Bio-corrosion Resistance Research Articles

Enhanced Biocorrosion Resistance and Cellular Response of a Dual-Phase High Entropy Alloy through Reduced Elemental Heterogeneity.

The leaching out of toxic elements from metallic bioimplants has serious repercussions, including allergies, peripheral neuritis, cancer, and Alzheimer's disease, leading to revision or replacement surgeries. The development of advanced structural materials with excellent biocompatibility and superior corrosion resistance in the physiological environment holds great significance. High entropy alloys (HEAs) with a huge compositional design space and outstanding mechanical and functional properties can be promising for bioimplant applications. However, microstructural heterogeneity arising from elemental segregation in these multiprinciple alloy systems is the Achilles heel in the development of next-generation HEAs. Here, we demonstrate a pathway to homogenize the microstructure of a biocompatible dual-phase HEA, comprising refractory elements, namely, MoNbTaTiZr, through severe surface deformation using stationary friction processing (SFP). The strain and temperature field during processing homogenized the elemental distribution, which was otherwise unresponsive to conventional annealing treatments. Nearly 15 min of the SFP treatment resulted in a significant elemental homogenization across dendritic and interdendritic regions, similar to a week-long annealing treatment at 1275 K. The SFP processed alloy showed a nearly six times higher biocorrosion resistance compared to its as-cast counterpart. X-ray photoelectron spectroscopy was used to investigate the nature of the oxide layer formed on the specimens. Superior corrosion behavior of the processed alloy was attributed to the formation of a stable passive layer with zirconium oxide as the primary constituent and higher hydrophobicity. Biocompatibility studies performed using the human mesenchymal stem cell line, showed higher viability for the processed HEA compared to its as-cast counterpart as well as conventional metallic biomaterials including stainless steel (SS316L) and titanium alloy (Ti6Al4V).

Microstructure, Texture Characteristics, Mechanical and Bio-Corrosion Properties of High Strain Rate Rolled Mg–Zn–Sr Alloys

Microstructure, texture characteristics, mechanical and bio-corrosion properties of the Mg–5Zn–xSr alloys (x = 0, 0.2, 0.6, 1.0) prepared by high strain rate rolling are carefully studied. A low level of Sr addition enhances dynamic precipitation of nano-scale MgZn2 particles in the as-rolled Mg–5Zn alloy, with 0.6%Sr showing the maximum efficiency. These high-density MgZn2 particles can pin grain boundaries of dynamic recrystallization grains and inhibit their growth. A low level of Sr addition (≤ 0.6%) enhances the (0002) basal texture, but 1.0%Sr is just the reverse. The as-rolled Mg–5Zn–0.6Sr alloy exhibits the best combination of ultimate tensile strength (359 MPa) and elongation to rupture (20%). The high strength can be attributable to a reduced grain size, precipitation and basal texture strengthening. The Mg–5Zn–xSr alloys exhibit excellent bio-corrosion resistance, but a minor Sr addition cannot bring about further bio-corrosion resistance improvement due to the multiple actions of grain size, DRX degree, dynamic precipitates and texture characteristics. The 0.6%Sr addition can greatly improve the strength of the as-rolled alloy at no expense of bio-corrosion resistance.

On the bio-corrosion and biocompatibility of TiTaNb medium entropy alloy films

Some high or medium entropy alloys (HEAs and MEAs) have been demonstrated to exhibit great mechanical and bio-corrosion properties to meet the demands as bio-implant materials. However, the difference in Young’s modulus between these alloys and human bone would induce stress shielding effects. Therefore, HEA or MEA coating films appear to be potential materials since these films can be coated on appropriate implant devices as surface modification. This study employs sputtering to produce equimolar TiTaNb MEA film and a titanium-based Ti-10Ta-6Nb film in order to compare their mechanical and bio-corrosion properties. The results indicate that the TiTaNb MEA films have higher hardness, higher wear resistance, greater biocompatibility and superior bio-corrosion resistance, likely to be a high potential bio-implant coating materials. The underlying related chemical reactions and mechanisms are also explored and discussed.

