Corrosion Resistance Of Alloy Research Articles

Constructing sodium alginate/carboxymethyl chitosan coating capable of catalytically releasing NO or CO for improving the hemocompatibility and endothelialization of magnesium alloys

Although significant progress in developing biodegradable magnesium alloy materials in cardiovascular stents has been achieved recently, they still face challenges such as rapid in vivo corrosion degradation, inferior blood compatibility, and limited re-endothelialization after the implantation. Hydrogel coating that can catalyze the liberation of gas signal molecules offers a good solution to alleviate the corrosion rate and enhance the biocompatibility of magnesium and its alloys. In this study, based on alkaline heat treatment and construction of polydopamine coating on the surface of magnesium alloy, sodium alginate/carboxymethyl chitosan (SA/CMCS) gel was simultaneously covalently grafted onto the surface to build a natural polymer hydrogel coating, and selenocystamine (SeCA) and CO release molecules (CORM-401) were respectively immobilized on the surface of the hydrogel coating to ameliorate the anticoagulant performance and accelerate endothelial cells (ECs) growth by catalyzing the release of endogenous gas signal molecules (NO or CO). The findings verified that the as-prepared hydrogel coating can catalyze the liberation of CO or NO and significantly improve the corrosion resistance of magnesium alloy. At the same time, owing to the excellent hydrophilicity of the hydrogel coating, the good anticoagulant property of sodium alginate, and the ability of CMCS to promote the ECs growth, the modified magnesium alloy could significantly improve the albumin adsorption while preventing the adsorption of fibrinogen, hence significantly augmenting the anticoagulant properties and promoting the ECs growth. Under the catalytic release of NO or CO, the released gas molecules further enhanced hemocompatibility and promoted endothelial cell (EC) growth and the expression of vascular endothelial growth factor (VEGF) and NO of ECs. Therefore, the bioactive coatings that can catalyze the release of NO or CO have potential applications in constructing surface bioactive coatings for magnesium alloy materials used for intravascular stents.

Effect of Citric Acid Hard Anodizing on the Mechanical Properties and Corrosion Resistance of Different Aluminum Alloys.

Hard anodizing is used to improve the anodic films' mechanical qualities and aluminum alloys' corrosion resistance. Applications for anodic oxide coatings on aluminum alloys include the space environment. In this work, the aluminum alloys 2024-T3 (Al-Cu), 6061-T6 (Al-Mg-Si), and 7075-T6 (Al-Zn) were prepared by hard anodizing electrochemical treatment using citric and sulfur acid baths at different concentrations. The aim of the work is to observe the effect of citric acid on the microstructure of the substrate, the mechanical properties, the corrosion resistance, and the morphology of the hard anodic layers. Hard anodizing was performed on three different aluminum alloys using three citric-sulfuric acid mixtures for 60 min and using current densities of 3.0 and 4.5 A/dm2. Vickers microhardness (HV) measurements and scanning electron microscopy (SEM) were utilized to determine the mechanical characteristics and microstructure of the hard anodizing material, and electrochemical techniques to understand the corrosion kinetics. The result indicates that the aluminum alloy 6061-T6 (Al-Mg-Si) has the maximum hard-coat thickness and hardness. The oxidation of Zn and Mg during the anodizing process found in the 7075-T6 (Al-Zn) alloy promotes oxide formation. Because of the high copper concentration, the oxide layer that forms on the 2024-T6 (Al-Cu) Al alloy has the lowest thickness, hardness, and corrosion resistance. Citric and sulfuric acid solutions can be used to provide hard anodizing in a variety of aluminum alloys that have corrosion resistance and mechanical qualities on par with or better than traditional sulfuric acid anodizing.

Pulsed laser surface texturing enhancing corrosion resistance of rare-earth WE43 magnesium alloys in simulated body fluid environment

