Biodegradable Magnesium Alloys Research Articles

Enhancing Corrosion Resistance of Biodegradable Magnesium Alloys through Hydrophobic Surface Modification: Experimental Analysis and ANN Modeling

Enhancing Corrosion Resistance of Biodegradable Magnesium Alloys through Hydrophobic Surface Modification: Experimental Analysis and ANN Modeling

Comparative investigation on corrosion resistance of MgF2 coated, PLA coated and composite coated biodegradable magnesium alloy wires for medical application

The fluorinated treatment coating (MgF2), polylactic acid (PLA) coating, and composite coating (MgF2/PLA) were prepared on biodegradable Mg-2.2Zn-0.3Ca alloy wires to improve the corrosion properties. The composition characteristics and microstructure of the samples were investigated by field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS). The corrosion resistance of all samples were investigated by immersion tests and electrochemical techniques in vitro simulated body fluid (SBF). The results indicated single MgF2 and PLA coating performed opposite protective behaviors in the short and long term immersion tests. The corrosion rate of MgF2-coated samples was lower than that of PLA-coated samples, but the corrosion fracture lifetime of MgF2-coated samples was shorter than that of PLA-coated samples. The MgF2/PLA composite coating exhibited superior short and long term protective effect for Mg wires. These results exhibit that single MgF2 or PLA coating cannot behave strong anti-corrosion ability, only the MgF2/PLA-coated Mg-2.2Zn-0.3Ca alloy wires has high corrosion resistance in vitro immersion, and it has promising potential for surgical implant applications.

Ce-doped MgO films on AZ31 alloy substrate for biomedical applications: preparation, characterization and testing

Magnesium ions, MgO nanoparticles and thin films, magnesium alloys and cerium compounds are materials intensively studied due to their corrosion protection, antibacterial and pharmacological properties. In this work, we have designed, prepared and investigated, novel thin films of MgO doped with cerium, deposited on Mg alloy (AZ31) for temporary implants, in order to enhance their life time. More precisely, we report on microstructure and corrosion behavior of MgO pure and doped with 0.1 at % Ce films, fabricated by sol–gel route coupled with spin-coating technique, on AZ31 alloy substrate. A modified sol–gel method that start from magnesium acetylacetonate, cerium nitrate and 2–methoxyethanol (as a stabilizer for the sol) was been used successfully for cerium doped MgO sol precursor preparation. The structure and morphology of the surface of the coatings, before and after immersion for 7–30 d in Hank’s solution at 37 °C, were characterized by x-ray diffraction (XRD), scanning electron microscopy, high-resolution transmission electron microscope, x-ray photoelectron spectroscopy and Fourier infrared transmittance spectrum (FT–IR). A comparison between the corrosion protection of undoped MgO and MgO doped with 0.1 at % Ce coatings on the AZ31 alloy substrate is performed by electrochemical tests and immersion tests using open circuit potential and electrochemical impedance spectroscopy in Hank’s solution, at 37 °C. The electrochemical results showed that the protection of the AZ31 alloy substrate against corrosion was better with the doped with 0.1 at % Ce MgO film deposited than with pure MgO coting. The investigations of the films after immersion in Hank’s solution, at 37 °C, for 7, 21 and 30 d indicated that the grown layer on the film is bone like apatite that suggests a good bioactivity of 0.1 at % Ce–doped MgO coating. Our work demonstrates that the performance corrosion protection of the biodegradable magnesium alloys used for orthopedic applications, in simulated physiological environments (Hank and Ringer) can be enhanced through coating with Ce3+ doped MgO sol–gel thin film.

Metal-organic complex coating for enhanced corrosion control and biocompatibility on biodegradable magnesium alloy for orthopaedic implants.

