Search Results (418)

To investigate the corrosion resistance and service life of water-based epoxy-coated reinforcing bars under severe environmental conditions, HRB400 ribbed reinforcing bars were used as the substrate. Four types of water-based epoxy-coated reinforcing bars were prepared, containing 0.3% graphene–polyaniline (PAG), 0.3% iron oxide, 10% zinc phosphate, and 10% zinc–iron powder, respectively, with a bare reinforcing bar control group also included. In accordance with standards such as the ‘Design Standard for Durability of Concrete Structures’, durability tests were conducted under various conditions, including long-term immersion in marine chloride solutions, wet–dry cycling, de-icing salt freeze–thaw cycles, baking and immersion in saline soil, and concrete mixed with seawater. Corrosion current density (I_corr) was monitored using a three-electrode system and the linear polarisation method, and service life was predicted based on the Wiener process. The results indicate that, under all severe environmental conditions, the corrosion current density of the coated reinforcing bars was significantly lower than that of the bare reinforcing bars (BRBs). After 70 cycles of marine wet–dry cycling, the corrosion current density of the bare reinforcing bars reached 0.4569 μA·cm⁻², whilst that of the 0.3% PAG coating was 0.1103 μA·cm⁻², substantially lower than that of the bare bars (0.4569 μA·cm⁻²); after 110 freeze–thaw cycles in a de-icing salt environment, the corrosion current density of the bare reinforcing bars was 0.4480 μA·cm⁻², whilst that of the PAG-coated bars was 0.1003 μA·cm⁻². After 80 cycles of baking and immersion in a saline soil environment, the corrosion current density of the graphene–polyaniline-coated steel increased from 4.97 × 10⁻³ μA·cm⁻² to 0.1021 μA·cm⁻² (approximately a 20-fold increase), whilst that of the bare steel rose to 0.4489 μA·cm⁻². In concrete mixed with seawater, the corrosion current density of bare reinforcing bars reached as high as 8.60 μA·cm⁻² after 120 days, whereas that of coated reinforcing bars was 0.24 μA·cm⁻², markedly lower than 8.60 μA·cm⁻² for the bare bars. Lifespan predictions indicate that, provided that the specifications for concrete strength and protective layer thickness are met, water-based epoxy coatings have the potential to delay the onset of severe corrosion (I_corr ≥ 1 μA·cm⁻²) beyond the 50-year design threshold in seawater wet–dry cycling zones and saline soil environments, and are projected to meet the 100-year design requirements in de-icing salt environments. It should be noted that these projections are based on accelerated tests and require validation through long-term field performance data. Graphene-containing polyaniline nanocomposite coatings exhibited the best overall protective performance, whilst zinc phosphate coatings demonstrated outstanding stability in high-chloride environments. For the specific formulations tested in this study, the enhanced corrosion resistance is attributed to the synergistic combination of the epoxy matrix, inorganic fillers (TiO₂ and BaSO₄) and functional additives; these components collectively provide physical shielding, chemical passivation and dynamic pore-blocking effects. Within the scope of this study, the nanocomposite coating containing 0.3 per cent PAG exhibited the best overall protective performance. Full article

The initiation of electrochemical corrosion on steel surfaces begins with water molecule aggregation, though the atomic-scale mechanisms from adsorption and wetting to corrosive microdroplet formation remain unclear. Using molecular dynamics simulations, this work investigates the formation of corrosive aqueous micro-environments on iron-based surfaces during early condensation. It focuses on the regulatory effects of surface roughness and local hydrophilic sites on condensation nucleation, droplet growth, and wetting. Results show a linear correlation between droplet contact angle and solid–liquid interaction energy, with temperature dependence controlled by the substrate’s intrinsic wettability. For fence-type rough surfaces, we clarify the transition from a critical to a mixed (Cassie–Wenzel) wetting state, confirming that roughness enhances intrinsic wettability. Condensation analysis reveals that stronger solid–liquid interaction promotes water adsorption and induces a shift from dropwise to filmwise condensation, with interphase temperature difference driving heat transfer. On hydrophobic surfaces with local hydrophilic sites, these sites serve as preferential nucleation points. Their size effect can pin the three-phase contact line, leading to droplet growth in a high-contact-angle mode. This study offers an atomic-scale view of how condensation creates the initial aqueous environment required for electrochemical corrosion, providing theoretical insight into phase-change heat transfer and interfacial behaviour on complex surfaces. The findings guide the design of surfaces resistant to condensation-induced corrosion. Full article

