Zn-based Materials Research Articles

Recent Developments in Zn-Based Biodegradable Materials for Biomedical Applications.

Zn-based biodegradable alloys or composites have the potential to be developed to next-generation orthopedic implants as alternatives to conventional implants to avoid revision surgeries and to reduce biocompatibility issues. This review summarizes the current research status on Zn-based biodegradable materials. The biological function of Zn, design criteria for orthopedic implants, and corrosion behavior of biodegradable materials are briefly discussed. The performance of many novel zinc-based biodegradable materials is evaluated in terms of biodegradation, biocompatibility, and mechanical properties. Zn-based materials perform a significant role in bone metabolism and the growth of new cells and show medium degradation without the release of excessive hydrogen. The addition of alloying elements such as Mg, Zr, Mn, Ca, and Li into pure Zn enhances the mechanical properties of Zn alloys. Grain refinement by the application of post-processing techniques is effective for the development of many suitable Zn-based biodegradable materials.

Antibacterial Activity of Two Zn-MOFs Containing a Tricarboxylate Linker.

Metal-organic frameworks (MOFs) can be used as reservoirs of metal ions with relevant antibacterial effects. Here, two novel Zn-based MOFs with the formulas [Zn4(μ4-O)(μ-FA)L2] (GR-MOF-8) and [Zn4(μ4-O)L2(H2O)] (GR-MOF-9) (H3L: 5-((4-carboxyphenyl)ethynyl) in isophthalic acid and FA (formate anion) were solvothermally synthetized and fully characterized. The antibacterial activity of GR-MOF-8 and 9 was investigated against Staphylococcus aureus (SA) and Escherichia Coli (EC) by the agar diffusion method. Both bacteria are among the most relevant human and animal pathogens, causing a wide variety of infections, and are often related with the development of antimicrobial resistances. While both Zn-based materials exhibited antibacterial activity against both strains, GR-MOF-8 showed the highest inhibitory action, likely due to a more progressive Zn release under the tested experimental conditions. This is particularly evidenced in the inhibition of SA, with an increasing effect of GR-MOF-8 with time, which is of great significance to ensure the disappearance of the microorganism.

Electrocatalytic CO2 reduction using self-supported zinc sulfide arrays for selective CO production

As the issue of responding to climate change has emerged as a global concern, CO2 utilization technologies have been extensively studied. Recently, electrochemical reduction of CO2 to CO coupled with renewable energy sources is considered as the most promising approach in the industrial fields. However, expensive noble metals such as Ag and Au have been mainly used to exhibit high electrocatalytic performances, selectivity, and durability with low overpotential for CO2 electrochemical reduction reactions. In this study, we are interested in Zn-based materials with attractive possibilities as alternative materials due to good CO selectivity and controllable composition or microstructures. We successfully synthesized the zinc-blende structured ZnS electrocatalysts via a one-pot hydrothermal method using different sulfur sources. Especially the TA-ZnS electrocatalyst shows excellent CO2ER performance, which is around 83 % of CO Faraday efficiency under the potential of −1.9 V vs Ag|AgCl with suppression of hydrogen production. Furthermore, it exhibits that the characteristic stability maintains over around 80 % of CO Faraday efficiency over the wide range of potential, originating from the structural and electrochemical durability. Therefore, this work provides new insight into developing an efficient electrocatalyst with selectivity and durability as a promising candidate for CO2ER application.