Magnesium alloy is currently regarded as the most favourable biodegradable metal; however, obstacles remain to be overcome in terms of managing its corrosion and ensuring its biocompatibility. In this study, a metal-organic complex comprising Ca ions incorporated in tannic acid (TA) was prepared and used to coat magnesium alloy by chemical conversion and dipping processes, followed by modification with stearic acid (SA). This metal-organic complex coating was demonstrated to be homogeneous and compact, and it significantly improved the electrochemical corrosion resistance and long-term degradation behaviour of the coated samples. Consequently, the well-controlled release of Mg and Ca ions, as well as the osteo-compatible TA and SA molecules, promoted the proliferation of osteoblast cells. This metal-organic complex coating offers a promising modifying strategy for magnesium-based orthopaedic implants.

Investigating the microstructure, mechanical properties and corrosion behavior of dissimilar welding of biodegradable magnesium alloy AZ31 to Ti-6Al-4V alloy by friction welding

Investigating the microstructure, mechanical properties and corrosion behavior of dissimilar welding of biodegradable magnesium alloy AZ31 to Ti-6Al-4V alloy by friction welding

High strength and ductility in a new Mg–Zn–Ga biocompatible alloy by drawing and rotary forging

A comparative study of the effect of drawing and rotary forging on the structure, mechanical and corrosion properties of a new biodegradable magnesium alloy Mg–2Zn–2Ga was carried out. The original 6 mm diameter bars obtained by hot extrusion were reduced to the diameters in the range 5.5–3.3 mm by drawing or rotary forging. Optical microscopy, scanning electron microscopy and EBSD grain orientation mapping were used to characterize the material microstructure. Tensile testing was performed to determine the mechanical properties. The optimum temperature for rotary forging and annealing after each drawing pass for defect-free bar production was found to be 300 °C. The combination of the highest strength and ductility was achieved in the 4.2 mm diameter drawn bar and is explained by the formation of numerous twin boundaries in the alloy structure. The 3.3 mm diameter bar obtained by drawing as well as the 5.5 mm diameter bar obtained by rotary forging showed a balance between high strength (260–310 MPa) and large elongation (9–12 %). The analysis of the stress-strain curves using Hollomon's equation was conducted. The hydrogen evolution test in Hanks' solution revealed that the drawn bars of diameters 4.2 and 5.2 mm, as well as the rotary forged bar of 5.5 mm possessed 3 times lower corrosion resistance reduced in comparison with the original 6 mm extruded bar. The 3.3 mm diameter drawn bar exhibited the lowest nominal corrosion rate of 0.11 mm/year that offers excellent opportunities for use in medical implants.

Biodegradable Magnesium Alloys for Biomedical Implants: Properties, Challenges, and Surface Modifications with a Focus on Orthopedic Fixation Repair

Biomedical devices made from high-modulus and hardness materials play a critical role in enhancing the quality of life for people with bone-related ailments. While these materials have been successfully used in orthopedic applications, concerns including stress-shielding have necessitated the exploration of alternative solutions. An ideal biomedical implant requires a delicate balance of mechanical performance, corrosion resistance, tissue biocompatibility, and other properties such as tribological performance and osseointegration. This review explores the suitability of biodegradable magnesium (Mg) alloys as a promising material for biomedical implants. It delves into the essential properties of biomedical implants, emphasizing the importance of matching mechanical characteristics with human bone properties to mitigate stress shielding. The corrosion properties of implant materials are discussed, highlighting the need for controlled degradation to ensure the safety and longevity of implants. The focus then shifts to the potential of magnesium alloys as biomedical implants, examining their benefits, limitations, and the challenges associated with their high degradation rates and less-than-satisfactory mechanical properties. Alloying with elements such as aluminum, zinc, and others is explored to improve magnesium alloys’ mechanical performance and corrosion resistance. Furthermore, this review discusses surface modification techniques, including chemical conversion coatings and biomimetic deposition, as effective strategies to enhance the corrosion resistance and biocompatibility of magnesium and its alloys. These modifications offer opportunities to improve the long-term performance of magnesium-based biomedical implants. This review provides a comprehensive overview of the properties, challenges, and potential solutions associated with biodegradable magnesium alloys as a promising material for biomedical implants. It underscores the importance of addressing problems related to mechanical performance, corrosion resistance, and biocompatibility to advance the development of safe and effective biomedical implant materials.

