Corrosion Resistance Research Articles

A novel BCC-L21-BCC hierarchical heterostructure high entropy alloy with excellent corrosion resistance and mechanical properties in as-cast state

In this paper, a novel as-cast CrFeNiAl0.35Si0.1Ti0.1 high entropy alloy (HEA) with micron-to-nano hierarchical heterostructure was designed, and its microstructure, mechanical properties and corrosion resistance have been systematically investigated. It is found that, this novel HEA exhibits well-dispersed L21 phases with various sizes from micron-scale to nano-scale in the BCC matrix, while nano-sized BCC lamellas could also emerge in the L21 phase with large diameter. Moreover, this HEA exhibits not only excellent corrosion resistance in 3.5 wt.% NaCl solution that close to super-stainless steels, but also high mechanical properties combining yield strength of 1712±56 MPa, compressive plasticity of 21.2%±0.5% and hardness of ∼560 Hv. Such outstanding comprehensive properties for this HEA are possibly resulted from the complex hierarchical BCC-L21-BCC heterostructure with stable passive film and low diversity in work function between different phases. This work provides a novel route in the development of high-performance corrosion-resistant HEAs for structural and coating applications.

Optimized Designation of Mesoscopic Configuration of Zr/Ti Layered Metal Composites for Strength-ductility Synergy Improvement

Zirconium (Zr) and its alloys are highly promising for extreme service environments due to their excellent radiation and corrosion resistance. However, a major challenge in Zr-based materials lies in the strength-ductility trade-off, which limits their broader structural applications. This study aims to address this challenge by fabricating Zr/Ti layered metal composites (LMCs) with different layer thickness ratios (LTRs) and investigating the effects of LTR on the mechanical properties of Zr/Ti LMCs. Zr/Ti LMCs with varying LTRs were fabricated to explore how mesoscopic configurations influence their deformation mechanisms. The results reveal that an optimized layer thickness (~50 μm for Zr and ~40 μm for Ti) maximizes the hetero-deformation-induced (HDI) strengthening effect, resulting in a synergy improvement in strength and ductility. Stable and constrained cracks observed in the Zr layers contributed to local stress relief and improved ductility. The anisotropic deformation between the Zr and Ti layers transformed the local stress states into triaxial states. In addition, the localized stress state and inter-layer strain transmission also promote prismatic <a> slip near the interfaces. This study provides key insights into the design of Zr-based composites with improved mechanical performance, offering potential solutions for their application in demanding environments.

Enhancing corrosion resistance of T91 F/M steel in liquid lead-bismuth (LBE) by slurry FeAl coating

A FeAl coating was fabricated on T91 steel via slurry aluminizing. The corrosion behavior of coated and uncoated samples was assessed in static LBE (lead-bismuth eutectic) with two both high and low dissolved oxygen concentrations at 550 °C. The coating was mostly intact and exhibited great corrosion resistance compared to the uncoated specimens regardless of the oxygen concentration. That is because the coating can form a protective alumina film on the surface at extremely low dissolved oxygen level. This coating is of significant engineering value in enhancing the corrosion resistance of Fe base alloy in LBE.

Titanium surface functionalization via directed energy deposition of CuNiTi ternary alloy

Pure titanium is a soft material that tends to degrade quickly during service due to wear and microbiologically influenced corrosion. Therefore, current research aims at the deposition, microstructural characterization, and surface functionalization of the TiCuNi coatings on pure titanium substrate to improve its surface properties. Cu–Ni premixed elemental powders are deposited on the pure Ti by laser-directed energy deposition (LDED) using a novel method of extracting Ti from the substrate through melt pool convection. The single-track deposit geometry and integrity characterization using dilution percentage, heat-affected zone width (HAZ), and microhardness values show the sound metallurgical bonding with the substrate. The X-ray diffraction (XRD) pattern and microstructure image reveal the presence of NiTi binary (B2) and Ti2CuNi ternary (B19) hard phases and equiaxed dendritic morphology, respectively, demonstrating ternary alloy coating formation. The microhardness value of the coatings is thrice that of the substrate due to the presence of hard NiTi (B2) binary and Ti2CuNi (B19) ternary phases. The coating’s wear resistance is significantly (80%) higher than the substrate, owing to hard phases and Cu as a solid lubricant. The wear track consists of small grooves, adhered debris, and a smooth profile, mainly due to a significant reduction in adhesion and abrasion compared to the substrate. Moreover, the polarisation corrosion potential and current density are increased and decreased by 53% and 97%, respectively, displaying symbolic improvement in the corrosion resistance. Hence, this work has presented the LDED ability to enhance the pure Ti anti-wear and corrosion resistance properties by depositing CuNiTi ternary alloy coating for potential aerospace, marine, and biomedical applications.

