In this work,a method to improve the protection against corrosion of porous sintered stainless steel is presented.It is based on the electrodeposition of polypyrrole(PPy)layers doped with a large size counterion such ...In this work,a method to improve the protection against corrosion of porous sintered stainless steel is presented.It is based on the electrodeposition of polypyrrole(PPy)layers doped with a large size counterion such as dodecylbenzenesulphonic acid(DBSA),a conducting polymer with high corrosion resistance and good biocompatibility.The efficacy of PPy coating depends on the adequate adhesion between the metal substrate and the coating layer.The protection against corrosion has been tested using 316 L stainless steel(SS)powder sintered at different conditions to evaluate the effect of the sintering atmosphere(nitrogen and vacuum)and cooling rates(furnace and water)on corrosion resistance,while wrought 316 L SS has been used as reference material.In addition,two electrochemical deposition techniques have been tested to select the most adequate.Open circuit potential evolution,anodic polarization measurements and electrochemical impedance spectra have been used to evaluate corrosion protection in phosphate buffer saline medium.It has been evidenced that a more homogeneous and stable coating was obtained in the case of porous stainless steel.The corrosion potential shifted to nobler values and the anodic polarization branch became more stable.Coated porous samples have a good passivation performance with a lower stable passive current density and a higher breakdown potential.The transfer electronic resistance and the impedance module increase more than one order of magnitude.Therefore,the porosity of sintered stainless steel is seen as an advantage for the improvement of the adherence of the PPy coatings.The best corrosion protection is found for samples sintered in nitrogen and water-cooled.展开更多
Medical implants manufactured using biomaterial Ti–6Al–4V exhibit some disadvantages.Its higher elastic modulus than that of natural bone can cause stress shielding problems.This can be avoided using Ti–6Al–4V wit...Medical implants manufactured using biomaterial Ti–6Al–4V exhibit some disadvantages.Its higher elastic modulus than that of natural bone can cause stress shielding problems.This can be avoided using Ti–6Al–4V with pores in the implant structure.However,poor corrosion and tribocorrosion behaviors are yielded because of the large area exposed to the medium.To mitigate both issues,coating technologies can be applied.The plasma electrolytic oxidation(PEO)process is a cost‐effective process that has been used successfully in nonporous Ti alloys.In this study,two PEO coatings with different amounts of Ca/P are used.However,reports regarding their application in porous materials are scarce.The effects of PEO treatments on corrosion and tribocorrosion in Ti–6Al–4V powder metallurgy are analyzed herein.The porous materials provide an efficient surface for PEO coatings,as demonstrated via scanning electron microscopy(SEM)and atomic force microscopy(AFM),and the porosity of the substrates improved the adherence of the coatings.The corrosion resistance measured via electrochemical impedance spectroscopy confirmed the beneficial effect of the coatings,particularly for long exposure time.The lower roughness,small pore size,and more compact film observed in the PEO–Ca/P sample resulted in favorable tribological and corrosion properties.展开更多
基金financially supported by the MINECO-FEDER(No.AGL2015-67482-R)the Junta de Castilla y Leon and FEDER(No.VA275P18)Junta de Castilla y León for a grant(BOCYL-D-4112015-9).
文摘In this work,a method to improve the protection against corrosion of porous sintered stainless steel is presented.It is based on the electrodeposition of polypyrrole(PPy)layers doped with a large size counterion such as dodecylbenzenesulphonic acid(DBSA),a conducting polymer with high corrosion resistance and good biocompatibility.The efficacy of PPy coating depends on the adequate adhesion between the metal substrate and the coating layer.The protection against corrosion has been tested using 316 L stainless steel(SS)powder sintered at different conditions to evaluate the effect of the sintering atmosphere(nitrogen and vacuum)and cooling rates(furnace and water)on corrosion resistance,while wrought 316 L SS has been used as reference material.In addition,two electrochemical deposition techniques have been tested to select the most adequate.Open circuit potential evolution,anodic polarization measurements and electrochemical impedance spectra have been used to evaluate corrosion protection in phosphate buffer saline medium.It has been evidenced that a more homogeneous and stable coating was obtained in the case of porous stainless steel.The corrosion potential shifted to nobler values and the anodic polarization branch became more stable.Coated porous samples have a good passivation performance with a lower stable passive current density and a higher breakdown potential.The transfer electronic resistance and the impedance module increase more than one order of magnitude.Therefore,the porosity of sintered stainless steel is seen as an advantage for the improvement of the adherence of the PPy coatings.The best corrosion protection is found for samples sintered in nitrogen and water-cooled.
基金Financial support by Ministry of Education and Science(RTI2018‐097990‐B‐I00)the Junta de Castilla y Leon(VA275P18 and VA044G19)is gratefully acknowledged.
文摘Medical implants manufactured using biomaterial Ti–6Al–4V exhibit some disadvantages.Its higher elastic modulus than that of natural bone can cause stress shielding problems.This can be avoided using Ti–6Al–4V with pores in the implant structure.However,poor corrosion and tribocorrosion behaviors are yielded because of the large area exposed to the medium.To mitigate both issues,coating technologies can be applied.The plasma electrolytic oxidation(PEO)process is a cost‐effective process that has been used successfully in nonporous Ti alloys.In this study,two PEO coatings with different amounts of Ca/P are used.However,reports regarding their application in porous materials are scarce.The effects of PEO treatments on corrosion and tribocorrosion in Ti–6Al–4V powder metallurgy are analyzed herein.The porous materials provide an efficient surface for PEO coatings,as demonstrated via scanning electron microscopy(SEM)and atomic force microscopy(AFM),and the porosity of the substrates improved the adherence of the coatings.The corrosion resistance measured via electrochemical impedance spectroscopy confirmed the beneficial effect of the coatings,particularly for long exposure time.The lower roughness,small pore size,and more compact film observed in the PEO–Ca/P sample resulted in favorable tribological and corrosion properties.
