Search Results (859)

This study was conducted to explore how varying the concentration of nano-La₂O₃ particles in the plating bath influences the morphology, constitution, and corrosion resistance of Ni-B composite coatings deposited on N80 carbon steel via electroless plating. The novelty of this work lies in the systematic investigation on the co-deposition behavior and grain refinement mechanism of nano-La₂O₃ in electroless Ni-B system, which has been rarely reported in previous studies. The microstructure and chemical composition of the coatings were characterized through a combination of SEM, EDS, XPS and XRD analyses. SEM confirmed that a dense Ni-B/La₂O₃ composite coating was formed, with a uniform thickness of approximately 10 μm, and the nano-La₂O₃ particles were evenly distributed. XPS analysis verified the presence of B, C, O, Ni and La, while XRD analysis revealed a refinement in crystalline size due to the addition of the nanoparticles. The corrosion resistance enhancement mechanism is attributed to the triple synergistic effect: nano-La₂O₃ pins grain boundaries and refines Ni-B grains to the minimum average size of 12.943 nm at the optimal concentration of 8 g·L⁻¹; the refined grain structure promotes the formation of a continuous and dense Ni(OH)₂ passive film; the uniformly dispersed nanoparticles act as physical barriers to block the penetration of corrosive media. Electrochemical measurements demonstrated that this coating exhibited outstanding anti-corrosion performance, as confirmed by a remarkably positive corrosion potential (E_corr = −0.37189 V) and a minimal corrosion current density (I_corr = 3.7524 μA/cm²). The results conclusively show that nano-La₂O₃ reinforcement effectively enhances the corrosion protection performance of electroless Ni-B alloy coatings. Full article

In view of the fact that there are few reports on the preparation of NbC coating by high-power pulsed magnetron sputtering (HiPIMS) technology. In this study, the effects of NbC interlayer thickness on the microstructure, corrosion resistance and electrical conductivity of Nb/NbC/C multilayer coatings for proton exchange membrane fuel cell (PEMFC) bipolar plates were studied by using the high ionization characteristics of HiPIMS technology. A series of Nb/NbC/C multilayer coatings with varying NbC interlayer thicknesses was deposited via HiPIMS by modulating the deposition time (20, 40, and 60 min). The microstructure and properties of the coatings were characterized using scanning electron microscopy (SEM), Raman spectroscopy, interfacial contact resistance (ICR), and corrosion current, among other methods. The results indicate that as the NbC interlayer thickness increases, the total coating thickness increases from 0.43 μm to 1.42 μm. All coatings exhibit a uniform and dense microstructure lacking typical coarse columnar structures. Raman and XPS analyses show that the I_D/I_G ratio increases from 1.98 to 4.04, indicating an increase in sp²-hybridized bond content and a decrease in sp³ content. At a deposition time of 60 min, the coating achieved optimal performance, yielding a critical load (Lc1) of 31.9 N, the lowest average friction coefficient (0.27), the minimum corrosion current density, and an interfacial contact resistance of 7.5 mΩ·cm². These results demonstrate that the NbC interlayer thickness significantly governs the structure and properties of the Nb/NbC/C multilayer coatings. Specifically, an appropriate increase in the NbC interlayer thickness optimizes the sp²/sp³ hybrid bond ratio, thereby enhancing the overall coating performance. Full article

Carbon steel pickled with hydrochloric acid can suffer from considerable dissolution, greater acid consumption, and poor surface quality. This research assessed the effectiveness of a commercially available corrosion inhibitor for carbon steel pickled under industrially representative conditions (13.2 wt.% (weight percent) HCl (hydrochloric acid), 28 g·L⁻¹ dissolved iron, 80–85 °C, and brief periods of contact with pickling solution at 32, 56, and 113 s). Mass loss and inhibitor efficiency (IE) were determined through gravimetric analysis under dynamic pickling conditions using varying concentrations of inhibitor and duration of contact. The results indicate that the extent of mass loss decreases considerably with increasing inhibitor concentration. The optimal concentration was found to be 0.6 g·L⁻¹, giving an inhibitor efficiency greater than 90% under preliminary screening conditions and 70–79% under industrially relevant conditions, with further increases in inhibitor concentration providing little additional protection, suggesting nearly complete surface coverage. Observations of the surface showed better pickling uniformity and brilliance. The optimal inhibitor concentration resulted in reductions of 21% in inhibitor usage and over 27% in acid regeneration compared to a non-optimized inhibitor dosage. Full article

