Corrosion Resistance Of Mg Alloy Research Articles

Investigation on corrosion behaviour of metal oxide nanoparticles reinforced magnesium composites by salt spray and immersion corrosion test methods

ABSTRACT This study explores the increasing utilisation of lightweight materials, particularly magnesium (Mg) alloy, in sectors such as automobile, aerospace, and marine due to its notable advantages such as high strength-to-weight ratio, good castability, and excellent damping capacity. Despite these merits, Mg alloy faces challenges, notably in wear and corrosion resistance. The research focuses on enhancing the corrosion resistance of Mg alloy by incorporating Zinc Oxide (ZnO), Manganese Oxide (MnO), and Titanium Oxide (TiO2) nanoparticles. The alloy AZ91D and three nanocomposites, namely AZ91D + 1% ZnO, AZ91D + 1% MnO, and AZ91D + 1% TiO2, were manufactured using a stir squeeze casting technique combined with an ultrasonication process. To confirm the even distribution of reinforcement particles, Optical Microscope (OM), Scanning Electron Microscope (SEM) and High-Resolution Scanning Electron Microscope (HR-SEM) were employed. X-ray Diffraction (XRD) analysis revealed the presence of matrix and reinforcement material with intermetallic precipitates around the grain boundaries. Corrosion properties were assessed following ASTM standards and utilising a 3.5% NaCl concentration. The study found that AZ91D + 1% TiO2 nanocomposites exhibited superior corrosion resistance compared to the AZ91D alloy, showing a remarkable 77.78% and 69.89% improvement in corrosion behaviour under salt spray and immersion environments, respectively, after 48 hours.

Biocompatibility and corrosion resistance of drug coatings with different polymers for magnesium alloy cardiovascular stents

Recently, advances in enhancing corrosion properties through various techniques, and the clinical application of biodegradable cardiovascular stents made from magnesium (Mg) alloys face challenges to corrosion resistance, blood compatibility, and biocompatibility. Drug-eluting stents (DES) offer a solution to enhance the corrosion resistance of Mg alloys while simultaneously reducing the occurrence of restenosis. In this study, WE43 Mg alloy was pretreated using electropolishing technology, and different polymers (PEG and PLLA) were used as drug-polymer coatings for the Mg alloy. At the same time, PTX, an anticoagulant, was incorporated to achieve drug coating of different polymers on WE43 Mg alloy. The corrosion resistance of different polymer-drug coatings was assessed using a plasma solution. Furthermore, in vitro and in vivo tests were used to evaluate the blood biocompatibility of these coatings. The results indicated the PTX-PEG-coated WE43 Mg alloy exhibited the highest corrosion resistance and the most stable drug release profile among the tested coatings. Its hemolysis rate of 0.6 % was within the clinical requirements (<5 %). The incorporation of PEG prevents non-specific protein adsorption and nanoparticle aggregation, enhancing the surface hemocompatibility of WE43 Mg alloy. Therefore, the PTX-PEG coating shows promising potential for application in the development of drug-coated Mg alloy.

Mechanism for corrosion protection of β-TCP reinforced ZK60 via laser rapid solidification

It remains the primary issue to enhance the corrosion resistance of Mg alloys for their clinical applications. In this study, β-tricalcium phosphate (β-TCP) was composited with Mg-6Zn-1Zr (ZK60) using laser rapid solidification to improve the degradation behavior. Results revealed rapid solidification effectively restrained the aggregation of β-TCP, which thus homogenously distributed along grain boundaries of α-Mg. Significantly, the uniformly distributed β-TCP in the matrix promoted the formation of apatite layer on the surface, which contributed to the formation of a compact corrosion product layer, hence retarding the further degradation. Furthermore, ZK60/8β-TCP (wt. %) composite showed improved mechanical strength, as well as improved cytocompatibility. It was suggested that laser rapidly solidified ZK60/8β-TCP composite might be a potential materials for tissue engineering.