Mechanical and corrosion properties of biodegradable magnesium mini-tubes with different grain morphologies: Size and distribution

Biodegradable magnesium (Mg) alloys have received much attention due to their biocompatibility and biodegradation. In this study, to uncover the effects of grain morphologies, including grain size and distribution on mechanical and corrosion properties, biodegradable Mg-2.1Nd-0.2Zn-0.5Zr (wt.%) (denoted as JDBM) alloy mini-tubes for stent application with three typical microstructures were achieved successfully by adjusting drawing parameters. Samples with the bimodal structure exhibit the highest strength-ductility balance attributed to the combined effects of fine grains and coarse grains, but show the fastest corrosion rate of about 1.00 ± 0.136 mm/year mainly due to the formation of micro galvanic couples between coarse and fined grains. Samples with fine equiaxed grains show the lowest corrosion rate of about 0.17 ± 0.059 mm/year, as well as uniform corrosion mode and mechanical properties of yield strength (YS) 256 ± 5.7 MPa, ultimate tensile strength (UTS) 266 ± 3.8 MPa, and elongation to failure (EL) 13.5% ± 1.8%, attributed to the high-density grain boundaries. Samples with coarse equiaxed grains exhibit medium corrosion resistance and mechanical properties of about 175 ± 4.8 MPa, 221 ± 4.0 MPa, and 21.53% ± 4.1%. Considering the mechanical and in vitro corrosion properties, biodegradable JDBM alloy implants are recommended to be composed of fine equiaxed grains, which can be used as microstructural targets for fabrication and processing.

Investigating in-vitro degradation, fatigue behavior, and fracture toughness of electrical discharge-processed Mg alloys for biodegradable implant applications

Biodegradable magnesium (Mg) alloys hold great potential for revolutionizing the field of biomedical engineering by offering temporary support during tissue healing and degrading without leaving permanent residues. However, their clinical applications have been limited due to their relatively high degradation rate. This study focuses on evaluating the in-vitro degradation, fatigue resistance, and fracture toughness properties of Mg alloys under cyclic loading conditions, mimicking real-life scenarios. Wire Electrical Discharge Machining (WEDM) was used to prepare spark-processed Mg samples with complex surface texture, and fine-polished Mg samples were used for comparison. The structural characterization, electrochemical corrosion behavior, degradation assessment, and mechanical integrity of the samples were comprehensively analysed. The results show that the Electrical Discharge processed (EDed) Mg sample exhibited uniformly distributed overlapped craters on the surface, which led to a lower charge transfer resistance and higher corrosion potential compared to the Pristine Mg sample. The rough surface topography and alkaline pH microenvironment of the EDed Mg sample facilitated rapid apatite mineralization, but the resulting Ca-deficient apatite compromised its structural stability. Both EDed and Pristine Mg samples exhibited a significant reduction in fatigue life and lower fracture toughness with prolonged immersion. These findings provide valuable insights into the performance of Mg alloys and their potential applications in biodegradable implants, guiding the design of robust implant materials for enhanced patient outcomes.

Multifunctional poly(allylamine hydrochloride)/bioactive glass layer by layer surface coating on magnesium alloy for biomedical applications

The present study reports on a novel multilayer coating for biodegradable magnesium (Mg) alloy substrates. This coating contains soy protein hydrolysate (SPH), poly(allylamine hydrochloride) (PAH), and folic acid (FA) templated bioactive glass (BG) nano particles. The multilayer, designated as SPH/(PAH/BG)n, was coated onto an alkaline-treated Mg alloy surface (AMgS) through a dip-coating process with various numbers of cycles (n = 5and 7) using a layer-by-layer (LbL) assembly. The BG particles had an average diameter of 12.53 ± 2.22 nm and were embedded with therapeutic FA molecules. Scratch testing, wettability, and roughness tests showed excellent adherence of the SPH/(PAH/BG)7 coating on AMgS, making it suitable for cell attachment. Electrochemical measurements in Hanks balanced salt solution (HBSS) demonstrated that the SPH/(PAH/BG)7 coating improved the corrosion resistance of the Mg alloy. SPH/(PAH/BG)7 coated substrate showed a maximum protective efficacy of 98.4041 %, thanks to the bioactive nature of BG. High-resolution XPS and XRD analyses on SPH/(PAH/BG)7/AMgS confirmed the corrosion deposition of Mg(OH)2, MgHPO4.H2O, CaHPO4.H2O, SiO2, MgCO3 and CaCO3 on the substrate surface after immersion in HBSS for 10 d at 37 °C. The LbL coated Mg substrate also showed excellent cytocompatibility by hemolysis assay These results suggest that the SPH/(PAH/BG)7/AMgS material has multifunctional properties and can be a possible alternative for biomedical applications of Mg alloys.

