopic performance of IOTC undergoing different chloride diffusion times (0–180 d) were explored in detail. Chloride ion profiles at 0–180 d were analyzed via chemical titration, while X-ray computed tomography (CT) and scanning electron microscopy (SEM) were employed to characterize microstructural evolution. The results demonstrate that IOTC exhibited superior chloride resistance compared to conventional concrete (GC). While both materials showed early strength gain (<60 d) due to hydration and pore-filling effects, IOTC experienced only a 23.9% strength loss after long-term exposure (180 d) significantly less than the 37.2% reduction in GC. Chloride profiling revealed that IOTC had 43.5% lower free chloride ions (C_f) and 32% lower total chloride ions (C_t) at 1 mm depth after 180 d, alongside reduced chloride diffusion coefficients (D_a). The CT analysis revealed that IOTC exhibited a significantly denser and more uniformly distributed pore structure than GC, with a porosity of only 0.67% under chloride-free conditions. SEM confirmed IOTC’s more intact matrix and fewer microcracks. Full article

Bolted spherical joints (BSJs) are widely used in spatial grid structures owing to their clear force transmission paths and ease of on-site assembly. This study investigates the corrosion behavior and tensile performance of BSJs fabricated with #45 carbon steel joint spheres and 40Cr high-strength bolts (grade 10.9S) under chloride exposure under varying bolt screwing depths. Accelerated salt spray corrosion tests were conducted across different exposure cycles (20, 40, 60, and 80 cycles) and at screwing depths ranging from 0.8 d to 1.2 d, followed by uniaxial tensile testing. Results revealed that chloride-induced pitting corrosion was more pronounced on bolts than on joint spheres, with four distinct types of microscopic corrosion morphologies identified. Inadequate screwing depth (<1.0 d) led to pull-out failure, while greater depths (≥1.0 d) generally resulted in bolt fracture. Chloride exposure significantly reduced the ultimate tensile capacity of BSJs. For bolts with λ < 1.0, post-corrosion tensile strength dropped below the specification threshold, indicating a critical safety concern. Full article

The increasing restriction of lead in industrial alloys, particularly in copper–zinc-based materials such as CuZn40Pb2, necessitates the development of environmentally safer alternatives. ZnAl15Cu1Mg (ZEP1510), a zinc-based wrought alloy composed of 15% aluminum, 1% copper, 0.03% magnesium, with the remainder being zinc, has emerged as a promising candidate for lead-free applications due to its favorable forming characteristics and corrosion resistance. This study investigates the performance of ZEP1510 compared to conventional leaded copper alloys and galvanized steel. Corrosion behavior was evaluated using neutral salt spray testing, cyclic climate chamber exposure, and electrochemical potential analysis in chloride- and sulfate-containing environments. ZEP1510 exhibited corrosion resistance comparable to brass and significantly better performance than galvanized steel in neutral and humid atmospheres. Combined with its low processing temperature and high recyclability, ZEP1510 presents itself as a viable and sustainable alternative to brass with lead for applications in sanitary, automotive, and electrical engineering industries. Full article

The corrosion behaviour of lean duplex S32101 (1.4162—X2CrMnNiN21-5-1) stainless steel was assessed in various corrosive environments relevant to the pulp and paper industry. Electrochemical techniques, including open-circuit potential measurements and cyclic polarisation, were used to evaluate the corrosion resistance of S32101 stainless steel in various acidic, saline, and industrial liquors such as black, green, and white liquors, as well as dissolved chlorine dioxide bleaching solutions. To evaluate the extent of damage and corrosion mechanisms, post-exposure surface analysis was conducted using scanning electron microscopy (SEM). The results showed that S32101 experienced pitting corrosion in chloride-containing solutions, particularly in salt and acidified-salt environments. Corrosion rates increased with rising temperatures across all solutions. The highest corrosion rate of 3.17 mm/yr was observed in the highly alkaline white liquor at 50 °C, whilst chlorine dioxide induced the least aggressive effects at all temperatures. The suitability of S32101 stainless steel in handling pulp and paper liquors is shown in its corrosion resistance against the bleaching medium and low-temperature saline solutions, but it is not recommended for prolonged exposure to high alkaline liquors or chloride-rich solutions. Full article

