Mg-2.2Nd-xSr-0.3Zr alloys （x=0, 0.4 and 0.7, mass fraction, %） were prepared by gravity casting. Solution treatment was conducted on the as-cast alloys to homogenize microstructure, and hot extrusion was subsequentl...Mg-2.2Nd-xSr-0.3Zr alloys （x=0, 0.4 and 0.7, mass fraction, %） were prepared by gravity casting. Solution treatment was conducted on the as-cast alloys to homogenize microstructure, and hot extrusion was subsequently conducted. Microstructure was observed using an optical microscope and a scanning electron microscope. Biocorrosion behaviors of the alloy in simulated body fluid were analyzed by mass loss, hydrogen evolution and Tafel polarization experiments. The results show that the amount of residual eutectic phase of the solution treated alloys increases with increasing Sr addition, and the grains are significantly refined after hot extrusion. The corrosion resistance of the solution treated alloys deteriorates apparently with increasing Sr addition, while the corrosion resistance of the as-extruded alloys is improved with Sr addition. Nevertheless, the biocorrosion behavior of the as-extruded alloys obtained by Tafel polarization shows different trends from those obtained by the other two methods.展开更多
Mechanical properties and biocorrosion behaviors in simulated body fluid(SBF)of newly developed Mg-5.8 Zn-0.5 Zr-x Yb(ZK60-X Yb,x=0,1.0,2.0wt%)magnesium alloys in the solution-treated(T4)and artificially-aged(T6)condi...Mechanical properties and biocorrosion behaviors in simulated body fluid(SBF)of newly developed Mg-5.8 Zn-0.5 Zr-x Yb(ZK60-X Yb,x=0,1.0,2.0wt%)magnesium alloys in the solution-treated(T4)and artificially-aged(T6)conditions were investigated.The results of mechanical properties show that with Yb addition,the microhardness and the ultimate tensile strength(UTS)of the tested alloys are significantly increased despite a slight decrease in tensile elongation in both T4 and T6 conditions.Especially,after the T6 treatment,the microhardness and the UTS of the samples were further improved,which was mainly attributed to the precipitation strengthening.The biocorrosion behaviors of the tested alloys were studied using electrochemical examinations and immersion tests.The results indicate that the biocorrosion resistance of the tested alloys is significantly improved by Yb addition in both T4 and T6 conditions.Although the corrosion resistance was slightly deteriorated after T6 treatment,the aged ZK60-2.0 Yb alloy still exhibited a favorable corrosion behavior,which was mainly ascribed to the corrosion barrier effect of a more compact and uniform protective film induced by the dispersed nano-scale precipitates.Electrochemical measurements also confirmed these observations.Given the favorable comprehensive performance in mechanical and biocorrosion behaviors,the T6 treated ZK60-2.0 Yb alloy may be considered as a promising candidate for biomedical applications.展开更多
Biodegradable metals(BMs)gradually degrade in vivo by releasing corrosion products once exposed to the physiological environment in the body.Complete dissolution of biodegradable implants assists tissue healing,with n...Biodegradable metals(BMs)gradually degrade in vivo by releasing corrosion products once exposed to the physiological environment in the body.Complete dissolution of biodegradable implants assists tissue healing,with no implant residues in the surrounding tissues.In recent years,three classes of BMs have been extensively investigated,including magnesium(Mg)-based,iron(Fe)-based,and zinc(Zn)-based BMs.Among these three BMs,Mg-based materials have undergone the most clinical trials.However,Mg-based BMs generally exhibit faster degradation rates,which may not match the healing periods for bone tissue,whereas Fe-based BMs exhibit slower and less complete in vivo degradation.Zn-based BMs are now considered a new class of BMs due to their intermediate degradation rates,which fall between those of Mg-based BMs and Fe-based BMs,thus requiring extensive research to validate their suitability for biomedical applications.In the present study,recent research and development on Zn-based BMs are reviewed in conjunction with discussion of their advantages and limitations in relation to existing BMs.The underlying roles of alloy composition,microstructure,and processing technique on the mechanical and corrosion properties of Zn-based BMs are also discussed.展开更多
The factors that influence magnesium（Mg）corrosion in vitro are systematically evaluated from a review of the relevant literature. We analysed the influence of the following factors on Mg biocorrosion in vitro：（i）...The factors that influence magnesium（Mg）corrosion in vitro are systematically evaluated from a review of the relevant literature. We analysed the influence of the following factors on Mg biocorrosion in vitro：（i） inorganic ions,including both anions and cations,（ii） organic components such as proteins, amino acids and vitamins, and（iii） experimental parameters such as temperature, p H, buffer system and flow rate. Considerations and recommendations towards a standardised approach to in vitro biocorrosion testing are given. Several potential simulated body fluids are recommended. Implementing a standardised approach to experimental parameters has the potential to significantly reduce variability between in vitro biocorrosion tests, and to help build towards a methodology that accurately and consistently mimics in vivo corrosion. However, there are also knowledge gaps with regard to how best to characterise the in vivo environment and corrosion mechanism. The assumption that blood plasma is the correct bodily fluid upon which to base in vitro methodologies is examined, and factors that influence the corrosion mechanism in vivo, such as specimen encapsulation, bear consideration for further studies.展开更多
The key to use magnesium alloys as suitable biodegradable implants is how to adjust their degradation rates. We report a strategy to prepare biocompatible ceramic coating with improved biocorrosion resistance property...The key to use magnesium alloys as suitable biodegradable implants is how to adjust their degradation rates. We report a strategy to prepare biocompatible ceramic coating with improved biocorrosion resistance property on AZ91D alloy by microarc oxidation （MAO） in a silicate-K2ZrF6 solution with and without Ca（H2PO4）2 additives. The microstructure and biocorrosion of coatings were characterized by XRD and SEM, as well as electrochemical and immersion tests in simulated body fluid （SBF）. The results show that the coatings are mainly composed of MgO, Mg2SiO4, m-ZrO2 phases, further Ca containing compounds involve the coating by Ca（H2PO4）2 addition in the silicate-K2ZrF6 solution. The corrosion resistance of coated AZ91D alloy is significantly improved compared with the bare one. After immersing in SBF for 28 d, the Si-Zr5-CaO coating indicates a best corrosion resistance performance.展开更多
