Search Results (3,423)

Traditionally, repairing coated substrates requires completely removing damaged, wear-resistant layers before recoating. This process leads to high costs, extended downtime, and material waste. Flexible brazing tapes, which are composed of alloy powder and an organic binder, offer an alternative to full coating removal for targeted repairs. Despite this, the process of vacuum brazing these tapes may lead to the formation of defects, including pores caused by trapped gases or residual binder, which compromise coating durability and corrosion resistance. This study focuses on the utilization of laser remelting as a method for post-processing nickel- and iron-based mixed alloy brazing tapes, with the aim of improving the integrity of the coating. Surface quality was assessed via microscopy and microhardness testing by systematically varying laser power, scanning speed, and hatch distance. Among the parameters studied, the most suitable laser parameter combination was found to be 350 W laser power, 250 mm/s scanning speed, and a hatch distance of 0.02 mm. These parameters yielded crack- and pore-free coatings with a remelting depth of 160.3 ± 17.2 µm and a microhardness of 701 ± 23 HV1, which is an 85% increase over as-brazed samples. Wear testing revealed a reduced coefficient of friction, and electrochemical corrosion tests showed lower corrosion current density and enhanced repassivation behavior in remelted coatings. These improvements demonstrate that laser remelting significantly enhances the microstructure, hardness, wear resistance, and corrosion performance of brazed coatings, providing an effective method for localized repair while minimizing material consumption and processing duration. Full article

To evaluate the behavior of industrial equipment from a corrosion point of view, it is mandatory to consider both the material that equipment is made from and the working conditions such as temperature, pH, and the existing microorganisms in the working environment. Our studies regarding ecotoxicological monitoring of biological suspensions Diatomee, Saccharomyces, and Spirulina (DSS) are focused on three directions: (1) the evolution of chemical and biological parameters of the reaction environment (pH, conductivity, TDS, DO, OD), the kinetics of DSS microorganisms’ growing curve; (2) the analysis of biofilm forming on the exposed metallic surface and (3) the analysis of corrosion degree (phenomena) of tested metals in five media, by using the corrosion indices: volumetric index, gravimetric index, and penetration index. The viability of microorganisms in the presence of aluminum, zinc, and iron shows the following sequence: Al _Diat > Fe _Diat > Zn _Diat > Al _Spir > Zn _Spir> Al _Sach > Zn _Sach > Fe _Spir > Fe _Sach. The development of biofilms on the surface of metal plates followed the sequence outlined below: Al _Diat > Fe _Diat > Zn _Diat > Fe _Spir > Zn _Sach > Fe _Sach > Al _Sach > Zn _Spir > Al _Spir. Iron exhibits the most favorable performance, displaying a very low Ip value across all tested environments, including salt water. Aluminum demonstrates sensitivity to specific biological environments, with the highest degree of corrosion observed in Spirulina, indicating that not all biological environments confer protection to aluminum. Diatoms and Saccharomyces suspensions exert an inhibitory effect on corrosion. Zinc is the most susceptible metal, experiencing the greatest corrosion in Spirulina, followed by salt water, while biological environments only partially mitigate the corrosion rate. Full article

With the depletion of river sand and the rapid expansion of marine infrastructure, seawater–sea-sand concrete (SSC) has attracted increasing attention due to its low cost and sustainability. However, the high chloride content in SSC accelerates steel corrosion. This significantly limits its use in conventional reinforced concrete structures. In recent years, the rise in FRP–steel composite confinement has offered a new solution to this durability bottleneck. Based on this background, scholars have proposed a new type of FRP–steel composite tube confined seawater–sea-sand concrete (FCTSSC) column. This paper reviews the research progress on SSC, CFST, FCFST, and FCTSSC. The latter systems are developed based on the former. The results show that advanced FCTSSC columns exhibit strong synergistic confinement between the FRP and the steel tube when compared with CFST and FCFST. This synergy enhances the bearing capacity, ductility, and post-peak behavior of SSC. Both external and internal FRP configurations can reduce the brittleness and expansion of SSC. They also effectively restrain local buckling of the steel tube. Existing studies mainly focus on short columns. Research on intermediate slender and slender columns remains limited. This includes structural behavior, rational design models, and long-term durability. Finally, future research directions are proposed to support the practical application of FCTSSC in marine engineering. Full article

