The influence of intermetallic Al-Mn particles on the corrosion behavior of in-situ formed Mg-Al layered double hydroxide(Mg-Al-CO32--LDH)steam coating on AZ31 Mg alloy was investigated.The alloy was pretreated with H...The influence of intermetallic Al-Mn particles on the corrosion behavior of in-situ formed Mg-Al layered double hydroxide(Mg-Al-CO32--LDH)steam coating on AZ31 Mg alloy was investigated.The alloy was pretreated with H3PO4,HCl,HNO3or citric acid(CA),followed by hydrothermal treatment,for the fabrication of Mg-Al-LDH coating.The microstructure,composition and corrosion resistance of the coated samples were investigated.The results showed that the surface area fraction of Al-Mn phase exposed on the surface of the alloy was significantly increased after CA pretreatment,which promotes the growth of the Mg-Al-LDH steam coating.Further,the LDH-coated alloy pretreated with CA possessed the most compact surface and the maximum coating thickness among all the coatings.The corrosion current density of the coated alloy was decreased by three orders of magnitude as compared to that of the bare alloy.展开更多
A hexagonal nanosheet Mg(OH)2 coating was prepared through a one-step hydrothermal method using LiOH solution as mineralizer and then modified by ethylenediaminetetraacetic acid(EDTA) to minimize the rapid corrosion o...A hexagonal nanosheet Mg(OH)2 coating was prepared through a one-step hydrothermal method using LiOH solution as mineralizer and then modified by ethylenediaminetetraacetic acid(EDTA) to minimize the rapid corrosion of AZ31 Mg alloy.The performance of the coating was evaluated using electrochemical technique,hydrogen evolution measurements, nanoscratch test,Fourier-transform infrared spectroscopy(FTIR), X-ray diffraction(XRD) patterns and field-emission scanning electron microscopy(FESEM).The results suggested that the corrosion rate of bare AZ31 Mg alloys was significantly reduced by one and two orders of magnitude through the protection from Mg(OH)2 coating and modification with EDTA(i.e., EDTA-Mg(OH)2 coating), respectively.FESEM micrographs indicated that the modification in EDTA elicits to the formation of an EDTA-Mg(OH)2 composite with a thickness as twice as that of as-prepared Mg(OH)2 coating.Nanoscratch tests revealed strong adhesion between the composite or Mg(OH)2 coating and the substrate.The study of formation and corrosion mechanisms of the coatings manifested that Mg(OH)2 was first formed near the intermetallic compound AlMn particles and gradually covered the entire surface, wherein the AlMn particles played an important role in the coating growth process.And it also proved that EDTA accelerated the formation of Mg(OH)2.展开更多
The microstructure and chemical compositions of the solid solution-treated Mg-3 Nd-1 Li-0.2 Zn alloy were characterized using optical microscope,scanning electron microscope(SEM),transmission electron microscope(TEM),...The microstructure and chemical compositions of the solid solution-treated Mg-3 Nd-1 Li-0.2 Zn alloy were characterized using optical microscope,scanning electron microscope(SEM),transmission electron microscope(TEM),electron probe micro-analyzer(EPMA)and X-ray photoelectron spectroscopy(XPS).The corrosion behaviour of the alloy was investigated via electrochemical polarization,electrochemical impedance spectroscopy(EIS),hydrogen evolution test and scanning Kelvin probe(SKP).The results showed that the microstructure of the as-extruded Mg-3 Nd-1 Li-0.2 Zn alloy containedα-Mg matrix and nanometric second phase Mg_(41)Nd_(5).The grain size of the alloy increased significantly with the increase in the heat-treatment duration,whereas the volume fraction of the second phase decreased after the solid solution treatment.The surface film was composed of oxides(Nd_(2)O_(3),Mg O,Li_(2)O and Zn O)and carbonates(Mg CO3 and Li_(2)CO3),in addition to Nd.The as-extruded alloy exhibited