The influence of phosphating bath at different temperatures on the formation and corrosion property of calcium-modified zinc phosphate conversion coating （Zn-Ca-P coating） on Mg-Li-Ca alloy was investigated. The mor...The influence of phosphating bath at different temperatures on the formation and corrosion property of calcium-modified zinc phosphate conversion coating （Zn-Ca-P coating） on Mg-Li-Ca alloy was investigated. The morphologies, elemental distribution and chemical structures of the coatings were examined via SEM, EPMA, EDS, XRD and FT-IR. The corrosion resistance was assessed by hydrogen evolution, potentiodynamic polarization and EIS. The results show that the coating is composed of single element Zn and ZnO at below 45 ℃;whereas the coatings are predominantly characterized by Zn3（PO4）2·4H2O and small amount of element zinc and ZnO at above 50 ℃. Mg-Li-Ca alloy with Zn-Ca-P coatings prepared at 55 ℃ has the highest corrosion resistance. However, the hydrogen evolution rates of the coatings obtained at 40-50 ℃ is accelerated due to the galvanic corrosion between the imperfection of the single element Zn coating and the Mg substrate.展开更多
Globally,vast research interest is emerging towards the development of biodegradable orthopedic implants as it overcomes the toxicity exerted by non-degradable implants when fixed in the human body for a longer period...Globally,vast research interest is emerging towards the development of biodegradable orthopedic implants as it overcomes the toxicity exerted by non-degradable implants when fixed in the human body for a longer period.In this context,magnesium(Mg)plays a major role in the production of biodegradable implants owing to their characteristic degradation nature under the influence of body fluids.Also,Mg is one of the essential nutrients required to perform various metabolic activities by the human cells,and therefore,the degraded Mg products will be readily absorbed by the nearby tissues.Nevertheless,the higher corrosion rate in the biological environment is the primary downside of using Mg implants that liberate H2gas resulting in the formation of cavities.Further,in certain cases,Mg undergoes complete degradation before the healing of damaged bone tissue and cannot serve the purpose of providing mechanical support.So,many studies have been focused on the development of different strategies to improve the corrosion-resistant behavior of Mg according to the requirement.In this regard,the present review focused on the limitations of using pure Mg and Mg alloys for the fabrication of medical implants and how the calcium phosphate conversion coating alters the corrosive tendency through the formation of hydroxyapatite protective films for enhanced performance in medical implant applications.展开更多
In this study, Mg–6.0Zn–3.0Sn–0.5Mn(ZTM630) magnesium alloy was pre-activated by colloidal Ti, oxalic acid, and phosphoric acid,and a phosphate conversion coating(PCC) was prepared on the alloy surface. The morphol...In this study, Mg–6.0Zn–3.0Sn–0.5Mn(ZTM630) magnesium alloy was pre-activated by colloidal Ti, oxalic acid, and phosphoric acid,and a phosphate conversion coating(PCC) was prepared on the alloy surface. The morphology and corrosion resistance of the prepared PCCs were investigated. Surface morphology studies showed that the phosphate crystals that formed the coating were the smallest for the sample pre-activated by phosphoric acid. The coating on the colloidal Ti and the phosphoric acid samples had the largest and the smallest thickness and surface roughness, respectively. The reason for the discrepancy was analyzed by comparing the surface morphologies of alloy samples immediately after the pre-activation treatment and various phosphating treatments. X-ray diffraction analysis revealed that all three PCCs contained the same compounds. The corrosion resistance time from the copper sulfate drop test and the electrochemical data from the potentiodynamic polarization curves showed that the coating pre-activated by phosphoric acid had the best corrosion resistance. Finally, the 1500 h neutral salt spray corrosion test confirmed that the phosphating treated magnesium alloy, which was pre-activated by phosphoric acid,exhibited excellent corrosion resistance and behavior.展开更多
In order to obtain a more protective phosphate conversion coating with a denser architecture,the nucleation kinetics of phosphate chemical conversion coating on Mg-Gd-Y-Zr magnesium alloy was tuned in this work.A pret...In order to obtain a more protective phosphate conversion coating with a denser architecture,the nucleation kinetics of phosphate chemical conversion coating on Mg-Gd-Y-Zr magnesium alloy was tuned in this work.A pretreatment process was proposed and organic additives were incorporated,which aims at increasing the ionic produce(J_(sp))at the interface for increasingσ,and decreasing the critical ionic product(J_(C,sp)),respectively.Results prove that the pretreatment of bare alloys in a phosphate bath could increase the ion products of MgHPO_(4)/MnHPO_(4).The addition of benzalkonium chloride could neutralize the charges of crystals,and in turn promote the nucleation kinetics.A denser and more protective conversion coating could consequently be obtained.展开更多