Q355 carbon steel was exposed for 0.5 and 1 year in Pingtan Strait to examine how surface-wetness changes affect early rust-layer evolution and localized corrosion. Environmental monitoring, corrosion-rate measurements, rust-phase analysis, and electrochemical characterization were combined to characterize corrosion in this humid, salt-laden marine atmosphere. The exposure regime shifted from sustained wetness during the first half-year to frequent wet–dry cycling during the second. Although the average corrosion rate remained nearly unchanged, localized corrosion intensified and adjacent pits became interconnected. This change was closely associated with the evolution of the rust-phase assemblage and its spatial distribution. After 0.5 years, β-FeOOH was dominant, consistent with a long time of wetness (TOW) and Cl⁻ enrichment in surface electrolyte films, and pits remained largely isolated. After 1 year, Fe₃O₄ increased substantially and became the dominant phase, possibly because frequent wet–dry cycling altered oxygen transport within the rust and repeatedly produced locally oxygen-deficient conditions. Fe₃O₄ enrichment promoted continued pit deepening, followed by pit expansion and coalescence. Meanwhile, local α-FeOOH enrichment developed in relatively oxygen-rich regions near the rust surface and inhibited lateral pit propagation. Thus, shifts in the wetting regime of the humid, salt-rich Pingtan atmosphere markedly regulate localized corrosion of Q355 steel by controlling rust-phase evolution and spatial distribution. Full article

To investigate the effect of femtosecond laser scanning path on the surface integrity of 7075 aluminum alloy after paint removal, parallel, Z-shape, and loop-shape scanning were compared in terms of surface morphology, microstructure, chemical composition, roughness, wettability, and corrosion resistance. Parallel scanning effectively removed the paint while maintaining a surface roughness of 0.27 μm, close to that of the original substrate. The resulting regular unidirectional laser-induced periodic surface structures (LIPSS) yielded a water contact angle of 85°, consistent with the Wenzel wetting model. X-ray photoelectron spectroscopy (XPS) showed the lowest C 1s and O 1s peak intensities, the lowest lattice-oxygen fraction in Al₂O₃, the strongest metallic Al⁰ signal, and limited thermal oxidation. Electrochemical measurements showed the most positive corrosion potential (−0.974 V), the highest film resistance and charge-transfer resistance, and the best corrosion resistance for parallel scanning. By contrast, energy accumulation at the ends during Z-shape scanning and thermal accumulation at the corners and center during loop-shape scanning increased pit and recast-defect densities, oxidation, and corrosion degradation. Loop-shape scanning produced a surface roughness of 3.60 μm and a contact angle of 140.7°, indicating superhydrophobicity, but also the highest corrosion current density and the poorest corrosion resistance, showing that superhydrophobicity does not necessarily correspond to high corrosion resistance. The results show that scanning path affects LIPSS evolution, oxide-film integrity, and corrosion resistance through the spatial distribution of laser energy and thermal accumulation. Among the three paths, parallel scanning provided the best combination of paint removal, low substrate damage, and corrosion resistance, supporting its use in femtosecond-laser paint removal from aircraft aluminum alloy skins. Full article