Effect of melting method on the bio-corrosion resistance of Mg67Zn28Ca5 cast magnesium alloy in simulated body fluid

In recent years, biodegradable magnesium alloys have attracted considerable attention in medical devices, such as permanent implants and stents. However, poor corrosion resistance is a major problem limiting the practical application of magnesium alloys. In this study, Mg67Zn28Ca5 alloys were prepared via two different methods, namely, vacuum induction melting and ulfur hexafluoride shielded melting. The effect of melting method on the bio-corrosion resistance of MgZnCa cast magnesium alloy was also studied. The microstructure and phase composition of Mg67Zn28Ca5 alloys were investigated by optical microscopy and X-ray diffraction. The element distribution and surface morphology of Mg67Zn28Ca5 alloys were examined by scanning electron microscopy and energy-dispersive spectroscopy. The corrosion resistance of Mg67Zn28Ca5 alloys was measured via electrochemical and immersion tests. Results showed uniform composition of the Mg67Zn28Ca5 alloy melted by vacuum induction. Immersed in the simulated body fluid, the corrosion rate of Mg67Zn28Ca5 by vacuum induction melting (0.2618 mm/a) was lower than that by ulfur hexafluoride shielded melting (0.9686 mm/a); the corrosion potential of Mg67Zn28Ca5 melted by vacuum induction (−1313 mV) was nobler than that by ulfur hexafluoride shielded melting (−1483 mV); the corrosion current of Mg67Zn28Ca5 by vacuum induction melting (1.202 × 10−5 A) was lower than that by ulfur hexafluoride shielded melting (4.332 × 10−5 A). The Mg67Zn28Ca5 by vacuum induction melting showed uniform corrosion behavior.

Growth of TiO2 Nanotube on Titanium Substrate to Enhance its Biotribological Performance and Biocorrosion Resistance

TiO2 nanotubes (NTs) have a great potential in improving the osetointegration of titanium (Ti)-based biomaterials. Much efforts have been made to evaluate the biological performance of the TiO2 nanotube in regulating protein adsorption and cells attachments. As often used in orthopaedic applications, although biotribological performance and biocorrosion are important issues in these applications, few researches have been reported on the biotribological performance of NT layers. This paper reports the preparation of a structure-optimised TiO2 NT (SO-NT) material via a multi-step oxidation strategy, as well as its biotribological and biocorrosion behaviours. In this procedure, an interfacial bonding layer of approximately 120 nm - 150 nm was first formed on the titanium substrate, which was then joined to the NT bottoms. The mechanical testing with respect to impact, bending, and biotribological performance have demonstrated the resultant SO-NT layer possess improved mechanical stability compared to conventional NT. The uniform hyperfine interfacial bonding layer with nano-sized grains exhibited a strong bonding to NT layer and Ti substrate. It was observed that the layer not only effectively dissipates external impacts and shear stress but also acts as a good corrosion resistance barrier to prevent the Ti substrate from corrosion. Theoretical models were proposed to analyze and predict the shear performance and corrosion-resistance mechanisms of the resultant material. The obtained results demonstrated that the SO-NT material has great potential in orthopaedic applications.

Enhanced corrosion resistance and biocompatibility of polydopamine/dicalcium phosphate dihydrate/collagen composite coating on magnesium alloy for orthopedic applications

Magnesium (Mg) and its alloys have been suggested as a promising next-generation orthopedic implant material. However, fast degradation in the physiological environment and potential cytotoxicity hinder their further clinic application. To enhance the biocorrosion resistance and cytocompatibility of Mg alloys, a multifunctional composite coating composed of polydopamine (PDA), dicalcium phosphate dihydrate (DCPD), collagen (Col) was prepared by a two-step chemical method. The surface morphology, chemical composition, thickness, corrosion performance, and cytotoxicity of the coating were investigated. The results showed that the PDA/DCPD/Col coating significantly improved the biocorrosion resistance and biomineralization ability of Mg alloys. Moreover, the PDA/DCPD/Col coating has a similar composition to natural bone, providing a more favorable interface for cell viability and adhesion. The PDA/DCPD/Col coating greatly enhanced the cytocompatibility and osteogenic differentiation ability compared with Mg alloy and PDA/DCPD coating. With enhanced cytocompatibility, osteogenic differentiation ability and corrosion resistance, the PDA/DCPD/Col composite coating exhibits great potential in bone tissue engineering.