The authors regret that due to negligence,the picture was misplaced in the original manuscript,resulting in Fig.6d being incorrectly included.The correct version of Fig.6d is provided below for reference.This error do...The authors regret that due to negligence,the picture was misplaced in the original manuscript,resulting in Fig.6d being incorrectly included.The correct version of Fig.6d is provided below for reference.This error does not affect the conclusions of the study,and we apologize for any confusion it may have caused.展开更多
Magnesium(Mg)and its alloys are lightweight as well as biocompatible and possess a high strength-to-weight ratio,making them suitable for many industries,including aerospace,automobile,and medical.The major challenge ...Magnesium(Mg)and its alloys are lightweight as well as biocompatible and possess a high strength-to-weight ratio,making them suitable for many industries,including aerospace,automobile,and medical.The major challenge is their high susceptibility to corrosion,thereby limiting their usability.The considerably lower reduction potential of Mg compared to other metals makes it vulnerable to galvanic coupling.The oxide layer on Mg offers little corrosion resistance because of its high porosity,inhomogeneity,and fragility.Chemical conversion coatings(CCs)belong to a distinct class because of underlying chemical reactions,which are fundamentally different from other types of coating.Typically,a CC acts as an intermediate sandwich layer between the base metal and an aesthetic paint.Although chromate CCs offer superior performance compared to phosphate CCs,yet still they release carcinogenic hexavalent chromium ions(Cr^(6+));therefore,their use is prohibited in most European nations under the Registration,Evaluation,Authorization and Restriction of Chemicals legislation framework.Phosphate-based CCs are a cost-effective and environment-friendly alternative.Accordingly,this review primarily focuses on different types of phosphate-based CCs,such as zinc,calcium,Mg,vanadium,manganese,and permanganate.It discusses their mechanisms,current status,pretreatment practices,and the influence of various parameters-such as pH,temperature,immersion time,and bath composition-on the coating performance.Some challenges associated with phosphate CCs and future research directions are also elaborated.展开更多
The corrosion-resistant coating formed on the surface of sintered Nd-Fe-B magnet by a phosphate chemical conversion(PCC)treatment was studied.The morphology,phase composition and thickness of the coating were investig...The corrosion-resistant coating formed on the surface of sintered Nd-Fe-B magnet by a phosphate chemical conversion(PCC)treatment was studied.The morphology,phase composition and thickness of the coating were investigated by field emission scanning electron microscopy(FE-SEM),energy-dispersive spectrometer(EDS),Fourier transform infrared(FTIR)spectrometer and coating thickness gauge.The corrosion behaviour of the phosphated magnet was evaluated by copper sulphate spot test,neutral salt spray test and electrochemical potentiodynamic polarization experiment.The magnetic properties of the phosphated magnet were also tested.The experimental results show that the phosphate coating has such characteristics as dense granular growth,uniform distribution and thickness range of 10-18μm.The corrosion resistance of the magnet is significantly improved by phosphate coating without losing magnetic properties.Therefore,this highly efficient PCC was a good way for increasing the corrosion resistance of the sintered Nd-Fe-B magnets.展开更多
A phosphate solution free of chromate, fluoride and nitrite was prepared and an environment-friendly film was obtained on AZ31 magnesium alloy surface via the chemical deposition method. The morphology, composition, p...A phosphate solution free of chromate, fluoride and nitrite was prepared and an environment-friendly film was obtained on AZ31 magnesium alloy surface via the chemical deposition method. The morphology, composition, phase structure and its corrosion resistance were studied. The effects of film-forming temperature and free acid on corrosion resistance, microstructure and electrochemical behavior of the film were discussed. The results indicate that the corrosion resistance of AZ31 with the phosphate film was better than blank AZ31 substrate, which was most attributed to the great inhibitive action on the anodic dissolution and cathodic hydrogen evolution of the film.展开更多