the best corrosion resistance after an initial soaking of 10 min,whereas the alloy with 4 h-solution-treatment possessed the lowest corrosion rate after a longer immersion(1 h).This can be attributed to the formation of Nd-containing oxide film on the alloys and a dense corrosion product layer.The dealloying corrosion of the second phase was related to the anodic Mg_(41)Nd_(5)with a more negative Volta potential relative toα-Mg phase.The preferential corrosion of Mg_(41)Nd_(5)is proven by in-situ observation and SEM.The solid solution treatment of Mg-3 Nd-1 Li-0.2 Zn alloy led to a shift in corrosion type from pitting corrosion to uniform corrosion under long-term exposure.展开更多
Magnesium is a candidate metal for biodegradable implant applications for its biodegradation tendency and excellent biocompatibility.Unfortunately,the high degradation rate of magnesium and also its localized degradat...Magnesium is a candidate metal for biodegradable implant applications for its biodegradation tendency and excellent biocompatibility.Unfortunately,the high degradation rate of magnesium and also its localized degradation in physiological conditions are the main issues for its successful implant applications.The degradation rate of magnesium has been reduced to some degree via alloying,but the localized degradation susceptibility is a great concern.For many years,hydroxyapatite(HAp),a biocompatible ceramic material,has been extensively used for bio-implant applications.Recently,a substantial amount of research has been carried out on coating HAp on magnesium-based materials for improved degradation resistance in particular and also to enhance the biocompatibility.This review article focuses on the different methods of HAp coating on magnesium-based materials and also the recent cutting-edge advancements made in the coating process for improved degradation resistance and biocompatibility.The mechanical stability of the HAp coated magnesium-based materials is also discussed.展开更多
Mg alloys possess biodegradability,suitable mechanical properties,and biocompatibility,which make them possible to be used as biodegradable implants.However,the uncontrollable degradation of Mg alloys limits their gen...Mg alloys possess biodegradability,suitable mechanical properties,and biocompatibility,which make them possible to be used as biodegradable implants.However,the uncontrollable degradation of Mg alloys limits their general applications.In addition to the factors from the metallic materials themselves,like alloy compositions,heat treatment process and microstructure,some external factors,relating to the test/service environment,also affect the degradation rate of Mg alloys,such as inorganic salts,bioorganic small molecules,bioorganic macromolecules.The influence of bioorganic molecules on Mg corrosion and its protection has attracted more and more attentions.In this work,the cutting-edge advances in the influence of bioorganic molecules(i.e.,protein,glucose,amino acids,vitamins and polypeptide)and their coupling effect on Mg degradation and the formation of protection coatings were reviewed.The research orientations of biomedical Mg alloys in exploring degradation mechanisms in vitro were proposed,and the impact of bioorganic molecules on the protective approaches were also explored.展开更多
In this study,the effects of intermetallic compounds(Mg_(17)Al_(12)and Al_(8)Mn_(5))on the Mg-Al layered double hydroxide(LDH)formation mechanism and corrosion behavior of an in-situ LDH/Mg(OH)_(2)steam coatings on AZ...In this study,the effects of intermetallic compounds(Mg_(17)Al_(12)and Al_(8)Mn_(5))on the Mg-Al layered double hydroxide(LDH)formation mechanism and corrosion behavior of an in-situ LDH/Mg(OH)_(2)steam coatings on AZ80 Mg alloy were investigated.Citric acid(CA)was used to activate the alloy surface during the pretreatment process.The alloy was first pretreated with