Search Results (314)

Concrete structures in western saline soil regions are subjected to extreme environments with coupled dry-wet cycles and high concentrations of erosive ions such as Cl⁻, SO₄²⁻, and Mg²⁺, leading to severe degradation of mechanical properties. This study employed a simulated accelerated, high-concentration solution (Solution A, ~8× seawater salinity) similar to the composition of actual saline soil to perform accelerated dry-wet cycling corrosion tests on ordinary C40 concrete specimens for six corrosion ages (0, 5, 8, 10, 15, and 20 months). For each age, three replicate cube specimens were tested per property. The changes in cube compressive strength, splitting tensile strength, prism stress–strain full curves, and microstructure were systematically investigated. Results show that in the initial corrosion stage (0–5 months), strength exhibits a brief increase (compressive strength by 11.87%, splitting tensile strength by 9.23%) due to pore filling by corrosion products such as ettringite, gypsum, and Friedel’s salt. It then enters a slow deterioration stage (5–15 months), with significant strength decline by 20 months, where splitting tensile strength is most sensitive to corrosion. Long-term prediction models for key parameters such as compressive strength, splitting tensile strength, elastic modulus, peak stress, and peak strain were established based on grey GM(1,1) theory using the measured data from 0 to 20 months, achieving “excellent” accuracy (C ≤ 0.1221, p = 1). A segmented compressive constitutive model that considers the effect of corrosion time was proposed by combining continuous damage mechanics and the Weibull distribution. The ascending branch showed high consistency with the experimental curves. Life prediction indicates that under natural dry-wet cycling conditions, the service life of ordinary concrete in this region is only about 7.5 years when splitting tensile strength drops to 50% of initial value as the failure criterion, far below the 50-year design benchmark period. This study provides reliable theoretical models and a quantitative basis for durability design and life assessment of concrete structures in western saline soil regions. Full article

The steering linkage represents a key subsystem of any automobile, playing a direct role in vehicle handling, driving safety, and overall comfort. Within this mechanism, the tie rod and tie rod end are crucial for transmitting steering forces from the gear to the wheel hub. A typical issue that gradually develops in these components is the clearance appearing in the spherical joint, caused by wear, corrosion, and repeated operational stresses. Even small clearances can noticeably reduce stiffness and natural frequencies, making the system more sensitive to vibration and premature failure. In this work, the effect of spherical joint clearance on the dynamic behavior of the tie rod-tie rod end assembly was analyzed through numerical simulation combined with experimental observation. Three-dimensional CAD models were meshed with tetrahedral elements and subjected to modal analysis under several clearance conditions, while boundary constraints were set to replicate real operating conditions. Experimental measurements on a dedicated test rig were used to assess joint clearance and wear in service parts. The results indicate a strong nonlinear relationship between clearance magnitude and modal response, with PTFE bushing degradation identified as the main source of clearance. These findings link the evolution of clearance to the change in vibration characteristics, providing useful insight for diagnostic approaches and predictive maintenance aimed at improving steering reliability and vehicle safety. Full article

This paper is the first to reveal that the conventionally built aluminium alloy (AA) 7085-T7452 has mechanical properties, viz: a yield stress, ultimate strength, and an elongation to failure, that are similar to that of laser powder bed fusion (LPBF) built Scalmalloy^®. Following this observation, the growth of cracks that nucleated from corrosion pits in AA7085-T7452 specimens that had been exposed to a 5 wt% NaCl salt fog environment at 35 °C according to ASTM B117-19 standard for fourteen days is then studied. The specimen geometries were chosen to be identical to those associated with a similar study on Boeing Space, Intelligence, and Weapon Systems (BSI&WS) LPBF built Scalmalloy^®. This level of prior exposure led to pits in AA7085-T7452 that were approximately 0.5 mm deep with a surface width/diameter of up to approximately 1.5 mm. These pit sizes are broadly consistent with those leading to fatigue crack growth (FCG) in AA 7050-T7451 structural parts on the RAAF F/A-18 Classic Hornet fleet operating in a highly corrosive environment. Fatigue tests on these AA7085-T7452 specimens, under the same spectrum as used in the BSI&WS LPBF Scalmalloy^® study, reveals that AA7085-T7452 and Scalmalloy^® have similar crack growth histories. This, in turn, leads to the discovery that the growth of naturally occurring three-dimensional (3D) cracks in AA 7085-T7452 could be predicted using the crack growth equation developed for BSI&WS LPBF Scalmalloy^®, albeit with allowance made for their different fracture toughness’s. These findings suggest that Scalmalloy^® may be suitable for printing parts for both current and future attritable aircraft. Full article