Battery packs for new energy vehicles have evolved from simple load-bearing and protective assemblies into multifunctional safety structures integrating structural support, crash protection, thermal-runaway mitigation, flame retardancy, electrical insulation, electromagnetic interference shielding, waterproof sealing, and long-term reliability. Fiber-reinforced polymer composites are promising for upper covers, underbody shields, trays, cross beams, side frames, and local protective structures because of their low density, corrosion resistance, design flexibility, and functional-integration potential. However, composite-part performance is strongly governed by forming. Resin flow, impregnation, curing or cooling shrinkage, fiber orientation, filler dispersion, and interfacial bonding may induce voids, dry spots, resin-rich regions, delamination, warpage, and fiber waviness, thereby affecting load bearing, sealing, thermal protection, and durability. This review focuses on composite-forming technologies for new energy-vehicle battery packs. It summarizes component-level service requirements and material systems and compares representative forming routes, including sheet molding compound (SMC), prepreg compression molding/wet compression molding (PCM/WCM), resin transfer molding/high-pressure resin transfer molding (RTM/HP-RTM), vacuum-assisted resin transfer molding (VARTM), long-fiber thermoplastic direct processing (LFT-D), glass-mat thermoplastic (GMT), thermoplastic sheet forming, pultrusion, and multi-material joining. These routes are evaluated from six dimensions: material form, forming cycle, typical defects, representative mechanical performance, applicable components, and engineering maturity. The review further discusses defect mechanisms, performance effects, detection and control methods, and the roles of in-line monitoring, non-destructive testing, process simulation, machine learning, and digital twins in closed-loop quality manufacturing. Finally, engineering challenges are examined in multi-material joining, thermal-safety integration, low-carbon recycling, and standard certification. Composite-material battery-pack structures should therefore be developed as coordinated design and closed-loop manufacturing systems linking materials, processes, defects, performance, and validation. 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

Hydrophobic and superhydrophobic coatings have attracted considerable attention due to their ability to provide water repellency, self-cleaning, anti-corrosion, anti-icing, and anti-fouling properties, making them promising for a wide range of industrial applications. This review summarizes recent advances in the development of hydrophobic and superhydrophobic coatings, with particular emphasis on wetting mechanisms, material selection, coating formation approaches, durability issues, commercial implementation, and environmental aspects. The analysis examines the principal classes of materials used for coating fabrication, including polymeric materials, inorganic compounds, and composite systems. The mechanisms responsible for the formation of hydrophobic and superhydrophobic surfaces are discussed in terms of surface chemistry modification and hierarchical roughness generation. Attention is devoted to factors limiting long-term performance, such as mechanical wear, chemical degradation, ultraviolet exposure, climatic effects, hydrodynamic erosion, and adhesion-related failures, as well as to current strategies for improving durability. Commercially available technologies and their application areas are reviewed, and the environmental challenges associated with fluorinated compounds are considered. The analysis demonstrates that the combination of controlled surface morphology and reduced surface energy remains an effective approach for achieving durable hydrophobicity, with optimized coating systems reaching contact angles of 160–170° and retaining superhydrophobic properties for more than 500 h under demanding operating conditions. Future developments are expected to focus on environmentally friendly, multifunctional, and long-lasting coating systems. Full article

Severe localized corrosion in crude unit overhead systems is a critical integrity concern, particularly under transient wetting conditions. This study combines high-frequency online ultrasonic (UT) monitoring with a simplified dew-point temperature margin (ΔT) to evaluate short-term changes in corrosion severity during operation. Wall-thickness data obtained at 12 h intervals were used to derive long-term thinning trends and a short-interval corrosion rate indicator (CR_12h). CR_12h increased as ΔT decreased, indicating that reduced dew-point margin was associated with increased corrosion severity. Although ΔT is not an exact thermodynamic dew-point prediction, it served as a practical operational proxy for transient wet-corrosion propensity. The evaluation supported partial replacement of the affected column-top region with Alloy C-276 cladding. Follow-up inspection after four years showed approximately 0.1 mm of pitting, corresponding to about 0.025 mm/y, which was approximately one order of magnitude lower than the previous Type 405 stainless-steel cladding. These results demonstrate a practical approach for linking continuous corrosion-monitoring data with operational indicators and material-selection decisions in crude unit overhead systems. The study further illustrates how monitoring-derived insights can be translated into repair planning and subsequently validated through long-term field performance following material upgrade. Full article