Stabilization of oxidation state in ZnO decorated-CeO2 for enhanced formation of CO in CO2 electroreduction

Electrochemical CO2 reduction (ECR) is regarded as a potential approach to generate renewable fuel and realize carbon cycling. Zn-based materials have been considered as effective catalysts to reduce CO2 into CO. Unfortunately, low selectivity for CO and Zn metallization impede the development of Zn-based materials. Herein, we propose a strategy in utilizing the changeable valence state of Ce ions to stabilize oxidation state of ZnO, in which the Zn-O-Ce model is constructed by CeO2-modified ZnO nanofibers through electrospinning technique. The effective stabilization of ZnO oxidation state during electroreduction has been verified via operando Raman spectra and other characterizations. Besides, we also find that the introduction of trace amount of inactive CeO2 can not only suppress the hydrogen evolution reaction (HER), but also greatly enlarge active sites. The catalyst with optimized molar ratio of CeO2 to ZnO exhibits high Faradaic efficiency (FE) of 90.00 % for CO at −0.69 V vs reversible hydrogen electrode (RHE) in a flow cell. This work suggests stabilization of oxidation state via introduction of secondary metal-oxide by strong interactions between atoms can be improved.

Microstructure, Mechanical Performance and Anti-Bacterial Activity of Degradable Zn-Cu-Ag Alloy

Zn-based materials have attracted increasing attention in the biodegradable materials field due to their unique combination of suitable biodegradability and good biological functionalities. However, the currently existing Zn alloys exhibited poor mechanical reliability and insufficient anti-bacterial activity. In this study, the microstructure, mechanical properties, corrosion behavior and antibacterial properties of Zn-1Cu-0.5Ag and Zn-1Cu-1Ag alloys were investigated. The average grain size of the alloys decreased from 1.91 μm in the Zn-1Cu-0.5Ag alloy to 1.64 μm in the Zn-1Cu-1Ag alloy with the increasing Ag concentration. Due to the grain refinement effect, Zn-1Cu-1Ag exhibited higher ductility (elongation of 36.0%) compared with its Zn-1Cu-0.5Ag counterparts (elongation of 26.3%). In the meantime, the Zn-1Cu-1Ag alloy possessed the ultimate tensile strength (UTS) of 292.04 MPa, the yield strength (YS) of 269.49 MPa, and the Vickers hardness value of 96.9. The anti-bacterial properties of the material were evaluated by the inhibition zone test. The addition of Cu and Ag endowed strong anti-bacterial activity to staphylococcus aureus (S. aureus) and escherichia coli (E. coli) with the zinc matrix. The Zn-1Cu-1Ag alloy exhibited improved mechanical properties, a moderate degradation rate of 0.0484 mm/y, acceptable cytocompatibility, and efficient anti-bacterial properties which should be useful for orthopedic applications.

In vitro cytocompatibility and antibacterial studies on biodegradable Zn alloys supplemented by a critical assessment of direct contact cytotoxicity assay.

In vitro cytotoxicity assessment is indispensable in developing new biodegradable implant materials. Zn, which demonstrates an ideal corrosion rate between Mg- and Fe-based alloys, has been reported to have excellent in vivo biocompatibility. Therefore, modifications aimed at improving Zn's mechanical properties should not degrade its biological response. As sufficient strength, ductility and corrosion behavior required of load-bearing implants has been obtained in plastically deformed Zn-3Ag-0.5Mg, the effect of simultaneous Ag and Mg additions on in vitro cytocompatibility and antibacterial properties was studied, in relation to Zn and Zn-3Ag. Direct cell culture on samples and indirect extract-based tests showed almost no significant differences between the tested Zn-based materials. The diluted extracts of Zn, Zn-3Ag, and Zn-3Ag-0.5Mg showed no cytotoxicity toward MG-63 cells at a concentration of ≤12.5%. The cytotoxic effect was observed only at high Zn2+ ion concentrations and when in direct contact with metallic samples. The highest LD50 (lethal dose killing 50% of cells) of 13.4mg/L of Zn2+ ions were determined for the Zn-3Ag-0.5Mg. Similar antibacterial activity against Escherichia coli and Staphylococcus aureus was observed for Zn and Zn alloys, so the effect is attributed mainly to the released Zn2+ ions exhibiting bactericidal properties. Most importantly, our experiments indicated the limitations of water-soluble tetrazolium salt-based cytotoxicity assays for direct tests on Zn-based materials. The discrepancies between the WST-8 assay and SEM observations are attributed to the interference of Zn2+ ions with tetrazolium salt, therefore favoring its transformation into formazan, giving false cell viability quantitative results.

