Search Results (434)

Mechanical scratches that penetrate the protective layers expose the steel substrate and establish a zinc–steel galvanic couple beneath an electrolyte film. This study develops a mechanism-oriented multiphysics model of scratch-width-dependent galvanic protection loss in hot-dip galvanized (HDG) steel enclosures. The model couples Butler–Volmer interfacial kinetics with equilibrium potentials related through the Nernst framework, Nernst–Planck transport of Zn²⁺, OH⁻, Na⁺, Cl⁻, and dissolved O₂, electrolyte charge conservation, reaction-derived boundary fluxes, a simplified corrosion-product deposition and transport-resistance treatment, and level-set tracking of interface evolution. Numerical field cases at scratch widths of 1, 3, and 5 mm show that widening the scratch increases the exposed-steel cathodic demand and lengthens the ionic-current path from the zinc edges to the scratch center. The resulting ohmic drop reduces the protective current and permits local iron dissolution when the center can no longer be maintained at a sufficiently negative potential. NSS morphology, cross-sectional SEM/EDS, corrosion-depth trends, and XRD observations show qualitative consistency with this mechanism. Under the investigated NSS conditions, a marked descriptive change occurs between the experimentally sampled widths of 2 and 3 mm, with 3 mm representing the first sampled condition showing pronounced protection loss. Because replicate-level corrosion-depth data and independent electrochemical measurements are unavailable, no statistical significance or quantitative model validation is claimed. Full article

This study investigates the direct tensile mechanical behavior of cement mortar plates reinforced with a galvanized steel mesh and randomly incorporated alkali-resistant glass fibers. An experimental program was executed using direct tensile tests on thin mortar specimens containing fiber volumetric fractions of 0%, 4%, 6%, 8%, and 10% relative to the cement volume. To rigorously characterize the mechanical response, the study quantified the apparent initial stiffness, 0.2% offset stress, ultimate tensile strength, and post-offset energy absorption capacity. Results indicate that increasing alkali-resistant glass-fiber content systematically modified the global tensile response of the composite system. At 10% glass-fiber content, the mean crosshead-derived apparent initial tensile stiffness was 10.43 times that of the reference group without glass fibers. The characteristic stress determined using the adopted 0.2% offset criterion and the ultimate tensile strength increased by 154.5% and 74.1%, respectively, while the apparent post-offset energy absorption increased by 68.4%. Because strain was derived from crosshead displacement, the apparent stiffness and energy-absorption parameters represent the global specimen–grip–machine response rather than intrinsic material properties. The experimental results exhibited acceptable repeatability, although the apparent tensile stiffness showed greater variability than the strength-related parameters. These findings support the continued development of the investigated composite configuration for thin cementitious elements requiring improved tensile response and damage tolerance. Full article

The aim of this work is to investigate the influence of different welding technologies on the mechanical properties and corrosion resistance of welded joints of SGH340D + ZMA steel with a Zn–Mg–Al (ZMA) protective coating. Two different welding technologies were used: the gas metal arc welding(GMAW) process at a welding speed of 0.8 m/min and laser welding at speeds of 2 and 4 m/min. Mechanical properties were determined using tensile testing and hardness testing. Corrosion resistance was estimated using a salt spray test. Residual stresses were determined experimentally using the drill hole method. The highest residual stresses were measured in GMAW-welded joints, while the lowest were measured in laser-welded joints at a speed of 4 m/min. The sample welded by laser at a speed of 4 m/min exhibited hardness values close to the upper acceptable limit, indicating that further increases in welding speed without preheating may lead to excessive hardness. All samples exhibited good corrosion resistance in a salt chamber. According to the results, increased welding speed reduced residual stresses but increased the risk of brittle fracture. Full article

Aluminium remains relatively uncommon in civil structures; however, its durability and light-weight nature make it an attractive alternative for vehicular bridges. Recent applications use aluminium bridge decks supported by steel girders. However, galvanic corrosion and thermal incompatibility limit full and optimised behaviour. This research explores the use of Bobbin Tool Friction Stir Welding (BTFSW), which improves the welded aluminium behaviour while significantly improving fatigue detail classification, as it is critical for bridges. This configuration optimises material use, reduces structural weight, and supports Accelerated Bridge Construction (ABC) practices by enabling modular prefabrication and rapid installation. The findings highlight aluminium’s potential as a primary bridge material. Full article