Corrigendum to “Additively manufactured porous Ti6Al4V Alloy with excellent mechanical properties, corrosion resistance, in vitro and in vivo biocompatibility” [J. Alloy. Compd. 1009 (2024) 176982]

Corrigendum to “Additively manufactured porous Ti6Al4V Alloy with excellent mechanical properties, corrosion resistance, in vitro and in vivo biocompatibility” [J. Alloy. Compd. 1009 (2024) 176982]

Bridging the gap between high-entropy alloys and metallic glasses: Control over disorder and mechanical properties of coatings

High-entropy alloys (HEAs) and high-entropy metallic glasses (HEMGs) represent two intensively researched classes of materials with high technological interest for applications as functional coatings with high strength, hardness, toughness, and corrosion resistance. The distinctive structural difference between single-phase crystalline solid solutions for HEAs and liquid-like disorder for HEMGs generates a seemingly insuperable contrast. In this work, we demonstrate that we can deliberately choose between crystalline or glassy properties by introducing structural disorder in HfMoNbTiZr thin films of identical composition. Using pulsed laser deposition (PLD) at different growth conditions, we reproducibly tune the structure of HfMoNbTiZr coatings from crystalline to fully amorphous. We show that the level of disorder has a profound impact on the mechanical properties of the coatings using the hardness derived from nanoindentation measurements as an example. While the hardness of polycrystalline HfMoNbTiZr layers already exceeds the single-phase bulk value, the amorphous HfMoNbTiZr is even clearly harder, demonstrating a distinctive improvement with introducing disorder. Our findings bridge the two seemingly different concepts of HEAs and HEMGs and demonstrate that structural disorder is not a given material property. Instead, disorder can serve as a useful design parameter for customizing the properties of functional coatings.

Excellent combinations of strength-ductility and corrosion resistance in SAF 2205 duplex stainless steel with multi-scale grain distribution

In this work, a multi-scale grain structure was obtained in SAF 2205 duplex stainless steel (DSS) by severe deformation and short-term annealing process. The influence of th is structure on the mechanical properties and electrochemical behavior is systematically investigated. Experimental results indicate that the sample subjected to short-term annealing at 1000 °C (SA-1000 °C) exhibits the best comprehensive properties, with a yield strength (YS) of 652.6 MPa and an elongation (EL) of 39.9 %. Both strength and ductility surpass those of the original sample and long-term annealed (LA-1000 °C) samples. The strength-ductility product is increased by 32 % compared to the original sample and by 18 % compared to the LA-1000 °C sample. The increase in YS is predominantly attributed to dislocation strengthening and grain refinement strengthening, and the heterogeneous microstructure leads to good ductility. Moreover, the multi-scale distribution of the grain structure exhibits enhanced corrosion resistance due to the increased low-Σ grain boundaries and the promotion of stable passivation film formation by a limited number of defects, thereby mitigating the corrosion rate.

Healing the high-temperature-retrogression-caused wide precipitation-free zones in Al-Zn-Mg-Cu alloy via strain-aging induced precipitates