Revealing the mechanical and degradation properties of the Zn-Cu-Ti alloy with ununiform heterostructure

Zn alloy has attracted much attention in recent years as a new biomedical degradable material. However, how to simultaneously achieve its high strength and high ductility is a bottleneck problem to be solved. In this study, the Zn-2.0Cu-0.1Ti alloy with ununiform heterostructure, consisting of the barren areas without CuZn5 phase and the regions enriched with CuZn5 phase, was designed and successfully fabricated through controlled stir casting and hot extrusion. Uniaxial tensile test and Vickers hardness test were applied to reveal the mechanical properties of the Zn-2.0Cu-0.1Ti alloy, while electrochemical test and immersion test were used to characterize its degradation properties. The novel heterostructure was systematically examined by optical microscope (OM), scanning electron microscope (SEM), and transmission electron microscope (TEM). It was found that the yield strength and ultimate tensile strength of the present Zn-2.0Cu-0.1Ti alloy reach 241.2 ± 4.7 MPa and 265.8 ± 1.3 MPa, showing 294.4% and 230.3% improvement over those of pure Zn. Even more surprising is that the improved strength can be achieved without sacrificing ductility. The substantially increased strength can be mainly attributed to the strengthening mechanisms of grain refinement and Orowan looping, and the maintenance of good ductility thanks to the excellent dislocation storage ability of the present heterostructure. At the same time, the corrosion rate of the alloy in simulated body fluids also reaches the industry standard for orthopedic implants. This study not only sheds light on the design and fabrication of Zn-based material for surgical implantation application but also provides a feasible route to improve the mechanical properties of other precipitates reinforced alloys.

Fabrication, in vitro and in vivo properties of β-TCP/Zn composites

In recent years, biodegradable Zn-based materials became a hopeful approach for new generation biomedical implants due to their acceptable mechanical performance, moderate biodegradation rate, and good biocompatibility. In this study, the combination of high-energy planetary milling and spark plasma sintering process were employed to fabricate n vol% β-TCP (n = 0, 0.5, 1, 3, 5, 10)/Zn composites with uniform microstructure and high relative density. The microstructure investigation, mechanical performance, degradation behavior, in vitro and in vivo properties of the composites were systematically investigated. As a result, β-TCP nanoparticles were homogeneously dispersed in the whole composites and possessed a good bonding interface with the Zn matrix. The degradation of pure Zn and β-TCP/Zn composites in vitro and vivo is a uniform corrosion process. Enhanced corrosion resistance attributed to the addition of β-TCP with a optimized content. The evaluation of osteogenic differentiation process showed that the addition of β-TCP induced the up-regulated expression of osteogesis-related genes (ALP) in mouse preosteoblasts, thus improving the osteogenic ability. As revealed by animal experiments, six months after implantation of pure Zn and 3TCP/Zn components, the blood biochemical parameters of rats showed no obvious tissue inflammation, indicating excellent in vivo biocompatibility of experimental materials. Histological investigation showed that with prolonged implantation time, the 3TCP/Zn components were more effective than pure Zn in promoting new bone formation. In summary, 3TCP/Zn matrix components developed in the present study should be useful for orthopedic implants.

Nanocrystalline structure and electrochemical hydrogen storage properties of the as-milled Mg–V–Ni–Fe–Zn-based materials

Among the electrode materials for Ni-MH batteries, the Mg alloy electrodes such as MgNi, Mg2Ni, REMg12, La2Mg17 are considered the most suitable anode materials due to their high discharge capacity and low cost. However, the poor electrochemical cycling stability prevents its practical application. In this paper, Mg50-xVxNi45Fe3Zn2 (x = 0, 1, 2, 3, 4) + 50 wt% Ni alloys were prepared by partially replacing Mg with V and using mechanical ball milling techniques with amorphous and nanocrystalline structures. Electrochemical tests showed that the ball-milled alloy had good electrochemical uptake and release performance. The maximum release performance is achieved in the first cycle. After that, the discharge level and cycle stability increased significantly with increasing ball grinding time and V content.