This study systematically investigates the effects of Ni and Al addition to a zinc bath on the microstructure, corrosion resistance and Vickers hardness of hot–dip galvanized coatings on Q235 steel. The Zn, Zn–0.04 wt.% Ni and Zn–0.04 wt.% Ni–1 wt.% Al coatings are characterized by scanning electron microscopy (SEM), X–ray diffraction (XRD), neutral salt spray (NSS) testing, electrochemical measurements and Vickers hardness testing. The addition of Ni refines and thins the ζ phase, increases the thickness of the δ phase, reduces the total coating thickness to 56.33 ± 0.89 μm and improves the corrosion resistance. With further Al addition, a continuous and dense inhibition layer forms at the interface, and the coating consists solely of this inhibition layer and the η phase; the total thickness is drastically reduced to 17.66 ± 1.78 μm, accompanied by a substantial improvement in both corrosion resistance and hardness. Electrochemical analysis reveals that the Zn–0.04 wt.% Ni–1 wt.% Al coating exhibits the most negative corrosion potential (0.61 V) and the smallest corrosion current density (2.07 μA·cm⁻²). Characterization of the corrosion products reveals that Al helps to stabilize Zn₅(OH)₈Cl₂·H₂O and Zn₅(OH)₆(CO₃)₂, thereby enhancing the corrosion resistance of the coating. Full article

Global decarbonization represents one of the defining challenges of the 21st century. Geothermal energy offers a robust alternative for reducing fossil fuel dependency for both residential and industrial heating and cooling. While shallow geothermal systems are versatile and high-performing, comprehensive Life Cycle Assessments (LCA) remain scarce in the literature. This study evaluates the environmental impact of the manufacturing and installation processes of next-generation coaxial probes featuring a galvanized steel outer tube and an internal polyethylene pipe. The LCA identifies material composition as the primary environmental driver: steel production accounts for 41% of the total impact, while the hot-dip galvanization process contributes 30%, significantly affecting the “climate change” and the “resource use” categories. A comparative LCA with conventional double U-tube installations shows similar overall environmental impacts. A sensitivity analysis on the coaxial probes was conducted to explore potential mitigation strategies aimed at reducing the associated environmental impacts, providing indications for sustainable eco-design. The LCA results demonstrate that optimizing the design, specifically by reducing the steel quantity in the coaxial outer tube and avoiding the zinc coating process, results in a 34% reduction in total environmental impact, confirming that LCA is a fundamental tool for supporting the environmental sustainability of developing technologies. Full article

Long-span transmission towers in the Yangtze River basin are exposed to coupled low-temperature, high-humidity and strong-wind conditions, which promote nonuniform ice accretion on steel members and increase structural loads and ice-shedding risks. Although superhydrophobic coatings are promising passive anti-icing materials for civil infrastructure, most existing evaluations use idealized flat or cylindrical specimens and do not capture the geometry, substrate condition and coating uniformity of in-service tower members. Here, a multifactor coupled icing simulation system was developed, and comparative icing tests were conducted on three representative steel members (aged plain circular steel tube, new galvanized circular steel tube and new galvanized angle steel) under controlled temperature, wind speed, spray rate and icing duration. For uncoated members, ice mass increased with supercooling degree and spray rate, first increased and then decreased with wind speed, and exhibited a decelerating growth pattern within 24 h. The superhydrophobic coating reduced ice mass, ice thickness and circumferential nonuniformity under all tested conditions, but its effectiveness depended strongly on environmental loading and member geometry. Under reference conditions, the ice-reduction rates reached 41%, 45% and 38% for the three members, respectively, and remained 27–32% after 24 h of icing. Smooth circular substrates showed the best coating response, whereas angle steel was less effective because edge-induced flow distortion and poor coating uniformity promoted local wetting failure. Performance degradation under harsh conditions was associated with accelerated freezing, water-film formation and localized wetting failure. These findings define the applicability and durability limits of superhydrophobic coatings for passive anti-icing protection of long-span transmission tower steel members. Full article