CA and then subjected to a hydrothermal process using ultrapure water to produce Mg-Al-LDH/Mg(OH)_(2)steam coating.The effect of different time of acid pretreatment on the activation of the intermetallic compounds was investigated.The microstructure and elemental composition of the obtained coatings were analyzed using FE-SEM,EDS,XRD and FT-IR.The corrosion resistance of the coated samples was evaluated using different techniques,i.e.,potentiodynamic polarization(PDP),electrochemical impedance spectrum(EIS)and hydrogen evolution test.The results indicated that the CA pretreatment significantly influenced the activity of the alloy surface by exposing the intermetallic compounds.The surface area fraction of Mg_(17)Al_(12)and Al_(8)Mn_(5)phases on the surface of the alloy was significantly higher after the CA pretreatment,and thus promoted the growth of the subsequent Mg-Al-LDH coatings.The CA pretreatment for 30 s resulted in a denser and thicker LDH coating.Increase in the CA pretreatment time significantly led to the improvement in corrosion resistance of the coated AZ80 alloy.The corrosion current density of the coated alloy was lower by three orders of magnitude as compared to the uncoated alloy.展开更多
Smart micro-arc oxidation(MAO)/epoxy resin(EP) composite coatings were formed on AZ31 magnesium(Mg) alloy. Mesoporous silica nanocontainers(MSN) encapsulated with sodium benzoate(SB) corrosion inhibitors were strategi...Smart micro-arc oxidation(MAO)/epoxy resin(EP) composite coatings were formed on AZ31 magnesium(Mg) alloy. Mesoporous silica nanocontainers(MSN) encapsulated with sodium benzoate(SB) corrosion inhibitors were strategically incorporated in the MAO micropores and in the top EP layer. The influence of the strategic positioning of the nanocontainers on the corrosion protective performance of coating was investigated. The experimental results and analysis indicated that the superior corrosion resistance of the hybrid coating is ascribed to the protection mechanisms of the nanocontainers. This involves two phenomena:(1) the presence of the nanocontainers in the MAO micropores decreased the distance between MSN@SB and the substrate, demonstrating a low admittance value(^5.18 × 10^(-8)Ω^(-1)), and thus exhibiting significant corrosion inhibition and self-healing function;and(2) the addition of nanocontainers in the top EP layer densified the coating via sealing of the inherent defects, and hence the coating maintained higher resistance even after 90 days of immersion(1.13 × 10^(10)Ω cm^(2)).However, the possibility of corrosion inhibitors located away from the substrate transport to the substrate is reduced, reducing its effective utilization rate. This work demonstrates the importance of the positioning of nanocontainers in the coating for enhanced corrosion resistance,and thereby providing a novel perspective for the design of smart protective coatings through regulating the distribution of nanocontainers in the coatings.展开更多
Protein exerts a critical influence on the degradation behavior of absorbable magnesium(Mg)-based implants.However,the interaction mechanism between protein and a micro-arc oxidation(MAO)coating on Mg alloys remains u...Protein exerts a critical influence on the degradation behavior of absorbable magnesium(Mg)-based implants.However,the interaction mechanism between protein and a micro-arc oxidation(MAO)coating on Mg alloys remains unclear.Hereby,a MAO coating was fabricated on AZ31 Mg alloy.And its degradation behavior in phosphate buffer saline(PBS)containing bovine serum albumin(BSA)was investigated and compared with that of the uncoated alloy.Surface morphologies and chemical compositions were studied using Field-emission scanning electron microscope(FE-SEM),Fourier transform infrared spectrophotometer(FT-IR)and X-ray diffraction(XRD).The degradation behavior of the bare Mg alloy and its MAO coating was studied