Marine pollution is a well-recognized phenomenon that has many negative effects on the marine environment.The effects of marine pollution are due to the discharge of hazardous materials,toxins,or other pollutants into...Marine pollution is a well-recognized phenomenon that has many negative effects on the marine environment.The effects of marine pollution are due to the discharge of hazardous materials,toxins,or other pollutants into the marine environment,which includes seas,estuaries,oceans,and other water bodies,and this unwanted input affects the blue economy.The blue economy,which includes industries and research associated with marine and ocean resources,is often affected by marine pollution on multiple levels,such as economic costs,direct resource impacts,health risks,and infrastructure damage.In one report,the pollution-related issues in many countries were estimated at 9 t/inh and clean-up costs between$12 to$160/t.More extensive pollution mitigation projects might take up to 15 years to conclude and cost up to$500/t.To better understand the role of marine pollution and its impact on the blue economy,some key parameters are discussed as follows:the role of biofouling,volatile organic compounds,the impact of metals,anionic pollutants,and antifouling coatings.The review findings also highlight the impact of marine pollution on ecosystems and associated economic activities,which could be reduced through measures such as better international cooperation,waste management,and the development of sustainable practices.Related information on the strategies and policies that could be adopted for sustainable blue economy are stated after each section.展开更多
Magnesium is one of the largely available elements in the earth’s crust. It has a low structural density with high specific strength. This unique material property has forced an increase in the use of magnesium and i...Magnesium is one of the largely available elements in the earth’s crust. It has a low structural density with high specific strength. This unique material property has forced an increase in the use of magnesium and its alloys in various applications pertaining to industrial sector,automobiles, aerospace and biomedical. Since magnesium is a highly reactive metal, it is prone to higher rate of corrosion as compared to its counterparts. Thus, it is essential to analyze the corrosion behavior of magnesium and its alloys in its applications. An appropriate process is to be followed in the design and development of magnesium alloys which overcome the limitations of magnesium and enhance the desired material properties in accordance to their applications. This review paper summarizes the importance of magnesium and its material properties. The influence of various alloying elements on the mechanical properties of magnesium is reviewed. The broad classification of Mg alloys and their behavioral trends are detailed. The corrosion behavior of magnesium and the influence of corrosion products on the material characteristics of magnesium, in aqueous medium, are discussed. The manufacturing techniques of magnesium alloys along with the secondary techniques are also covered. The various applications and the limitations of magnesium in these applications are covered. A complete section is dedicated towards detailing the recent trends of magnesium(Mg) alloys, i.e., the biodegradable nature and applications of Mg alloys. The influence of biocorrosion on Mg alloys and techniques to overcome it have been deliberated. This paper provides a thorough review on recent developments of magnesium with respect to engineering applications.展开更多
Biomedical degradable materials would be subjected to different degrees and forms of static stress after being implanted in the human body.In this work,the biocorrosion behaviors of AZ31B magnesium alloy under differe...Biomedical degradable materials would be subjected to different degrees and forms of static stress after being implanted in the human body.In this work,the biocorrosion behaviors of AZ31B magnesium alloy under different stress forms with different magnitudes(20~150MPa)were studied.It was found that the corrosion behaviors at stressed conditions were severer than those at unstressed conditions and corrosion rates were obviously accelerated.The biocorrosion behaviors are more sensitive to the effects of tensile loads than to compressive loads.A biocorrosion numerical model on the degradation process of Mg alloy under static loads was established.The corrosion current density(i_(corr))of Mg alloy and the applied static stress(σ)matches a linear relationship of ln i_(corr)~σwell during the early stage(within 24 hrs)while deviated gradually in the latter period of corrosion.This work could provide a guidance and theoretical reference for further researches on the biocorrosion behaviors and practical clinical applications of the biomedical materials subjected to physiological loads.展开更多
Magnesium(Mg)metal matrix composites(MMCs)reinforced with graphene nanoplatelets(GNPs)have been developed by powder metallurgy(PM).GNPs with different concentrations(0.1,0.2,and 0.3 wt.%),layer thicknesses(5 nm and 9 ...Magnesium(Mg)metal matrix composites(MMCs)reinforced with graphene nanoplatelets(GNPs)have been developed by powder metallurgy(PM).GNPs with different concentrations(0.1,0.2,and 0.3 wt.%),layer thicknesses(5 nm and 9 nm),and particle sizes(15μm and 5μm)were dispersed into Mg powder by high-energy ball-milling processes.The microstructure and mechanical properties of the fabricated composites were characterized using transmission electron microscopy(TEM),scanning electron microscopy(SEM),energy dispersive X-ray spectroscopy(EDX),X-ray diffraction(XRD),Raman spectroscopy(RS),and compression tests.The corrosion resistance was evaluated by electrochemical tests and hydrogen evolution measurements.The cytotoxicity of Mg-GNPs composites was assessed using osteoblast-like SaOS2 cells.The results indicate that GNPs are excellent candidates as reinforcements in Mg matrices for the manufacture of biodegradable Mg-based composite implants.GNP addition improved the mechanical properties of Mg via synergetic strengthening modes.Moreover,retaining the structural integrity of GNPs during processing improved the ductility,compressive strength,and corrosion resistance of the Mg-GNP composites.Cytotoxicity assessments did not reveal any significant toxicity with the addition of GNPs to Mg matrices.This study demonstrates that Mg-xGNPs with x<0.3 wt.%,may constitute novel biodegradable implant materials for load-bearing applications.展开更多
Ti47Cu38-xZr7.5Fe2.5Sn2Si1Ag2Nbx（x = 0, 1, 2; at%） bulk metallic glasses （BMGs） with superior biocorrosion resistance were synthesized by copper mold casting. Although the minor addition of Nb to the Ti-Cu- Zr-Fe-...Ti47Cu38-xZr7.5Fe2.5Sn2Si1Ag2Nbx（x = 0, 1, 2; at%） bulk metallic glasses （BMGs） with superior biocorrosion resistance were synthesized by copper mold casting. Although the minor addition of Nb to the Ti-Cu- Zr-Fe-Sn-Si-Ag BMG slightly decreases the glass-forming ability （GFA）, the Nb-bearing Ti-based alloys could be casted in a bulk glassy rod form with diameters up to 3 mm. It is found that partial substitution of Cu with Nb is effective on enhancing the bio-corrosion resistance of the Ti-based BMG. Potentiodynamic polarization measurements show that Nb addition to Ti-based BMG leads to higher open-circuit potential and pitting potential as well as lower passive current density in Hank＇s solution. Electrochemical impedance spectroscopy （EIS） results indicate that with Nb content increasing, the charge transfer resistance values of the Ti-based BMGs become larger, demonstrating that the surface oxide films are more protective. The Nb-bearing Ti-based BMGs also exhibit good in vitro biocompatibility comparable to that of Ti-6Al-4V alloy. The enhanced bio-corrosion resistance, excellent in vitro biocompatibility and good mechanical properties of the Nb-bearing Ti-based BMGs are favorable for biomedical applications.展开更多