The efficiency of cathodic protection in the tidal zone, in particular in its highest part, remains questionable. To address this problem, experimental vertical structures were designed and set in a commercial seaport. Each structure was composed of 10 cm × 10 cm carbon steel coupons and 50 cm × 10 cm carbon steel strips to obtain a 5.1 m long continuous structure extending all along the tidal zone. Cathodic protection of the structures was carried out with an Al-Zn-In galvanic anode permanently immersed in seawater. The mineral layers formed on the coupons after 32 and 52 months were analyzed by XRD and µ-Raman spectroscopy. The evolution of the mineral layer from the low water zone to the splash zone was due to (i) the decreasing efficiency of the cathodic protection and (ii) the changes in corrosion processes, from those typical of a permanent immersion to those typical of atmospheric corrosion. In particular, brucite Mg(OH)₂ was found up to the high tide zone and, in agreement with the estimated degradation of the coupons, its formation was an indicator of the altitude at which the cathodic protection remained efficient. Full article

This study investigates the design, microstructure, and performance profile of a novel composite coating combining a high-entropy alloy (HEA) matrix with cermet reinforcement. A 50wt.%CoCrFeMnNi_0.8V–50wt.% Cr₃C₂-Ni₈₀Cr₂₀ powder mixture was successfully deposited onto steel substrates via high-velocity oxy-fuel (HVOF) thermal spraying. Microstructural analysis revealed a highly dense, well-bonded coating architecture (450–500 μm thick) where partially melted, spherical HEA splats were uniformly surrounded by the Cr₃C₂-Ni₈₀Cr₂₀ phase. X-ray diffraction confirmed a complex multiphase evolution consisting of FCC, BCC, and σ-NiCr phases driven by the rapid solidification inherent to the HVOF process. Tribological evaluations via ball-on-disc testing demonstrated that incorporating the Cr₃C₂-Ni₈₀Cr₂₀ reinforcement significantly improves wear resistance compared to the monolithic HEA coating. The composite’s wear behavior is governed by a synergistic mechanism: the ductile HEA matrix accommodates plastic deformation, while the harder carbide particles enhance load-bearing capacity, transitioning from adhesive wear to mild third-body abrasion and protective tribo-oxidation. Conversely, electrochemical testing in a 3.5 wt.% NaCl solution showed that the composite coating exhibits higher corrosion current densities (10.53 × 10⁻⁶ A/cm²) and more active corrosion potentials than the pure HEA matrix. This behavior is attributed to localized micro-galvanic cells forming at the heterogeneous interfaces between the different phases, alongside chloride-induced destabilization of the surface oxide film. Overall, the novel composite coating offers a compelling, sustainable alternative for surface engineering applications requiring a balanced trade-off between mechanical toughness and acceptable environmental durability. This behavior is also verified by the comparison with previous results dealing with monolithic CoCrFeMnNi_0.8V and 75wt.%CoCrFeMnNi_0.8V–25wt.% Cr₃C₂-Ni₈₀Cr₂₀ thermal sprayed coatings, where it is evident that the increase of the reinforcing phase leads to an optimum combination of properties. Full article

Selective laser melting (SLM) can effectively suppress metallurgical defects inherent to conventional manufacturing; however, subsequent aging treatments essential for engineering applications introduce secondary precipitates that alter the electrochemical homogeneity of the matrix. The underlying mechanism by which such precipitation behavior governs corrosion resistance remains elusive. In this study, a Fe-30Mn-8Al-1.5C-2.5Ni steel was investigated to elucidate the corrosion morphology and electrochemical behavior of the as-built, 450 °C-aged, and 750 °C-aged specimens during immersion in a 3.5 wt.% NaCl solution. The results demonstrate that the inherent Mn microsegregation and high-density subgrain boundaries induced by SLM trigger preferential localized anodic dissolution on the surface of the as-built sample, culminating in the formation of a loose, porous manganese oxide product layer. Aging treatment at 450 °C induces extensive precipitation of κ-carbides within grain interiors and along grain boundaries, accompanied by localized depletion of Al and Mn at the phase interfaces. A pronounced micro-galvanic coupling established between the κ-carbides and the adjacent Al-depleted zones directly compromises the continuity of the passive film, thereby further deteriorating the corrosion resistance. In contrast, aging at 750 °C relieves the residual stress and eliminates the as-built elemental microsegregation. The resulting compositional homogenization of the matrix reduces the localized electrochemical driving force, which promotes a uniform reaction of Al at the surface to construct a continuous, compact Al-rich passive film, thereby sustaining the highest charge-transfer resistance during long-term immersion. This work elucidates the correlation among the intrinsic defects of SLM, aging-induced solute-depleted zones, κ-carbide precipitation, and localized micro-galvanic corrosion, providing a fundamental basis for tailoring the microstructure and corrosion resistance of additively manufactured lightweight steels. Full article