Preparation and corrosion behavior of MAO based MOFs coatings with excellent film-forming and adhesion properties

Magnesium (Mg) alloys can be applied in many fields, but their poor corrosion resistance limits their widespread applications. Metal-organic frameworks (MOFs) are often used as fillers in the field of corrosion protection due to their poor adhesion. In order to improve the film-forming performance and adhesion of MOFs coatings, and enhance the corrosion resistance of AZ31 Mg alloys, various MOFs coatings were prepared on the Mg alloy micro-arc oxidation (MAO) coating. The results demonstrated that the MAO facilitated film-forming of MOFs and enhanced their adhesion. Moreover, MOFs crystals can seal the pores of MAO, capture corrosive ions, and form insoluble chelates, significantly improving the corrosion resistance of Mg alloys. Among them, the Ce-MOF exhibited the highest corrosion resistance and the lowest corrosion rate, with a corrosion current density of 8.68 × 10−8 A/cm2 after immersing for 30 min. Moreover, MOFs coatings exhibited good stability and durability, and even after immersing in 3.5 wt% NaCl solution for 14 days, their corrosion protection effects were still superior than MAO.

Improved protective properties of Mg alloy AZ31 using bis-[triethoxysilylpropyl] tetrasulfide silane films modified with nano TiO2 by electrochemically assisted deposition

Magnesium (Mg) and its alloys were favored by biomedical practitioners thanks to availability of bioactivity and degradability. However, the mismatch between the degradation properties of Mg alloys and the rate of osteogenesis often led to implant failure and bacterial infections within the desired period. The goal of this study was to improve the corrosion resistance of Mg alloys, providing theoretical guidance for solving the problems of implantable Mg-based materials. In this experiment, we prepared a dense and uniform BTESPT/TiO2 film layer on the surface of Mg substrate by electrochemically assisted deposition. The BTESPT/TiO2 film layer provided a physical barrier to avoid direct contact between AZ31 and the corrosive medium. When the addition amount was 2 g/L TiO2, the coating had the best corrosion resistance behavior, its corrosion current density could be up to 9.973×10−8 A/cm2. The BTESPT/TiO2 revealed good cell viability as well as osteogenic differentiation potential on MC3T3-E1 cells.

Surface microstructure and corrosion characterization of AZ31 magnesium alloys fabricated by laser surface-modification

This study aimed to improve the corrosion resistance of Mg alloys, and to this end, AZ31 Mg alloy was subjected to laser surface re-melting using a fiber laser. Subsequently, a comparative analysis was conducted on the microstructures of the re-melted surfaces under various laser power settings, and the influence of laser surface re-melting on corrosion characteristics was investigated through a potentiodynamic polarization test. The test results show that laser surface re-melting produced a distinct reduction in the crystallite size of magnesium, ranging from 11.23–15.80 μm within the laser-melted layers. The maximum melted layer thickness of 820 μm was achieved with a laser power of 2100 W. The process of laser surface re-melting notably heightened the hardness, particularly as the power increased, which was attributed to swift solidification. The most noteworthy hardness measurement of 92.1 HV0.02 was recorded at 2100 W. Thus, the study shows that laser surface re-melting significantly enhances the corrosion resistance of Mg alloys, primarily owing to the formation of a corrosion product. The smaller grain size on the surface contributes to the formation of a dense product film.

A Review of Corrosion-Resistant PEO Coating on Mg Alloy

The corrosion problem of Mg alloy limits its application in many engineering fields. Plasma electrolytic oxidation (PEO) is an economical and eco-friendly technology that can create a dense oxide layer on Mg alloy, offering a solution to the corrosion issue. This research summarizes the use of PEO technology in developing corrosion-resistant coatings for Mg alloys and examines the growth mode and corrosion process of PEO coatings. It is concluded that current efforts to enhance the corrosion resistance of PEO coatings on Mg alloys can be categorized into two approaches: improving the internal structure of the coating and enhancing the phase composition. This includes optimizing coating thickness, roughness, and density; repairing micropores and cracks; and introducing corrosion-resistant compounds by doping. Micropores and cracks are identified as vulnerable points for corrosion, and sealing is an effective strategy to address this. By modifying the phase composition of the coating, corrosion occurrence can be minimized, significantly boosting the corrosion resistance of Mg alloys. Finally, future challenges and potential advancements in corrosion-resistant PEO coatings for Mg alloys are discussed.