The utilization of treated dredged sludge as a partial replacement for natural sand and gravel in construction projects offers a promising approach to reducing the exploitation of natural resources. The conventional vacuum preloading (VP) method, while widely used for soft soil improvement, is often associated with prolonged consolidation periods and high energy consumption in its later stages. Conversely, the electroosmosis (EO) technique is effective in enhancing drainage in low-permeability soft clays but is constrained by issues including anode corrosion, high operational costs, and uneven soil reinforcement. This study presents an experimental investigation into an alternating vacuum preloading and electroosmosis method for sludge treatment based on the underlying reinforcement theory. A series of laboratory model tests was conducted using a self-made vacuum–electroosmosis alternating test device. The reinforcement efficiency was assessed through the continuous monitoring of key performance indicators during the tests, including water discharge, surface settlement, electric current, electrode corrosion, and energy consumption. Post-test evaluations of the final soil shear strength and moisture content were also performed. The test results demonstrate that the alternating vacuum–electroosmosis yielded more significant improvement than their synchronous application. Specifically, the alternating vacuum–electroosmosis increased total water discharge by 46.1%, reduced final moisture content by 20.8%, and enhanced shear strength by 35.6% relative to the synchronous mode. Furthermore, an alternating VP-EO mode was found to be particularly advantageous during the electroosmosis phases, facilitating a more stable and sustained dewatering process. In contrast, the application of vacuum preloading alone resulted in inefficient performance during the later stages, coupled with relatively high energy consumption. Full article

Accurately predicting the fatigue life of long-distance natural gas pipelines with internal corrosion defects is essential to ensure structural integrity and operational safety. While data-driven models offer potential in this regard, many lack interpretability. To address this, we propose a novel, interpretable machine learning framework that combines an Extreme Gradient Boosting (XGBoost, v3.0.3) model, optimized via Particle Swarm Optimization (PSO), with SHapley Additive exPlanations (SHAP) based post hoc interpretation. A dataset of 510 samples was generated through FE simulations, incorporating realistic pipe geometry, material properties, and statistically representative corrosion defect parameters. The optimized PSO-XGBoost model demonstrated exceptional predictive performance on the test set, with a coefficient of determination (R²) of 0.9921, and a Mean Absolute Error (MAE) of 2.7491 years, significantly outperforming benchmark models. Crucially, the SHAP analysis provided global and local interpretations, revealing that the defect width coefficient (k₃) and pipe diameter (D) are the most influential features, while operational pressure (P) had a minimized impact due to multicollinearity handling. The research findings can provide a basis for pipeline risk assessment and integrity management. Full article

Conventional amine-based solvents such as monoethanolamine (MEA) and diethanolamine (DEA) are widely used for CO₂ removal from natural gas but this technology suffers from drawbacks including high regeneration energy, solvent degradation, and corrosion issues. To overcome these limitations, this study investigates the use of newly synthesized hydrophobic protic ionic liquids (HPILs) composed of ammonium cations coupled with the bis(trifluoromethane)sulfonylimide ([Tf₂N]⁻) anion for CO₂ absorption using the pressure-drop method. The results show that CO₂ solubility increases with pressure but decreases with temperature. Among the studied ionic liquids (ILs), [BEHA][Tf₂N] exhibits the highest CO₂ capacity at 298.15 K within the pressure range of 1–20 bar, which is consistent with its free volume (V_f) value. Furthermore, a comparison study indicates that all ILs demonstrate superior CO₂ selectivity over methane (CH₄) at 298.15 K. The recyclability study shows that [BEHA][Tf₂N] maintains its structural integrity over two CO₂ absorption cycles at 20 bar across all tested temperatures. Full article