Direct hot press forming (DHPF) of Zn-coated press-hardening steel (PHS) has not been widely adopted by industry due to liquid metal embrittlement (LME), which occurs when coated steel is hot stamped above the Fe-Zn peritectic temperature (~782 °C). In the present study, low-temperature hot stamping was performed on a 2.0 wt% Mn PHS to avoid LME by preventing liquid zinc formation during plastic deformation while achieving target mechanical properties (yield strength (YS) ≥ 1100 MPa and ultimate tensile strength (UTS) ≥ 1500 MPa) and preserving corrosion performance. The enhanced hardenability, indicated by a critical cooling rate (CCR) of 10 °C/s, enabled a predominantly martensitic microstructure following DHPF at 550–700 °C. Tensile testing of samples extracted from U-shaped panels yielded similar results for uncoated and Zn-coated samples, with a YS of ~1170 MPa, a UTS of ~1600 MPa, a uniform elongation (UE) of 0.05, and a total elongation (TE) of 0.09, demonstrating the preservation of baseline mechanical properties in the coated samples. Microstructural analysis confirmed the absence of LME-induced substrate cracking. Additionally, XRD, SEM-BSE, and EDS analyses confirmed Γ-Fe₃Zn₁₀ formation in DHPF galvanized coatings, with volume fractions averaging ~0.6, well above the critical value of 0.15, irrespective of the DHPF temperature, demonstrating the formation of a cathodically protective coating microstructure. Full article

The objective of this study was to quantitatively evaluate the effect of metallic pipe thickness on position-dependent temperature rise characteristics in vertical pipe firestop systems. Carbon steel (CS) pipes, stainless steel (SS) pipes, and a 0.5 mm galvanized steel spiral duct (GSD) were tested under the same 120 min standard fire exposure, and temperatures at key measurement positions were compared. Thinner metallic pipes produced higher temperature rises, with the clearest difference observed at the upper insulation. At 120 min, CS 3.0 and SS 2.8 reached approximately 200 and 195 °C, whereas CS 7.0 and SS 7.0 remained at approximately 106 and 114 °C, respectively. GSD 0.5 showed the highest initial rise rate at the pipe surface (~3.4 °C/min during 0–30 min). Regression analysis showed a clear relationship between cross-sectional area and upper-insulation temperature, with R² values of 0.921 and 0.878 for CS and SS at 60 min and 0.999 and 0.865 at 120 min. Conversely, the ratio of room-temperature thermal conductivity to cross-sectional area did not consistently improve this relationship. These results indicate that pipe thickness and metallic cross-sectional area should be considered when determining approval ranges for metallic pipe firestop systems. Full article