Corrosion resistance study of ZIF-67/Co-Fe LDHs composite coating on the surface of AZ31 magnesium alloy micro-arc oxidation film

Magnesium (Mg) alloys can be applied in many fields, but their poor corrosion resistance limits their widespread applications. This study prepared a zeolitic imidazolate framework (ZIF-67)/Co-Fe layered double hydroxides (LDHs) composite coating on micro-arc oxidation (MAO) coated Mg alloy AZ31. The surface, interface, and corrosion resistance of the composite coating were studied. The results demonstrate that the ZIF-67/LDHs composite coating showed lower corrosion current density icorr (1.31×10−8 A∙cm–2) than AZ31 (5.20×10−5 A∙cm–2), MAO (1.16×10−7 A∙cm–2) or LDHs (7.78×10−8 A∙cm–2). After immersing in a 3.5 wt% NaCl solution for 14 days, its icorr still remained the lowest, exhibiting excellent corrosion resistance to AZ31. It was of great significance in improving the corrosion resistance of Mg alloys, and this compositely growth technology was expected to be applied to other metals.

In situ electrochemical deposition enables dense polypyrrole grown on AZ31 surface for improving corrosion resistance

This study addresses the poor corrosion resistance of Mg alloy. Based on an in-situ electrochemical strategy, poly(pyrrole) coatings were selectively prepared on the surface of Mg alloys with controlled thickness using constant current and cyclic voltammetry techniques. The results indicate that PPy-CV coatings possess greater thickness and a denser structure. Combining studies on corrosion behaviors such as electrochemical analysis, and immersion, it was found that the coatings effectively prevent solution intrusion, thereby enhancing the alloy's resistance to corrosion. And also provides a new avenue for designing corrosion-resistant coatings, particularly for conductive materials such as polyaniline, poly(3,4-ethylenedioxythiophene), etc.

Low-temperature induced enhancement of corrosion/wear resistance in inverse nacre-like graphene-based waterborne coatings

The poor corrosion resistance of Mg alloys severely limits their industrial application. In this work, an inverse nacre-like waterborne coating composed of polyvinyl alcohol/glutaraldehyde (PVA/GA) and graphene oxide/glutaraldehyde (GO/GA) was prepared on Mg alloys. The in-situ heat treatment was applied to reduce hydrophilic transport channels within the bonding network and multilayer GO. The hydrophobicity of RGO sheets was increased owing to the thermal removal of oxygen-containing functional groups. Meanwhile, the heat-treated PVA/GA enriched with acetal linkage network performs “interlock effect” between the reduced graphene oxide/glutaraldehyde (RGO/GA) layers, inhibiting the interface delamination. Therefore, the thermally reduced graphene-based waterborne coating exhibited stable maze effect with extended hydrophobic barrier path. Besides, the low shear coordination of PVA/GA and RGO/GA weakened the contradictory relationship between the relative slipping and bonding strength of GO/RGO sheets, which effectively decreased the wear rate of samples, forming mechanical durability protection for the substrate. Therefore, the coating exhibits integrated corrosion/wear protection performance.