This study systematically investigates the effect of solution treatment on the microstructure and corrosion resistance of duplex stainless steel SAF2507 fabricated by direct hot isostatic pressing (HIP). The HIP specimens were solution treated at 1080 °C for 1 h, followed by comprehensive characterization using SEM, EDS, EBSD, XRD, XPS, and electrochemical testing in 3.5 wt% NaCl solution. Results indicate that solution treatment effectively dissolved intermetallic precipitates, promoted a more uniform distribution of ferrite and austenite phases, and reduced microstructural heterogeneity. Electrochemical impedance spectroscopy and potentiodynamic polarization tests showed that the treated samples exhibited a wider passive region and higher charge transfer resistance, indicating enhanced passivation behavior. XPS analysis further revealed an increased proportion of Cr₂O₃ and O²⁻ and decreased ${\mathrm{Fe}}_{\mathrm{hy}}^{3+}$ and H₂O content in the passive film, suggesting improved compactness and chemical stability. Surface morphology analysis confirmed a significant reduction in pitting corrosion after treatment. These findings demonstrate that solution treatment is an effective post-processing method to enhance the corrosion resistance of HIP-fabricated SAF2507 duplex stainless steel. Full article

Steel–concrete composite beams are widely used in bridge infrastructure but are vulnerable to deterioration due to uniform and pitting corrosion, particularly at the lower flange. This study investigates the flexural behavior of corroded steel–normal strength concrete (NSC) composite beams and evaluates rehabilitation using ultra-high-performance concrete (UHPC) slab replacement, with and without additional steel plate strengthening. A comprehensive finite element analysis was conducted considering three beam spans (5, 7, and 9 m), two corrosion types, and three corrosion levels. The results indicate that both corrosion types significantly reduce flexural capacity due to cross-sectional loss, with pitting corrosion causing greater strength reduction than uniform corrosion at the same weight loss because of stress concentration effects. Replacing the NSC slab with a UHPC slab effectively restores and often enhances load-carrying capacity beyond that of intact beams while reducing dead load, demonstrating the superiority of the proposed rehabilitation approach. The combined use of UHPC slab replacement and welded steel plate strengthening provides the greatest improvement, revealing a strong synergistic effect. A case study of a corroded steel bridge in Pennsylvania confirms the practical applicability of the method, showing that UHPC-based rehabilitation increases the load rating from below unity to above unity. These findings highlight UHPC as an efficient and sustainable solution for extending the service life of aging steel bridges. Full article

Thick paint coatings on ship hulls must be periodically removed before repainting; however, conventional abrasive blasting generates secondary waste and poses environmental and occupational health concerns. This study investigates nanosecond pulsed laser cleaning as a non-contact alternative for removing thick marine paint coatings from KE36 shipbuilding steel. A two-layer coating system consisting of anti-fouling and anti-corrosive layers with a total thickness of approximately 1000 μm was examined. The effects of pulse energy, pulse overlap number, and scanning pitch on removal depth, cleaning efficiency, and surface morphology were systematically evaluated. Increasing the pulse energy enhanced coating ablation and enabled complete removal when sufficient heat input density was supplied. A higher pulse overlap number promoted cumulative energy deposition and improved removal depth. Smaller scanning pitches improved spatial overlap between adjacent scan paths and produced more uniform cleaning, whereas excessive pitches caused incomplete removal and periodic surface undulations. The cleaning efficiency approached 100% at a heat input density of approximately 4–5 J/mm². These results indicate that heat input density is a useful process indicator for determining the minimum energy conditions required for full removal of thick coating layers while minimizing thermal effects on the substrate. Full article