With rapid development of marine infrastructures,materials with better biocorrosion resistance and antibiofouling performance will be highly demanded.Ti6Al4V alloy is susceptible to the above.The inhibition to the mic...With rapid development of marine infrastructures,materials with better biocorrosion resistance and antibiofouling performance will be highly demanded.Ti6Al4V alloy is susceptible to the above.The inhibition to the microbiologically influenced corrosion of Ti6Al4V-5Cu alloy against Pseudomonas aeruginosa was investigated using antibacterial test,electrochemical techniques,surface analysis,and weight loss test conducted for 2.5 months.At a sputtering depth of 0 nm,the passive film of Ti6Al4V-5Cu alloy was mainly composed of ideal oxide TiO_(2).With increasing sputtering thickness to 6 nm,Ti_(2)O_(3)and TiO were detected with a relative fraction of 14.6%and 14.8%,respectively,in the oxide layer of Ti6Al4V-5Cu alloy.In contrast,the outermost layer of Ti6AlV alloy was predominantly composed of TiO_(2)but Ti_(2)O_(3)(22.8%),Al_(2)O_(3)and V_(2)O_(5) were also detected.With increasing sputtering depth to 6 nm,fitting revealed the presence of Ti_(2)O_(3)and TiO with relative fractions of 25.3%and 35.8%,respectively.Yet,a spot of TiO(8%)was also observed at 12 nm in the oxide layer of Ti6Al4V alloy.Although the addition of Cu into Ti6Al4V alloy generated the self-healing property of passive film in the presence of P.aeruginosa,it also reduced resistance to corrosion in general condition.展开更多
In this study,Mg-based composites,by the addition of ZnO,Ca_(2)ZnSi_(2)O_(7),Ca_(2)MgSi_(2)O_(7),and CaSiO_(3)as bioactive agents,were fabricated using friction stir processing.The microstructure and in vitro assessme...In this study,Mg-based composites,by the addition of ZnO,Ca_(2)ZnSi_(2)O_(7),Ca_(2)MgSi_(2)O_(7),and CaSiO_(3)as bioactive agents,were fabricated using friction stir processing.The microstructure and in vitro assessment of bioactivity,biodegradation rate,and corrosion behavior of the resultant composites were investigated in simulated body fluid(SBF).The results showed that during the immersion of composites in SBF for 28 d,due to the release of Ca^(2+)and PO_(4)^(3-)ions,hydroxyapatite(HA)crystals with cauliflower shaped morphology were deposited on the surface of composites,confirming good bioactivity of composites.In addition,due to the uniform distribution of bioceramic powders throughout Mg matrix,grain refinement of the Mg matrix,and uniform redistribution of secondary phase particles,the polarization resistance increased,and the biodegradation rate of composites significantly reduced compared to monolithic Mg matrix.The polarization corrosion resistance of Mg-ZnO increased from 0.216 to 2.499 kΩ/cm^(2)compared to monolithic Mg alloy.Additionally,Mg-ZnO composite with the weight loss of 0.0217 g after 28 d immersion showed lower weight loss compared to other samples with increasing immersion time.Moreover,Mg-ZnO composite with the biodegradation rate of 37.71 mm/a exhibited lower biodegradation rate compared to other samples with increasing immersion time.展开更多
Drawbacks associated with permanent metallic implants lead to the search for degradable metallic biomaterials. Magnesium alloys have been highly considered as Mg has a high biocorrosion potential and is essential to b...Drawbacks associated with permanent metallic implants lead to the search for degradable metallic biomaterials. Magnesium alloys have been highly considered as Mg has a high biocorrosion potential and is essential to bodies. In this study, corrosion behaviour of pure magnesium and magnesium alloy AZ31 in both static and dynamic physiological conditions (Hank's solution) has been investigated. It is found that the materials degrade fast at beginning, then stabilize after 5 days of immersion. High purity in the materials reduces the corrosion rate while the dynamic condition accelerates the degradation process. In order to slow down the degradation process to meet the requirement for their bio-applications, an anodized coating is applied and is proved as effective in controlling the biodegradation rate.展开更多
Biocorrosion, as well as the biodeterioration of crude oil and its derivatives, is one of the major environmental, operational and economic problems in the Venezuelan oil industry. Fungal contaminants are able to prod...Biocorrosion, as well as the biodeterioration of crude oil and its derivatives, is one of the major environmental, operational and economic problems in the Venezuelan oil industry. Fungal contaminants are able to produce large quantities of biomass and synthesize peroxides and organic acids, causing severe damage on metal surfaces and promoting the contamination and biodeterioration of fuels. No evidences regarding fungal strains have been reported to be associated to petroleum naphtha, widely used as a diluent of extra heavy crude oil (EHCO) in the exploitation processes of the Orinoco Oil Belt, the biggest proven reserve of EHCO worldwide. The aims of this paper were to isolate and identify fungal strains from the naphtha storage tank and the naphtha distribution network from an oil field operator in Venezuela. The results showed the isolation of four different fungal strains. The molecular identification by 28S rRNA sequencing and phylogenetic tree analysis allowed us to identify the presence of: 1) a new uncultured Ascomycota fungus species BM-103, with high identity to novel hyphomycetes Noosia banksiae and Sporidesmium tengii, in the naphtha storage tank;2) two yeasts, Rhodotorula mucilaginosa BM-104 (Phylum Basidiomycota) and Wickerhamia sp. BM-105 (Phylum Ascomycota), in a highly damaged naphtha pipeline branch and;3) Cladosporium cladosporioides BM-102 (Phylum Ascomycota) in a cluster oil well. DNA fingerprinting analysis using ERIC-PCR primers pairs also allowed us to detect the presence of R. mucilaginosa BM-104 right in the access of the studied naphtha system. Interestingly, R. mucilaginosa and C. cladosporioides were previously reported as predominant fungal contaminants of diesel and jet fuel and of kerosene and fuel storage systems, respectively. This paper represents the first evidence of fungal strains isolated and identified from the naphtha systems in the Venezuelan oil industry. The results obtained are discussed.展开更多
The composition of tightly bound exopolymeric substances (EPS) obtained from biofilm and plan- ktonic cell subpopulations of Stenotrophomonas maltophilia 5426 UKM was analyzed to study an impact of mild steel presence...The composition of tightly bound exopolymeric substances (EPS) obtained from biofilm and plan- ktonic cell subpopulations of Stenotrophomonas maltophilia 5426 UKM was analyzed to study an impact of mild steel presence in the cultivation medium. The overall protein production was found to increase in the presence of a steel coupon. Some amino acids such as lysine, valine, iso-leucine, tyrosine and phenylalanine were found to be secreted in higher amounts in the presence of mild steel, while its absence leads to an increase of arginine, asparagine, serine, glutamine, proline, glycine, cysteine, leucine, methionine production levels. Biofilm cells EPS contained more arginine, glycine, cysteine, valine, methionine and leucine, comparing to EPS of planktonic cells. The chang- es of tightly bound EPS aggregation around the cells induced in the presence of steel coupons were revealed by transmission electron microscopy. The results suggested the transition of S. maltophilia 5426 UKM cells from planktonic to biofilm lifestyle to be a complex process involving more than a single step.展开更多