Improved Corrosion Properties of Mg-Gd-Zn-Zr Alloy by Micro-Arc Oxidation

In order to improve the corrosion resistance of Mg-3Gd-1Zn-0.4Zr (GZ31K) alloys for biomedical application, the alloy was micro-arc oxidation (MAO)-treated using silicate electrolyte system under various voltages (400 V, 425 V, 450 V, 475 V). The effects of voltage on the microstructure and corrosion properties of MAO coating were investigated via X-ray diffraction (XRD) and a scanning electron microscope (SEM) combined with an energy-dispersive spectrometer (EDS), X-ray photoelectron spectroscope (XPS), and electrochemical experiments. The results showed that, with the increase in voltage, the MAO coatings became thicker and the micropores on the MAO coating increased in diameter. The main phase compositions of the MAO coatings were MgO and Mg2SiO4. Potentiodynamic polarization curve results showed that MAO coatings could enhance corrosion resistances, where the corrosion current density decreased by six orders of magnitude and the corrosion potential of the specimens increased by 300 mV for the voltage of 450 V in the MAO treatment; nevertheless, the corrosion resistance rapidly deteriorated due to the creation of large micropores in the MAO coating, which provide a pathway for corrosive media when the voltage is 475 V. The electrochemical impedance spectroscopy results showed that MAO treatments could increase low-frequency modulus resistance and increase the corrosion resistance of Mg alloys. In addition, MAO-treated GZ31K alloys still exhibited uniform corrosion, which is desirable for biomedical applications.

Effect of bath temperature on the growth kinetics and characteristics of permanganate conversion coating on LZ91 magnesium alloy

Permanganate conversion coating is one of the possible alternatives to chromate conversion coating for magnesium (Mg) alloys. Permanganate conversion coating enhances the corrosion resistance of Mg alloys, which is closely related to the thickness and defects of the coating. In this study, the growth kinetics of the permanganate conversion on the LZ91, a dual-phase magnesium alloy, as affected by the bath temperature ranging from 15 to 60 °C, was detailed. The permanganate conversion coating was mainly composed of MnO2/MnOOH and MgO/Mg(OH)2. Increasing the bath temperature reduced the growth rate and thickness of the coating although the bath temperature hardly influenced the composition and crystallinity of the coating. The permanganate conversion coating formed at 15 °C for 10 s was nonuniform with a thickness ranging from 100 to 300 nm, which was prone to cracking after post-coating drying at room temperature. The presence of cracks on the permanganate conversion coating was detrimental to the corrosion resistance. On the other hand, the permanganate conversion coating formed at 40 and 60 °C for 10 s was more uniform with a thickness of less than 100 nm, yet exhibited better corrosion resistance than the counterpart formed at low temperatures (15 and 25 °C).

Use of Multi-pass FSP treatment for improving mechanical properties and corrosion resistance of Mg-2Zn-HA composite

Magnesium (Mg) alloys are very popular among the biomaterials for biodegradable bone implants due to their suitable properties matching with that of human cortical bone. However, their poor corrosion resistance in biological fluid is a major constraint to become an ideal choice for bioimplants. The corrosion resistance of Mg-alloys is further retarded with microstructural impurities such as micro-pores, micro cracks, heterogeneous distribution of alloying element etc., which is commonly present in as-cast Mg-alloys. In present study, Friction stir processing (FSP) has been performed on Mg-2Zn alloy to refine the microstructures as well as to develop Mg-Zn-HA composites by using HA powder reinforcement. HA powder reinforcement was added using micro-grooves and multiple FSP passes on as-cast Mg-2Zn alloy having average grain size of 63.86 µm. Filling HA powder in 2-grooves and using 3-pass FSP, a refined microstructure having an average grain size of 7.15 µm and homogeneous distribution of HA powder was obtained for the developed Mg-Zn-HA composite. The Mg-Zn-HA composite developed with 3-pass FSP treatment has shown significant improvement in tensile strength and corrosion resistance as compared with as-cast Mg-alloy.

Anodization and Plasma Electrolytic Oxidation Treatments of AZ91D Mg Alloy in Alkaline Aqueous Solutions