This study focuses on ways to improve the adhesion of organic coatings in a duplex anticorrosion protection system for S235JRG2 steel. To this end, the steel was mechanically pretreated by blasting with synthetic corundum (F40). Subsequently, the effect of this treatment on the indirect increase in the adhesion of the organic coating applied to the inorganic coating was analyzed. The inorganic coatings comprised electrogalvanized zinc and hot-dip galvanized zinc, while the organic system consisted of a water-borne coating. The reference specimens comprised cold-rolled steel surfaces (without mechanical pretreatment) and chemically pretreated zinc layers (prepared by Cr³⁺-based passivation). The mechanical surface pretreatments were characterised by surface roughness parameters (ISO 21920-2). The quality of the deposited inorganic coatings was evaluated using metallographic cross-sections. The adhesion of the organic coatings was assessed by a pull-off adhesion test (ISO 4624). The quantitative evaluation (pull-off strength) was carried out using a universal testing machine, while the qualitative analysis, namely the extent of adhesive and cohesive failure, was performed by digital image analysis in ImageJ. Degradation testing was conducted in a neutral salt spray environment (ISO 9227). The results indicate that the most pronounced increase in adhesion can currently be achieved by means of a conversion interlayer. In terms of indirect adhesion enhancement, a statistically significant increase relative to the rolled reference specimen was demonstrated for the electrogalvanized zinc layer. The degradation test results likewise suggest a positive effect on the operational reliability of the components. These findings open up new scope for further research into more environmentally friendly mechanical surface pretreatment methods. Full article

HVAC air filtration systems can be designed as either disposable or reusable units, with each approach involving different material, operational, and end-of-life requirements. However, the environmental performance of reusable HVAC filtration systems remains insufficiently characterized. This study conducted a cradle-to-grave Life Cycle Assessment (LCA) comparing reusable and disposable HVAC air filters under equivalent service conditions using the TRACI 2.1 impact assessment method in accordance with ISO 14040 and ISO 14044 standards. The analysis compared one reusable Delta M filter with eight equivalent disposable filters over the same filtration service period. Initial single-cycle comparisons showed that the reusable filter exhibited higher impacts due to increased structural material requirements associated with durable design. However, repeated refurbishment and reuse substantially reduced overall life cycle environmental burdens. At the defined functional unit, the reusable filtration system reduced global warming potential by approximately 69% (6.20 vs. 20.27 kg CO₂ eq) while also reducing ozone depletion, smog formation, acidification, eutrophication, respiratory effects, ecotoxicity, fossil fuel depletion, and non-carcinogenic impacts relative to the disposable filtration system. Environmental break-even analysis indicated that the reusable system began outperforming the disposable alternative after approximately two operational filtration cycles, while end-of-life material recovery further improved environmental performance beyond the baseline landfill scenario. Contribution analysis identified PVC frame production, polyester filtration media manufacturing, and galvanized steel mesh production as the dominant environmental hotspots. The results demonstrate that combining durable product design, repeated reuse, and end-of-life material recovery can substantially improve the long-term environmental performance of commercial HVAC filtration systems while supporting circular economy and sustainable building objectives. Full article

6061 aluminum alloy is lightweight and has good thermal conductivity, while 304 stainless steel possesses excellent mechanical properties and corrosion resistance; both have broad application prospects in cooling circuits. Propylene glycol coolant shows great potential in liquid cooling systems due to its low toxicity and good antifreeze properties. However, during operation, galvanic corrosion may occur when the two metals come into direct contact within the coolant, thereby threatening system safety and service life. This study focuses on 6061 aluminum alloy, 304 stainless steel, and their galvanic couples. Electrochemical testing, SEM, 3D confocal microscopy, and XPS were used to systematically investigate their self-corrosion and galvanic corrosion behavior in propylene glycol coolant at pH values of 4.8, 6.8, and 8.8. The results indicate that 6061 aluminum alloy is more sensitive to pH changes; its corrosion resistance first increases and then decreases as pH rises, with the least corrosion occurring at pH = 6.8 and the most severe at pH = 4.8. 304 stainless steel exhibited lower corrosion rates at pH 6.8 and 8.8, but corrosion significantly worsened at pH 4.8. For the 6061 aluminum alloy/304 stainless steel couple, the galvanic current first decreased and then increased with rising pH, while the galvanic potential first increased and then decreased. The 6061 aluminum alloy consistently acted as the anode, and the 304 stainless steel consistently acted as the cathode, with the highest sensitivity to galvanic corrosion observed at pH 4.8. XPS analysis shows that under different pH conditions, the corrosion products of 6061 aluminum alloy are Al(OH)₃ and Al₂O₃, while the main components of the passivation film on 304 stainless steel remain unchanged. Full article