The addition of rare earth (RE) elements in Magnesium (Mg) alloys could optimize alloy microstructures and improve the mechanical property. The corrosion resistance however is a tough issue that limits its application as biomedical materials in human bodies. In this work, a green, fast and economical method of pulsed laser surface texturing (PLST) was employed to modify the RE WE43 Mg alloys and the corresponding corrosion resistance after the PLST treatment in simulated body fluid (SBF) was further examined. The microstructural results show that the surface exhibits petal-like microstructures and an oxide film composed of various oxides with remelting particles are also generated on laser-processed areas after PLST treatment. The electrochemical results reveal that the WE43 sample treated by PLST exhibits a superior corrosion resistance in SBF compared with the as-cast one. As for the PLST treated sample with 24 W, the corrosion potential (Ecorr) positively shifts from −1.788 V to −1.556 V after being immersed in SBF for 7 days, which is also nobler than that of the as-cast one, −1.915 V. While the corrosion current density (icorr) drops to the value of 8.3 μA/cm2, considerably lower than that of the as-cast sample, 1380 μA/cm2. The enhancement of corrosion resistance in the early stage is mainly due to the protective oxide film induced by PLST. Furthermore, long-term immersion in SBF further accelerates the formation of deposited hydroxyapatite (HA) products layer on petal-like microstructures, which would further contribute to its enhancement in corrosion resistance in the long-term service in human bodies.

Thermal properties and microstructure of Al–Sn alloys

The Al–Sn alloys feature excellent wear and corrosion resistance, along with good mechanical properties. They are mostly used as bearing materials. However, the application of these alloys as phase change materials (PCMs) for thermal energy storage (TES) has recently been suggested. To assess the adequacy of these alloys in a given area, a detailed evaluation of their thermal properties is required. In the present study, Al–Sn alloys with 11.7, 22.4, 32.8, 41.1, and 53.4 at.% Sn were produced by melting of pure metals. The melt was continuously stirred to avoid segregation, after which casting was carried out in a stainless steel mold. The obtained ingots had a homogeneous microstructure without the appearance of cracks and pores. The thermal diffusivities of the solid Al–Sn alloys in the temperature interval 25–150 °C were measured using the light flash method. The densities at room temperature were measured by the Archimedes method, and the specific heat capacities at different temperatures were calculated using the calculation of phase diagrams (CALPHAD) method. Then the thermal conductivities for studied Al–Sn alloys were obtained by the specific conversion equation. The phase transition temperatures and related heat effects were studied using differential scanning calorimetry (DSC). Variations of thermal conductivity with composition and temperature were determined as well as variation of latent heat of fusion with alloy composition. Moreover, the microstructures and phase compositions of the alloys were examined using scanning electron microscopy (SEM) combined with energy dispersive spectrometry (EDS). The present research results provide important information on the thermal properties and microstructure of the Al–Sn alloys for designing new PCM for thermal energy storage.

Exploring the role of Fe in the wear and corrosion resistance of Ti-based alloys produced with conventional powder metallurgy

In this study, the Ti-6Al-XFe alloy was produced by conventional powder metallurgy at varying Fe contents (3.5, 7.0, 10.5, 14.0, 17.5, and 21.0 wt%) to investigate its potential as a substitute for Nb and V. The primary aim was to assess the impact of Fe content on the mechanical, tribological, and electrochemical properties of the alloys, focusing on their suitability for biomedical implants. XRD and SEM analyses revealed a decrease in the α-Ti phase and an increase in the β-Ti and FeTi phases with higher Fe content. The lowest porosity (0.8 %) and highest hardness (348.4 Hv0.2) were observed in the Ti-6Al-17.5Fe alloy. Tensile and flexural strengths peaked at 238.3 MPa and 680 MPa, respectively, in the 17.5Fe alloy. The Ti-6Al-14.0Fe alloy showed the smallest change in specific wear rate (0.274 × 10−6 mm3/N·m) under dry conditions, while the Ti-6Al-7.0Fe alloy had the smallest change (0.565 × 10−6 mm3/N·m) under wet conditions. The 7.0Fe alloy demonstrated the highest corrosion resistance, with the lowest Icorr (1.02 × 10−8 mm3/N·m) and corrosion rate (14.02 × 10−3 mpy), and the highest charge transfer resistance in EIS analysis.

Influence of Equal Channel Angular Pressing Processing on the Microstructure, Hardness and Corrosion Resistance of Al-Si Alloy

In this study, the impact of heat treatment and Equal Channel Angular Pressing (ECAP) processing routes on refining the microstructure, hardness, and corrosion resistance of Al-7.5% S alloy in a 3.5% NaCl solution was examined. The alloy underwent T5 and T6 heat treatments, followed by ECAP processing via routes A and Bc in a mold with a channel angle of 120° at room temperature. The results indicate that dendritic α-Al grains transformed to globular and fiber shapes after processing routes Bc and A, respectively. Both processing routes fragmented coarse and brittle Si particles into smaller sizes in the eutectic phase. The use of a combination of heat treatment and the Equal Channel Angular Pressing (ECAP) process significantly improved the hardness and corrosion resistance of the samples. The hardness of the heat-treated samples increased considerably from 68 to 116 and 129 HV after three and four passes, respectively. Reducing the area ratio between the noble silicon particles and the less noble eutectic aluminum phase greatly enhances the resistance of alloy to pitting corrosion.