through electrochemical and hydrogen evolution tests.Cytotoxicity assay was applied to evaluate the biocompatibility of Mg alloy substrate and MAO coating.Results indicated that the presence of BSA decreased the degradation rate of Mg alloy substrate because BSA(RCH(NH2)COO‾)molecules combined with Mg2+ions to form(RCH(NH2)COO)2Mg and thus inhibited the dissolution of Mg(OH)2 by impeding the attack of Cl‾ions.In the case of MAO coated Mg alloy,the adsorption of BSA on MAO coating and the formation of(RCH(NH2)COO)2Mg exhibited a synergistic effect and enhanced the corrosion resistance of the coated alloy significantly.Furthermore,cell bioactive assay suggested that the MAO coating had good viability for MG63 cells due to its high surface area.展开更多
Molecular recognition was utilized to fabricate bioinspired calcium phosphate(Ca-P)coating on bioabsorbable magnesium alloys through small biomolecules such as Vitamin C(VC).Ca-P and VC hybrid coating(Ca-P_(VC))was su...Molecular recognition was utilized to fabricate bioinspired calcium phosphate(Ca-P)coating on bioabsorbable magnesium alloys through small biomolecules such as Vitamin C(VC).Ca-P and VC hybrid coating(Ca-P_(VC))was successfully fabricated on AZ31 Mg alloy.The surface morphology and chemical composition of the coatings were investigated using SEM,XRD,and FTIR together with XPS.The results showed that the Ca-P_(VC)coating was composed of bamboo leaf-like Ca-P particles with a thickness of about three times that of the Ca-P coating.The surface roughness of the Ca-P_(VC)coating(1.12±0.12μm)was lower than that(3.14±1.93μm)of Ca-P coating,suggesting the formation of refined Ca-P particles resulting from the VC addition.The corrosion resistance of the coated samples was characterized via electrochemical polarization,impedance spectroscopy,and immersion hydrogen evolution tests.The cell toxicity of the coated samples was evaluated utilizing mouse MC3T3-E1 pre-osteoblasts.The charge transfer resistance(Rct)of the Ca-P_(VC)coated alloy increased as compared to the bare and Ca-P coated alloy samples.The Ca-P_(VC)coated alloy exhibited minimal corrosion current density(1.36×10-6A cm-2),which is one order of magnitude lower in comparison to that of the Ca-P coated alloy.These results confirm that VC addition greatly enhanced the coating resistance on AZ31 Mg alloy.It was also noticed that the Ca-P_(VC)coated samples rapidly induced the formation of apatite after immersion in Hank’s solution.VC was mainly transformed to L-Threonic acid,which facilitated the nucleation process of the Ca-P_(VC)coating and significantly increased the thickness,density,and bonding strength of the coating.With enhanced corrosion resistance property and excellent biocompatibility,Ca-P_(VC)coating has great potential for application in biodegradable Mg-based alloys.展开更多
基金supported by the National Natural Science Foundation of China(Nos.51601108 and 52071191)the Natural Science Foundation of Shandong Province,China(No.ZR2020ME011)。
文摘The influence of intermetallic Al-Mn particles on the corrosion behavior of in-situ formed Mg-Al layered double hydroxide(Mg-Al-CO32--LDH)steam coating on AZ31 Mg alloy was investigated.The alloy was pretreated with H3PO4,HCl,HNO3or citric acid(CA),followed by hydrothermal treatment,for the fabrication of Mg-Al-LDH coating.The microstructure,composition and corrosion resistance of the coated samples were investigated.The results showed that the surface area fraction of Al-Mn phase exposed on the surface of the alloy was significantly increased after CA pretreatment,which promotes the growth of the Mg-Al-LDH steam coating.Further,the LDH-coated alloy pretreated with CA possessed the most compact surface and the maximum coating thickness among all the coatings.The corrosion current density of the coated alloy was decreased by three orders of magnitude as compared to that of the bare alloy.