The start and the course of bio-corrosion are conditioned by many factors which include biological effects like the influence of vegetation and microorganisms causing the deterioration of materials. The influence of b...The start and the course of bio-corrosion are conditioned by many factors which include biological effects like the influence of vegetation and microorganisms causing the deterioration of materials. The influence of bacteria causing the deterioration of concrete has been linked to the generation of biogenic sulphuric and nitric acids which originate in corrosion process by dissolution of calcium containing minerals from the concrete matrices. This paper primarily focuses on the investigation of influence of sulphur-oxidising bacteria Acidithiobacillus thiooxidans and sulphate-reducing bacteria Desulfovibrio desulfuricans at the resistance degree of cement composites. Various concrete composites with 5% addition of black coal fly ash as cement replacement as well as the reference samples without coal fly ash addition were studied in the experiments environments of sewage system proceeded during 90 days. The The laboratory experiments as well as experiments in situ in real corrosion was manifested by surface changes and weight changes of cement composites samples as well as changes in pH values of leachates. Considerable surface changes were detected in all investigated samples by microscopic methods. Crystals precipitated on concrete samples surface were identified by EDX as mixture of gypsum and ettringite. The roughness increases of surface of cement microscopy. composites were determined by confocal laser scanning展开更多
In caves and monuments, biocorrosion caused by bats occurs partly under accumulations of guano. Tests were carried out both at cave temperature and under hot conditions in the laboratory on 4 different limestones. A c...In caves and monuments, biocorrosion caused by bats occurs partly under accumulations of guano. Tests were carried out both at cave temperature and under hot conditions in the laboratory on 4 different limestones. A comparison of the results obtained using these two methods shows that the processes leading to the weathering of the limestones are the same, and that the hot laboratory tests accelerate them in a well-constrained way. The higher the porosity and capillarity of the limestone, the faster the weathering process. The presence of large calcite crystals also favors weathering. In caves, the ablation rates obtained (8 mm/ka) are sufficient to destroy engravings in a few decades. In monuments, ablation rates are even higher because of the temperature, and could theoretically reach 32 cm/ka in extreme conditions at 80˚C. The laboratory test developed here can be adapted to the temperature of each case study. It has already demonstrated the mechanisms that lead from weathering to the formation of a phosphate crust.展开更多
The relationship between reactive oxygen and nitrogen species(ROS-RNS)secretion and the concomitant biocorrosion of degradable magnesium(Mg)materials is poorly understood.We found that Mg foils implanted short term in...The relationship between reactive oxygen and nitrogen species(ROS-RNS)secretion and the concomitant biocorrosion of degradable magnesium(Mg)materials is poorly understood.We found that Mg foils implanted short term in vivo(24 h)displayed large amounts of proinflammatory F4/80+/iNOS+macrophages at the interface.We sought to investigate the interplay between biodegrading Mg materials(98.6%Mg,AZ31&AZ61)and macrophages(RAW 264.7)stimulated with lipopolysaccharide(RAW 264.7^(LPS))to induce ROS-RNS secretion.To test how these proinflammatory ROS-RNS secreting cells interact with Mg corrosion in vitro,Mg and AZ61 discs were suspended approximately 2 mm above a monolayer of RAW 264.7 cells,either with or without ^(LPS).The surfaces of both materials showed acute(24 h)changes when incubated in the proinflammatory RAW 264.7^(LPS) environment.Mg discs incubated with RAW 264.7^(LPS) macrophages showed greater corrosion pitting,while AZ61 showed morphological and elemental bulk product changes via scanning electron microscopy-energy dispersive X-ray spectroscopy(SEM-EDX).X-ray photoelectron spectroscopy(XPS)analysis showed a reduction in the Ca/P ratio of the surface products for AZ61 disc incubated with RAW 264.7^(LPS),but not the Mg discs.Moreover,RAW 264.7^(LPS) macrophages were found to be more viable in the acute biodegradative environment generated by Mg materials,as demonstrated by calcein-AM and cleaved(active)caspase-3 staining(CC3).^(LPS) stimulation caused an increase in ROS-RNS,and a decrease in antioxidant peroxidase activity.Mg and AZ61 were found to change this ROS-RNS balance,independently of physiological antioxidant mechanisms.The findings highlight the complexity of the cellular driven acute inflammatory responses to different biodegradable Mg,and how it can potentially affect performance of these materials.展开更多
The real physiological environment of human body is complicated with different degrees and forms of dynamic loads applied to implanted medical devices due to the daily activities of the patients,which would have impac...The real physiological environment of human body is complicated with different degrees and forms of dynamic loads applied to implanted medical devices due to the daily activities of the patients,which would have impacts on the degradation behaviors of magnesium alloy implants.In this work,the bio-corrosion behaviors of AZ31B magnesium alloy under alternating cyclic dynamic loads with different low frequencies(0.1-2.5 Hz)were specially investigated.It was found that the bio-degradation performances under external dynamic stressed conditions were much severer than those under unstressed conditions and static loads.The corrosion rates were generally accelerated as the rise of cyclic frequency.Hereby a numerical model for the degradation process of Mg alloy was established.The corrosion current density icorr of Mg alloy and the applied loading frequency f matches a linear relationship of ln icorr∝f,which is the result of interactions between the cyclic alternating load and corrosive environment.This work could provide a theoretical reference and an experimental basis for further researches on the biodegradation behaviors of biomedical materials under dynamic conditions.展开更多
基金Project(51301089)supported by the National Natural Science Foundation of ChinaProject(BK20130745)supported by the Natural Science Foundation of Jiangsu Province,China+1 种基金Project(13KJB430014)supported by the Natural Science Foundation of the Higher Education Institutions of Jiangsu Province,ChinaProject supported by the Qing Lan Project of Jiangsu Province,China
文摘Mg-2.2Nd-xSr-0.3Zr alloys （x=0, 0.4 and 0.7, mass fraction, %） were prepared by gravity casting. Solution treatment was conducted on the as-cast alloys to homogenize microstructure, and hot extrusion was subsequently conducted. Microstructure was observed using an optical microscope and a scanning electron microscope. Biocorrosion behaviors of the alloy in simulated body fluid were analyzed by mass loss, hydrogen evolution and Tafel polarization experiments. The results show that the amount of residual eutectic phase of the solution treated alloys increases with increasing Sr addition, and the grains are significantly refined after hot extrusion. The corrosion resistance of the solution treated alloys deteriorates apparently with increasing Sr addition, while the corrosion resistance of the as-extruded alloys is improved with Sr addition. Nevertheless, the biocorrosion behavior of the as-extruded alloys obtained by Tafel polarization shows different trends from those obtained by the other two methods.