Coal gangue concrete (CGC) is an effective green building material that can promote the resource utilization of solid waste. To study its durability performance and degradation mechanism under sulfate attack with dry-wet cycles, and to realize the intelligent prediction of mechanical properties, this study prepared CGC specimens with a water-to-binder ratio of 0.4, a fine aggregate replacement rate of 20%, and coarse aggregate replacement rates of 0%, 20%, 50%, 80%, and 100%. The specimens were tested under 30, 60, 90, and 120 dry-wet cycles in 10% MgSO₄ solution. Mass loss, relative dynamic elastic modulus, and compressive and flexural strength corrosion resistance coefficients were used as evaluation indices, and SEM and XRD were adopted to analyze microstructural deterioration. A database compiled from literature data was established, and six machine learning models-random forest (RF), artificial neural network (ANN), decision tree (DT), support vector machine (SVM), particle swarm optimization-artificial neural network (PSO-ANN), and particle swarm optimization-support vector machine (PSO-SVM) were constructed to predict the strength corrosion resistance coefficients. Test results indicate that all macroscopic indices first increased and then decreased with the number of dry-wet cycles. Early ettringite and gypsum products filled internal pores, while prolonged sulfate attack caused decalcification and structural degradation of C-S-H gel, resulting in obvious performance loss. The PSO-SVM model showed the best prediction accuracy, with R² values of 0.912 and 0.981 for compressive and flexural strength corrosion resistance coefficients, respectively. Feature importance analysis shows that dry-wet cycles had the most significant negative impact, followed by the coal gangue fine aggregate replacement rate. This study provides support for the durability evaluation and intelligent prediction of coal gangue concrete in sulfate environments. Full article

The corrosion-protection performance of zinc oxide-hybrid polymeric coatings is traditionally attributed to the individual contributions of their constituent phases. This study reveals that the calcination temperature of zinc oxide (ZnO) filler is a critical, previously overlooked processing parameter that dictates not only filler crystallinity but also the collective synergistic failure mechanism of the entire coating system. Herein, we demonstrate that incorporating ZnO calcined at 500 °C yields a ternary chitosan–graphene oxide–zinc oxide/epoxy (CS–GO–ZnO/EP) composite coating with a highly compact, dense morphology, minimal internal porosity, and exceptional filler dispersion, as validated by FTIR, XRD, and SEM analyses. The optimized CS–GO–ZnO/EP coating applied to carbon steel exhibits outstanding dry and wet pull-off adhesion strengths, the highest surface hydrophobicity (102.2°), and superior electrochemical barrier protection. Notably, after a 120-h immersion period in an aggressive 3.5 wt.% NaCl electrolyte, the CS–GO–ZnO/EP (500 °C) maintains excellent coating resistance (R_coat = 1.06 × 10⁵ Ω) and a minimized corrosion rate (CR = 0.074 mm/y). This thermal threshold is a key processing window that improves chemical bonding and compatibility between the different parts of the hybrid matrix without causing the severe nanoparticle sintering, phase aggregation, and micro-cracking that happen at 650 °C. This work offers a significant advancement in the design of eco-friendly, high-performance hybrid coatings, demonstrating that precise control of the inorganic phase’s thermal history provides a direct pathway toward superior durability, hydrophobicity, and electrochemical stability for carbon steel protection in aggressive marine environments. Full article