Mg alloys, such as AZ91 (Mg-9mass%Al-1mass%Zn), are lightweight materials with excellent mechanical properties. The applications of Mg alloys in automobiles could significantly contribute to reducing carbon dioxide emissions. Mg alloys are fully recyclable and abundantly available, which increases their desirability in light of rising environmental consciousness. However, the low corrosion resistance of Mg alloys is one of the major limitations to further applications.In Mg alloys, corrosion behavior is known to be related to the microstructure. During the real-time in situ observation of the corrosion process under galvanostatic polarization, filiform corrosion proceeded along the outside of the β phase (in lamellar α + β microstructure and along the α-mother phase 1. Furthermore, the β phase exhibited a higher potential in the OCPs of each phase and a small area with the boundary in 0.1 M NaCl at pH 8.0 2. Thus, the surface films of β phases was thought to suppress the corrosion of Mg alloys. Mg alloys can be treated by anodic oxidation or plasma electrolytic oxidation to obtain excellent corrosion resistance. The latter is similar to anodic oxidation but applies a higher voltage, which causes a discharge on the electrode surface and the resulting plasma modifies the oxide film significantly.In this study, anodic oxidation and plasma electrolytic oxidation were performed on AZ91D Mg alloy in alkaline solutions such as sodium phosphate. This study aims to compare the two methods in the same solution and to produce an Al-rich surface film with excellent corrosion resistance.In anodic oxidation, the size of the electrode area was approximately 1 cm2. The surface of the specimen was coated with epoxy resin, followed by paraffin. The reference electrode was Ag / AgCl (3.33 M KCl). The experiments were performed at 25 ℃. The scan rate of potentiodynamic polarization was set at 23 mV min-1. The starting potential was set at 20 mV lower than the open-circuit potential. The anodic oxidation treatments were terminated at 0 V, 3 V, and 5 V. Plasma electrolytic oxidation was performed with a liquid volume of 500 mL. The sample was mounted on a resin holder. The electrode surface was approximately 50 mm2. A Pt plate was used as the counter electrode. The sample and the counter electrode were fixed at a distance of 0.5 cm. A plasma-generating power supply was used. The solution was cooled down to 20 ℃ while the voltage was applied. The frequency and the pulse interval were adjusted. The voltage and type of solution were changed to produce the film. Z. Shao, M. Nishimoto, I. Muto, and Y. Sugawara, Corrosion Science, 192, 109834 (2021).Z. Shao, M. Nishimoto, I. Muto, and Y. Sugawara, Journal of Magnesium and Alloys, 11, 137-153 (2023).

Enhanced corrosion resistance of Mg alloy embedded in Cl--containing Portland cement with the formation of CaCO3-coated Mg(Al)O passive film via one-step pulse electrodeposition

In this study, a novel CaCO3/Mg(Al)O coating system was successfully synthesized via one-step pulse electrodeposition. The thickness of inner passivation layer and outer CaCO3 layer was tailored by modulating the pulse voltage. Anticorrosion performance of the coated Mg alloy was assessed by both electrochemical methods and embedment tests. The coated Mg alloy demonstrated improved corrosion resistance, attributed to the synergistic impact of a compact outer CaCO3 layer and an Al-assisted inner passivation layer. Both layers' quality primarily governed the alloy's anticorrosion performance. Remarkably, embedment tests revealed a re-passivation phenomenon instead of corrosion, with its mechanism discussed comprehensively.

Effect of Mn and Ca on mechanical, corrosion and surface roughness of Mg-5Sn alloy

Magnesium and its alloys have an extensive application prospect in the aerospace, automotive industry, sports equipment, biomedical and energy storage due to their high specific strength and low density compared with iron and Aluminum alloys. However, the strength and the corrosion resistance of Mg alloys is still the major drawback that hampers their application. Alloying is generally used to improve mechanical and corrosion properties. The mg-Sn alloy system was extensively studied and the Mg-5Sn alloy was chosen as the base composition owing to the addition of 5 wt% Sn improves the strength and corrosion resistance of pure Mg. The present work aims to investigate the effect of Mn and Ca addition on mechanical, corrosion and roughness properties of as-cast Mg-5Sn-Mn-Ca alloy. The addition of Mn and Ca elements significantly refined α-Mg grains. Mn-rich phase precipitated alongside intermetallic eutectic Mg2Snphases and CaMgSn eutectics observed on the grain boundaries. The strength, hardness, roughness, and corrosion resistance of Mg-5Sn alloy are observed to be improved by the addition of Mn and Ca.