Many special structures such as pipeline, revolving gears, and tanks suffer from biofouling used in marine environment, which could induce serious results in the ship system such as blockage and stuck, consequently lead to failure of the mechanical system and power system. Generally, coatings with antifouling agents are used for protecting metal structures from biofouling, but coatings are not conveniently applicable in the high velocity flowing seawater and narrow space. Electrochlorination and electrolysis of copper and aluminum anode are usually used in these circumstances, but the electric power will lead to stray current corrosion to the component. For the sake of convenience and safety, Cu-Ti pseudo alloy antifouling anode was proposed in this work for antifouling in pipeline and other narrow spaces without external electric power. Four Cu-Ti pseudo alloy antifouling anodes with different Ti contents (mass fraction) of 0 wt.%, 5 wt.%, 10 wt.%, and 15 wt.% were investigated with computational method, and a 15 wt.% Ti content Cu-Ti pseudo alloy antifouling anode was prepared by cold spray, and the microstructure and composition of the anode were observed by scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). Electrochemical tests were conducted to obtain the corrosion potential, potentiodynamic polarization curve, and micro zone electrochemical information in natural seawater, and the Cu ions releasing behavior were analyzed using inductively coupled plasma (ICP). The results indicated that in natural seawater, copper particles, and titanium particles on the surface of anode samples can form micro galvanic couples. With the increase in Ti mass fraction, the number of micro primary cells composed of copper particles and titanium particles increases, and the corrosion rate of Cu particles increased. When the Ti mass fraction is 15%, the corrosion rate is the fastest, and the copper ion release rate increases by nearly ten times, reaching 147 μg/(cm²·d). This method can effectively accelerate the releasing rate of Cu ions in Cu-Ti pseudo alloy anode and promote the antifouling effect. Full article

This work describes the preparation and characterization of chitosan-based biopolymer coatings containing silver, zinc, and hydroxyapatite nanoparticles deposited on the Ti13Zr13Nb alloy by the EPD method. It was intended to evaluate the influence of surface pretreatments and deposition parameters on the structural, electrochemical, and biological properties of coatings. The morphology and composition were characterized by means of SEM/EDS, AFM, XRD, and FTIR analysis. The obtained results indicated uniform continuous layers with homogeneously distributed nanoparticles and the presence of characteristic functional groups originating from chitosan and hydroxyapatite. Corrosion investigations performed in SBF solution revealed a significant enhancement in corrosion resistance for chitosan/nanoAg/nanoZn/nanoHAp coatings, reflected in a drastic decrease in corrosion current density compared with uncoated Ti13Zr13Nb alloy. The contact angle measurements confirmed their hydrophilic nature, which favors better biointegration ability. Biological tests (MTT and LDH) performed on human osteoblasts (hFOB 1.19) confirmed high biocompatibility (>85% cell viability) in the case of all coatings with the addition of hydroxyapatite, whereas in the case of coatings without HAp, cytotoxicity was observed, probably due to the uncontrolled release of metallic nanoparticles. These findings suggest that the presence of hydroxyapatite in chitosan-based coatings efficiently enhances corrosion protection and cytocompatibility, showing very good prospects for biomedical applications such as the surface modification of titanium implants. Full article

This study evaluated locust bean gum (LBG), a polysaccharide thickening agent, as an anti-corrosion active compound against sweet corrosion for N80 carbon steel used in the oil and gas sector. The assessment involved weight loss and electrochemical measurements at different temperatures (e.g., 25 °C and 80 °C) and immersion durations (up to 168 h) in a CO₂-saturated 2 wt.% KCl solution. The electrochemical results showed that LBG effectively inhibited sweet corrosion at both temperatures, and its efficacy increased with its concentration, reaching maximum inhibition efficiency of 84.11% at 25 °C and 55.81% at 80 °C, using 0.3 g L⁻¹ of LBG after 24 h of immersion. At 25 °C, and with 0.3 g L⁻¹ of LBG, the inhibition action of LBG did not change, even after 168 h of immersion (e.g., 83.97%). At 80 °C, LBG showed a good inhibition up to 72 h (e.g., 47.04%), after which LBG had no additional protective effect. This result is attributed to the formation of a FeCO₃ layer that covered the entire metal surface, blocking the adsorption of LBG. Potentiodynamic tests revealed that LBG’s inhibitory effect is of a mixed type. The Temkin adsorption isotherm model accurately described the data, indicating that LBG adsorption involves primarily physical interactions, with some chemical contributions. Activation energy and heat of adsorption calculations support the physical nature of LBG’s adhesion. FTIR analysis confirmed the interaction between LBG and N80 carbon steel, while SEM-EDS provided visual evidence of LBG’s influence on the metal surface. Full article