Influence of surface polishing on the degradation behavior of biodegradable Magnesium alloy

Mechanical polishing can significantly improve the surface integrity of Mg alloys to reduce the corrosion rate (CR) by minimizing the galvanic corrosion sites. In this study, an emery-polishing attachment on a lathe machine has been used for surface polishing of as-turned cylindrical ZM21 Mg alloy. Using Taguchi’s L9 orthogonal array, three process variables with three levels were investigated and optimized for minimum surface roughness (Ra and Rz values) of Mg-alloy samples. The minimum surface roughness values of Ra; 195 nm and Rz; 1481 nm were obtained corresponding to emery paper (EP) grade; 2000, rotational speed; 250 rpm, and polishing time; 2 min. An in-vitro immersion study was conducted in simulated body fluid (SBF) for up to 28 days to investigate the degradation behavior of as-turned and as-polished Mg alloy samples. In-vitro study showed that the as-turned samples (surface roughness; Ra: 640 nm, Rz: 4640 nm) had a higher degradation rate (CR: 3.9 mm year−1 after 28 days) with a higher volume of H2 evolution rate, whereas the polished sample with the minimum surface roughness (Ra: 195 nm, Rz: 1481 nm) exhibited lower weight loss, H2 release rate, degradation rate (CR: 0.95 mm year−1 after 28 days) and minimum loss of mechanical strength. Based on the present study, polishing is recommended as a secondary operation after machining of Mg alloy to reduce the corrosion rate for biodegradable implant applications.

Enhanced biocompatibility of biodegradable magnesium alloy modified by TiO2-MgO-GO coating

Enhanced biocompatibility of biodegradable magnesium alloy modified by TiO2-MgO-GO coating

Tuning the long-term corrosion behaviour of biodegradable WE43 magnesium alloy by PEO coating

Plasma electrolytic oxidation (PEO) coatings can control fast degradation of next-generation biodegradable magnesium alloys for biomedical applications. In this work, we studied the effect of a PEO coating on the long-term corrosion behaviour of medical-grade WE43 magnesium alloy. In vitro experiments were performed for periods of up to 4 weeks in an organic fluid Dulbecco's Modified Eagles' Medium (DMEM). The average corrosion rates were measured using the hydrogen evolution method, and the degradation of the mechanical integrity were quantified by tensile test. Susceptibility towards localized corrosion was evaluated by scanning electron microscopy (SEM) images of cross-sections. Moreover, energy-dispersive X-ray spectroscopy (EDS) mappings and X-ray diffraction (XRD) were utilised for analysing the corrosion layer. Experimental results reveal significant changes in the product layer formation due to the PEO coating in phosphate-based electrolyte. The porous morphology of the coating with an initial thickness of ∼20 ± 5 μm changed significantly during the corrosion process, and a growing Mg-O-rich layer of 32 μm after 28 days was detected at the substrate interface. In contrast to the non-coated control group, no carbon-enriched area was observed. These findings imply significant long-term corrosion protection of the PEO coating. The results provide valuable information for a better understanding of the in vitro degradation process in PEO-coated magnesium alloys.