Cement-based grouting materials may suffer strength loss and impermeability degradation when exposed to oil- and gas-bearing corrosive environments. In this study, 7.0% waterborne epoxy resin was used as a polymer admixture to improve the durability of cement-based grout under coupled corrosive exposure. Actual corrosive fluid from an engineering site and accelerated dry–wet cycling were used to simulate the service environment. The evolution of mechanical properties, impermeability, and dominant microstructural damage was then examined. The results show that the unmodified grout deteriorated markedly during cyclic exposure. After 120 cycles, its compressive strength decreased from 37.4 MPa to 26.2 MPa, the elastic modulus decreased by 44.1%, and the impermeability pressure dropped from 0.9 MPa to 0.3 MPa. By contrast, the grout containing 7.0% waterborne epoxy resin showed better durability. The strength and modulus losses were limited to 17.4% and 21.0%, respectively, and the impermeability pressure remained at 0.6 MPa, about twice that of the unmodified grout. Microscopic results indicate that dry–wet alternation promoted aggressive ingress and crack growth. The epoxy phase formed a relatively continuous film in the matrix, reduced penetration pathways, and slowed internal damage development. Based on the observed damage evolution, a mechanical prediction model and a new impermeability grading method were established. These findings show the potential of polymer admixture modification for improving the long-term performance of cement-based grouting materials in aggressive environments. Full article

Municipal solid waste (MSW) incineration power generation has become the dominant waste treatment technology in China. However, acid flue gas dominated by HCl and SO₂ induces severe boiler corrosion, a surge in hazardous fly ash, and uncontrolled operational costs, significantly hindering the industry’s low-carbon transition. While conventional dry, semi-dry, and wet deacidification processes meet emission standards, they face an irreconcilable trilemma, failing to concurrently optimize removal efficiency, economic viability, and solid waste reduction. This review clarifies that high-temperature in-furnace deacidification represents a future development direction yet identifies two critical limitations: above 700 °C, external mass transfer remains the rate-controlling step, and the combined effects of CaSO₃ decomposition and sorbent sintering lead to inefficient desulfurization. Meanwhile, in the 130–400 °C range, HCl preferentially occupies active sites, inhibiting SO₂ adsorption. To address these challenges, this study proposes an innovative staged temperature–gradient synergistic deacidification pathway driven by catalytic oxidation. This strategy utilizes transition metals at high temperatures to oxidize SO₂ into SO₃, which is subsequently converted into thermally stable CaSO₄, while decoupling SO₂ pre-removal from the targeted capture of HCl in their respective optimal windows. Finally, four executable development directions are systematically proposed: industrial waste-based bifunctional sorbents, multi-field coupled gas–solid mass transfer intensification, staged deacidification processes, and full-process AI closed-loop control. These findings provide systematic theoretical support and actionable technical references for upgrading MSWI technology under China’s “Dual Carbon” and “Waste-Free City” initiatives. Full article

External corrosion of buried ferrous water mains remains the dominant driver of structural failure in aging water distribution networks, yet the mechanisms linking soil physical and chemical heterogeneity to corrosion kinetics and product phase evolution have not previously been synthesized into a unified critical framework. This review evaluates three partially competing accounts of electrochemical degradation—anodic dissolution coupled to oxygen reduction within porous rust layers, redox cycling of iron oxide phases driven by seasonal soil moisture fluctuations, and microbially influenced corrosion (MIC) mediated by direct extracellular electron transfer (EMIC) and chemical metabolite pathways (M-MIC)—and assesses the weight of evidence for each. We demonstrate that corrosion products retain electrochemical activity long after formation, functioning as dynamic redox mediators that continue the reactions responsible for their own growth: the reduction of lepidocrocite under anoxic conditions regenerates Fe²⁺ ions that sustain anodic dissolution and catalyze oxygen reduction, while repeated soil moisture cycles drive the irreversible transformation of γ-FeOOH to Fe₃O₄, which fundamentally alters the conductivity and cathodic capacity of the rust layer. The widely cited universal critical-moisture threshold of 65% water-holding capacity (WHC) is evaluated and found to be a single-point approximation contradicted by texture-resolved experimental data that show the critical degree of saturation ranges from S_r ≈ 0.5 in sand to S_r ≈ 0.8 in clay. Modern machine learning analyses of field corrosion databases confirm that chloride content, pH, pipe-to-soil potential, and water content are the four highest-ranked predictors of maximum pit depth, consistent with the mechanistic framework developed here. The classical cathodic depolarization model of SRB-driven corrosion is evaluated against EMIC evidence and found insufficient: measured pure-culture SRB corrosion current densities range from 14 to 135 µA cm⁻², not the milliampere-level values reported in some earlier reviews. An explicit research agenda is proposed to address the five most consequential unresolved mechanistic questions. Full article