Influence of Ag alloying on the antibacterial properties, bio-corrosion resistance and biocompatibility of α-Nb5Si3 nanocrystalline coating

To improve the corrosion resistance and impart the bioactivity and antibacterial functionalities to titanium alloys for biomedical applications, α-(Nb1-xAgx)5Si3 compounds, with three different Ag contents, were deposited on Ti–6Al–4V by double cathode glow discharge method. The new α-(Nb1-xAgx)5Si3 coatings, each about 16 μm in thickness, exhibited a compact uniform structure, composed of equiaxed nanocrystalline grains. Nanoindentation measurements revealed that Ag alloying reduced the hardness (H) and elastic modulus (E) values of the α-(Nb1-xAgx)5Si3 coatings. Compared to Ti–6Al–4V, the α-(Nb1-xAgx)5Si3 coatings exhibited improved corrosion resistance in Ringer’s physiological solution, as well as newly added in-vitro bioactivity and antibacterial ability against both E. coli and S. aureus. A MTT assay experiment shows that the two α-(Nb1-xAgx)5Si3(x = 0 and 0.05) coatings were as non-cytotoxic as bare Ti-6Al-4V. However, the MC3T3-E1 osteoblast-like cell viability for the α-(Nb0.9Ag0.1)5Si3 coating was slightly reduced, suggesting that the proliferation of MC3T3-E1 osteoblast-like cell was affected to some degree by excess Ag added to α-Nb5Si3. Overall, the α-(Nb0.95Ag0.05)5Si3 coating provides an attractive combination of good bioactivity, high corrosion resistance and new antibacterial function, and thus demonstrates great potential for applications in orthopedic devices.

Effect of ageing treatment on microstructure and mechanical properties of α+β type titanium alloy used for biomaterials

The high strength Ti-Al-V alloy is a α+β type that could be extensively used for many special applications like health care instruments owing to their unique combination of better mechanical properties, superior biocorrosion resistance with excellent biocompatibility, and aerospace applications. This high strength titanium alloy system has a combination of α+β stabilizing elements such as aluminium 7.18 wt.%, and vanadium 7.69 wt.% with high nitrogen content. But special purpose of nitrogen content is α stabilizer that acts as solid solution strengthener, enhancement of mechanical properties and increasing the strain (ε) of this alloy. This experimental work has been dealt with the results of influencing the microstructure of as-received titanium alloy by solution treatment at 860oC for 1h followed by immediately quenching into oil (STQoq) and water (STQwq). These solution treated alloys were preferred for ageing at 500oC for 5h then air cooling (STA). The heat treated alloy was examined likely to OM, SEM, Vicker’s hardness measurement and tensile testing. The optimum tensile properties have been achieved after STQwq+STA treatment such as YS 915 MPa, UTS 1234 MPa, Strain (ε) 40%, RA 18.34%, and YS to UTS ratio of 0.74, respectively.

In Vitro Osteocompatibility and Enhanced Biocorrosion Resistance of Diammonium Hydrogen Phosphate-Pretreated/Poly(ether imide) Coatings on Magnesium for Orthopedic Application.

Magnesium, as a biodegradable metal, is a promising candidate for biomedical applications. To modify the degradation behavior of magnesium and improve its osteocompatibility, chemical conversion and spin coating methods were combined to develop a diammonium hydrogen phosphate-pretreated/poly(ether imide) (DAHP/PEI) co-coating system. The diammonium hydrogen phosphate pretreatment was employed to enhance the attachment between PEI coatings and the magnesium substrate; meanwhile, it could serve as another bioactive and anticorrosion layer when PEI coatings break down. Surface characterization, electrochemical tests, and short-term immersion tests in DMEM were performed to evaluate DAHP/PEI coatings. Electrochemical measurements showed that DAHP/PEI coatings significantly improved the corrosion resistance of pure magnesium. No obvious changes of the chemical compositions of DAHP/PEI coatings occurred after 72 h of immersion in DMEM. An in vitro cytocompatibility study confirmed that viability and LDH activity of human osteoblast-like cells on DAHP/PEI coatings showed higher values than those on the DAHP-pretreated layer and pure magnesium. The DAHP-pretreated layer could still enhance the ALP activity of MG-63 cells after the degradation of PEI in DAHP/PEI coatings. Besides that, the in vitro cellular response to the treated magnesium was investigated to gain knowledge on the differentiation and proliferation of human adipose-derived stem cells (hADSCs). Cell distribution and morphology were observed by fluorescence and SEM images, which demonstrated that DAHP/PEI coatings facilitated cell differentiation and proliferation. The high level of C-terminals of collagen type I production of hADSCs on DAHP/PEI coatings indicated the potential of the coating for promoting osteogenic differentiation. Positive results from long-term cytocompatibility and proliferation tests indicate that DAHP/PEI coatings can offer an excellent surface for hADSCs.