This manuscript evaluates the electrochemical corrosion resistance of diamond-like carbon (DLC) coatings deposited via High-Power Impulse Magnetron Sputtering (HiPIMS) on AISI 52100 steel in synthetic seawater. While AISI 52100 steel is valued for its hardness, it is highly susceptible to localized and uniform corrosion in chloride-rich marine environments. In this study, samples were characterized using Raman spectroscopy to analyze sp²/sp³ bonding, and their corrosion behavior was assessed through potentiodynamic polarization, linear polarization resistance (LPR), and electrochemical impedance spectroscopy (EIS) over 24 h of immersion. Results demonstrated that the DLC coatings significantly enhanced electrochemical stability, shifting corrosion potentials toward more noble values and reducing the corrosion current density from (1.81 ± 0.12) × 10⁻⁷ to (1.03 ± 0.09) × 10⁻⁹ mA·cm⁻². EIS data revealed high polarization resistance and effective barrier properties, despite a calculated total porosity of 3.06% resulting from intrinsic micro-defects. Although localized subsurface degradation and minor flaking were observed at defect sites, the HiPIMS-deposited DLC coatings effectively mitigated the corrosive impact of synthetic seawater, providing a significant contribution to the electrochemical barrier despite the persistence of electrolyte accessibility mediated by localized defects. Full article

This study aims to investigate the performance and mechanism of N′-[(E)-phenylmethylidene] furan-2-carbohydrazide (FNH), a hydrazone Schiff base, as a corrosion inhibitor for carbon steel in 1.0 M HCl. The research was conducted by coupling electrochemical testing (Tafel analysis and Impedance spectroscopy) with surface characterization (SEM and AFM) and advanced computational tools, including quantum-chemical modeling and classical molecular dynamics (MD) simulations. Tafel analysis revealed that FNH acts as a mixed-type inhibitor, concurrently slowing iron oxidation and hydrogen reduction. Impedance data showed that the Faradaic resistance grew monotonically with FNH dosage, reaching 95% protection at 1 × 10⁻⁴ M. Fitting the results to the Langmuir model indicated a joint physical–chemical anchoring pathway, further confirmed by SEM/AFM inspection which disclosed a uniform organic deposit. Quantum-chemical modeling revealed that protonated species broaden the molecule’s capacity for bidirectional electron exchange, while MD simulations on the Fe (110) slab confirmed a flat-lying geometry that maximizes heteroatom–metal contact. The consistency between laboratory observables and atomic-scale predictions provides a detailed, mechanism-oriented picture of how this organic protective layer curtails acid corrosion. Full article

Steel pipelines for oil and gas transportation serve as the lifeline of energy conveyance, and their long-term safe operation constitutes a crucial safeguard for energy security. Nevertheless, in complex service environments, local defects formed on the inner pipe wall due to medium corrosion have emerged as a prominent hidden danger endangering pipeline integrity. Accurate evaluation of the residual strength of pipelines with corrosion defects is not only the technical foundation for ensuring the safe operation of pipelines, but also the key basis for formulating scientific maintenance strategies and prolonging the service life of pipelines. Taking three grades of steel pipelines (X52, X65 and X80), which represent the typical strength grades commonly used in long-distance oil and gas transmission pipelines, as the research objects, this paper establishes a three-dimensional finite element model of single-point uniform corrosion defects considering the nonlinear material behavior, and systematically investigates the influence laws of geometric parameters (depth, length and width) of corrosion defects on the failure pressure of pipelines under the action of monotonic internal pressure load. The accuracy of the proposed finite element model is verified by comparison with the test data from thirteen groups of full-scale burst experiments. On the basis of parametric analysis results, an explicit and high-precision predictive model for failure pressure is developed. The research findings reveal that corrosion depth acts as the dominant factor affecting pipeline failure pressure with a distinctly nonlinear influence characteristic: the load-bearing capacity of pipelines drops drastically when the relative depth d/t exceeds 0.6, where d is the corrosion depth and t is the pipe wall thickness. There exists a critical value for the impact of corrosion length, beyond which its weakening effect on failure pressure tends to level off. Within the commonly encountered engineering range (20~100°), corrosion width exerts a negligible influence on pipeline failure pressure and thus can be overlooked in engineering evaluation. In comparison with conventional industry assessment methods such as ASME B31G, DNV RP-F101, PCORRC and SY/T 6151, the newly established predictive model features higher prediction accuracy and broader applicability, which provides on-site engineers with a powerful theoretical tool and practical formula for the rapid and accurate evaluation of the residual strength of corroded pipelines. Full article