The electrodeposition of rare earth metal alloys has attracted considerable interest, not only due to the challenges associated with the reduction in metal ions, but also because of their unique material properties and promising technological applications. This review presents a comprehensive analysis of the state-of-the-art in the electrochemical deposition of these alloys, focusing on various electrolytic systems, including aqueous solutions, organic molecular solvents, ionic liquids, and deep eutectic solvents. Despite inherent problematic factors such as low reduction potentials, competing hydrogen evolution reactions, and difficulties in controlling metal formation, recent advancements have enabled improved control over film formation, typically through the induced codeposition of lanthanides with iron-group metals. The influence of key factors, such as electrolyte composition and current/potential modes, on alloy codeposition, elemental and phase composition, structure, and deposition efficiency is discussed. The magnetic properties, electrocatalytic behavior, and corrosion resistance of the deposited films are also shown, highlighting their relevance for high-performance applications. Full article

The corrosion of prestressed tendons in concrete structures remains a major durability concern, especially for post-tensioned members exposed to aggressive environments. High-strength aluminum alloy (AA) bars exhibit favorable characteristics such as corrosion resistance, low density, and high ductility and may therefore provide an alternative or supplementary prestressing material in durability-oriented structural design. In this study, a bonded post-tensioned T-shaped concrete beam with hybrid prestressing combining prestressed steel (PS) strands and 7075 AA bars was investigated. A refined finite element model was developed by considering the bond-slip relationship between the AA tendons and grout inside corrugated tubes. The flexural behavior of the beam was analyzed through a combination of finite element simulation and sectional theoretical analysis. In addition, a fatigue-life assessment framework was established based on vehicle fatigue loads and material fatigue constitutive models, and the fatigue performance of the proposed hybrid beams was compared with that of conventional prestressed concrete beams. The theoretical predictions agreed reasonably well with the numerical results. Results indicated that partial replacement of PS strands with corrosion-resistant AA bars could alter the governing fatigue failure mode and improve the fatigue durability of prestressed beams under corrosive conditions. These findings highlight the potential of hybrid AA–PS prestressing as a durability-oriented strategy for concrete beams in corrosive environments. Full article

This study elucidates the impact of laser volumetric energy density (VED) on the densification behavior, microstructural evolution, wear resistance, and corrosion resistance of high-Nb TiAl alloys fabricated via laser powder bed fusion (LPBF). Experimental characterization results showed that relative density first increased and then decreased with increasing VED, reaching a maximum density of 97.13% at 66.67 J/mm³. Across the process windows, the high-Nb TiAl alloys were primarily composed of γ-TiAl, α2-Ti3Al, and β/B2 phases with varied proportions. Mechanical property analysis showed that the alloy attained a maximum average hardness of 422 HV_0.5 at 81.48 J/mm³, due to the accumulation of harder α2 and B2 phases. However, the high-Nb TiAl alloys fabricated at 66.67 J/mm³ exhibited excellent wear resistance, as evidenced by wear track widths and depths of 971.71 μm and 21.83 μm, respectively. Abrasive and oxidative wear were identified as the primary mechanisms. Meanwhile, this specimen also exhibited excellent corrosion resistance, a corrosion current density of 1.421 × 10⁻⁶ A/cm², attributed to the coupled dense passive film of TiO₂ and Al₂O₃ that prevented chloride ingress. The findings in this work may provide a critical experimental reference and theoretical underpinnings for LPBF-fabricated lightweight structural materials. Full article

Offshore pipeline systems associated with floating platforms operate under complex environmental and operational conditions that significantly influence their structural integrity and inspection requirements. Limited accessibility, harsh marine environments, and time-dependent degradation mechanisms require inspection planning to be supported by structured decision-making frameworks capable of explicitly accounting for both degradation processes and failure consequences. In this study, a Risk-Based Inspection (RBI)-driven integrity assessment is applied to three carbon steel pipeline systems associated with a SPAR offshore platform. The analysis integrates system description, identification of dominant damage mechanisms, and RBI quantification to evaluate probability of failure and consequence-related risk under offshore operating conditions. Internal corrosion is identified as the dominant long-term degradation mechanism for all analyzed pipelines, while external corrosion governs short-term inspection interval definition due to its higher growth rate and sensitivity to insulation characteristics and environmental exposure. Although all pipelines are classified within the same overall qualitative risk category, significant differences in failure probability, risk intensity, and consequence-driven risk behavior are observed, reflecting variations in system configuration, insulation systems, length, and functional role within the offshore production infrastructure. To enable meaningful comparison between pipeline systems of significantly different total lengths, normalized risk indicators per unit length are introduced. These indicators provide additional insight into local risk intensity and spatial risk distribution that are not evident from absolute risk values alone. The results highlight the importance of treating risk as a dynamic quantity rather than a static classification and demonstrate that RBI-based assessment supported by normalized risk metrics can enhance inspection prioritization and maintenance decision-making for SPAR-associated offshore pipeline systems. Full article