Multifunctional zinc-nickel alloy enabling high-performance aqueous zinc ion batteries

Aqueous zinc ion batteries are considered to be the new type of secondary batteries that have the potential to replace lithium-ion batteries as the most widely used in the future due to their green environment, high specific capacity and abundant zinc resources. However, due to the contact between the zinc anode and electrolyte, the generation of by-products and corrosion phenomena are not completely avoided, which can easily lead to problems such as short cycle life and poor electrochemical performance of the battery. In this study, uniform zinc-nickel alloy (ZnNi) was prepared by melting method. The element nickel has excellent corrosion resistance and is widely used to improve the corrosion resistance of metal alloys, so the introduction of nickel effectively enhances the corrosion resistance of ZnNi alloys. In addition, metallic nickel shows strong attraction to Zn2+, which can promote the uniform distribution and deposition of Zn2+ and inhibit the dendrites growth to prolong the battery life. Notably, the ZnNi-assembled symmetric cell exhibited excellent cycling performance compared with the Zn//Zn cell (100 h), with a cycle life of up to 1000 h at 2 mA cm−2. In addition, the capacity retention rate of the ZnNi//MnO2 full cell was still as high as 90.6 % after 1000 cycles. The preparation of the ZnNi alloy anode may provide a new idea for future alloying strategies.

In-situ incorporation of polydopamine surface modified bioactive glass nanoparticles into a plasma electrolytic oxidation coating on biodegradable AZ31 Mg alloy: A study of bioactivity and corrosion performance

Magnesium alloys are promising candidates for next-generation biodegradable biomaterials. However, their poor corrosion resistance has limited their medical applications. In this study, to improve the bioactivity performance and control the degradation rate of an AZ31 Mg alloy, anodic oxide coatings containing bioactive glass (BG) were created on the alloy using plasma electrolytic oxidation (PEO). First, BG nanoparticles were synthesized through the sol-gel method and surface-modified with polydopamine (BG/PDA). These nanoparticles were then dispersed in an alkaline phosphate electrolyte and incorporated into the coatings grown using unipolar and bipolar waveforms. According to EDS results, incorporation of BG/PDA nanoparticles was higher when the bipolar waveform was applied. Electrochemical impedance spectroscopy revealed that the coatings significantly enhanced the corrosion resistance of the AZ31 Mg alloy, with the BG/PDA nanoparticle-containing coatings demonstrating the lowest degradation rate during long-term immersion. These coatings achieved the highest faradic resistance of ∼ 12 kΩ.cm² after 28 days of immersion. The incorporation of BG and BG/PDA nanoparticles enhanced the bioactivity performance of the coatings, facilitating hydroxyapatite formation on the coating surface. Based on the results, the newly developed BG-coated alloy shows promising potential for biomedical applications.

Effect of High Deformation without Preheating on Microstructure and Corrosion of Pure Mg

In this study, the relationship between the extrusion ratio and the corrosion resistance of pure Mg deformed using extrusion with an oscillating die (KoBo) without preheating of the initial billet was investigated. The materials investigated in this study were extruded at high deformation ratios, R1 5:1, R2 7:1, and R3 10:1, resulting in significant grain refinement from the very coarse grains formed in the initial billet to a few µm in the KoBo-extruded samples at room temperature, which is not typical for hexagonal structures. Our research clearly shows that KoBo extrusion improves the corrosion performance of pure Mg, but there is no straightforward dependence between the extrusion ratios and corrosion resistance improvement. Although it was expected that the smallest grain size should provide the highest corrosion resistance, the dislocation density accumulated in the grain interiors during deformation at the highest extrusion ratio, R3 10:1, supports dissolution reactions. This, in turn, provides the answers for the greater grain size observed after deformation at R2 7:1, where dynamic recovery prevailed over dynamic recrystallization. This situation led to the annihilation of dislocation, leading to better corrosion resistance of the respective alloy. Therefore, the alloy with the greatest grain size has the best corrosion resistance.