Cracking and low thickness are major obstacles to the high corrosion performance of conversion coating on magnesium alloy.In this work,the ratio of total acidity to p H(TA/p H)was applied as an indicator,and new princ...Cracking and low thickness are major obstacles to the high corrosion performance of conversion coating on magnesium alloy.In this work,the ratio of total acidity to p H(TA/p H)was applied as an indicator,and new principles regarding the design of conversion bath were proposed.The treatment bath should be composed of species that can be categorized into two groups:the first group of species that react with Mg substrate to increase the local p H at the interface;the second group that precipitate and contributes to the growth of coating.The species belong to second group exists in a supersaturated state and its precipitation process is almost independent on the reactions of the species in first group.By this way,a thick and crack-free two-layered conversion coating is obtained.Moreover,the nature of the adjustment of TA/p H and the roles of the oxidizing agent and catalyst were discussed.展开更多
To improve corrosion resistance of phosphate chemical conversion coatings(PCCs)on magnesium alloy Mg-10Gd-3Y-0.4Zr,a new route was proposed.The phosphate conversion treatment was preceded by two nucleation pretreatmen...To improve corrosion resistance of phosphate chemical conversion coatings(PCCs)on magnesium alloy Mg-10Gd-3Y-0.4Zr,a new route was proposed.The phosphate conversion treatment was preceded by two nucleation pretreatment processes in the form of physical adhesion and chemical adsorption.The present study focused on the effects of two nucleation pretreatments of silane coupling agent KH-550+nano-SiO_(2)sol process and Ti/Zr surface modification treatment on microstructure and corrosion resistance of PCCs on magnesium alloy Mg-10Gd-3Y-0.4Zr.Results demonstrate that nucleation pretreatment can prefabricate dispersed nuclei on substrate's surface,which significantly enhances the nucleation rate during the initial stage of coating formation,and decreases the crystal size of PCCs.Corrosion resistance of the PPCs was increased by a factor of 4.The Ti/Zr pretreatment demonstrates a superior application perspective due to the ease-of-fabrication and simplicity.展开更多
基金Project(51241001)supported by the National Natural Science Foundation of ChinaProject(ZR2011EMM004)supported by the Natural Science Foundation of Shandong Province,China+1 种基金Project(SKLCP21012KF03)supported by the Open Foundation of State Key Laboratory for Corrosion and Protection,ChinaProject(TS20110828)supported by Taishan Scholarship Project of Shandong Province,China
文摘The influence of phosphating bath at different temperatures on the formation and corrosion property of calcium-modified zinc phosphate conversion coating （Zn-Ca-P coating） on Mg-Li-Ca alloy was investigated. The morphologies, elemental distribution and chemical structures of the coatings were examined via SEM, EPMA, EDS, XRD and FT-IR. The corrosion resistance was assessed by hydrogen evolution, potentiodynamic polarization and EIS. The results show that the coating is composed of single element Zn and ZnO at below 45 ℃;whereas the coatings are predominantly characterized by Zn3（PO4）2·4H2O and small amount of element zinc and ZnO at above 50 ℃. Mg-Li-Ca alloy with Zn-Ca-P coatings prepared at 55 ℃ has the highest corrosion resistance. However, the hydrogen evolution rates of the coatings obtained at 40-50 ℃ is accelerated due to the galvanic corrosion between the imperfection of the single element Zn coating and the Mg substrate.
文摘Globally,vast research interest is emerging towards the development of biodegradable orthopedic implants as it overcomes the toxicity exerted by non-degradable implants when fixed in the human body for a longer period.In this context,magnesium(Mg)plays a major role in the production of biodegradable implants owing to their characteristic degradation nature under the influence of body fluids.Also,Mg is one of the essential nutrients required to perform various metabolic activities by the human cells,and therefore,the degraded Mg products will be readily absorbed by the nearby tissues.Nevertheless,the higher corrosion rate in the biological environment is the primary downside of using Mg implants that liberate H2gas resulting in the formation of cavities.Further,in certain cases,Mg undergoes complete degradation before the healing of damaged bone tissue and cannot serve the purpose of providing mechanical support.So,many studies have been focused on the development of different strategies to improve the corrosion-resistant behavior of Mg according to the requirement.In this regard,the present review focused on the limitations of using pure Mg and Mg alloys for the fabrication of medical implants and how the calcium phosphate conversion coating alters the corrosive tendency through the formation of hydroxyapatite protective films for enhanced performance in medical implant applications.