This study explores how variations in mechanical alloying time and sintering temperature influence the microstructure, mechanical properties, and corrosion resistance of MnAlCuFeTi high-entropy alloys (HEAs). The MnAlCuFeTi alloy was produced by means of mechanical alloying for 5, 10, 15, and 20 h. Afterward, the alloy samples were sintered at two different temperatures: 550 °C and 650 °C. Structural properties were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). Analysis of grain sizes, calculated using the Scherrer formula from SEM images, confirmed that grain size had decreased to the nanostructured regime and that microstructural homogeneity had improved. Corrosion behavior was evaluated using polarization curves, corrosion current density (I_corr), and corrosion rate measurements. The results show that increasing the mechanical alloying time reduces the alloy’s grain size, thereby improving its mechanical and corrosion resistance. At a sintering temperature of 550 °C, I_corr and corrosion rate decrease with increasing grinding time, whereas at 650 °C, although high temperatures accelerate diffusion processes and increase phase homogeneity, they weaken corrosion resistance. These findings emphasize the importance of balancing alloying time and sintering temperature to optimize performance in high-corrosion-resistant HEA applications. Full article

This study clarifies the catalytic role of chloride ions on the corrosion performance of SS316L alloy immersed in molten LiNaK carbonate salt at 700 °C. Accordingly, isothermal static immersion corrosion tests were systematically conducted under different experimental conditions. Our results revealed that the presence of Cl significantly accelerates the corrosion process: the rate constant of the corroded samples increased from 11.3 × 10⁻² mg/cm² to 13.8 × 10⁻² mg/cm² with the addition of Cl. Continuous migration of Cl₂ and volatile metal chlorides leads to the formation of obvious pores, transverse cracks along grain boundaries, surface wrinkles, and partial spalling of the oxide scale, thereby severely aggravating substrate degradation. Notably, no chlorine-containing compounds or chlorine-rich regions were detected in the corroded samples, confirming that chlorine is not consumed in the corrosion process, rather it acts as an autocatalyst through the cyclic process of “oxidation–diffusion–reaction–regeneration”. Full article

Aluminum–lithium (Al-Li) alloys have attracted great interests in aerospace, solid propellants, and explosives industries. However, the practical use of Al-Li remains challenging because of instability during storage. Poor corrosion resistance and passivation of the Al-Li alloys are ascribed to the surface cracking of the oxidation layer. Using a variety of ab initio quantum chemistry methods, the cracking mechanisms of Al/Li/O oxides induced by H₂O, LiOH, and Li₂O have been revealed theoretically by means of Al₄O₆ and Al₈O₁₂ cluster models. All six reactions are shown to be highly exergonic dissociative adsorption processes. In terms of the Gibbs free energy profiles, the adsorption energy and reactivity are in the order Li₂O > LiOH > H₂O, which is independent of sizes of clusters. However, cluster size does have an impact on the adsorption energies of H₂O, LiOH, and Li₂O. For the reactions of H₂O, the energetic routes are dominated by proton transfer and followed by the O-Al bond cleavage to generate trench or protrusion structures. However, proton transfer is inhibited considerably by the O-Li interaction. As the Li atom migrates to form various Li-O coordinates along with the O-Al bond cleavage, the alumina clusters are cracked stepwisely through the interlayer O-Al bond association or displacement. The edge Al sites are always less reactive than the topmost surface Al. The Li atoms are prone to migrate from the edge to the surface as accompanied by the O-Al bond rearrangement. Present calculations provide a deep understanding of the oxidation behavior of the Al-Li alloys and present new insights towards increasing storage stability. Full article

Magnesium–air battery anodes suffer from self-corrosion, chunk effect, and poor removal of discharge products, resulting in low anode efficiency. Although various modification strategies for Mg anodes have been reported, the effects of Ge content on the microstructure and performance of AZ61 Mg anodes at a fixed La content remain unclear. In this study, AZ61-1La-xGe alloys (x = 0, 0.25, 0.7, and 0.9 wt.%) were prepared, and their microstructure, corrosion behavior, and discharge performance after solution treatment were systematically investigated. Among them, AZ61-1La-0.7Ge exhibited the best overall performance, mainly due to the appropriate addition of Ge, which promoted a uniform distribution of secondary phases and grain refinement, thereby suppressing self-corrosion and chunk effect, improving discharge uniformity, and enhancing anode utilization by facilitating the formation of a loose discharge product layer. This study provides a basis for optimizing the Ge content in La-modified AZ61 Mg alloy anodes. Full article