Ultrasound methods for determining the influence of yttrium in Mg-0.5Ca-xY

Biodegradable materials are used as alternative implants for orthopedic applications due suitable strength, fatigue resistance, ductility and biocorrosion resistance which are features for biodegradable implants. Mechanical properties can be improved by adding alloying elements. Mg alloys have been designed to meet the requirements of bone repair implant materials by adding Calcium and Yttrium. Usually Ca is added to control corrosion rate of Mg alloys and thinning grain boundaries. The system is defined as Mg-0.5Ca-xY (x=0.5, 1, 1.5), varying the Y concentration in order to slow the degradation process. Beside morphological characterization with SEM, EDX, noninvasive testing is required to be carried out the determination of mechanical characteristics. The paper presents the influence of Yttrium over elastic properties of these alloys in order to choose the best values appropriate with human bones, using Resonant Ultrasound Spectroscopy and ultrasound method.

Improving the mechanical properties and biocorrosion resistance of extruded Mg-Zn-Ca-Mn alloy through hot deformation

Mg-Zn-Ca-Mn alloys have been developed due to their great potential as new generation of biomaterials while thermo-mechanical processes can promote its mechanical and corrosion properties. In this study, effect of hot deformation parameters such as temperature and strain rate on mechanical behavior and corrosion properties of Mg-4Zn-0.5Ca-0.75Mn alloy was investigated. Therefore, hot extrusion process at 450 °C with ratio of 12:1 and hot deformation tests at various conditions (300–450 °C and 0.001–1 s−1) were carried out to refine the grain size and improve both mechanical and corrosion properties of Mg-Zn-Ca-Mn alloy. Electrochemical tests were carried out in simulated body fluid (SBF) solution at room temperature using Ivium-n-Stat. The microstructural results and flow curves showed the fine grain microstructure and twinning-free grains as well as fully recrystallized grains achieved at 350 °C and 400 °C at lower strain rates. Also, polarization curves indicated that the corrosion potential shifts toward more noble potential by increasing the temperature parameter. The corrosion rate decreased from 0.31 to 0.12 mm/year at 400 °C and 0.001 s−1 due to the fine grain microstructure. Indeed, the protective passive film covered the grain boundaries surface which decreases the corrosion rate and retards the breakdown of passive film and pitting corrosion. Fine grain and fully recrystallized microstructure through hot compression test at 400 °C of Mg-Zn-Ca-Mn alloy provided a great potential for biomedical application owing to the combination of both improved mechanical properties and enhanced corrosion resistance. Finally, the lowest corrosion rate of the Mg-Zn-Ca-Mn alloy was obtained at 400 °C which is nearly similar with the coated samples and Mg alloys reinforced with hydroxyapatite.

Enhancement in bio-corrosion resistance of metallic glass by severe surface deformation

Amorphous metals, also known as bulk metallic glasses, are promising materials for advanced healthcare applications. This is attributed to their exceptional properties, unseen in crystalline materials. Their unique ability to undergo relaxation during low temperature annealing provides opportunity to develop tailored properties. Here, we show a new pathway to significantly accelerate the relaxation kinetics in a zirconium based metallic glass through severe surface deformation using thermo-mechanical processing. The combined strain and thermal field during thermo-mechanical processing significantly reduced the relaxation time compared to vacuum annealing concurrent with remarkable enhancement in its bio-corrosion resistance. The corrosion resistance was found to have a direct correlation with the wetting behavior and oxide layer composition. The surface of relaxed glass was found to be rich in zirconium oxide compared to its as-cast state with higher fraction of aluminum oxide. The difference in oxide layer composition was attributed to annihilation of free volume in relaxed glass resulting in limited atomic transport. Relaxed metallic glass exhibited more hydrophobic nature likely due to its lower surface energy state as a consequence of structural densification. In addition, the relaxed glass showed better cell proliferation, thereby, enhancing its appeal as a next-generation biomaterial.

Effects of Electropolishing on Mechanical Properties and Bio-Corrosion of Ti6Al4V Fabricated by Electron Beam Melting Additive Manufacturing.