This study investigates the impact of KNO₃-based salt bath nitriding on the microstructure, hardness, and corrosion resistance of 20MnCr5 steel. The nitriding process was conducted at 600 °C for 3 h and resulted in a nitrogen diffusion zone with a thickness that varied across the specimen, reaching a maximum of 70 μm. X-ray diffraction (XRD) analysis revealed no detectable nitrides, indicating nitrogen primarily occupied interstitial sites in the ferrite lattice and caused a lattice expansion of ~0.16%. Nanoindentation measurements showed an 80% increase in surface hardness (10.2 GPa) compared to the substrate (5.67 GPa), attributed to the solid solution strengthening mechanism. In contrast, however, an 18% decrease in Young’s modulus was observed near the surface, likely due to nitrogen-induced lattice distortions and crystal defects. Electrochemical tests in a 3.5 wt.% NaCl solution showed improved corrosion resistance, with the nitrided specimen exhibiting a 58% lower corrosion rate (1.275 mm/year) compared to untreated steel (3.04 mm/year). Despite a cathodic shift in corrosion potential, indicating localized susceptibility, the surface layer acted as a partial barrier to chloride ingress. The study demonstrates that KNO₃-based salt nitriding is an environmentally friendly alternative to cyanide-based processes that offers good surface hardness and corrosion resistance, but needs to be further optimized. Full article

Salt lakes and the surrounding saline soils distributed across northwestern China and Inner Mongolia impose severe physicochemical corrosion on cement-based concrete. Understanding the corrosion products and mechanisms are crucial scientific and technological factors in ensuring the durability and service life of concrete structures in these regions. In this study, various analytical techniques—including X-ray diffraction, thermogravimetric–differential thermal analysis, X-ray fluorescence, and scanning electron microscopy coupled with energy-dispersive spectroscopy—were employed to systematically analyze the corrosion products of ordinary Portland cement (OPC) and high-performance concrete (HPC) specimens after eight years of field exposure in the Qarhan Salt Lake area of Qinghai. The study provided an in-depth understanding of the physicochemical corrosion mechanisms involved. The results showed that, after eight years of exposure, the corrosion products comprised both physical corrosion products (primarily sodium chloride crystals), and chemical corrosion products (associated with chloride, sulfate, and magnesium salt attacks). A strong correlation could be observed between the chemical corrosion products and the strength grade of the concrete. In C25 OPC, the detected corrosion products included gypsum, monosulfate-type calcium sulfoaluminate (AFm), Friedel’s salt, chloro-ettringite, brucite, magnesium oxychloride hydrate 318, calcium carbonate, potassium chloride, and sodium chloride. In C60 HPC, the identified corrosion products included Kuzel’s salt, Friedel’s salt, chloro-ettringite, brucite, calcium carbonate, potassium chloride, and sodium chloride. Among them, sulfate-induced corrosion led to the formation of gypsum and AFm, whereas chloride-induced corrosion resulted in chloro-ettringite and Friedel’s salt. Magnesium salt corrosion contributed to the formation of brucite and magnesium oxychloride hydrate 318, with Kuzel’s salt emerging as a co-corrosion product of chloride and sulfate attacks. Furthermore, a conversion phenomenon was evident between the sulfate and chloride corrosion products, which was closely linked to the internal chloride ion concentration in the concrete. As the chloride ion concentration increased, the transformation sequence of sulfate corrosion products occurred in the following order: AFm → Kuzel’s salt → Friedel’s salt → chloro-ettringite. There was a gradual increase in chloride ion content within these corrosion products. This investigation into concrete durability in salt-lake ecosystems offers technological guidance for infrastructure development and material specification in hyper-saline environments. Full article

The molten salt reactor is a fourth-generation nuclear power plant considered a long-term eco-friendly energy source with high efficiency and the potential for green hydrogen production. The selection of alloys for such reactors, which can operate for more than 30 years, is a primary concern because of corrosion by high-temperature molten salt. In this study, three Fe- and Ni-based alloys were selected as structural material candidates. Corrosion immersion tests were conducted in NaCl–KCl molten salt for 48 h at 800 °C and 40% RH conditions in an air environment. In the absence of moisture and oxygen removal, ClNaK salt-induced damage was observed in the investigated alloys. The corrosion behavior of the alloys was characterized using various techniques, including scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and Auger electron spectroscopy. The results show that the corrosion process can be explained by salt-induced surface damage, internal ion migration, and depletion to the surface. The corrosion rate is high in SS316L (16Cr-Fe), N10003 (7Cr-Ni), and C-276 (16Cr-Ni), in decreasing order. Based on the corrosion penetration, ion elution, and interfacial diffusion results, C-276 and N10003 are good candidates for structural materials for MSRs. Therefore, Ni-based alloys with high Cr content minimize surface damage and ion depletion in unpurified molten salt environments. This indicates that Ni-based alloys with high Cr content exhibit highly corrosion resistance. Full article