Mechanical properties, degradation behavior and cytocompatibility of biodegradable 3vol%X (X = MgO, ZnO and CuO)/Zn matrix composites with excellent dispersion property fabricated by graphene oxide-assisted hetero-aggregation

Metal matrix composites have been recognized as a feasible approach to obtain a new generation of biodegradable Zn-based material. Nevertheless, there is a great challenge in achieving good dispersion properties of the bioactive reinforcements within zinc matrix. A novel and facile approach, namely graphene oxide (GO)-assisted hetero-aggregation, were developed to achieve uniformly dispersed nanoceramics in the Zn matrix, by using very low-content (0.03 vol%) GO as a linker between the Zn matrix and reinforcement. The negatively-charged GO becomes a suitable “bridge” connected the positively-charged metallic powder and bioactive reinforcement by charge neutralization in polarity solvent. Three kinds of reinforcements, including MgO, ZnO and CuO, were used to verify the feasibility of the above-mentioned method. As-sintered 3CuO/Zn matrix composites, which possessed uniformly distributed reinforcement, uniaxial compressive strength of 301.2 MPa, failure strain over 40%, moderate corrosion rate of 0.063 mm·y−1, acceptable cytocompatibility and antibacterial property, should be a useful material for orthopedic applications.

Microstructure and properties of β-TCP / Zn - 1Mg composites processed by hot extrusion combination of multi-pass ECAP

To further improve the comprehensive service performance of Zn, hot extrusion combined multi-pass equal channel angular pressing route were applied to process Zn-1(wt%)Mg alloy and 1(vol%)β-TCP/Zn-1Mg composites. As-cast cylinders specimens with a diameter of 60 mm were finally processed to the ECAP-processed specimens with the dimensions of 15 mm × 15 mm × 120 mm. The evolution and corresponding mechanism of the microstructure, mechanical properties, corrosion behavior, and biocompatibility of 1β-TCP/Zn-1Mg composites and Zn-1Mg components were systematically investigated. As a result, compared with Zn-1Mg alloy, the grain refinement effect of ECAP was enhanced in the 1β-TCP/Zn-1Mg composites with exact the same ECAP conditions. Among all the experimental specimens, the minimum average grain size of 3.0 ± 0.3 µm was achieved in 1β-TCP/Zn-1Mg composites processed by 8 ECAP passes. With the increase of ECAP processing times, the texture strength increased, and the texture direction changed to be (0 0 0 1) base plane parallel to TD-axis. Consequently, the 1β-TCP/Zn-1Mg composites after 8 passes of the ECAP process exhibited the highest compressive yield strength (CYS) of 288.05 ± 6.87 MPa and an elongation greater than 50%. Moreover, these composites also showed a moderate degradation rate of 0.04496 mm·y−1 in the simulated body fluid solution. The in vitro cytotoxicity and cytocompatibility evaluation revealed that both ECAP-processed Zn-1Mg alloy and 1β-TCP/Zn-1Mg composites showed non-cytotoxicity to MC3T3-E1 cells, and the addition of β-TCP could improve the biocompatibility of the experimental materials. Above all, the combination of hot extrusion and ECAP should be a useful route to obtain biodegradable Zn-based materials with excellent comprehensive service performance as orthopedic implants. The 1β-TCP/Zn-1Mg composites, which were processed by hot extrusion and subsequent 8 passes ECAP, exhibited the highest CYS, moderate degradation rate, and good biocompatibility, should be a promising candidate for the application of bone repair and bone replacement.