Retrogression and re-aging (RRA) treatments have been demonstrated to effectively increase the corrosion resistance of high-strength Al-Zn-Mg-Cu alloys. However, RRA-treated Al-Zn-Mg-Cu alloys still suffer from poor ductility and intergranular corrosion because the wide precipitation-free zones (PFZs) caused by high-temperature retrogression treatment cannot be eliminated during the following re-aging process. Herein, inspired by the fact that retrogression dissolves part of the existing precipitates to obtain supersaturation in the matrix and dislocations as heterogeneous nucleation sites for precipitation are more prone to accumulate into the soft PFZs, a strategy of introducing pre-deformation after retrogression to trigger the secondary precipitation in the retrogression-caused PFZs during the subsequent re-aging is developed to heal this inherent weakness. Furthermore, the dislocations aggregation around the precipitated phases within grains accelerate the transformation of their morphology from platelet-like to circle-like after re-aging. In particular, the precipitates in the dislocation-dense band structures become coarser than those in the out-of-band regions. The synergy of the secondary precipitation at retrogression-caused PFZs and the circle-like and band-distributed precipitates within grains weakens the strength and electrochemical difference between the grain interior and the grain boundary. Compared with the traditional RRA treatment, this innovative technique further enhances the corrosion resistance and ductility of the fully recrystallized Al-8.99Zn-2.12Mg-1.98Cu-0.092Hf-0.12Zr alloy without sacrificing strength. This finding offers practical and straightforward implications for overcoming the current limitation in RRA-treated Al-Zn-Mg-Cu alloys and has the potential to expand to other aging-hardening alloys.

Enhanced hydrophobic properties, wear and corrosion resistance of plasma electrolyte oxidation coatings on AZ31B magnesium alloys with addition of TiO2 nanoparticles

Nanocomposite coatings were fabricated on AZ31B magnesium alloy by means of plasma electrolyte oxidation (PEO) with the addition of TiO2 nanoparticles into the alkaline electrolyte, followed by low surface energy modification in the ethanol solution of lauric acid. The dual-layered nanocomposite PEO coatings composed of MgO, Mg2SiO4, anatase-TiO2, rutile-TiO2, and Mg2TiO4 were formed, and the TiO2 nanoparticles incorporated into the PEO coatings via both inertia and reactive modes. Besides, the penetration and adsorption of TiO2 nanoparticles created a distribution gradient in the coating thickness direction. The wear rate of the PEO coatings with TiO2 nanoparticles in 4 g/L was approximately 82 % lower than that of the bare substrate and approximately 39 % lower than that of the PEO coatings without TiO2 addition, respectively. The enhancement in wear resistance was due to the synergistic effect of the lower coefficient of friction (COF), the higher microhardness and the denser microstructure with finer micropores and less microcracks on the coatings than that of the TiO2-free coatings. Besides, the hydrophobic property was enhanced for the low surface energy modified PEO coatings with the addition of TiO2 nanoparticles in the electrolyte. Moreover, a significant enhancement in the corrosion resistance was achieved for the PEO coating with the addition of TiO2 nanoparticles in 4 g/L. It exhibited a higher corrosion inhibition efficiency and a lower corrosion rate than that in other concentrations and without TiO2 addition. The improvement in anti-corrosion property was originated from the formation of phases including TiO2 and Mg2TiO4 in the coating, and denser microstructure with better hydrophobic properties for the PEO coatings with TiO2 nanoparticles in 4 g/L compared with that in other concentrations. Accordingly, the hydrophobic, wear-resistant and corrosion-resistant PEO coatings with TiO2 nanoparticles exhibited significant advantages in the field of Mg alloys protection.

Bulk self-healing behaviour based on water-excited chemically bonded phosphate ceramic coating and its anti-corrosion resistance

Since industrial metal equipment is subjected to rigorous corrosion and wear, traditional inorganic coatings lack rapid self-healing to limit application. A chemically bonded phosphate ceramic (CBxPA) coating was successfully fabricated by two-component spraying, which exhibited significant corrosion protection and water-excited bulk self-healing ability. Results confirmed that MgKPO4·6H2O crystal stacking formed the denser and uniform coating, the unreacted ions were stored in the coating waiting for the water to excite to generate rapidly bulk self-healing “Whisker Clouds” layer at room temperature. The coating possessed a significant anti-corrosion self-healing efficiency value of 68.61 % in less than 36 h and showed rust-free after 500 h of exposure to a salt solution. Based on these observations, it provides a facile strategy to construct self-healing and anti-corrosion coating.