Electrochemical corrosion study of biomaterials: A bibliometric study based on co-word analysis

Demand for better biomaterials has been increasing. To meet this demand, testing is necessary to screen potential options. Corrosion testing is essential as it relates to durability and biocompatibility. Usually, electrochemical tests are employed in screening candidates for in vivo testing. Researching in the biomaterials field, or any field for that matter, requires continuous consultation of the literature. When conducting a literature search, the amount of information available is often overwhelming. Identifying relevant research trends that can guide decisions about future projects becomes challenging. This study employs bibliometric analysis to identify research trends in electrochemical corrosion studies of biomaterials. By doing this, researchers interested in the subject are provided with relevant information on which to base decisions about future research projects. The method used is called co-word analysis. Keywords have been downloaded from Web of Science using an appropriate search query. The analysis period includes the months from January 2013 to December 2021. This period is divided into three subperiods of three years each: 2013–15, 2016–18, and 2019–21. Evolution analysis identified 5 areas of interest that remained active throughout the entire period: biodegradable magnesium alloys, titanium and its alloys, hydroxyapatite coatings, general biomaterial characterization, and the use of electrochemical impedance spectroscopy. All of them are likely to remain of interest in the following years. One area related to titanium anodization appears to be an active research area with few publications, leaving room for new research. Methodological limitations are properly addressed.

The Synergistic Effect of Trace Ag and Hot Extruding on the Microstructure and Properties of a Biodegradable Mg-Zn-Sr-Ag Alloy.

To further improve the mechanical properties and corrosion resistance of the biodegradable magnesium (Mg) alloy, the Mg-4Zn-0.5Sr-xAg alloy (x = 0.2 wt.%, 0.5 wt.%, 1.0 wt.%, and 2.0 wt.%) was smelted in vacuum under the protection of inert gas. The effect of the Ag content on the microstructure and mechanical properties of Mg-4Zn-0.5Sr was tested. The results show that the comprehensive properties of Mg-4Zn-0.5Sr-0.5Ag are best. The grain size of the Mg-4Zn-0.5Sr-0.5Ag alloy is minimal, that is, 83.28 μm. The average tensile strength (σb), yield strength (σs), elongation (ε), and hardness for the Mg-4Zn-0.5Sr-0.5Ag alloy is 168.00 MPa, 88.00 MPa, 12.20%, and 59.90 HV, respectively. To further improve the properties of cast Mg-4Zn-0.5Sr-0.5Ag alloy, extruding treatment was conducted. After extrusion deformation, the grain size of the alloy was significantly refined to 9 μm; at the same time, fine second phases were formed and evenly distributed in the matrix. And then, the mechanical properties of the alloy are significantly enhanced due to the effect of fine crystal strengthening and dispersion strengthening. The σb, σs, ε, and hardness value for the extruded Mg-4Zn-0.5Sr-0.5Ag alloy are 236.00 MPa, 212.00 MPa, 18.97%, and 65.42 HV, respectively. Under the synergistic action of adding the Ag element and extrusion treatment, the grain size of the alloy was significantly refined and the coarse second phase in the alloy became refined to disperse in the matrix, which benefits the formation of electric couples characterized as small cathode-large anode between the second phase and Mg matrix. During full immersion, corrosion products covered on the large anode surface could reduce the galvanic corrosion tendency.

The effect of medical biodegradable magnesium alloy in vivo degradation and bone response in a rat femur model with long-term fixation.

It is of great significance to understand the effect of the different corrosion behaviors of magnesium (Mg) alloys manufactured using different casting methods and implanted with different methods on the long-term implantation to expand the application of Mg-based biomedical implants. The effects of four different casting and rolling speeds on the microstructure of an Mg-rare earth (Mg-Re) alloy were analyzed using electron backscatter diffraction (EBSD). Four Mg alloys were obtained using vertical two-roll casting (TRC) at 10m/min, 16m/min, 24m/min, and 30m/min, and their microstructure, corrosion behavior and bone reaction in vivo were studied. The corrosion resistance of the alloy increases with an increase in casting speed and finer grain size of the cast-rolled parts. The Mg-Re alloys with TRC-10m/min and TRC-30m/min were selected for animal experiments. The two Mg alloys were made into metal rods and inserted into the rat femur to simulate the effect of Mg-Re on femoral healing under an injury condition. The rods were implanted for a long time to judge the effects of the Mg-Re alloy on the body. The TRC-30m/min implants obtained highly mature new bone tissue in the case of bone injury. The in vivo experiments showed that the corrosion resistance of the TRC-30m/min implant was better than that of the TRC-10m/min implant. After 32 weeks of implantation, there were no pathological changes in the liver, heart, or kidney of rats in the TRC-30m/min group, and the cell structure was normal.