基金financially supported by the National Natural Science Foundation of China (No.51571134)the Shandong University of Science and Technology Research Fund (No.2014TDJH104)
文摘A hexagonal nanosheet Mg(OH)2 coating was prepared through a one-step hydrothermal method using LiOH solution as mineralizer and then modified by ethylenediaminetetraacetic acid(EDTA) to minimize the rapid corrosion of AZ31 Mg alloy.The performance of the coating was evaluated using electrochemical technique,hydrogen evolution measurements, nanoscratch test,Fourier-transform infrared spectroscopy(FTIR), X-ray diffraction(XRD) patterns and field-emission scanning electron microscopy(FESEM).The results suggested that the corrosion rate of bare AZ31 Mg alloys was significantly reduced by one and two orders of magnitude through the protection from Mg(OH)2 coating and modification with EDTA(i.e., EDTA-Mg(OH)2 coating), respectively.FESEM micrographs indicated that the modification in EDTA elicits to the formation of an EDTA-Mg(OH)2 composite with a thickness as twice as that of as-prepared Mg(OH)2 coating.Nanoscratch tests revealed strong adhesion between the composite or Mg(OH)2 coating and the substrate.The study of formation and corrosion mechanisms of the coatings manifested that Mg(OH)2 was first formed near the intermetallic compound AlMn particles and gradually covered the entire surface, wherein the AlMn particles played an important role in the coating growth process.And it also proved that EDTA accelerated the formation of Mg(OH)2.
基金supported by the National Natural Science Foundation of China(52071191)the SDUST Research Found(2014TDJH104)。
文摘The microstructure and chemical compositions of the solid solution-treated Mg-3 Nd-1 Li-0.2 Zn alloy were characterized using optical microscope,scanning electron microscope(SEM),transmission electron microscope(TEM),electron probe micro-analyzer(EPMA)and X-ray photoelectron spectroscopy(XPS).The corrosion behaviour of the alloy was investigated via electrochemical polarization,electrochemical impedance spectroscopy(EIS),hydrogen evolution test and scanning Kelvin probe(SKP).The results showed that the microstructure of the as-extruded Mg-3 Nd-1 Li-0.2 Zn alloy containedα-Mg matrix and nanometric second phase Mg_(41)Nd_(5).The grain size of the alloy increased significantly with the increase in the heat-treatment duration,whereas the volume fraction of the second phase decreased after the solid solution treatment.The surface film was composed of oxides(Nd_(2)O_(3),Mg O,Li_(2)O and Zn O)and carbonates(Mg CO3 and Li_(2)CO3),in addition to Nd.The as-extruded alloy exhibited the best corrosion resistance after an initial soaking of 10 min,whereas the alloy with 4 h-solution-treatment possessed the lowest corrosion rate after a longer immersion(1 h).This can be attributed to the formation of Nd-containing oxide film on the alloys and a dense corrosion product layer.The dealloying corrosion of the second phase was related to the anodic Mg_(41)Nd_(5)with a more negative Volta potential relative toα-Mg phase.The preferential corrosion of Mg_(41)Nd_(5)is proven by in-situ observation and SEM.The solid solution treatment of Mg-3 Nd-1 Li-0.2 Zn alloy led to a shift in corrosion type from pitting corrosion to uniform corrosion under long-term exposure.
基金National Natural Science Foundation of China(Grant No.52071191)Open Foundation of Hubei Key Laboratory of Advanced Technology for Automotive Components(No.XDQCKF2021006)。
文摘Magnesium is a candidate metal for biodegradable implant applications for its biodegradation tendency and excellent biocompatibility.Unfortunately,the high degradation rate of magnesium and also its localized degradation in physiological conditions are the main issues for its successful implant applications.The degradation rate of magnesium has been reduced to some degree via alloying,but the localized degradation susceptibility is a great concern.For many years,hydroxyapatite(HAp),a biocompatible ceramic material,has been extensively used for bio-implant applications.Recently,a substantial amount of research has been carried out on coating HAp on magnesium-based materials for improved degradation resistance in particular and also to enhance the biocompatibility.This review article focuses on the different methods of HAp coating on magnesium-based materials and also the recent cutting-edge advancements made in the coating process for improved degradation resistance and biocompatibility.The mechanical stability of the HAp coated magnesium-based materials is also discussed.