Achieving Dendrite-Free Zinc Deposition by Large-Size Anion-Reinforced Solvated Structures for Highly Reversible Zinc Anode

The electrochemical instability of zinc anode caused by surface side reactions and irregular zinc deposition severely hinders the practical application of aqueous zinc ion batteries (AZIBs). In this work, diethylenetriaminepentaacetic acid, pentasodium salt (DTPA) was used as a novel electrolyte additive to modulate the electrochemical stability of Zn anode. The DTPA anion can strongly coordinate with Zn2+, thus enabling the formation of a unique large-size anion-enhanced solvation structure of electrolyte. In this, not only the generation of by-products on Zn anode can be effectively inhibited, but more importantly, the deposition kinetics of Zn2+ can be well regulated to induce even and stable zinc deposition. In addition, DTPA is more prone to chemically adsorbed on the surface of Zn anode than H2O, contributing to the resistance of electrochemical corrosion. Synergistically, the Zn anode demonstrates excellent cycling stability (3850 h at 1 mA cm−2, 1 mAh cm−2, and 500 h at 10 mA cm−2, 10 mAh cm−2), enhanced coulombic efficiency (99.83% upon 3500 cycles at 5 mA cm−2, 1 mAh cm−2), and high reversibility of 1050 h even at a stringent discharge depth of 80%. Particularly, the full cell assembled with NaV3O8·1.5H2O (NaVO) cathode can also operate stably for 1800 cycles at 2 A g−1 with a high capacity retain of 90.8%. This work may pave a new route to achieve high-performance AZIBs by regulating the deposition process of Zn2+ based on large-size anion-enhanced solvation structure of electrolyte.

Design of new β-type Ti alloys with outstanding corrosion and wear resistance for dental application

β-type Ti alloys have drawn extensive attention as potential metallic implants. In this work, the microstructure, corrosion behavior, and wear performance of Ti−17.3Nb−1.8Fe (TNF) and Ti−22Nb−30Zr−4Cr (TNZC) biomedical alloys were experimentally investigated, and CP−Ti and Ti6Al4V alloy were also used for comparisons. TNF and TNZC alloys after solution treatment at 1273K showed a single β phase. It was found that TNF and TNZC alloys revealed better corrosion resistance than CP−Ti and Ti6Al4V alloy in different artificial saliva containing 0.15wt.% NaF with the pH values of 3.9 and 5.7, which could be ascribed to the formation of a double-layer passive film composed of multiple species oxides. Moreover, TNF and TNZC alloys exhibited higher wear resistance compared with CP−Ti and Ti6Al4V alloy, whose wear mechanism was adhesive wear and abrasive wear. The present results shows that TNF and TNZC alloys are nice candidates for dental application.

Unlocking the potential of titanium and its alloys: A mini-review on innovative surface modification techniques

Titanium and its alloys are widely utilized in various fields, such as biomedical and aerospace, and in other industrial applications. However, its surface modification is essential to further enrich its properties to enhance its effectiveness. Researchers across the globe are continuously working on a variety of surface modification methods to enhance the properties of titanium and its alloys. This paper presents a comprehensive review of surface modification methods utilized for titanium and its alloys. Some of the important modification techniques discussed in this paper includes mechanical, chemical, electrochemical, thermal, and physical surface modification methods. This paper also provides insights into surface modification methods in terms of improving corrosion and wear resistance, biocompatibility, and hardness of titanium and its alloys.

Evaluation of the corrosion and oxidation resistance of NiCoCrAlY cladding on CMSX-4 by laser cladding

This study uses laser cladding to investigate the hot corrosion and oxidation behavior of CMSX-4 claddes with NiCoCrAlY powder. High-temperature oxidation tests were conducted at 1050°c for 50, 100, 150, and 200 h on 4 samples, while 6 samples underwent hot corrosion testing at 850°c for 6 h. The innovative application of laser cladding enables the creation of a γ′ and β interdendritic phase microstructure. High-temperature oxidation tests reveal a growth rate of 0.05 μm/h in oxide layer thickness between 50 and 200 h, accompanied by a surface weight increase rate of approximately 0.8 mg/cm2.h. The oxide layer's regeneration, continuity, and density are observed at 200 h, highlighting the innovative potential of this technique. Fracture oxidation is observed at 150 h in some TGO layer regions, but at 200 h of oxidation, the TGO layer's regeneration, continuity, and dense TGO was observed at the cladding interface. The TGO forms at 1050°c consist of Al2O3, Cr2O3, and CoO oxides, with Al2O3 as the main oxide phase. The study's findings demonstrate the ability of laser cladding to enhance the thermal protection of CMSX-4, showcasing a promising innovation in the field.