Improved deposition quality of calcium-phosphate coating on the surface of WE43 magnesium alloy via FCVA sputtering pretreatment

Calcium-phosphate (CaP) coatings have been widely used in the field of biodegradable magnesium alloys. This paper provides a novel pretreatment method before depositing CaP coatings on the surface of WE43 biomedical magnesium alloys. The surface morphology, phase composition, corrosion resistance and in vitro biological properties of coated samples were investigated. The results showed that a uniform and dense CaP coating formed on the surface of WE43 magnesium alloy pretreated by FCVA (Filtered Cathode Vacuum Arc Technology) possessed better corrosion resistance. Compared with WE43 substrate, Icorr of FCVA/CaP sample decreased by 85.56%. The ALP activity, OD value of COL secretion and mineralization of FCVA/CaP sample reached nearly 2 times higher than that of bare WE43.

Fucoidan-based coating on magnesium alloy improves the hemocompatibility and pro-endothelialization potential for vascular stent application

Biodegradable magnesium alloy stents have great application potential in the treatment of cardiovascular diseases. However, bare magnesium alloy stents are still limited by some problems such as too fast degradation, poor hemocompatibility, and inability to regulate the behaviors of vascular cells in clinical applications. Surface modifications are highly requested to improve the corrosion resistance and biocompatibility of magnesium alloy stents. Herein, a fucoidan-based coating consisting of MgF2 layer, polydopamine (PDA) and fucoidan was constructed on Mg-Zn-Y-Nd (ZE21B) alloy to improve its corrosion resistance, hemocompatibility and rapid endothelialization for vascular stent application. Compared to bare ZE21B alloy, the modified ZE21B alloy exhibited better corrosion resistance and hemocompatibility. More importantly, the endothelial cells (ECs) and smooth muscle cells (SMCs) exhibited a distinct dose-dependent behaviors towards the fucoidan grafting density. The relatively low fucoidan grafting density promoted the proliferation, spreading and migration of ECs, but suppressed these behaviors of SMCs. The results of in vivo implantation experiments indicated that the fucoidan-based coating modified ZE21B alloy can inhibit intimal hyperplasia, relieve tissue inflammation, and promote the rapid endothelialization. Thus, the fucoidan-based coating provides a simple and effective strategy to develop novel magnesium alloy stents with improved corrosion resistance, good hemocompatibility and pro-endothelialization potential.

Fabrication of an antibacterial zinc oxide film on biodegradable magnesium alloy and its biocompatibility

Fabrication of an antibacterial zinc oxide film on biodegradable magnesium alloy and its biocompatibility

Surface modification of WE43 magnesium alloy via alkali/stearic acid treatment for biodegradable drug-eluting stent applications

WE43 is a biodegradable magnesium alloy with a high potential for cardiovascular stent applications. Although it has many adequate properties, there are barriers to using it as a drug-eluting stent vehicle. Corrosion and hydrogen gas formation have an adverse effect on the surface, causing attached drug carriers to separate, which limits its functionality as a stent. An alkali treatment in 1 M NaOH solution at various applied potentials was utilized to fix this issue. Subsequently, a stearic acid layer was formed by two different methods to reduce corrosion by decreasing water uptake of the surface. The anodic film's surface morphology and phase structure were analysed using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Nanoindentation tests were carried out to evaluate the anodic layer's mechanical properties. Its corrosion behaviour was characterized using potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS) and hydrogen evolution tests. The adhesive, thin yet effective oxide layers achieved in all the potentials showed increased corrosion resistance. It significantly decreased hydrogen formation, which were then sealed with stearic acid, and the surface became hydrophobic. This sealing layer acted as an additional barrier and enhanced the corrosion resistance of the magnesium alloy up to fifteen times bigger.