Laser Additive Manufacturing of Zinc Targeting for Biomedical Application.

Biodegradable zinc (Zn) is expected to be used in clinical application like bone tissue engineering scaffolds, since it possesses favorable biocompatibility and suitable degradation rate. Laser powder bed fusion (LPBF), which is a typical additive manufacturing technique, offers tremendous advantages in fabricating medical devices with personalized geometric shape and complex porous structure. Therefore, the combination of LPBF and biodegradable Zn has gained intensive attention and also achieved rapid development in recent years. However, it severely challenges the formation quality and resultant performance of LPBF-processed Zn-based materials, due to the evaporation and element loss during laser processing. In this study, the current research status and future research trends for LPBF of Zn-based implants are reviewed from comprehensive viewpoints including formation quality, microstructure feature, and performance. The influences of powder characteristics and process parameters on formation quality are described systematically. The microstructure evolution, mechanical properties, as well as the degradation behavior are also discussed. Finally, the research perspectives for LPBF of Zn are summarized, aiming to provide guideline for future study.

Resistance Spot Weld Ability of Mild Steel Coated with Zn, Galfan and ZA12

In this study, the weldability of mild steel coated with different Zn-based materials to prevent corrosion with resistance spot welding process was investigated. For this purpose, the surfaces of mid steel were coated with pure Zn, Galfan (Zn5Al) and ZA12 (Zn11Al1Cu) alloys. Hot dipping technique was used for coating. Mild steels with dimension of 1.5X15X40 mm were immersed in the melted Zn and alloys, and the surfaces were coated by waiting for 2 minutes. Steel and coated steel pairs were joined by resistance spot welding process. The welding interface microstructures were examined under light optical microscopy (LOM). Weld interface strengths were measured by axial shear tests. The tests were performed at the room temperature and with a tensile speed of 5mmmin-1. Microstructure investigations showed a good bonding occurred between the coating and the steel and between the welded materials. Mechanical tests have shown that coating the steel reduces the weld strength and the decrease in strength continues with the increase of alloying elements in the coating.

Long-term in vitro corrosion behavior of Zn-3Ag and Zn-3Ag-0.5Mg alloys considered for biodegradable implant applications

In this paper, Zn-3Ag and Zn-3Ag-0.5Mg alloys were studied in terms of applicability as biodegradable implant materials. The performed tensile, compression and bending tests indicate a high strengthening effect induced by the Ag and Mg additions, additionally resulting in grain size refinement. It was shown that sustaining plastic strain during deformation depends on the applied stress causing asymmetric mechanical behavior of the tested Zn-based materials. Electrochemical measurements and immersion tests in Hanks' solution lasting up to 180 days revealed that Ag and Mg contribute to the change of the Zn matrix's open circuit potential and the formation of micro-galvanic cells between the Zn grains and precipitates. The fine-grained microstructure and evenly distributed small precipitates led to uniform corrosion occurring via pit formation on the corroded surface due to intergranular and micro-galvanic corrosion mechanisms. The corrosion rate of the Zn-3Ag-0.5Mg alloy after 180 days was almost twice that of pure Zn and the Zn-3Ag alloy.

The one-pot synthesis of a ZnSe/ZnS photocatalyst for H2 evolution and microbial bioproduction

Low-cost photocatalysts are being developed for the conversion of visible light into H2 and to drive CO2 reduction. Hybrid photosynthesis is a promising approach to convert CO2 and visible light into multicarbon compounds where a photocatalyst energizes the metabolism of an autotrophic microbe. Here, a heterostructure ZnSe/ZnS photocatalyst was synthesized by a simple one-pot method and evaluated for photocatalytic H2 evolution (PHE) as well as for hybrid photosynthesis with the bioplastic-producing bacterium Ralstonia eutropha. ZnSe/ZnS nanoparticles exhibited a PHE 5.5 times higher than pure ZnSe. Photoluminescence and photoelectrochemical characterization of ZnSe/ZnS demonstrated more efficient charge separation probably caused by ZnS defects. Furthermore, ZnSe/ZnS improved 1.3 times bioplastic production from CO2 by R. eutropha, which was not the case for pure ZnSe. These results show ZnSe/ZnS potential for both PHE as well as hybrid photosynthesis and provide insights on the photocatalytic reaction mechanisms involved when the two Zn-based materials are combined.