To address the issues of insufficient protection and poor durability in concrete during service, this study developed a novel polymer–silicate composite gel system by combining silane with fluorocarbon resin emulsion and applied it to mortar specimens. The chloride ion resistance enhancement of mortar provided by the novel gel system was evaluated using the RCM method and natural chloride ion penetration tests, with SEM images employed to analyze its anti-permeation mechanism. Results indicate that the chloride ion migration coefficient of the novel composite gel system is 4.91 × 10⁻¹² m²/s, representing a 63.97% reduction compared to the single fluorocarbon gel system. Within the 0–5 mm depth range, free chloride ion contents at 14, 28, and 56 days decreased by 55.35%, 50.10%, and 43.64%, respectively, demonstrating excellent resistance to chloride penetration. Acid and alkali resistance tests demonstrated that the system retained the inherent corrosion resistance of the fluorocarbon component. Carbonation tests demonstrated that the system exhibited a slight decrease in carbonation resistance compared with the pure fluorocarbon gel system, while still maintaining a satisfactory performance level. Overall, the polymer-silicate composite gel system significantly enhanced the mortar’s resistance to chloride ion penetration. Full article

The seawater corrosion behavior of a plain carbon steel covered with hydrothermally carbonized coating was studied. Hydrothermal carbonization of sugar (sucrose) dissolved in water with a concentration of 10 wt.% at 200 °C for 4 h was carried out to produce a carbonized coating on the steel. The corrosion resistance of the steel with and without the carbonized coating was evaluated by polarization tests in seawater. The Tafel slopes were calculated using polarization data. The corrosion current and the potential of corrosion were determined to examine the effect of the carbonized coating on the corrosion behavior of the steel. In addition, AC impedance measurements on the steel without and with the hydrothermal carbonization coating were performed in a three-electrode cell with a Ag/AgCl reference electrode, platinum counter electrode, and seawater electrolyte. It was found that hydrothermal carbonization of sugar generated a continuous carbon-rich layer on the surface of the steel. This carbon layer is highly corrosion-resistant as shown by the decrease in the corrosion current. It is concluded that the hydrothermally carbonized coating has the nature of passivation films, and it can slow down the corrosion rate of the plain carbon steel in seawater. The impedance of the steel without hydrothermal carbonization coating is very low. With hydrothermal carbonization coating, an increase in the resistance and the capacitive response of the coating/seawater interface was observed. Full article

The corrosion of steel bridge structures, caused by anthropogenic or natural sources, can significantly impact the safety and integrity of these structures. The quick and accurate detection of corrosion is crucial for identifying areas that require strengthening and repair. This study proposes an image-based detection method, referred to here as CAM-K-OD, for identifying areas of corrosion in steel bridges using photographs captured with any device. The proposed method fuses a gradient-based class activation mechanism map (Grad-CAM) with K-means clustering applied to convolutional neural network (CNN) features and object localization modules to delineate corrosion zones. The detection pipeline leverages deep convolutional features, grouped through clustering, to extract attention-based visual patterns and identify defective areas. Labeled and masked image datasets were used to train and test the system, and its evaluation was conducted using IoU (the Intersection over Union metric used to measure the accuracy of object detection and segmentation algorithms). This method was tested alongside U-Net segmentation and EfficientDet detection models, which were used as benchmarks. The findings indicate that CAM-K-OD exhibits superior localization fidelity and robustness under varying imaging conditions. This model enables efficient and reliable corrosion identification, supporting real-world bridge maintenance by reducing inspection times and improving the targeting of repair efforts. Full article