基金This work was supported by the National Natural Science Foundation of China(grant number 51975484 and 51605392)Fundamental Research Funds for the Central Universities(grant number XDJK2020B001).
文摘Mechanical properties and biocorrosion behaviors in simulated body fluid(SBF)of newly developed Mg-5.8 Zn-0.5 Zr-x Yb(ZK60-X Yb,x=0,1.0,2.0wt%)magnesium alloys in the solution-treated(T4)and artificially-aged(T6)conditions were investigated.The results of mechanical properties show that with Yb addition,the microhardness and the ultimate tensile strength(UTS)of the tested alloys are significantly increased despite a slight decrease in tensile elongation in both T4 and T6 conditions.Especially,after the T6 treatment,the microhardness and the UTS of the samples were further improved,which was mainly attributed to the precipitation strengthening.The biocorrosion behaviors of the tested alloys were studied using electrochemical examinations and immersion tests.The results indicate that the biocorrosion resistance of the tested alloys is significantly improved by Yb addition in both T4 and T6 conditions.Although the corrosion resistance was slightly deteriorated after T6 treatment,the aged ZK60-2.0 Yb alloy still exhibited a favorable corrosion behavior,which was mainly ascribed to the corrosion barrier effect of a more compact and uniform protective film induced by the dispersed nano-scale precipitates.Electrochemical measurements also confirmed these observations.Given the favorable comprehensive performance in mechanical and biocorrosion behaviors,the T6 treated ZK60-2.0 Yb alloy may be considered as a promising candidate for biomedical applications.
基金support for this research by the Australian Research Council(ARC)through the discovery grant DP170102557 and ARC Future Fellowship(FT160100252)YL is also supported through an ARC Future Fellowship(FT160100252).
文摘Biodegradable metals(BMs)gradually degrade in vivo by releasing corrosion products once exposed to the physiological environment in the body.Complete dissolution of biodegradable implants assists tissue healing,with no implant residues in the surrounding tissues.In recent years,three classes of BMs have been extensively investigated,including magnesium(Mg)-based,iron(Fe)-based,and zinc(Zn)-based BMs.Among these three BMs,Mg-based materials have undergone the most clinical trials.However,Mg-based BMs generally exhibit faster degradation rates,which may not match the healing periods for bone tissue,whereas Fe-based BMs exhibit slower and less complete in vivo degradation.Zn-based BMs are now considered a new class of BMs due to their intermediate degradation rates,which fall between those of Mg-based BMs and Fe-based BMs,thus requiring extensive research to validate their suitability for biomedical applications.In the present study,recent research and development on Zn-based BMs are reviewed in conjunction with discussion of their advantages and limitations in relation to existing BMs.The underlying roles of alloy composition,microstructure,and processing technique on the mechanical and corrosion properties of Zn-based BMs are also discussed.
基金supported by the Australian Federal Government through an Australian Government Research Training Program Scholarshipsupport of the Australian Research Council (ARC) (DP170102557 "Biodegradable magnesium alloy scaffolds for bone tissue engineering")support of the ARC Research Hub for Advanced Manufacturing of Medical Devices
文摘The factors that influence magnesium（Mg）corrosion in vitro are systematically evaluated from a review of the relevant literature. We analysed the influence of the following factors on Mg biocorrosion in vitro：（i） inorganic ions,including both anions and cations,（ii） organic components such as proteins, amino acids and vitamins, and（iii） experimental parameters such as temperature, p H, buffer system and flow rate. Considerations and recommendations towards a standardised approach to in vitro biocorrosion testing are given. Several potential simulated body fluids are recommended. Implementing a standardised approach to experimental parameters has the potential to significantly reduce variability between in vitro biocorrosion tests, and to help build towards a methodology that accurately and consistently mimics in vivo corrosion. However, there are also knowledge gaps with regard to how best to characterise the in vivo environment and corrosion mechanism. The assumption that blood plasma is the correct bodily fluid upon which to base in vitro methodologies is examined, and factors that influence the corrosion mechanism in vivo, such as specimen encapsulation, bear consideration for further studies.
基金Acknowledgements The partial supports from the National Natural Science Foundation of China （NSFC Grant Nos. 51371071, 51321061 and 51275555）, the National Basic Science Research Program （Grant No. 2012CB933900）, the Fundamental Research Funds for the Central Universities （HIT.BRETIII.201202） and the Program for New Century Excellent Talents in University of China （NCET-08-0166） are gratefully acknowledged.
文摘The key to use magnesium alloys as suitable biodegradable implants is how to adjust their degradation rates. We report a strategy to prepare biocompatible ceramic coating with improved biocorrosion resistance property on AZ91D alloy by microarc oxidation （MAO） in a silicate-K2ZrF6 solution with and without Ca（H2PO4）2 additives. The microstructure and biocorrosion of coatings were characterized by XRD and SEM, as well as electrochemical and immersion tests in simulated body fluid （SBF）. The results show that the coatings are mainly composed of MgO, Mg2SiO4, m-ZrO2 phases, further Ca containing compounds involve the coating by Ca（H2PO4）2 addition in the silicate-K2ZrF6 solution. The corrosion resistance of coated AZ91D alloy is significantly improved compared with the bare one. After immersing in SBF for 28 d, the Si-Zr5-CaO coating indicates a best corrosion resistance performance.