Insights into the design of oxidation-resistant Mg alloy by alloying with rare-earth elements

The strategy of rare-earth elements addition into Mg alloys has been successfully developed and applied to enhance the mechanical performance and corrosion resistance of Mg alloys. Although this strategy has also been applied to enhance their high-temperature oxidation resistance, the mechanistic understanding of the beneficial effects remains elusive. Here, the oxidation of Mg–4Nd and Mg-4Nd–1Y alloys in Ar–20%O2 at 500 °C was studied and compared. It was found that even though a continuous layer of Nd2O3 did not form, the Nd addition could still enhance the oxidation tolerance of Mg–4Nd alloy by facilitating the generation of a more continuous and intact oxide scale and working as oxygen sinks to delay the violent oxidation of Mg. The formation of a continuous Y2O3 layer on Mg-4Nd–1Y alloy suggests that Y was more capable of facilitating the external oxidation due to its much faster diffusion rate in Mg matrix than that of Nd. However, the Nd addition could decrease the critical content of Y necessary for the oxidation transition from internal to external because of the synergistic effect of the Nd and Y addition. The dissolution of the thermal unstable Mg12Nd precipitates resulted in a localized increase of Nd content, accelerating the oxidation by increasing the preferential oxidation of Nd. Hence, in the design of oxidation-resistant Mg alloys, the addition of RE elements with faster diffusion rate and the addition of multiple alloy elements are preferred. In addition, the number of thermal unstable precipitates needs to be strictly controlled.

Designing organic-inorganic hybrid coating from composite and structures for the tribological property and corrosion resistance of Mg alloys

Magnesium alloys are promising materials for the regeneration of bioabsorbable implants, but restricted by its poor tribological property and the rapid corrosion. In this work, a robust organic–inorganic hybrid coating was fabricated on the surface of Mg-Nd-Zn-Zr alloys through a combination of chemical assembly technique of hydroxylated boron nitride (BNO) and plasma-enhanced chemical vapour deposition of vinyltriethoxysilane. The obtained hybrid coating simultaneously enhanced anti-wear and anti-corrosion properties in both the dry friction and simulated body fluid (SBF)-condition friction. The wear rates of the Mg alloy modified by BNO/siloxane hybrid coating were significantly reduced by 97.3% and 96.4% under dry and SBF conditions, respectively. This step-by-step coating modification method is applicable to various shapes of magnesium alloys and hence displays great potential in implant application.

Influence of Alloying Materials Al, Cu, and Ca on Microstructures, Mechanical Properties, And Corrosion Resistance of Mg Alloys for Industrial Applications: A Review.

Magnesium is renowned for its favorable low-density attributes, rendering it a viable choice for commercial engineering applications in which weight has substantial design implications. Magnesium (Mg) stands as a readily obtainable metallic element, exhibiting robustness, efficient heat dissipation, and excellent damping properties. The utilization of pure magnesium remains infrequent due to its susceptibility to instability under high temperatures and pronounced vulnerability to corrosion within humid environments. Hence, the incorporation of magnesium alloys into the design process of aircraft, automotive, and biomedical applications assumes paramount importance. This Review presents a comprehensive review of research endeavors and their resultant achievements concerning the advancement of magnesium alloys. Specifically focusing on aerospace, automotive, and biomedical applications, the Review underscores the pivotal role played by alloying constituents, namely aluminum (Al), copper (Cu), calcium (Ca), and PEO coatings, in influencing the microstructural attributes, mechanical potency, and resistance to corrosion.

Influence of texture on the corrosion behavior of an as-extruded Mg–8Al-0.5In alloy sheet

This work aims to clarify the influence of texture on the corrosion behavior of an as-extruded Mg–8Al-0.5In alloy sheet. The weight loss, hydrogen evolution and electrochemical results show that the sample with strong basal texture has the best corrosion resistance. The morphology examinations show the corrosion product film is thinner and more uniform with less cracks for the sample with (0001) plane. The inhomogeneity of corrosion product in samples with (10-10) and (-12-10) planes is the main cause of poor corrosion performance. The findings of this study confirm the corrosion resistance of Mg alloy could be regulated by controlling texture.