Fine-tuning of mechanical properties in a Zn–Ag–Mg alloy via cold plastic deformation process and post-deformation annealing

In recent years, Zn-based materials have been extensively investigated as potential candidates for biodegradable implant applications. The introduction of alloying elements providing solid-solution strengthening and second phase strengthening seems crucial to provide a suitable platform for the thermo-mechanical strengthening of Zn alloys. In this study, a systematic investigation of the microstructure, crystallographic texture, phase composition, and mechanical properties of a Zn–3Ag-0.5Mg (wt%) alloy processed through combined hot extrusion (HE) and cold rolling (CR), followed by short-time heat treatment (CR + HT) at 200 °C was conducted. Besides, the influence of different annealing temperatures on the microstructure and mechanical properties was studied. An adequate combination of processing conditions during CR and HT successfully addressed brittleness obtained in the high-strength HE Zn–3Ag-0.5Mg alloy. By controlling the microstructure, the most promising results were obtained in the sample subjected to 50% CR reduction and 5-min annealing, which were: ultimate tensile strength of 432 MPa, yield strength of 385 MPa, total elongation to failure of 34%, and Vickers microhardness of 125 HV0.3. The obtained properties clearly exceed the mechanical benchmarks for biodegradable implant materials. Based on the conducted investigation, brittle multi-phase Zn alloys' mechanical performance can be substantially enhanced to provide sufficient plasticity by grain refinement through cold deformation process, followed by short-time annealing to restore proper strength.

Solution‐phase‐reconstructed Zn‐based nanowire electrocatalysts for electrochemical reduction of carbon dioxide to carbon monoxide

The production of CO via electrochemical CO2 reduction has been recognised as a promising technology that overcomes the environmental issues caused by global warming. It also facilitates the conversion of CO2 into energy sources. Earth-abundant Zn is a well-known alternative to noble metal catalysts such as Au and Ag for the electrochemical CO2 reduction to CO. In particular, Zn-based materials in the form of nanowires are potentially applicable as electrocatalysts in the electrochemical CO2 reduction. However, the conventional methods for manufacturing the nanowire structure are difficult as they require harsh conditions such as high temperatures and excess energy. In this study, Zn-based nanowire catalysts are prepared by the facile electrodeposition of Zn nanostructures on a substrate followed by their energy-free solution-phase reconstitution. Further, their electrochemical performance in the CO2 reduction is investigated in a CO2-purged 0.5 M KHCO3 electrolyte. By optimising the deposition conditions, hexagonal Zn (h-Zn) plates with dominant Zn(101) facets, the favoured crystal structure for CO2 reduction, are fabricated on carbon paper. Furthermore, it is found that, during the solution-phase reconstruction over 16 hours, the h-Zn plate transforms to a nanowire owing to the differences between the oxidation rates of different crystal facets and the formation of a hydroxide complex. The activity of the reconstructed Zn-based nanowire catalyst is enhanced further by forming an oxide layer via thermal treatment in a H2 atmosphere. This treatment boosted the reaction kinetics, thereby enhancing the catalyst performance in the CO2 reduction.