基金Supported by the President’s International Fellowship Initiative of Chinese Academy of Sciences(No.2024 PVC 0010)。
文摘Marine pollution is a well-recognized phenomenon that has many negative effects on the marine environment.The effects of marine pollution are due to the discharge of hazardous materials,toxins,or other pollutants into the marine environment,which includes seas,estuaries,oceans,and other water bodies,and this unwanted input affects the blue economy.The blue economy,which includes industries and research associated with marine and ocean resources,is often affected by marine pollution on multiple levels,such as economic costs,direct resource impacts,health risks,and infrastructure damage.In one report,the pollution-related issues in many countries were estimated at 9 t/inh and clean-up costs between$12 to$160/t.More extensive pollution mitigation projects might take up to 15 years to conclude and cost up to$500/t.To better understand the role of marine pollution and its impact on the blue economy,some key parameters are discussed as follows:the role of biofouling,volatile organic compounds,the impact of metals,anionic pollutants,and antifouling coatings.The review findings also highlight the impact of marine pollution on ecosystems and associated economic activities,which could be reduced through measures such as better international cooperation,waste management,and the development of sustainable practices.Related information on the strategies and policies that could be adopted for sustainable blue economy are stated after each section.
文摘Magnesium is one of the largely available elements in the earth’s crust. It has a low structural density with high specific strength. This unique material property has forced an increase in the use of magnesium and its alloys in various applications pertaining to industrial sector,automobiles, aerospace and biomedical. Since magnesium is a highly reactive metal, it is prone to higher rate of corrosion as compared to its counterparts. Thus, it is essential to analyze the corrosion behavior of magnesium and its alloys in its applications. An appropriate process is to be followed in the design and development of magnesium alloys which overcome the limitations of magnesium and enhance the desired material properties in accordance to their applications. This review paper summarizes the importance of magnesium and its material properties. The influence of various alloying elements on the mechanical properties of magnesium is reviewed. The broad classification of Mg alloys and their behavioral trends are detailed. The corrosion behavior of magnesium and the influence of corrosion products on the material characteristics of magnesium, in aqueous medium, are discussed. The manufacturing techniques of magnesium alloys along with the secondary techniques are also covered. The various applications and the limitations of magnesium in these applications are covered. A complete section is dedicated towards detailing the recent trends of magnesium(Mg) alloys, i.e., the biodegradable nature and applications of Mg alloys. The influence of biocorrosion on Mg alloys and techniques to overcome it have been deliberated. This paper provides a thorough review on recent developments of magnesium with respect to engineering applications.
基金supported by the National Natural Science Foundation of China(Grant No.51771054,52171236)State Key Program of National Natural Science Foundation of China(Grant No.51631003)+5 种基金National Key Research and Development Program of China(Grant No.2016YFC1102402)Open Research Fund of Jiangsu Key Laboratory for Advanced Metallic Materials(Grant No.AMM2021A01)the Opening Project of Jiangsu Key Laboratory of Advanced Structural Materials and Application Technology(Grant No.ASMA201901)Postgraduate Research&Practice Innovation Program of Jiangsu Province(Grant No.KYCX20_0091)Natural Science Foundation of Jiangsu Province(BK20181020)the Introduction of Talent Research Fund in Nanjing Institute of Technology(YKJ201705)
文摘Biomedical degradable materials would be subjected to different degrees and forms of static stress after being implanted in the human body.In this work,the biocorrosion behaviors of AZ31B magnesium alloy under different stress forms with different magnitudes(20~150MPa)were studied.It was found that the corrosion behaviors at stressed conditions were severer than those at unstressed conditions and corrosion rates were obviously accelerated.The biocorrosion behaviors are more sensitive to the effects of tensile loads than to compressive loads.A biocorrosion numerical model on the degradation process of Mg alloy under static loads was established.The corrosion current density(i_(corr))of Mg alloy and the applied static stress(σ)matches a linear relationship of ln i_(corr)~σwell during the early stage(within 24 hrs)while deviated gradually in the latter period of corrosion.This work could provide a guidance and theoretical reference for further researches on the biocorrosion behaviors and practical clinical applications of the biomedical materials subjected to physiological loads.
基金The authors acknowledge the financial support for this research by the Australian Research Council(ARC)through the Future Fellowship(FT160100252)the Discovery Project(DP170102557)+1 种基金The authors also acknowledge the scientific and technical assistance of RMIT University’s Microscopy and Microanalysis Facility(RMMF)a linked laboratory of the Australian Microscopy&Microanalysis Research Facility.
文摘Magnesium(Mg)metal matrix composites(MMCs)reinforced with graphene nanoplatelets(GNPs)have been developed by powder metallurgy(PM).GNPs with different concentrations(0.1,0.2,and 0.3 wt.%),layer thicknesses(5 nm and 9 nm),and particle sizes(15μm and 5μm)were dispersed into Mg powder by high-energy ball-milling processes.The microstructure and mechanical properties of the fabricated composites were characterized using transmission electron microscopy(TEM),scanning electron microscopy(SEM),energy dispersive X-ray spectroscopy(EDX),X-ray diffraction(XRD),Raman spectroscopy(RS),and compression tests.The corrosion resistance was evaluated by electrochemical tests and hydrogen evolution measurements.The cytotoxicity of Mg-GNPs composites was assessed using osteoblast-like SaOS2 cells.The results indicate that GNPs are excellent candidates as reinforcements in Mg matrices for the manufacture of biodegradable Mg-based composite implants.GNP addition improved the mechanical properties of Mg via synergetic strengthening modes.Moreover,retaining the structural integrity of GNPs during processing improved the ductility,compressive strength,and corrosion resistance of the Mg-GNP composites.Cytotoxicity assessments did not reveal any significant toxicity with the addition of GNPs to Mg matrices.This study demonstrates that Mg-xGNPs with x<0.3 wt.%,may constitute novel biodegradable implant materials for load-bearing applications.