基金National Natural Science Foundation of China(Grant No.52071191)Open Foundation of Hubei Key Laboratory of Advanced Technology for Automotive Components(No.XDQCKF2021006)。
文摘Mg alloys possess biodegradability,suitable mechanical properties,and biocompatibility,which make them possible to be used as biodegradable implants.However,the uncontrollable degradation of Mg alloys limits their general applications.In addition to the factors from the metallic materials themselves,like alloy compositions,heat treatment process and microstructure,some external factors,relating to the test/service environment,also affect the degradation rate of Mg alloys,such as inorganic salts,bioorganic small molecules,bioorganic macromolecules.The influence of bioorganic molecules on Mg corrosion and its protection has attracted more and more attentions.In this work,the cutting-edge advances in the influence of bioorganic molecules(i.e.,protein,glucose,amino acids,vitamins and polypeptide)and their coupling effect on Mg degradation and the formation of protection coatings were reviewed.The research orientations of biomedical Mg alloys in exploring degradation mechanisms in vitro were proposed,and the impact of bioorganic molecules on the protective approaches were also explored.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.51601108 and 52071191)the Natural Science Foundation of Shandong Province(ZR2020ME011).
文摘In this study,the effects of intermetallic compounds(Mg_(17)Al_(12)and Al_(8)Mn_(5))on the Mg-Al layered double hydroxide(LDH)formation mechanism and corrosion behavior of an in-situ LDH/Mg(OH)_(2)steam coatings on AZ80 Mg alloy were investigated.Citric acid(CA)was used to activate the alloy surface during the pretreatment process.The alloy was first pretreated with CA and then subjected to a hydrothermal process using ultrapure water to produce Mg-Al-LDH/Mg(OH)_(2)steam coating.The effect of different time of acid pretreatment on the activation of the intermetallic compounds was investigated.The microstructure and elemental composition of the obtained coatings were analyzed using FE-SEM,EDS,XRD and FT-IR.The corrosion resistance of the coated samples was evaluated using different techniques,i.e.,potentiodynamic polarization(PDP),electrochemical impedance spectrum(EIS)and hydrogen evolution test.The results indicated that the CA pretreatment significantly influenced the activity of the alloy surface by exposing the intermetallic compounds.The surface area fraction of Mg_(17)Al_(12)and Al_(8)Mn_(5)phases on the surface of the alloy was significantly higher after the CA pretreatment,and thus promoted the growth of the subsequent Mg-Al-LDH coatings.The CA pretreatment for 30 s resulted in a denser and thicker LDH coating.Increase in the CA pretreatment time significantly led to the improvement in corrosion resistance of the coated AZ80 alloy.The corrosion current density of the coated alloy was lower by three orders of magnitude as compared to the uncoated alloy.
基金appreciate the financial support by the National Natural Science Foundation of China (52071191,52201077)the Natural Science Foundation of Shandong Province (ZR2022QE191)+1 种基金Elite Scheme of Shandong University of Science and Technology (0104060541123)Talent introduction and Research Start-up Fund of Shandong University of Science and Technology (0104060510124)。
文摘Smart micro-arc oxidation(MAO)/epoxy resin(EP) composite coatings were formed on AZ31 magnesium(Mg) alloy. Mesoporous silica nanocontainers(MSN) encapsulated with sodium benzoate(SB) corrosion inhibitors were strategically incorporated in the MAO micropores and in the top EP layer. The influence of the strategic positioning of the nanocontainers on the corrosion protective performance of coating was investigated. The experimental results and analysis indicated that the superior corrosion resistance of the hybrid coating is ascribed to the protection mechanisms of the nanocontainers. This involves two phenomena:(1) the presence of the nanocontainers in the MAO micropores decreased the distance between MSN@SB and the substrate, demonstrating a low admittance value(^5.18 × 10^(-8)Ω^(-1)), and thus exhibiting significant corrosion inhibition and self-healing function;and(2) the addition of nanocontainers in the top EP layer densified the coating via sealing of the inherent defects, and hence the coating maintained higher resistance even after 90 days of immersion(1.13 × 10^(10)Ω cm^(2)).However, the possibility of corrosion inhibitors located away from the substrate transport to the substrate is reduced, reducing its effective utilization rate. This work demonstrates the importance of the positioning of nanocontainers in the coating for enhanced corrosion resistance,and thereby providing a novel perspective for the design of smart protective coatings through regulating the distribution of nanocontainers in the coatings.