ZIF-8 derived ZnWO4 nanocrystals: Calcination temperature induced evolution of composition and microstructures, and their electrochemical performances as anode for lithium-ion batteries

Calcination temperature plays a key role in determining the phase purity, composition and microstructures for the zeolitic imidazolate frameworks (ZIFs) derived transition metal oxides materials, the investigation on the influences of the calcination temperature during ZIFs derivative process is helpful to dissect the reaction mechanism and the transformation process. The present work is aimed at constructing ZnWO4 nanocrystals derived from ZIF-8 via a facile strategy, and systematical study on the influences of calcination temperature during ZIFs derivative process on the microstructure, phase purity and composition of the final product. More importantly, the probable evolution mechanisms for the microstructure and the composition of the as-obtained final products are proposed. It is found that the crystallinity, composition, microstructure and electrochemical performances of the ZnWO4 samples strongly depend on the calcination temperature. When the calcination temperature is lower than 700 °C (500 and 600 °C), the ZnWO4/C composite nanocrystals can be obtained. Whereas the as-synthesized products are pure ZnWO4 nanocrystals featuring single crystalline under the higher calcination temperatures (700–900 °C). Due to the single crystalline structure and the optimal microstructures, the ZnWO4 sample obtained at 800 °C exhibits the superior electrochemical performances when applied as anode material for lithium-ion batteries such as excellent cyclic stability, higher capacity and better rate capability. The present work may provide the deep insight into the Zn-based materials derived from the ZIF-8, and paves a facile and general strategy for the precise control the microstructures and composition of the other transition metal oxides derived from ZIFs.

Chandler-Loop surveyed blood compatibility and dynamic blood triggered degradation behavior of Zn-4Cu alloy and Zn

Zinc (Zn) and its alloys have been considered promising absorbable metals for medical implants. However, the dynamic interaction between Zn-based materials and human blood after implantation remains unclear. In this study, a modified Chandler-Loop system was applied to assess the blood compatibility and initial degradation behavior of a Zn–4.0Cu (wt%) alloy (Zn-4Cu) and Zn with human peripheral blood under circulation conditions. In this dynamic in vitro model, the Zn-4Cu and Zn showed sufficient blood compatibility. The numbers of erythrocytes, platelets, and leukocytes were not significantly altered, and appropriate activations of the coagulation and complement system were observed. Concerning initial degradation behavior, the product layers formed on the surfaces comprise a mixture of organic and inorganic compounds while the inorganic constituents decrease toward the outer surface. Considering the corrosion morphology and electrochemical behaviors, Zn-4Cu exhibited milder and more uniform degradation than Zn. Additionally, long-term degradation tests of 28 days in human peripheral blood, human serum, and Dulbecco's phosphate-buffered saline (DPBS) demonstrated that the Zn-4Cu showed relatively uniform degradation in blood and serum. On the contrary, in DPBS, severe localized corrosion appeared along the grain boundary of the secondary phase, which was likely attributed to the acceleration of galvanic corrosion. The Zn was found with localized corrosion impeded in the blood albeit with apparently developed deep pitting holes in the serum and DPBS.

Albumins inhibit the corrosion of absorbable Zn alloys at initial stages of degradation

Understanding the surface interactions and reactivity of zinc (Zn)-based biomaterials with constituents of physiological fluids such as proteins and ions is essential for an accurate evaluation of biomaterial corrosion initiation and progression. In this paper, the effect of the albumin addition on the corrosion behavior of pure Zn and Zn–4Ag alloy is discussed. The corrosion behavior of Zn-based materials was studied using potentiodynamic polarization, electrochemical impedance spectroscopy, immersion tests and X-ray photoelectron spectroscopy. It was found that the addition of albumins largely affects the chemical composition, morphology and compactness of the protective films formed on biomaterials. A shift of the corrosion regime from localized to more general was observed in the protein-containing electrolytes. The proteins acted as corrosion inhibitors, reducing the corrosion current density and promoting passivation of the metallic surfaces. The increase in the corrosion resistance of the Zn–4Ag alloy is attributed to a selective Zn ion leaching that leaves the metal surface enriched with electrochemically more stable alloying element.