Effects of heat treatment on the microstructure and corrosion behavior of manganese aluminum bronzes

Abstract Due to a much lower nickel content, manganese aluminum bronzes (MAB) are a cost-effective alternative to nickel aluminum bronzes (NAB). When the material is processed, different microstructures are observable in the material which have an impact on the corrosion resistance of MAB alloys. MAB samples were annealed at 900 °C and quenched in water. After that, annealing treatments at 600, 500, 400 and 300 °C for up to 24 h were performed and the samples were again quenched in water. Metallographic sections were prepared from all samples and potentiostatic corrosion tests at different potentials were performed in synthetic seawater. It was found that the sample annealed at 900 °C and quenched in water as well as those samples which underwent a second annealing treatment at low temperatures for shorter times exhibited a greater corrosion tendency than those undergoing a second annealing treatment at higher temperatures. X-ray diffraction measurements revealed that phase transformations and changes in grain size occurred during the annealing treatments. The increase in corrosion resistance as a result of annealing at higher temperatures is probably due to the strong intergrowth of the phases that are formed.

Mechanism of alteration in passivity of additively manufactured Ni-Fe-Cr Alloy 718 caused by minor carbon variation

Unlike conventional alloys, where carbon content typically promotes carbide compound formation and reduces localized corrosion resistance, the impact of carbon in additively manufactured materials remains largely unexplored due to rapid cooling rates inhibiting carbide formation. This study addresses the novel question of whether reducing carbon content benefits corrosion performance and its underlying mechanisms in Ni-Fe-Cr-based alloy 718. Employing high-resolution techniques and microcapillary electrochemical methods, it was revealed that higher carbon content increases dislocation density at cell boundaries. This increased dislocation density facilitates the enhanced ejection of nickel and iron from the protective chromium oxide layer on the surface, leading to the formation of a defective outer Ni-Fe oxide layer. This compromised layer subsequently diminishes the alloy's corrosion resistance, particularly under tensile stress conditions.

Role of scandium addition to microstructure, corrosion resistance, and mechanical properties of AA7085/ZrB2+Al2O3 composites

The effect of varying amounts of scandium (Sc) on the mechanical performance and corrosion resistance of aluminum alloy (AA7085) composites reinforced with Zirconium diboride (ZrB2) and Aluminum oxide (Al2O3) nanoparticles was investigated. The specimens were made using an in-situ process with varying amounts of Sc up to 0.5 wt%, and their microstructural behavior, corrosion, and mechanical properties were explored in detail. Phase structural analysis revealed the successful incorporation of ZrB2 and Al2O3 into the matrix through in-situ synthesis, ranging from 30 to 61.7 nm. In addition, HRTEM and XRD analysis displays the Al3Zr prominence observed with 0.1 wt% Sc content, transforming to Al3(Sc, Zr) in the 0.3 wt% Sc composite, and finally becoming Al3Sc with 0.5 wt% Sc. Corrosion analysis revealed that the 0.3 wt% Sc composite exhibited fine Al3(Sc, Zr) precipitate phases that enhanced corrosion properties. The Sc addition leads to a significant improvement in the mechanical properties of AA7085/ZrB2+Al2O3 composites. The ultimate tensile strength of 678 ± 5 MPa for 0.5 wt% Sc under the hot rolled and T6 aged condition was achieved. The optimum content of Sc in AA7085/ZrB2+Al2O3 composites has identified both corrosion and mechanical properties enhancement at 0.3 wt% and 0.5 wt%, respectively.

DIELECTRIC BARRIER DISCHARGE BASED PLASMA DEVICE FOR COLD STERILIZATION IN WATER WITH ADDITIONAL ULTRASONIC CAVITATION

A prototype of plasma sterilizer based on dielectric barrier discharge (DBD) with additional ultrasonic cavitation for cold sterilization has been developed. It provides sterilization of reusable small dental instruments, and components made from corrosion-resistant metals and alloys (stainless steel, titanium, etc.), as well as surgical instruments, implants, small drills, plastic sundries, ozone resistant medical rubbers (silicone, etc.), polymers, epoxy resins and glass. The sterilizer is well suited for dentistry and can be used in medical, sanatorium, outpatient and other medical institutions, as well as in military field surgery. The volume of the sterilization bath is 2.5 l. The ozone concentration at the output of the ozone generator is 35…52 mg/l, the ozone concentration in the sterilizer chamber is 6.5…8 mg/l, depending on the water temperature and its volume in the bath. The dependence of the increase of ozone concentration in water on time at different oxygen flow rates is monitored.

