Papers by Keyword: Corrosion Resistance

Abstract: Quasicrystalline ingots of the following compositions were obtained and studied: Al₆₃Cu₂₅Fe₁₂; Al_62.735Cu₂₅Fe₁₂Sc_0.265; Al_62.56Cu₂₅Fe₁₂Sc_0.44. It is shown that 0.01% Sc is contained in the icosahedral quasicrystalline phase (Al_65.1Cu_22.57Fe_12.33Sc_0.01). In addition to this scandium is contained in the intermetallic Al_51.45Cu_37.29Sc_8.23 (hexagonal W phase). It is established that alloying of the quasicrystalline Al-Cu-Fe alloy with scandium in the amount of 0.44 at. % significantly increases the content of the quasicrystalline icosahedral phase in ingots from 50 to 65 vol.% which leads to an increase in the microhardness of ingots. The microhardness of Al-Cu-Fe quasicrystalline ingots in the range of 20 - 400 °C is weakly dependent on temperature and amounts to 7-8 GPa. With increasing temperature, the microhardness value begins to decrease and at 720 °C reaches a value of 0.5 GPa. The study of the electrochemical characteristics of the corrosion process of quasicrystalline ingots showed that alloying of Al-Cu-Fe quasicrystalline alloy with Sc decreased the corrosion rate of non-annealed samples, and simultaneously lowered both the corrosion potential and the pitting potential.

Abstract: This study investigates the effect of nano-TiO₂ (nTiO₂) reinforcement on the corrosion behaviour of cold work aluminium composites in a 0.3M H₂SO₄ environment. Al-nTiO₂ composites were fabricated with 0%, 1%, 2%, 3%, and 5% weight fractions of nano-TiO₂ using stir casting. The corrosion performance was evaluated using potentiodynamic polarization (PDP), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). The results show that increased TiO₂ content enhances corrosion resistance up to 5%, particularly at lower cold-working loads. Sample J (5% TiO₂, 2 kg load) exhibited the lowest corrosion rate (0.09474 mm/yr) and highest polarization resistance (809.58 Ω). SEM/EDX analysis revealed denser passive layers and reduced sulfur compound deposits in higher TiO₂ composites. This work highlights the effectiveness of nano-TiO₂ in improving electrochemical stability and corrosion morphology of aluminium composites in acidic environments.

Abstract: This work investigates the effect of anodized aluminum oxide films on the surface characteristics and corrosion behavior of AlSi10Mg alloy fabricated via laser powder bed fusion (PBF-LB). A ∼10 μm thick oxide layer was formed using sulfuric acid anodizing, under both as-built and stress-relieved (300 °C, 2 h) conditions. Surface morphology, microstructure, and corrosion performance were characterized using scanning electron microscopy, EDS, and immersion testing in 3.5% NaCl solution. Anodizing significantly reduced surface roughness (Ra) from ~14 µm to ~6 µm, with further reduction in extreme topographical features observed in heat-treated samples. Cross-sectional analysis confirmed uniform oxide growth, while immersion tests revealed delayed corrosion onset relative to uncoated material. However, localized pitting was still observed, particularly in heat-treated samples, likely due to Si-network fragmentation. These findings demonstrate that anodizing enhances surface finish and corrosion resistance of AM AlSi10Mg, while microstructural features, such as silicon morphology, remain critical to oxide layer integrity.

Abstract: Magnesium alloys are promising for bioabsorbable stents due to their biocompatibility and degradability. Unlike conventional stainless steel stents that remain in the body and may cause complications, magnesium stents gradually degrade, reducing risks like restenosis and thrombosis. However, magnesium has low corrosion resistance, and its corrosion resistance needs to be improved. The crystal structure is one factor affecting the corrosion properties of metallic materials. Several studies have been conducted on the relationship between crystal structure and corrosion properties to improve magnesium's corrosion resistance. It is essential to elucidate the relationship between crystallographic factors and corrosion mechanisms, in the case of stents, plastic deformation during expansion results in the formation of fine crystal grains and twinning deformation. Therefore, the purpose of this study is to investigate the influence of refined grains and twinning on the corrosion properties of magnesium. Hot rolling and compression are used to refine the crystal grains and form twinning in experiments. The crystal structure can be observed by optical microscopy and SEM-EBSD. Following the evaluation of the crystal structure, immersion tests in brine are conducted to measure the mass loss and observe the corrosion behaviour.