Electron beam melting (EBM) has become one of the most promising additive manufacturing (AM) technologies. However, EBM tends to result in products with rougher surfaces due to the melt pool which causes adjacent powder particles to be sintered to the surface without being melted. Hence, it is necessary to improve the surface quality by post processing. The current study evaluates the tensile response of Ti6Al4V EBMed samples subject to various electropolishing (EP) treatments. The surface roughness Ra readings can be improved from over 24 µm down to about 4.5 µm by proper EP, resulting in apparent tensile elongation improvement from 7.6% to 11.6%, or a tensile plasticity increment of 53%, without any loss of elastic modulus or tensile strength. Moreover, the in-vitro bio-corrosion test in simulating body fluid (SBF) of the as-EBMed and EP-processed samples is also conducted. The potentiodynamic polarization reveals that the bio-corrosion resistance is improved by the lower Ra through proper EP treatments. This is due to the formation of a denser and more completely passivated oxide layer with less defects after proper EP duration. But when the EBMed samples are over-electropolished, nano pitting would induce a degraded bio-corrosion performance.

Corrosion behavior of porous magnesium coated by plasma electrolytic oxidation in simulated body fluid

AbstractPorous magnesium has a great potential to be used as degradable bone scaffolds. In this study, porous magnesium with 35% percolating porosity has been successfully fabricated through powder metallurgy route utilizing space holders. The intrinsic mechanical properties of the porous magnesium were measured by nanoindentation testing and analyzed with the Oliver–Pharr method. Afterward, a ceramic coating on the surface of the porous magnesium was performed by plasma electrolytic oxidation (PEO) treatment in a silicate‐based solution. The morphology and composition results of the PEO coatings indicated that it is possible to apply a homogenous and adhesive ceramic coating layer on all free surface of the porous magnesium through PEO method. The protective performance of the PEO coatings was evaluated using by potentiodynamic polarization and electrochemical impedance spectroscopy tests in simulated body fluid. The results revealed the PEO coating significantly improves biocorrosion resistance of the porous magnesium. Therefore, it can be used as an effective method to control the degradation rate of porous magnesium implants in the human body.

Effects of a steady magnetic field on structure and bio-corrosion behavior of pure magnesium

A steady magnetic field (SMF) was imposed during solidification of pure Mg. The effects of SMF on structure and bio-corrosion behavior of pure Mg were investigated. Results show that no detectable difference can be discerned with regard to the influence of SMF on the macrostructure of pure Mg. The (0002) basal plane replaced the () pyramidal plane as the primary plane with SMF treatment. The (0002) plane was further intensified with the increase of magnetic field intensity, while the relative intensity of the () plane became lower and lower. Immersion testing and electrochemical measurements have indicated that the beneficial effect of SMF treatment on the bio-corrosion resistance of pure Mg. The bio-corrosion resistance of pure Mg was further increased as magnetic field intensity increased.

Improved bio-acceptability of thermomechanically processed ZM21 magnesium alloy

ZM21 alloy has been one of the most suitable candidate materials for implant owing to its bio-compatibility properties. However, the rapid corrosion of ZM21 alloy has been an issue questioning its adaptability in bio-implant applications. In the present study, an effort was taken to address this issue by optimising the thermo-mechanical process on the ZM21 alloy. ZM21 magnesium alloy was subjected to varying temperatures hot rolling (250, 300 and 350 °C) with 75% reduction followed by subsequent short annealing at 200 °C for 10 min In-vitro tests and tensile test were performed to determine the bio-corrosion behaviour and mechanical properties of the thermomechanically processed ZM21 alloys. These results converged to a recommendation that ZM21 rolled at 350 °C and subsequent short annealing at 200 °C exhibits the best bio-corrosion resistance and biocompatibility owing to the effect of its coarser grain structure and lesser twin density than those obtained with other parameters.