Magnesium alloys are used or considered for lightweight structures and biodegradable implants, but high electrochemical activity, limited wear resistance, and localized corrosion still limit their service reliability. Plasma electrolytic oxidation (PEO), also called micro-arc oxidation (MAO), forms an adherent ceramic scaffold. Discharge channels, interconnected pores, thermal cracks, and a mechanically weak outer layer mean that the as-formed coating is rarely a complete protective system. This review examines advanced PEO/MAO-based composite coatings through a process–structure–function lens and develops an application-oriented design framework. The discussion covers PEO/MAO process-window control, electrolyte and particle engineering, sol–gel and polymer sealing, layered double hydroxide/inhibitor systems, self-healing reservoirs, superhydrophobic and slippery interfaces, Ca-P/hydroxyapatite and polymer biofunctionalization, and duplex coatings for wear, electrical, and thermal functions. Emphasis is placed on how these modules regulate defect connectivity, mass transport, interfacial stability, damage response, tribocorrosion, and biodegradation, as well as on the evidence needed to support each claimed function. The analysis indicates that coating performance is governed not by multilayer complexity alone, but by the compatibility among the ceramic scaffold, functional module, dominant failure mode, and service-specific validation protocol. Chloride-exposed structures require durable pore sealing and active inhibition; wear-critical components require coupled corrosion–wear assessment; and biodegradable implants require a degradation window that balances corrosion moderation, cytocompatibility, biofunctionality, and residual mechanical integrity. Remaining challenges include interfacial durability, finite inhibitor reservoirs, wetting-state instability, process reproducibility, scale-up, and life-cycle impacts. The proposed process maps and validation criteria are intended to support modular, testable, and application-specific PEO/MAO surface systems for magnesium alloys. Full article

Bentonite slurry (BS) and steel slag powder (SS) were co-utilized to develop bentonite-slurry/steel-slag foamed concrete (BS-SSFC). The evolution of compressive strength and the associated deterioration mechanisms were examined after repeated wetting–drying exposure in four environments, namely H₂O, H₂SO₄, NaOH, and Na₂SO₄, by combining mechanical testing with microstructural observations. The mix-design results indicate that, for the SS-only mixtures, 20% SS replacement produced a relatively high strength, whereas the binary SS-BS system reached its maximum strength at 10% SS and 5% BS; this combination was consequently adopted for the durability experiments. After 20 cycles, the severity of degradation followed Na₂SO₄ > H₂SO₄ > NaOH > H₂O. XRD and SEM-EDS evidence shows that sulfate ions in the H₂SO₄ and Na₂SO₄ solutions favored ettringite-type expansive products, and Na₂SO₄ further caused salt-crystallization pressure during drying. For NaOH exposure, the main damage was related to reduced stability of cementitious phases together with ion redistribution and localized re-precipitation in a strongly alkaline pore environment. Based on fractal theory, an empirical strength–degradation correlation model was established by using SEM-derived two-dimensional apparent areal porosity as a structural parameter and by linking fractal dimension with the number of cycles. Within the scope of the present experiments, the model captures the empirical link between strength loss and apparent pore-structure deterioration in BS-SSFC; however, its use remains dependent on the image-acquisition procedure, thresholding method, and material system considered. The results provide useful support for using BS-SSFC in aggressive engineering settings such as saline ground and acid-rain regions. Full article