Synthesis and evaluation of an environmentally friendly phosphorus-free and nitrogen-free polymer as a scale and corrosion inhibitor

Polyepoxysuccinic acid (PESA) was modified by glycidyl (Gly) to obtain a phosphate-free and nitrogen-free polymer (Gly-PESA), and its scale and corrosion inhibition properties were studied.The effects of Gly-PESA concentration, calcium ion concentration and temperature to scale inhibition performance were studied by static scale inhibition method. The corrosion inhibition performance of Gly-PESA was studied by static weight-loss method. The morphology and structure of calcium scale and steel surface were characterized by spectroscopic and microscopic methods. The scale inhibition efficiency of Gly-PESA for CaCO3 and CaSO4 was 98.06% and 92.6%, respectively. Under the same experimental conditions, the scale inhibition effect of Gly-PESA was obviously better than that of PESA. Gly-PESA could effectively inhibit the growth of CaCO3 and CaSO4 crystals and cause their crystal lattice distortion or crystal dispersion. The corrosion inhibition efficiency of Gly-PESA for carbon steel was 78.17%. The adsorption of Gly-PESA on the surface of the steel test piece followed Langmuir adsorption isotherm, and formed a protective film, which increased the corrosion resistance of the steel test piece, thus effectively protecting the steel test piece. Therefore, Gly-PESA was a green scale and corrosion inhibitor, which solved the problem of environmental pollution.

Corrosion measurement of thermally sprayed carbide coatings on stainless steel pipes

The petrochemical industries face a formidable challenge from corrosion, which leads to high maintenance costs and lost production. Traditional corrosion monitoring methods frequently fail to provide accurate and reliable results. As a result, these components must be replaced or repaired promptly to avoid increasing costs and limiting component life, which will reduce operation efficiency. Novel techniques with demands for high surface qualities in the future will be applied to develop alloys with better performance and more diverse applications. This study examines the corrosion resistance of cermet coatings, such as tungsten carbide (WC) and Chromium carbide (Cr3C2), in acidic solution by electrochemical impedance spectroscopy and electrochemical potentiodynamic polarisation. Additionally, utilizing optical microscopy techniques, the microstructural characteristics of coatings were assessed. According to the results of the Tafel polarisation test, Cr3C2 coating exhibited a lower rate of corrosion than other coatings. The Cr3C2 coated, WC coated, and uncoated samples reported corrosion rates of 0.924, 1.122, and 2.599 mmpy respectively. The corrosion resistance of Cr3C2 and WC coatings was increased by 64% and 53%, respectively, in comparison to uncoated specimens. This suggests that the coating maximizes economy, minimizes maintenance costs, extends the structure's lifespan, and reduces down the rate of corrosion.

Investigation of various winglets using computational fluid dynamics for subsonic aircraft

Abstract The tiny, upturned, or downturned extensions at the tips of an aircraft’s wings are designated as winglets. By minimizing drag and improving fuel efficiency, they are introduced to increase the aircraft’s aerodynamic efficiency. Winglets are now a day’s employed in the commercial aircraft to minimise the induced effect caused by wing tip vortices produced at low subsonic speeds. In this article, we have selected NACA 2412, from which we have created a swept back wing with a 20-degree sweep angle that has eight distinct winglet configurations. SolidWorks 2023 is used for design work, and ANSYS 19.2 is used for analysis. The analysis is carried out by changing the angle of attack (AOA) from -6 degrees to 20 degrees with an incremental step of 2 degrees. Here, we have used the k-epsilon turbulence model to capture the turbulence and 100 m/s velocity is maintained throughout the analysis. From this analysis, a potential solution of aerodynamic co-efficient (lift, drag, cl, cd and cl/cd) are being observed. Blended winglet with cant angle 35 degrees produces high lift-to-drag ratio compared with another winglet configuration. The insights gained from the study are plotted in various graphs such as cl vs alpha, cd v/s alpha and cl/cd v/s alpha and the CFD results show a considerable improvement in aircraft’s performance after using winglets. Aluminium alloy’s high strength to weight ratio, robust corrosion resistance, enhanced conductivity, and outstanding ductility qualities will make it easier for us to manufacture winglets in the future.