The corrosion behaviors in chloride environment of two commercial low-alloy steel bars were studied. Through cyclic wetting tests, accelerated corrosion experiments ranging from 1 to 576 h were conducted on low-alloy bars and original bars. Techniques such as OM, SEM, EDS, AFM, and XRD were employed to characterize the corrosion emergence and expansion behaviors of these bars in a simulated marine wetting and sun exposure environment. The designed low-alloy corrosion-resistant rebar achieved a 500 MPa yield strength. In each corrosion cycle, its corrosion loss and rate were lower than those of same-strength ordinary rebars. Analysis of the rust layer’s macro and micro morphology and alloy element distribution revealed alloy elements had little effect at corrosion initiation. In later corrosion, their enrichment led to a denser rust layer, effectively blocking corrosion expansion and chloride salt infiltration. After 72 h of accelerated corrosion, the corrosion rate growth of both bars slowed. The inner rust layer’s electrochemical potential increased, and local corrosion pits turned into uniform corrosion. The inner rust layer of the rebar formed more stable chromic acid with ionic compounds, reducing corrosion sensitivity. This study offers insights into steel bar corrosion and alloy element roles, guiding the preparation of low-alloy corrosion-resistant steel bars. Full article

The corrosion properties of 316L stainless steel (316L SS) alloy within molten NaCl-KCl salt were explored through a static immersion experiment carried out at 700 °C under Ar flow for 25, 50, 100, 200, and 400 h. The loss in weight of the corroded 316L SS alloy increased from 0.06 to 1.71 mg/cm², while the maximum corrosion depth increased from 1.71 to 14.09 μm. However, the corrosion rate initially increased from 27.54 μm/year to 93.45 μm/year and then decreased to 47.22 μm/year as the soaking time was increased from 25 to 400 h. The impurities in the molten salts produced corrosive Cl₂ and HCl, which corroded the 316L SS matrix. The accelerated selective Cr dissolution with small amounts of Fe and Ni resulted in intergranular corrosion as the time of corrosion was increased. The depletion depths for Ni, Cr, and Fe at 400 h were found to be 0.87 μm, 3.94 μm, and 1.47 μm, respectively. The formation of Cr and Fe oxides might potentially play a vital role. The grain boundary and outward diffusion of Mo may prevent the outward diffusion of Cr, thereby mitigating alloy corrosion. Therefore, molten chloride salt purification and the selection of stainless steel are crucial for developing future concentrated solar power technologies. The findings of this study provide guidelines for the use of 316L SS in NaCl-KCl salt at high temperatures. Full article

In the context of the global energy structure transformation, concentrated solar power (CSP) technology has gained significant attention. Its future trajectory is oriented towards the construction of ultra-high temperature (700–1000 °C) power plants, aiming to enhance thermoelectric conversion efficiency and economic competitiveness. Chloride molten salts, serving as a crucial heat transfer and storage medium in the third-generation CSP system, offer numerous advantages. However, they are highly corrosive to metal materials. This paper provides a comprehensive review of the corrosion behaviors of stainless steels and high-temperature alloys in molten salts. It analyzes the impacts of factors such as temperature and oxygen, and it summarizes various corrosion types, including intergranular corrosion and hot corrosion, along with their underlying mechanisms. Simultaneously, it presents an overview of the types, characteristics, impurity effects, and purification methods of molten salts used for high-temperature heat storage and heat transfer. Moreover, it explores novel technologies such as alternative molten salts, solid particles, gases, liquid metals, and the carbon dioxide Brayton cycle, as well as research directions for improving material performance, like the application of nanoparticles and surface coatings. At present, the corrosion of metal materials in high-temperature molten salts poses a significant bottleneck in the development of CSP. Future research should prioritize the development of commercial alloy materials resistant to chloride molten salt corrosion and conduct in-depth investigations into related influencing factors. This will provide essential support for the advancement of CSP technology. Full article