基金financially supported by the National Natural Science Foundation of China (Nos.51161130526 and 51271008)
文摘Ti47Cu38-xZr7.5Fe2.5Sn2Si1Ag2Nbx（x = 0, 1, 2; at%） bulk metallic glasses （BMGs） with superior biocorrosion resistance were synthesized by copper mold casting. Although the minor addition of Nb to the Ti-Cu- Zr-Fe-Sn-Si-Ag BMG slightly decreases the glass-forming ability （GFA）, the Nb-bearing Ti-based alloys could be casted in a bulk glassy rod form with diameters up to 3 mm. It is found that partial substitution of Cu with Nb is effective on enhancing the bio-corrosion resistance of the Ti-based BMG. Potentiodynamic polarization measurements show that Nb addition to Ti-based BMG leads to higher open-circuit potential and pitting potential as well as lower passive current density in Hank＇s solution. Electrochemical impedance spectroscopy （EIS） results indicate that with Nb content increasing, the charge transfer resistance values of the Ti-based BMGs become larger, demonstrating that the surface oxide films are more protective. The Nb-bearing Ti-based BMGs also exhibit good in vitro biocompatibility comparable to that of Ti-6Al-4V alloy. The enhanced bio-corrosion resistance, excellent in vitro biocompatibility and good mechanical properties of the Nb-bearing Ti-based BMGs are favorable for biomedical applications.
基金financially supported by the National Natural Science Foundation of China(No.U1906226)the United Research&Development Program(No.E049A201)+1 种基金the National Key Research and Development Program(No.2017YFB0306201)the support of CAS-TWAS President Fellowship。
文摘With rapid development of marine infrastructures,materials with better biocorrosion resistance and antibiofouling performance will be highly demanded.Ti6Al4V alloy is susceptible to the above.The inhibition to the microbiologically influenced corrosion of Ti6Al4V-5Cu alloy against Pseudomonas aeruginosa was investigated using antibacterial test,electrochemical techniques,surface analysis,and weight loss test conducted for 2.5 months.At a sputtering depth of 0 nm,the passive film of Ti6Al4V-5Cu alloy was mainly composed of ideal oxide TiO_(2).With increasing sputtering thickness to 6 nm,Ti_(2)O_(3)and TiO were detected with a relative fraction of 14.6%and 14.8%,respectively,in the oxide layer of Ti6Al4V-5Cu alloy.In contrast,the outermost layer of Ti6AlV alloy was predominantly composed of TiO_(2)but Ti_(2)O_(3)(22.8%),Al_(2)O_(3)and V_(2)O_(5) were also detected.With increasing sputtering depth to 6 nm,fitting revealed the presence of Ti_(2)O_(3)and TiO with relative fractions of 25.3%and 35.8%,respectively.Yet,a spot of TiO(8%)was also observed at 12 nm in the oxide layer of Ti6Al4V alloy.Although the addition of Cu into Ti6Al4V alloy generated the self-healing property of passive film in the presence of P.aeruginosa,it also reduced resistance to corrosion in general condition.
文摘In this study,Mg-based composites,by the addition of ZnO,Ca_(2)ZnSi_(2)O_(7),Ca_(2)MgSi_(2)O_(7),and CaSiO_(3)as bioactive agents,were fabricated using friction stir processing.The microstructure and in vitro assessment of bioactivity,biodegradation rate,and corrosion behavior of the resultant composites were investigated in simulated body fluid(SBF).The results showed that during the immersion of composites in SBF for 28 d,due to the release of Ca^(2+)and PO_(4)^(3-)ions,hydroxyapatite(HA)crystals with cauliflower shaped morphology were deposited on the surface of composites,confirming good bioactivity of composites.In addition,due to the uniform distribution of bioceramic powders throughout Mg matrix,grain refinement of the Mg matrix,and uniform redistribution of secondary phase particles,the polarization resistance increased,and the biodegradation rate of composites significantly reduced compared to monolithic Mg matrix.The polarization corrosion resistance of Mg-ZnO increased from 0.216 to 2.499 kΩ/cm^(2)compared to monolithic Mg alloy.Additionally,Mg-ZnO composite with the weight loss of 0.0217 g after 28 d immersion showed lower weight loss compared to other samples with increasing immersion time.Moreover,Mg-ZnO composite with the biodegradation rate of 37.71 mm/a exhibited lower biodegradation rate compared to other samples with increasing immersion time.
文摘Drawbacks associated with permanent metallic implants lead to the search for degradable metallic biomaterials. Magnesium alloys have been highly considered as Mg has a high biocorrosion potential and is essential to bodies. In this study, corrosion behaviour of pure magnesium and magnesium alloy AZ31 in both static and dynamic physiological conditions (Hank's solution) has been investigated. It is found that the materials degrade fast at beginning, then stabilize after 5 days of immersion. High purity in the materials reduces the corrosion rate while the dynamic condition accelerates the degradation process. In order to slow down the degradation process to meet the requirement for their bio-applications, an anodized coating is applied and is proved as effective in controlling the biodegradation rate.
文摘Biocorrosion, as well as the biodeterioration of crude oil and its derivatives, is one of the major environmental, operational and economic problems in the Venezuelan oil industry. Fungal contaminants are able to produce large quantities of biomass and synthesize peroxides and organic acids, causing severe damage on metal surfaces and promoting the contamination and biodeterioration of fuels. No evidences regarding fungal strains have been reported to be associated to petroleum naphtha, widely used as a diluent of extra heavy crude oil (EHCO) in the exploitation processes of the Orinoco Oil Belt, the biggest proven reserve of EHCO worldwide. The aims of this paper were to isolate and identify fungal strains from the naphtha storage tank and the naphtha distribution network from an oil field operator in Venezuela. The results showed the isolation of four different fungal strains. The molecular identification by 28S rRNA sequencing and phylogenetic tree analysis allowed us to identify the presence of: 1) a new uncultured Ascomycota fungus species BM-103, with high identity to novel hyphomycetes Noosia banksiae and Sporidesmium tengii, in the naphtha storage tank;2) two yeasts, Rhodotorula mucilaginosa BM-104 (Phylum Basidiomycota) and Wickerhamia sp. BM-105 (Phylum Ascomycota), in a highly damaged naphtha pipeline branch and;3) Cladosporium cladosporioides BM-102 (Phylum Ascomycota) in a cluster oil well. DNA fingerprinting analysis using ERIC-PCR primers pairs also allowed us to detect the presence of R. mucilaginosa BM-104 right in the access of the studied naphtha system. Interestingly, R. mucilaginosa and C. cladosporioides were previously reported as predominant fungal contaminants of diesel and jet fuel and of kerosene and fuel storage systems, respectively. This paper represents the first evidence of fungal strains isolated and identified from the naphtha systems in the Venezuelan oil industry. The results obtained are discussed.