This work provides an integrated experimental and computational evaluation of the cationic surfactant Quaternium-22 (Q-22) as a potentially eco-compatible corrosion inhibitor for carbon steel (CS) in 1 M hydrochloric acid. Gravimetric analysis and electrochemical techniques, including electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP), were employed over a temperature range of 20–50 °C. Q-22 exhibited mixed-type inhibition behavior, with efficiency rising to 97% at an optimal concentration of 277 μmol L⁻¹. Performance was concentration-dependent but diminished with increasing temperature, indicating partial inhibitor desorption at elevated temperatures. Thermodynamic evaluation confirmed a spontaneous adsorption process consistent with the Langmuir isotherm, involving a combined physisorption and chemisorption mechanism. Surface characterization via scanning electron microscopy (SEM), atomic force microscopy (AFM), contact angle (CA) measurement, and X-ray photoelectron spectroscopy (XPS) confirmed the formation of a coherent, hydrophobic inhibitor layer that substantially reduced surface roughness and corrosion damage. Theoretical investigations using density functional theory (DFT), natural bond orbital (NBO) analysis, and molecular dynamics (MD) simulations revealed strong adsorption energies and favorable electronic properties consistent with the inhibitor’s high experimental efficacy. Overall, the results demonstrate that Q-22 is a highly effective, eco-compatible corrosion inhibitor for CS in acidic environments, operating through a stable adsorptive film-forming mechanism. Full article

High nitrogen austenitic stainless steels are an important engineering structural material. Under annealing conditions, the addition of interstitial solid solution element nitrogen can improve the yield strength and tensile strength of the alloy without reducing its plasticity. In addition, nitrogen can partly or completely replace the more expensive nickel element at a relatively cheap element cost to improve economic benefits, while maintaining or even enhancing the excellent corrosion resistance of stainless steels. However, the cracks and defects caused by high nitrogen austenitic stainless steels during hot working in high temperature ranges have always been the pain points in the engineering field. High nitrogen elements bring high temperature strength, but also narrow the hot working temperature range, the possibility of nitride precipitation and the tendency of heat induced cracking, which limit the further engineering application of high nitrogen austenitic stainless steels. It is urgent to analyze and study the hot deformation law of high nitrogen austenitic stainless steels in engineering. This article commences with an examination of the developmental trajectory of high nitrogen austenitic stainless steel, elucidates the role and strengthening mechanism of nitrogen, and delineates the factors influencing the mechanical behavior of high nitrogen austenitic stainless steel during hot working. These factors include the impact of nitrogen content and manufacturing processes, hot-working parameters, grain size distribution, and the presence of precipitated phases. This article synthesizes various studies, analyzes the causes of thermal cracking, and proposes potential solutions. Ultimately, it summarizes the practical applications and future prospects of high nitrogen austenitic stainless steel, highlighting its substantial potential. Full article

The mineralogical composition, textural characteristics, and uranium occurrence of sandstone-hosted uranium ores significantly influence the leaching performance during in situ recovery. This study investigates ore samples from the Zhenyuan uranium deposit, China, utilizing SEM, EPMA, XRD, and XRF to characterize their texture and mineralogy. Combined with thin-section leaching tests, batch stirring experiments, and pressurized column leaching experiments, the leaching behavior of pitchblende, associated gangue minerals, and the whole rocks were evaluated. The results indicate that: Uranium mainly occurs as nano-spherical and film-like pitchblende distributed along the edges of detrital grains and Ti-oxides. Minor uranium is incorporated into Ti-oxides and dolomite lattices via isomorphic substitution or adsorbed by chlorite. Under CO₂ + O₂ leaching conditions, pitchblende was almost completely dissolved, while U-bearing Ti-oxides experienced slight corrosion. Dolomite underwent partial dissolution, providing bicarbonate ions and improving rock permeability. Pyrite dissolution was limited during the early stage of leaching. The high dolomite content, low clay abundance, favorable pore structure, and easily leachable pitchblende suggest that the Zhenyuan deposit is well suited for CO₂ + O₂ in situ recovery. Increasing CO₂ pressure is recommended to enhance dolomite dissolution and improve uranium recovery efficiency. Full article