基金financially supported by National Key Research and Development Program of China (Nos. 2017YFB0103904, 2016YFB0301105)National Natural Science Foundation of China (No. 51804190)+2 种基金Youth Science Funds of Shandong Academy of Sciences (No. 2020QN0022)Youth Innovation and Technology Support Program of Shandong Provincial Colleges and Universities (No. 2020KJA002)Jinan Science & Technology Bureau (No. 2019GXRC030)。
文摘In this study, Mg–6.0Zn–3.0Sn–0.5Mn(ZTM630) magnesium alloy was pre-activated by colloidal Ti, oxalic acid, and phosphoric acid,and a phosphate conversion coating(PCC) was prepared on the alloy surface. The morphology and corrosion resistance of the prepared PCCs were investigated. Surface morphology studies showed that the phosphate crystals that formed the coating were the smallest for the sample pre-activated by phosphoric acid. The coating on the colloidal Ti and the phosphoric acid samples had the largest and the smallest thickness and surface roughness, respectively. The reason for the discrepancy was analyzed by comparing the surface morphologies of alloy samples immediately after the pre-activation treatment and various phosphating treatments. X-ray diffraction analysis revealed that all three PCCs contained the same compounds. The corrosion resistance time from the copper sulfate drop test and the electrochemical data from the potentiodynamic polarization curves showed that the coating pre-activated by phosphoric acid had the best corrosion resistance. Finally, the 1500 h neutral salt spray corrosion test confirmed that the phosphating treated magnesium alloy, which was pre-activated by phosphoric acid,exhibited excellent corrosion resistance and behavior.
基金the National Natural Science Foundation of China(No.52201066 and No.U21A2045)LiaoNing Revitalization Talents Program(NO.XLYC2002071)+2 种基金Gratitude is also expressed to the support from the Shanghai Aerospace Science and Technology Innovation Fund(SAST2020-046)the Fundamental Research Funds for the Central Universities(N2224002-21)the Natural Science Foundation of Shanghai(20ZR1424200).
文摘In order to obtain a more protective phosphate conversion coating with a denser architecture,the nucleation kinetics of phosphate chemical conversion coating on Mg-Gd-Y-Zr magnesium alloy was tuned in this work.A pretreatment process was proposed and organic additives were incorporated,which aims at increasing the ionic produce(J_(sp))at the interface for increasingσ,and decreasing the critical ionic product(J_(C,sp)),respectively.Results prove that the pretreatment of bare alloys in a phosphate bath could increase the ion products of MgHPO_(4)/MnHPO_(4).The addition of benzalkonium chloride could neutralize the charges of crystals,and in turn promote the nucleation kinetics.A denser and more protective conversion coating could consequently be obtained.
文摘The authors regret that due to negligence,the picture was misplaced in the original manuscript,resulting in Fig.6d being incorrectly included.The correct version of Fig.6d is provided below for reference.This error does not affect the conclusions of the study,and we apologize for any confusion it may have caused.
基金Uchchatar Avishkar Yojna(UAY)(Phase II)project(codeIITBBS_004)Prime M inister’s Research Fellows(PMRF)。
文摘Magnesium(Mg)and its alloys are lightweight as well as biocompatible and possess a high strength-to-weight ratio,making them suitable for many industries,including aerospace,automobile,and medical.The major challenge is their high susceptibility to corrosion,thereby limiting their usability.The considerably lower reduction potential of Mg compared to other metals makes it vulnerable to galvanic coupling.The oxide layer on Mg offers little corrosion resistance because of its high porosity,inhomogeneity,and fragility.Chemical conversion coatings(CCs)belong to a distinct class because of underlying chemical reactions,which are fundamentally different from other types of coating.Typically,a CC acts as an intermediate sandwich layer between the base metal and an aesthetic paint.Although chromate CCs offer superior performance compared to phosphate CCs,yet still they release carcinogenic hexavalent chromium ions(Cr^(6+));therefore,their use is prohibited in most European nations under the Registration,Evaluation,Authorization and Restriction of Chemicals legislation framework.Phosphate-based CCs are a cost-effective and environment-friendly alternative.Accordingly,this review primarily focuses on different types of phosphate-based CCs,such as zinc,calcium,Mg,vanadium,manganese,and permanganate.It discusses their mechanisms,current status,pretreatment practices,and the influence of various parameters-such as pH,temperature,immersion time,and bath composition-on the coating performance.Some challenges associated with phosphate CCs and future research directions are also elaborated.