Design of ZIF-8-based PVB composite coating on AZ31B Mg alloy surface with superhydrophobic, wear, corrosion protection and durability

Magnesium (Mg) alloys are susceptible to being attacked by corrosive ions in practical application environments, which limits their widespread application as the most promising engineering material. Herein, the superhydrophobic composite coating PVB/STA/ZIF-8@SiO2 (PSZS) has been designed on the surface of Mg alloy by using a drop coating method to improve its corrosion resistance. In this study, we provide an approachable decoration strategy for hydrophobic and hierarchical modification of zeolite imidazolate frameworks (ZIF-8) with stearic acid (STA) and SiO2, and combined with polyvinyl butyral (PVB) to form a composite coating with excellent performance on the substrate surface. Notably, the PSZS composite coating exhibited superhydrophobic and the contact angle is greater than 150° after 300 cm of mechanical friction. The electrochemical testing of the PSZS composite coating indicated that it greatly protected the Mg alloys from corrosion. Moreover, the PSZS coating displayed highly effective corrosion resistance even after being immersed in 3.5 wt% NaCl aqueous solution for 7 days. Overall, the PSZS composite coating with the advantages of corrosion resistance, corrosion durability, superhydrophobic, abrasion resistance and simple preparation process broadens the horizons of Mg alloy corrosion resistance research.

Zinc-doped phosphate coatings for enhanced corrosion resistance, antibacterial properties, and biocompatibility of AZ91D Mg alloy

Magnesium and its alloys have been foreseen as promising bone-implant owing to good biocompatibility, high strength, mechanical properties, and biodegradability to replace the conventional bio-metals (Titanium, stainless-steel, Co-Cr alloys) in orthopedic applications. However, high corrosion rate and high degradation rates adversely effects like abrupt evolution of H2 gas and localized alkalization in a physiological environment limit its medical applications. To overcome these issues, phosphate-based surface coating is developed on Mg-alloy to resist the high biodegradation and corrosion rate utilizing magnesium substrate as source of magnesium ion through a single-step hydrothermal process. Controlling the fast corrosion rate and localized alkalization would reduce the antibacterial character of magnesium-based implants therefore, the simple phosphate-based coatings has been induced by doping it with zinc ions due to its physiological tolerance and excellent antibacterial efficacy. The doping of zinc ions may provide a sustained drug-free antibacterial characteristic for potential application in orthopedics. The synthesized phosphate-based coating was characterized using advanced techniques like Scanning Electron Microscopy, X-ray Diffraction, and wettability test, followed by comprehensive electrochemical testing to assess its corrosion behavior. The in vitro immersion test in simulated body fluid (SBF) indicates that deposition of phosphate and zinc doped phosphate coatings reduces the degradation rate consequently minimized the fast dissolution of Mg2+ ions and OH- in physiological environment. Additionally, cytotoxicity and biocompatibility were evaluated using Alamar Blue and live/dead assays on the MC3T3-E1 mouse osteoblast cell line. These assays demonstrated good cell viability, indicating the coatings possess favorable cytocompatibility and support cellular metabolic activity.

Analysis, Assessment, and Mitigation of Stress Corrosion Cracking in Austenitic Stainless Steels in the Oil and Gas Sector: A Review

This comprehensive review examines the phenomena of stress corrosion cracking (SCC) and chloride-induced stress corrosion cracking (Cl-SCC) in materials commonly used in the oil and gas industry, with a focus on austenitic stainless steels. The study reveals that SCC initiation can occur at temperatures as low as 20 °C, while Cl-SCC propagation rates significantly increase above 60 °C, reaching up to 0.1 mm/day in environments with high chloride concentrations. Experimental methods such as Slow Strain Rate Tests (SSRTs), Small Punch Tests (SPTs), and Constant-Load Tests (CLTs) were employed to quantify the impacts of temperature, chloride concentration, and pH on SCC susceptibility. The results highlight the critical role of these factors in determining the susceptibility of materials to SCC. The review emphasizes the importance of implementing various mitigation strategies to prevent SCC, including the use of corrosion-resistant alloys, protective coatings, cathodic protection, and corrosion inhibitors. Additionally, regular monitoring using advanced sensor technologies capable of detecting early signs of SCC is crucial for preventing the onset of SCC. The study concludes with practical recommendations for enhancing infrastructure resilience through meticulous material selection, comprehensive environmental monitoring, and proactive maintenance strategies, aimed at safeguarding operational integrity and ensuring environmental compliance. The review underscores the significance of considering the interplay between mechanical stresses and corrosive environments in the selection and application of materials in the oil and gas industry. Low pH levels and high temperatures facilitate the rapid progression of SCC, with experimental results indicating that stainless steel forms passive films with more defects under these conditions, reducing corrosion resistance. This interplay highlights the need for a comprehensive understanding of the complex interactions between materials, environments, and mechanical stresses to ensure the long-term integrity of critical infrastructure.