Abstract: This study investigates the Mg-6.5Zn-7.24Sn-1.22Ca alloy, focusing on its microstructural evolution, corrosion resistance, and mechanical performance under varying thermal and mechanical treatments. The alloy was cast under an argon environment, homogenized at 400°C for 18 hours, and hot rolled at 400°C with a 15% thickness reduction. Microstructural analysis through XRD, SEM-EDS, and optical microscopy revealed grain refinement, phase redistribution, and reduced porosity after rolling. Corrosion behavior in 3.5% NaCl solution, assessed via electrochemical techniques and weight loss measurements, indicated superior corrosion resistance in the homogenized condition due to reduced micro-galvanic coupling. Rolling, however, increased corrosion susceptibility due to strain-induced defects. High-temperature ( 200°C- 350°C ) tensile tests at strain rates of 10-4 and 5×10-4 s-1 demonstrated that tensile strength decreases with temperature, driven by dynamic recrystallization and grain boundary sliding. Strain rate variations revealed increased tensile strength at higher rates due to enhanced dislocation density and strain hardening. These findings highlight the interplay between processing conditions, strain rates, and alloy performance, offering insights for optimizing magnesium alloys for advanced engineering applications.

Abstract: This comparative study explored the dynamic mechanical characteristics and resistance to corrosion of four distinct nanofillers; MXenes, Graphene Nanoplatelets (GNPs), Carbon Nanotubes (CNTs), and Halloysite Nanotubes (HNTs) within epoxy composites at low loading concentrations (0.1 wt.%). The study assessed the influence of nanofiller on dynamic mechanical properties, while Open Circuit Potential (OCP) and Tafel analyses were used to evaluate corrosion resistance of the coated samples. The dispersion analysis was carried out using both UV-Vis spectrophotometry and scanning electron microscope Scanning electron Microscopy (SEM) technique. It was observed, there is notable decrease in storage modulus arises from poor nanofiller dispersion within the matrix and limited interaction between nanofillers and polymer chains. The incorporation of nanofillers typically leads to an increase in T_g, as observed with the highest T_g value (83.79 °C) in the GNPs sample, indicating restricted molecular motion and reduced free volume due to filler dispersion, resulting in enhanced crosslinking and significant changes in polymer chain dynamics. The OCP curve significantly decreased for the MXenes/epoxy coating (from 0.1827 V to 0.0454 V), indicating increased coating stability and better corrosion resistance behaviour. However, further processing improvement is needed to enhance the dispersibility of MXenes in the polymer matrix, as shown by SEM images showing agglomerates within the nanocomposite sample.

Abstract: Nanoparticles of Cobalt oxide (Co₃O₄) was prepared by green chemistry method using plant resources. Leaf and stem extract of Trionella-Foenum Graecum (Fenugreek) was used for the synthesis of Co₃O₄ nanoparticles. The obtained nanoCo₃O₄ particles were used in elelctroplating bath solution to get Ni-CoO nanocoatings on aluminium alloy substrates. Characterization of nanoparticles and the composite coatings were carried out through EDAX, SEM, XRD and FTIR studies. EDAX confirms the presence of cobalt and oxygen in the nanoparticles as well as in the coatings. SEM studies showed the spherical morphology of the nanoparticles and the coatings exhibited rod like structure. XRD studies confirms the nanosize of particles and maximum peak was obtained at (311) confirming the presence of nanocobalt oxide. The developed coatings showed higher solar absorptance and low infrared emittance, indicating better solar selectivity of the coatings. The coatings also exhibited good corrosion resistance.

Abstract: This study examines the corrosion behavior of 2507 super duplex stainless steel (SDSS) subjected to artificial aging at various temperatures. Using optical microscopy, SEM, EDS, and XRD, we characterized the microstructural and phase changes. Electrochemical tests, including Tafel polarization and EIS, assessed corrosion resistance in 3.5 wt. % NaCl solution. Results show that aging at 1200°C enhances corrosion resistance, attributed to the dissolution of secondary phases and an increase in ferrite content. The optimized microstructure achieved at this temperature displayed the lowest corrosion current density and highest polarization resistance, offering insights for improving SDSS durability in corrosive environments.

Abstract: The core structure of the emulsion was hydrolyzed and condensed by vinyltriethoxysilane and phenyltriethoxysilane, and the shell structure was synthesized by radical polymerization of butyl acrylate, methyl methacrylate, and vinyltriethoxysilane. The Zeta potential of the prepared silicone emulsion was maintained at-40 mV. The emulsion has good stability. Transmission electron microscopy can be used to study the core-shell structure of latex particles. The water contact angle of silicone-modified acrylate coating can reach 94°, and its mechanical durability, alkali resistance, and salt corrosion resistance are better than that of pure acrylate coating.

Abstract: The acidic environment and polarization in proton exchange membrane fuel cells (PEMFC) result in severe electrochemical corrosion issues for the bipolar plates of metal-based fuel cells. AISI 304 stainless steel is studied in this paper as the bipolar substrate and treated with plasma nitriding to improve its corrosion resistance performance. The influence of process parameters on the growth pattern of nitrided layers was discussed, and the microstructure and properties of modified layers were systematically studied. Results show that an expanded austenite nitride layer is obtained when the nitriding temperature is under 450°C, which has good corrosion resistance. When CrN precipitates at higher nitriding temperatures, the corrosion resistance of the nitride layer sharply decreases. The presence of valence states of N and Cr atoms in the nitrided layer determines the corrosion resistance of nitrided stainless steel samples.