This study investigates the deterioration of corroded reinforced concrete pipes and their restoration using ultra-high performance concrete (UHPC), utilizing Three-Edge Bearing Tests and 3D finite element analysis under uniform corrosion-induced wall thinning. Unrepaired pipes exhibit elastic behavior, crack propagation, and yield stages, with failure driven by concrete cracking and rebar yielding. UHPC repair mitigates load drop during crack propagation, extends the yield phase, and enhances plastic deformation capacity. Pipe load-bearing capacity is negatively correlated with corrosion thickness and positively correlated with repair thickness (R² > 0.979) and repair compensation ratio. Interfacial performance analysis indicates natural bond degradation under sustained loading, transitioning the pipe to a unitized structure. Embedding steel nails significantly improves interfacial bond strength, increasing failure bearing capacity by 2.91 and 3.56 times compared to natural and PE film interfaces, respectively. Numerical simulations reveal that interface shear strength is five times more influential on bearing capacity decay than interface fracture energy, underscoring its critical role in durability design. An optimization strategy is proposed: reinforce stress-concentrated areas with nails to enhance shear strength and prioritize monitoring interfacial slip to ensure service safety. Full article

Corn stover (CS) is a highly abundant type of agricultural biowaste, largely composed of lignocellulosic material. CS may be a particularly rich pool of hydroxycinnamates, represented primarily by p-coumaric acid and ferulic acid; yet, these compounds are bound onto the lignocellulosic matrix, and their release requires an appropriate acid and/or alkaline catalysis. This being the case, this study herein aimed to develop an effective process to boost hydroxycinnamate recovery by employing acid-catalyzed hydrothermal and organosolv treatments. To this end, oxalic acid was tested as a benign, natural acid catalyst, along with the well-examined sulfuric acid. A kinetic assay showed that both the acid catalyst and the use of an organic solvent (ethanol) may greatly impact the rate and level of polyphenol recovery. Under optimized conditions, determined by implementing response surface methodology, it was demonstrated that the organosolv treatment was far more effective than the hydrothermal one, with regard to total polyphenol recovery, while the oxalic acid catalysis was equally efficient as the sulfuric acid one. This treatment afforded 17.8 ± 2.3 mg gallic acid equivalents per g of dry CS mass. However, a thorough insight into the polyphenolic composition of the extracts produced revealed that hydrothermal treatment may enable, apart from p-coumaric and ferulic acid release, the formation of a compound tentatively identified as an ester of p-coumaric acid with a pentose. Furthermore, it was shown that sulfuric acid-catalyzed organosolv treatment provided almost 25 and 34% higher yields for p-coumaric and ferulic acid, respectively, but it strongly inhibited p-coumaric acid-pentose ester formation. These compositional differences appeared to impact the antioxidant activity of the corresponding extracts. It was concluded that the oxalic acid-catalyzed ethanol organosolv treatment of CS may have important potential in a biorefinery context, but improvements are required to further enhance treatment performance. This would lead to replacing corrosive catalysts, such as sulfuric acid, with benign ones, thereby establishing a fully sustainable process for the recovery of bioactive phytochemicals. Full article

To investigate the corrosion behavior and mechanism of steel with galvalume coating (Zn–55%Al–1.6%Si) in marine atmospheric environments, an indoor accelerated corrosion test method was constructed. Both marine atmospheric exposure tests and spectrum-based accelerated corrosion tests were carried out to compare the corrosion kinetics, corrosion products, and electrochemical behavior. A corrosion prediction model was established using the weight-loss method. Surface morphologies were observed by scanning electron microscopy (SEM), the compositions of corrosion products were identified by X-ray diffraction (XRD), and electrochemical tests were conducted to elucidate the time-dependent electrochemical characteristics. The results showed that after two years of natural exposure and 16 cycles of accelerated testing, the specimens exhibited mainly uniform corrosion of the galvalume coating without significant localized corrosion. The corrosion products were primarily composed of ZnO, Zn₅(OH)₆(CO₃)₂, Zn₅(OH)₈Cl₂·H₂O, and Al₂O₃. The corrosion potential increased while the corrosion current density decreased with prolonged testing, indicating that the corrosion product film effectively inhibited corrosion and enhanced protection. By integrating the corrosion kinetics, product composition, and electrochemical mechanism from both outdoor and indoor tests, the constructed spectrum-based accelerated test method demonstrated good correlation with actual marine atmospheric corrosion processes, providing a reliable approach for evaluating the corrosion resistance and service life of steel with galvalume coating in marine environments. Full article