文摘The composition of tightly bound exopolymeric substances (EPS) obtained from biofilm and plan- ktonic cell subpopulations of Stenotrophomonas maltophilia 5426 UKM was analyzed to study an impact of mild steel presence in the cultivation medium. The overall protein production was found to increase in the presence of a steel coupon. Some amino acids such as lysine, valine, iso-leucine, tyrosine and phenylalanine were found to be secreted in higher amounts in the presence of mild steel, while its absence leads to an increase of arginine, asparagine, serine, glutamine, proline, glycine, cysteine, leucine, methionine production levels. Biofilm cells EPS contained more arginine, glycine, cysteine, valine, methionine and leucine, comparing to EPS of planktonic cells. The chang- es of tightly bound EPS aggregation around the cells induced in the presence of steel coupons were revealed by transmission electron microscopy. The results suggested the transition of S. maltophilia 5426 UKM cells from planktonic to biofilm lifestyle to be a complex process involving more than a single step.
文摘The start and the course of bio-corrosion are conditioned by many factors which include biological effects like the influence of vegetation and microorganisms causing the deterioration of materials. The influence of bacteria causing the deterioration of concrete has been linked to the generation of biogenic sulphuric and nitric acids which originate in corrosion process by dissolution of calcium containing minerals from the concrete matrices. This paper primarily focuses on the investigation of influence of sulphur-oxidising bacteria Acidithiobacillus thiooxidans and sulphate-reducing bacteria Desulfovibrio desulfuricans at the resistance degree of cement composites. Various concrete composites with 5% addition of black coal fly ash as cement replacement as well as the reference samples without coal fly ash addition were studied in the experiments environments of sewage system proceeded during 90 days. The The laboratory experiments as well as experiments in situ in real corrosion was manifested by surface changes and weight changes of cement composites samples as well as changes in pH values of leachates. Considerable surface changes were detected in all investigated samples by microscopic methods. Crystals precipitated on concrete samples surface were identified by EDX as mixture of gypsum and ettringite. The roughness increases of surface of cement microscopy. composites were determined by confocal laser scanning
文摘In caves and monuments, biocorrosion caused by bats occurs partly under accumulations of guano. Tests were carried out both at cave temperature and under hot conditions in the laboratory on 4 different limestones. A comparison of the results obtained using these two methods shows that the processes leading to the weathering of the limestones are the same, and that the hot laboratory tests accelerate them in a well-constrained way. The higher the porosity and capillarity of the limestone, the faster the weathering process. The presence of large calcite crystals also favors weathering. In caves, the ablation rates obtained (8 mm/ka) are sufficient to destroy engravings in a few decades. In monuments, ablation rates are even higher because of the temperature, and could theoretically reach 32 cm/ka in extreme conditions at 80˚C. The laboratory test developed here can be adapted to the temperature of each case study. It has already demonstrated the mechanisms that lead from weathering to the formation of a phosphate crust.
基金This work was partially funded by Michigan Tech Research Excellence Fund,National Institutes of Health[grant number R15GM135875(B.P.L.)]the National Science Foundation[grant number DMR 2001076(B.P.L.)],ZA was partially funded by Michigan Tech Undergraduate Research Internship Program.
文摘The relationship between reactive oxygen and nitrogen species(ROS-RNS)secretion and the concomitant biocorrosion of degradable magnesium(Mg)materials is poorly understood.We found that Mg foils implanted short term in vivo(24 h)displayed large amounts of proinflammatory F4/80+/iNOS+macrophages at the interface.We sought to investigate the interplay between biodegrading Mg materials(98.6%Mg,AZ31&AZ61)and macrophages(RAW 264.7)stimulated with lipopolysaccharide(RAW 264.7^(LPS))to induce ROS-RNS secretion.To test how these proinflammatory ROS-RNS secreting cells interact with Mg corrosion in vitro,Mg and AZ61 discs were suspended approximately 2 mm above a monolayer of RAW 264.7 cells,either with or without ^(LPS).The surfaces of both materials showed acute(24 h)changes when incubated in the proinflammatory RAW 264.7^(LPS) environment.Mg discs incubated with RAW 264.7^(LPS) macrophages showed greater corrosion pitting,while AZ61 showed morphological and elemental bulk product changes via scanning electron microscopy-energy dispersive X-ray spectroscopy(SEM-EDX).X-ray photoelectron spectroscopy(XPS)analysis showed a reduction in the Ca/P ratio of the surface products for AZ61 disc incubated with RAW 264.7^(LPS),but not the Mg discs.Moreover,RAW 264.7^(LPS) macrophages were found to be more viable in the acute biodegradative environment generated by Mg materials,as demonstrated by calcein-AM and cleaved(active)caspase-3 staining(CC3).^(LPS) stimulation caused an increase in ROS-RNS,and a decrease in antioxidant peroxidase activity.Mg and AZ61 were found to change this ROS-RNS balance,independently of physiological antioxidant mechanisms.The findings highlight the complexity of the cellular driven acute inflammatory responses to different biodegradable Mg,and how it can potentially affect performance of these materials.
基金This research was supported by the National Natural Science Foundation of China(Grant No.51771054)State Key Program of National Natural Science Foundation of China(Grant No.51631003)+5 种基金National Key Research and Development Program of China(Grant No.2016YFC1102402)the Open Research Fund of Jiangsu Key Laboratory for Advanced Metallic Materials(Grant No.AMM2021A01)the Opening Project of Jiangsu Key Laboratory of Advanced Structural Materials and Application Technology(Grant No.ASMA201901)Postgraduate Research&Practice Innovation Program of Jiangsu Province(Grant No.KYCX20_0091)Natural Science Foundation of Jiangsu Province(BK20181020)and the Introduction of Talent Research Fund in Nanjing Institute of Technology(YKJ201705).
文摘The real physiological environment of human body is complicated with different degrees and forms of dynamic loads applied to implanted medical devices due to the daily activities of the patients,which would have impacts on the degradation behaviors of magnesium alloy implants.In this work,the bio-corrosion behaviors of AZ31B magnesium alloy under alternating cyclic dynamic loads with different low frequencies(0.1-2.5 Hz)were specially investigated.It was found that the bio-degradation performances under external dynamic stressed conditions were much severer than those under unstressed conditions and static loads.The corrosion rates were generally accelerated as the rise of cyclic frequency.Hereby a numerical model for the degradation process of Mg alloy was established.The corrosion current density icorr of Mg alloy and the applied loading frequency f matches a linear relationship of ln icorr∝f,which is the result of interactions between the cyclic alternating load and corrosive environment.This work could provide a theoretical reference and an experimental basis for further researches on the biodegradation behaviors of biomedical materials under dynamic conditions.