W₂CoB₂ is a ternary boride-based cermet. Featuring high hardness, high melting point, excellent wear resistance and corrosion resistance, it has been widely used in numerous industrial fields such as cutting processing, surface protection and mold manufacturing. Toughening is a major issue that needs to be addressed for ceramic materials. In this study, the toughness of cermets is improved by the combined addition of CNTs and La₂O₃. The W₂CoB₂ cermets were fabricated via vacuum sintering, and the effects of CNTs and La₂O₃ on the microstructure and properties of the cermets were systematically investigated. The microstructure and phase composition of the specimens were characterized using a SEM and X-ray diffractometry (XRD), respectively. The density of the specimens was measured by the Archimedes drainage method. A Vickers microhardness tester was employed to determine the microhardness and fracture toughness of the specimens. The transverse rupture strength was tested using an electronic universal testing machine, while the wear resistance was evaluated via a wear tester. The results indicate that the addition of either CNTs or La₂O₃ can refine the grain size and improve the toughness of the cermets. The simultaneous incorporation of CNTs and La₂O₃ further enhances grain refinement and mitigates the issue of uneven dispersion of CNTs in the specimens. When 0.5 wt.% CNTs and 0.3 wt.% La₂O₃ are added, the specimen exhibits the following optimal properties: a density of 9.33 g/cm³, a microhardness of 2046 HV_0.5, a fracture toughness of 12.36 MPa·m^1/2, a transverse rupture strength of 985 MPa, and a friction coefficient reduced to 0.36. Synergistic addition of CNTs and La₂O₃ achieves grain refinement and uniform microstructure, which significantly improves the friction and wear performance and service stability of the cermet. The material retains high hardness and wear resistance, accompanied by enhanced comprehensive mechanical and service properties. Further studies will aim to cut costs while preserving material performances, facilitating its industrial application. Full article

The self-formed rust layer is significant for weathering steels because their corrosion resistance in a marine atmospheric environment mainly relies on the stability, uniformity and compactness of the rust layer. However, the initial stage of rust formation is vulnerable and prone to being disturbed by the external environment, compromising the protectiveness of the rust layer at a later stage. Therefore, weathering steel often requires the application of rust stabilization techniques. This study has developed a waterborne polyurethane (WPU)-based coating incorporated with mesoporous/hollow SiO₂ nanoparticles, acting as the primary components for the construction of pathways for gaseous H₂O and O₂, as well as for Cl⁻ dissolved in moisture, while blocking liquid water. Salt spray was applied to accelerate the rust formation process, and rust can form beneath the coating, which provides shelter for rust formation against the external environment. Hexamethyldisilazane (HMDS) was applied to further hydrophobize the nanoparticles, and a hydrophobic surface with self-cleaning properties was achieved. The hydrophobized and non-hydrophobized coatings with different thicknesses (10–80 µm) were systematically compared: the morphology of the rust layer and coating surface after salt spray was investigated, the ability of the rust layer to inhibit chloride ingress was compared, and the electrochemical behaviors were analyzed. This study presents a new strategy for weathering steel rust stabilization that features maneuverability, environmental friendliness and low cost. Full article

As an active reinforcement technology, prestressed anchor cables are susceptible to environmental corrosion during long-term service. Corrosion occurs and progresses more rapidly, especially in an alternating wet–dry environment, which can degrade the mechanical properties of prestressed anchor cables and may ultimately lead to failure. Current methods typically evaluate the mechanical properties of anchor cables based on cross-sectional loss calculated from the average weight loss ratio. However, this uniform-corrosion assumption may underestimate the effect of corrosion on mechanical performance. In this study, a testing apparatus for corroding prestressed anchor cables under alternating wet–dry conditions was developed. The apparatus enabled accurate loading and nondestructive sampling. Using this apparatus, alternating wet–dry corrosion tests and mechanical tensile tests were conducted on anchor cables under different stress levels. The relationship between weight loss ratio and mechanical properties was then analyzed. Based on this relationship, an equation was derived to calculate the breaking strength of corroded anchor cables in alternating wet–dry environments. The service life estimated using this equation was closer to that observed in actual anchor cable failure cases. This indicates that the proposed equation provides more accurate predictions than methods based on the uniform-corrosion assumption. Full article