In vitro Bioactivity, Bio-Corrosion Resistance and Antibacterial Property of Laser Cladded HA Coatings with Different Content of ZnO on Ti-6Al-4V Substrate

HA/ZnO coatings with varying content of ZnO were fabricated on Ti-6Al-4V substrate to enhance its bioactivity and antibacterial ability. The main phases are identified as CaTiO3, Ca3(PO4)2, ZnTiO3 and CaO. The coatings with higher ZnO content presented smaller grain size, resulting in a higher surface free energy and better wettability. Consequently, the mineralization of the ZnO/HA coatings, especially for the higher ZnO content samples were improved, indicating better enhanced in vitro bioactivity. The ZnO-HA coated Ti-6Al-4V presented better corrosion resistance than bare Ti-6Al-4V substrate. Furthermore, better corrosion resistance was obtained by increasing ZnO content in the precursor. The antimicrobial ratio of all coatings was approximately 100%, indicating the ZnO doped HA coatings presented excellent antibacterial ability.

Improvement of corrosion performance of DI pipe by newly invented CNSL based paint

Abstract Ductile iron (DI) pipes are one in which the graphite is present as tiny spheres and due to this morphology, they are having the relatively high strength and toughness similar to mild steel. The investigated DI pipes belong to the family of cast iron with carbon percentage ranging from 3.7-3.9 wt. % and having a tensile strength ≥ 420 MPa and elongation ≥10%. This study represents the comparison of two types of coating on DI pipes-(i) Zn-Al metallization as first layer followed by epoxy coating as second layer, and, (ii) Zn-Al-Cu metallization as first layer followed by CNSL (Cashew Nut Shell Liquid) based paint as second layer. These coatings are used to improve the corrosion resistant property of ductile iron pipelines. The pipe samples were examined under various circumstances - salt spray tests, potentiodynamic polarization tests through SEM analysis, the EDS analysis for the chemical composition of the certain coating specific region. The potentiodynamic polarization tests were performed on the pipe samples to find out the corrosion potential through the analysis of Tafel plots. The above analyses indicate the better performance of the CNSL coating than the epoxy coated DI pipes. The results of microorganism growth indicate that the newly invented CNSL based paint top coating on DI pipe shows better biocorrosion resistance compared to epoxy coating.

Si, Sr, Ag co-doped hydroxyapatite/TiO2 coating: enhancement of its antibacterial activity and osteoinductivity.

A multifaceted coating with favourable cytocompatibility, osteogenic activity and antibacterial properties would be of great significance and value due to its capability for improving osseointegration and alleviating prosthesis loosening. This study marks the first report on the coating of TiO2 nanotubular (TNT) arrays with Sr-and-Si-substituted hydroxyapatite (SSHA) endowed with antibacterial characteristics using silver ions. This TNT layer coated with Ag-substituted SSHA (SSAgHA) formed a composite coating with an interconnected microporous structure and a homogeneous distribution of Sr, Si and Ag; such a coating promoted cell adhesion and osteogenic potential. The anchoring effect of the TNT layer improved the adhesion strength of the SSAgHA/TNT coating to 16.9 ± 3.1 MPa, which was higher than the 15 MPa set in the ISO standard 13 779-4:2002. Moreover, the bio-corrosion resistance of the underlying Ti substrate was greatly enhanced by the composite coating. Hydroxyapatite (HA) and SSAgHA coatings provided a suitable environment for the adhesion, spreading and proliferation of mouse osteoblasts. The SSAgHA coating excellently inhibited bacterial activity and enhanced osteoinductivity with higher osteogenic differentiation compared with the HA coating. Sr and Si dopants increased the expression levels of the genes related to osteogenesis and successfully offset the potential cytotoxicity of Ag ions. Super-osteoinductivity was attributed to the rough and superhydrophilic surface of the composite coating. Therefore, the present study demonstrated the potential of the electrodeposited SSAgHA/TNT composite coating as a promising metallic implant with great intrinsic antibacterial activity and osteointegration ability.

In-situ formation of a gradient Mg2Si/Mg composite with good biocompatibility

A novel Mg2Si/Mg gradient composite was in-situ produced by electromagnetic directional solidification (EMDS). The microstructure of the composite changed longitudinally along with a primary Mg2Si-rich layer at the bottom and a Mg-rich eutectic layer at the top, respectively. The bio-corrosion behavior was investigated by electrochemical studies and static immersion tests. Both layers exhibited a much higher bio-corrosion resistance than high-pure Mg. Especially, the primary Mg2Si-rich phase revealed the greatest bio-corrosion resistance due to the corrosion blocking effect. Additionally, all the components originated from the gradient composite showed a good biocompatibility without obvious toxicity to osteoblasts. This work provided a new insight into the designing of gradient Mg2Si/Mg composite as a promising candidate for orthopedic implants.