Study on low temperature and narrow heating bands of post weld heat treatment for girth welds stress reduction of long-distance pipelines

Residual stress affects the service safety of pipelines, but there are few efficient methods to reduce the residual stress, especially for long-distance pipelines with large diameters. In this paper, a Secondary Post Weld Heat Treatment (S-PWHT) stress reduction method with low temperature and two narrow heating bands is proposed, and this method fully considers the failure of the corrosion resistance layer caused by high temperature. The temperature distribution and stress distribution under different S-PWHT parameters are compared to obtain the optimal S-PWHT parameters using finite element numerical simulation. The thermocouples are conducted to verify the temperature, and the coercivity experiment is used to verify the stress distribution. Results show that two heating bands width of 80 mm and a peak temperature of 120°C are the optimal S-PWHT parameters with the stress reduced by 61%. Besides, the levels of stress reduction on the inner surface and the HAZ are higher than those on the outer surface and the base metal, respectively. The high-stress zone is transferred from the inner surface to the outer surface, and from the HAZ to the base metal. Furthermore, the stress reduction mechanism of S-PWHT has been revealed through constraint theory. Temperature change is the initial force, and the constraint is the driving force for stress reduction.

Clarifying the Relationship Between Chemical States of P in Fe–P Alloys and Pitting Corrosion Resistance

Fe–0.002 P, Fe–0.05 P, Fe–0.2 P, and Fe–2 P alloys (numbers indicate the mass%) were fabricated, and their pitting potentials, depassivation pH values, and active dissolution rates were measured. The order of pitting potentials was (high) Fe–0.002 P ≥ Fe–0.05 P ≥ Fe–0.2 P ≫ Fe–2 P (low), and that of depassivation pH values was (low) Fe–0.002 P ≤ Fe–0.05 P ≤ Fe–0.2 P ≪ Fe–2 P (high). Both parameters changed significantly between the Fe–0.2 P and Fe–2 P alloys. No evidence of grain boundary segregation of P was observed in the Fe–0.05 P alloy. In the Fe–0.2 P alloy, grain boundary segregation of P was observed, but no pitting occurred at the grain boundaries. In the Fe–2 P alloy, Fe3P precipitated at the grain boundaries and in grains, but pitting corrosion occurred in the alloy matrix and not in Fe3P. This indicated that P in the solid solution was the main cause of the decrease in pitting corrosion resistance. The P concentration in the surface oxide film on Fe–2 P was higher than that on Fe–0.2 P, and the P in the films was determined to be FePO4. The decrease in the pitting resistance with an increasing P concentration was due to FePO4.

Functionalisation of the Aluminium Surface by CuCl2 Chemical Etching and Perfluoro Silane Grafting: Enhanced Corrosion Protection and Improved Anti-Icing Behaviour

This study aimed to prepare a facile hierarchical aluminium surface using a two-step process consisting of chemical etching in selected concentrations of CuCl2 solution and surface grafting through immersion in an ethanol solution containing 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane. The goal was to achieve superhydrophobic characteristics on the aluminium surface, including enhanced corrosion resistance, efficient self-cleaning ability, and improved anti-icing performance. The surface characterisation of the untreated aluminium and treated in CuCl2 solutions of different concentrations was performed using contact profilometry, optical tensiometry, and scanning electron microscopy coupled with energy dispersive spectroscopy to determine the surface topography, wettability, morphology, and surface composition. The corrosion properties were evaluated using potentiodynamic measurements in simulated acid rain solution and salt-spray test according to ASTM B117-22. In addition, self-cleaning and anti-icing tests were performed on superhydrophobic surfaces prepared under optimal conditions. The results showed that the nano-/micro-structured etched aluminium surface with an optimal 0.5 M concentration of CuCl2 grafted with a perfluoroalkyl silane film achieved superhydrophobic characteristics, with water droplets exhibiting efficient corrosion protection, self-cleaning ability, and improved anti-icing performance with decreased ice nucleation temperature and up to 545% increased freezing delay.