Viola odorata, commonly known as sweet violet, is valued for both its fragrance and medicinal properties. However, seeds of V. odorata exhibit non-deep physiological dormancy, resulting in poor and inconsistent germination. This dormancy can be overcome through physical or chemical treatments, including scarification, stratification, and hormone application. Although mechanical scarification is effective, many commonly used approaches have notable limitations, such as reliance on corrosive chemicals and a lack of uniformity. This study presents a simple and effective mechanical scarification technique using rat-tooth tweezers to gently crack the seed coat tip of V. odorata ‘Empress Augusta’ (EA). This method significantly improved germination. When combined with cold stratification at 4 °C, germination further increased, reaching 70% within 8 weeks. Germination was enhanced even further on Murashige and Skoog (MS) basal salt medium supplemented with 10 mg/L gibberellic acid (GA₃), achieving 97.5% germination by day 54. These findings suggest that this simple mechanical scarification method, when combined with cold stratification and GA₃ treatment, could provide a reliable and practical strategy for breaking dormancy and facilitating seed germination in V. odorata. Full article

A new finite element simulation methodology for analyzing the mechano-electrochemical effects of Al alloys with intermittent measurement and reconstructed boundary conditions is proposed. It enables the simulation of the coupled mechano-electrochemical effects within the entire elastoplastic range of Al alloys. The model’s accuracy was verified through measurements of galvanic current, coupled potential, and corrosion morphology. This study indicates that the non-uniform stress distribution on a metal surface results in inconsistent electrochemical properties, leading to the spontaneous formation of anodes and cathodes and facilitating galvanic corrosion. Regions with stress concentration act as anodes in the corrosion reaction, while other areas serve as cathodes. The electrolyte domain is approximately polarized to the same potential, but there are also minor differences between different regions. As the stress concentration gradually increases, the mixed potential decreases, leading to greater polarization and an accelerated corrosion reaction rate. The galvanic current and the coupled potential calculated by the model differ from the measured values by less than 15%. Moreover, the observed corrosion morphology is consistent with the calculated results, indicating that the model provides good predictions of coupled mechano-electrochemistry. Full article

Stray-current corrosion from DC-electrified railways drives premature failure of buried metallic infrastructure (pipelines, foundations, tunnel reinforcement), causing resource waste, repair-driven carbon emissions and service disruptions that undermine the sustainability of urban transit corridors. Conventional impressed-current cathodic protection (ICCP) design relies on uniform-anode rules of thumb or closed commercial codes that cannot quantify the trade-off between protection uniformity, energy use and hardware cost. We present an open MATLAB framework that couples a custom 3D finite element method (FEM) solver with multi-objective particle swarm optimisation (MOPSO) and minimises three competing objectives simultaneously: total impressed current, RMS deviation from the protection target, and number of active anodes. A laboratory-calibrated coupling factor ($\mathrm{CF}=1.98$, consistent with the image-method prediction of 2 for a highly conductive pipe inclusion) absorbs the pipe–soil interface kinetics into a single direct FEM solve, and a pre-computed Green’s-function basis accelerates each MOPSO evaluation by more than two orders of magnitude. The solver is validated against an instrumented prototype with RMSE $=14.9$ mV across ten Cu/CuSO₄ saturated reference electrode (CSE) measurements, and applied to a 500 m DC traction line. At an identical total current of 20.30 A across five anodes, the optimised design achieves an RMSE of 86.6 mV against the $-850$ mV NACE target, whereas a conventional uniform layout produces severe over-protection (RMSE $=1107$ mV)—a twelve-fold reduction. The framework is recommended as a transparent, reproducible engineering tool that simultaneously extends pipeline service life and reduces rectifier energy demand, supporting UN Sustainable Development Goals 9 and 11 for sustainable urban-rail infrastructure. Full article