基金supported by the National Natural Science Foundation of China(51571134)the SDUST Research Fund(2014TDJH104).
文摘Protein exerts a critical influence on the degradation behavior of absorbable magnesium(Mg)-based implants.However,the interaction mechanism between protein and a micro-arc oxidation(MAO)coating on Mg alloys remains unclear.Hereby,a MAO coating was fabricated on AZ31 Mg alloy.And its degradation behavior in phosphate buffer saline(PBS)containing bovine serum albumin(BSA)was investigated and compared with that of the uncoated alloy.Surface morphologies and chemical compositions were studied using Field-emission scanning electron microscope(FE-SEM),Fourier transform infrared spectrophotometer(FT-IR)and X-ray diffraction(XRD).The degradation behavior of the bare Mg alloy and its MAO coating was studied through electrochemical and hydrogen evolution tests.Cytotoxicity assay was applied to evaluate the biocompatibility of Mg alloy substrate and MAO coating.Results indicated that the presence of BSA decreased the degradation rate of Mg alloy substrate because BSA(RCH(NH2)COO‾)molecules combined with Mg2+ions to form(RCH(NH2)COO)2Mg and thus inhibited the dissolution of Mg(OH)2 by impeding the attack of Cl‾ions.In the case of MAO coated Mg alloy,the adsorption of BSA on MAO coating and the formation of(RCH(NH2)COO)2Mg exhibited a synergistic effect and enhanced the corrosion resistance of the coated alloy significantly.Furthermore,cell bioactive assay suggested that the MAO coating had good viability for MG63 cells due to its high surface area.
基金financially supported by the National Natural Science Foundation of China(No.52071191)
文摘Molecular recognition was utilized to fabricate bioinspired calcium phosphate(Ca-P)coating on bioabsorbable magnesium alloys through small biomolecules such as Vitamin C(VC).Ca-P and VC hybrid coating(Ca-P_(VC))was successfully fabricated on AZ31 Mg alloy.The surface morphology and chemical composition of the coatings were investigated using SEM,XRD,and FTIR together with XPS.The results showed that the Ca-P_(VC)coating was composed of bamboo leaf-like Ca-P particles with a thickness of about three times that of the Ca-P coating.The surface roughness of the Ca-P_(VC)coating(1.12±0.12μm)was lower than that(3.14±1.93μm)of Ca-P coating,suggesting the formation of refined Ca-P particles resulting from the VC addition.The corrosion resistance of the coated samples was characterized via electrochemical polarization,impedance spectroscopy,and immersion hydrogen evolution tests.The cell toxicity of the coated samples was evaluated utilizing mouse MC3T3-E1 pre-osteoblasts.The charge transfer resistance(Rct)of the Ca-P_(VC)coated alloy increased as compared to the bare and Ca-P coated alloy samples.The Ca-P_(VC)coated alloy exhibited minimal corrosion current density(1.36×10-6A cm-2),which is one order of magnitude lower in comparison to that of the Ca-P coated alloy.These results confirm that VC addition greatly enhanced the coating resistance on AZ31 Mg alloy.It was also noticed that the Ca-P_(VC)coated samples rapidly induced the formation of apatite after immersion in Hank’s solution.VC was mainly transformed to L-Threonic acid,which facilitated the nucleation process of the Ca-P_(VC)coating and significantly increased the thickness,density,and bonding strength of the coating.With enhanced corrosion resistance property and excellent biocompatibility,Ca-P_(VC)coating has great potential for application in biodegradable Mg-based alloys.