基金financially supported by the China National Major Special Project for the Rare Earth and Rare Metallic Materials(No.(2012)1743)。
文摘The corrosion-resistant coating formed on the surface of sintered Nd-Fe-B magnet by a phosphate chemical conversion(PCC)treatment was studied.The morphology,phase composition and thickness of the coating were investigated by field emission scanning electron microscopy(FE-SEM),energy-dispersive spectrometer(EDS),Fourier transform infrared(FTIR)spectrometer and coating thickness gauge.The corrosion behaviour of the phosphated magnet was evaluated by copper sulphate spot test,neutral salt spray test and electrochemical potentiodynamic polarization experiment.The magnetic properties of the phosphated magnet were also tested.The experimental results show that the phosphate coating has such characteristics as dense granular growth,uniform distribution and thickness range of 10-18μm.The corrosion resistance of the magnet is significantly improved by phosphate coating without losing magnetic properties.Therefore,this highly efficient PCC was a good way for increasing the corrosion resistance of the sintered Nd-Fe-B magnets.
基金Projects (2011CL08, 2011CL01) supported by Open Fund of Material Corrosion and Protection Key Laboratory of Sichuan Province, ChinaProject (2011RC02) supported by Talent Introduction Funds of Sichuan University of ScienceProject (12ZA261) supported by Key Project of Education Department of Sichuan Province, China
文摘A phosphate solution free of chromate, fluoride and nitrite was prepared and an environment-friendly film was obtained on AZ31 magnesium alloy surface via the chemical deposition method. The morphology, composition, phase structure and its corrosion resistance were studied. The effects of film-forming temperature and free acid on corrosion resistance, microstructure and electrochemical behavior of the film were discussed. The results indicate that the corrosion resistance of AZ31 with the phosphate film was better than blank AZ31 substrate, which was most attributed to the great inhibitive action on the anodic dissolution and cathodic hydrogen evolution of the film.
基金financial support from the National Natural Science Foundation of China(51531007 and 51771050)China Postdoctoral Science Foundation(2019M651128)+1 种基金the National Program for Young Top-notch Professionalsthe Fundamental Research Funds for the Central Universities(N170205002)
文摘Cracking and low thickness are major obstacles to the high corrosion performance of conversion coating on magnesium alloy.In this work,the ratio of total acidity to p H(TA/p H)was applied as an indicator,and new principles regarding the design of conversion bath were proposed.The treatment bath should be composed of species that can be categorized into two groups:the first group of species that react with Mg substrate to increase the local p H at the interface;the second group that precipitate and contributes to the growth of coating.The species belong to second group exists in a supersaturated state and its precipitation process is almost independent on the reactions of the species in first group.By this way,a thick and crack-free two-layered conversion coating is obtained.Moreover,the nature of the adjustment of TA/p H and the roles of the oxidizing agent and catalyst were discussed.
基金financially supported by the National Natural Science Foundation of China(Nos.51531007,51771050 and 52201066)the National Program for the Young Top-notch Professionals+3 种基金the Fundamental Research Funds for the Central Universities(Nos.N170205002 and N2224002-21)the Shanghai Aerospace Science and Technology Innovation Fund(No.SAST2020-046)the Natural Science Foundation of Shanghai(No.20ZR1424200)the Natural Science Foundation of Heilongjiang Province(No.LH2020E113)
文摘To improve corrosion resistance of phosphate chemical conversion coatings(PCCs)on magnesium alloy Mg-10Gd-3Y-0.4Zr,a new route was proposed.The phosphate conversion treatment was preceded by two nucleation pretreatment processes in the form of physical adhesion and chemical adsorption.The present study focused on the effects of two nucleation pretreatments of silane coupling agent KH-550+nano-SiO_(2)sol process and Ti/Zr surface modification treatment on microstructure and corrosion resistance of PCCs on magnesium alloy Mg-10Gd-3Y-0.4Zr.Results demonstrate that nucleation pretreatment can prefabricate dispersed nuclei on substrate's surface,which significantly enhances the nucleation rate during the initial stage of coating formation,and decreases the crystal size of PCCs.Corrosion resistance of the PPCs was increased by a factor of 4.The Ti/Zr pretreatment demonstrates a superior application perspective due to the ease-of-fabrication and simplicity.