Enhancing corrosion resistance of AZ31B magnesium alloy substrate in 3.5 % NaCl solution with Al-Si coating prepared by cold metal transfer-based wire arc additive manufacturing

In this study, we explored an innovative approach to enhance the corrosion resistance of AZ31B magnesium alloy in 3.5 wt% NaCl solution by applying an Al-Si coating using cold metal transfer (CMT)-based wire arc additive manufacturing (WAAM) technology. The findings indicate that the Al-Si coating improved the alloy’s corrosion performance, with a more noble self-corrosion potential (- 0.97 VSCE) and lower self-corrosion current density (3.68 μA/cm2) compared to untreated AZ31B. Long-term immersion tests demonstrated that AZ31B suffered from severe localized corrosion, while Al-Si coating maintained a uniform corrosion profile. Analysis of the corrosion products showed that the Al-Si coating primarily comprised oxidized Mg and hydroxide Al, with minimal oxidized Al and Si, in contrast to the mainly metallic and hydroxide Mg on AZ31B. By reducing the electrochemical activity and enhancing the stability of corrosion products, the Al-Si coating significantly improved the corrosion resistance of AZ31B substrate. This study suggests a promising avenue for advancing the durability of magnesium alloys in corrosive environments.

Effect of two-step anodizing on corrosion and adhesion resistance of A5052 aluminum alloy

Effect of two-step anodizing on corrosion and adhesion resistance of A5052 aluminum alloy

Influence of Cu and Si on the microstructure and properties of CoCrFeNiCu1-xSix alloys

The effect of Cu and Si on the microstructure and properties of CoCrFeNiCu1-xSix alloys (x = 0, 0.2, 0.5, 0.8 and 1) was studied in this work. The results indicate that as the x value increased from 0 to 1, the phase compositions of CoCrFeNiCu1-xSix alloys evolved from FCC + Cu-rich phases to FCC + Cu-rich + NiSi-rich phases to FCC + BCC + NiSi-rich phases. Therefore, the decrease in Cu content led to the decreasing Cu-rich phase content, whereas Si addition not only favored the formation of intermetallic compounds, but also promoted the phase transition from FCC to BCC. Due to the competition between BCC phase suppressing corrosion and Cu-rich + NiSi-rich phases inducing galvanic corrosion, the corrosion resistance of CoCrFeNiCu1-xSix alloys improved with the increasing x value. The microstructure change also resulted in an improvement in hardness and wear resistance, and a deterioration in fracture toughness of CoCrFeNiCu1-xSix alloys. Moreover, the main wear mechanism evolved from adhesive wear and abrasive wear to slight abrasive wear. Comparison among five alloys indicates that Cu0.2Si0.8 alloy exhibited the excellent comprehensive properties, revealed by the corrosion current density of 4.81 × 10−8 A/cm2, the hardness value of 510.5 HV, the fracture toughness of 8.57 MPa·m1/2 and the wear rate of 0.88 mm3·N−1 · m−1.

Effect of Si on the corrosion resistance of AlZrNbTi lightweight refractory high-entropy alloys in acidic environment

This study investigated the effect of Si content on the corrosion behavior of AlZrNbTiSix (x=0, 0.3, 0.6, 1.0 at%) lightweight refractory high-entropy alloys in a 1 M HNO3 solution. The results showed a transformation in the microstructures of AlZrNbTiSix from a single BCC phase (x=0) to a BCC matrix phase with Zr5Al3 hexagonal precipitated phases (x=0.3, 0.6, 1.0). AlZrNbTiSi0.6 exhibited the best corrosion resistance, attributed to the addition of Si promoting the growth of continuous and dense oxides. Microgalvanic corrosion affected the formation of the oxide film, triggering an excessive amount of Si worsening the stability of the passive film.