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Development and screening of(Ca-P-Si-F)-PEO coatings for biodegradability control of Mg-Zn-Ca alloys

Journal of Magnesium and Alloys 2022年第8期10卷 2220-2237页

作者： Lara Moreno Marta Mohedano Raul Arrabal Endzhe Matykina Departamento de Ingeniería Química y de Materiales Facultad de Ciencias QuímicasUniversidad Complutense de Madrid28040 MadridSpain

PEO coatings were developed on MgZnxCayalloys for biomedical applications using different treatment times and a novel transparent electrolyte containing Ca,P,Si and F.Surface characteristics and chemical composition of studied materials were evaluated using scanning electron microscopy,X-ray diffraction and optical metrology.Corrosion investigations were performed for uncoated and coated materials using potentiodynamic polarization,electrochemical impedance spectroscopy and hydrogen evolution measurements in three media(0.9wt.%NaCl,α-MEM and inorganic part ofα-MEM).Findings revealed that Zn-rich intermetallics favour the formation of large voids in the coatings.Ca,P,F and Si are successfully incorporated into the coatings.Coatings consist of crystalline phases(Mg O,Mg F_(2)and Ca,Si-rich compounds)and amorphous material.Aminoacids and organic components ofα-MEM solution accelerate corrosion of the bare substrates but have no significant influence on the corrosion resistance of coated specimens.Therefore,inorganicα-MEM can be considered as an appropriate medium for fast screening of PEO coatings.The relatively small amount of F content in the barrier layer facilitates early failure of the coatings,which show undercoating corrosion.Zn-rich intermetallic particles in the undercoating crevice induce a more aggressive corrosive environment and enhanced micro-galvanic couple effect with the Mg matrix.This leads to faster degradation of the coated alloys compared to the bare substrates.

关键词： Magnesium Biomaterials Plasma electrolytic oxidation Corrosion

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As-cast and extruded Mg-Zn-Ca systems for biodegradable implants:Characterization and corrosion behavior

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Journal of Magnesium and Alloys 2023年第3期11卷 1102-1120页

作者： Lara Moreno Endzhe Matykina Kiryl A.Yasakau Carsten Blawert Raul Arrabal Marta Mohedano Departamento de Ingeniería Química y de Materiales Facultad de Ciencias QuímicasUniversidad Complutense de Madrid28040 MadridSpain Department of Materials and Ceramic Engineering CICECO-Aveiro institute of materialsUniversity of Aveiro3810-193 AveiroPortugal Institute of Surface Science Helmholtz-Zentrum HereonMax-Planck Strasse 1Geesthacht 21502Germany

The aim of the present study is to evaluate the effect of alloy processing and composition as well as the pH control and testing medium on the in vitro corrosion performance of Mg-Zn-Ca systems for biodegradable implants.The grain size and secondary phases were analyzed by optical microscopy,scanning electron microscopy,transmission electron microscopy,and X-ray diffraction.Scanning kelvin probe force microscopy(SKPFM)was used to analyze the Volta potential values of the second phases.The corrosion performance of the three alloys was evaluated by electrochemical and hydrogen evolution methods inα-MEM with and without organic species(i.***.complete and inorganicα-MEM).Two strategies were followed to evaluate the influence of the pH on the corrosion behavior:daily solution replacement and CO_(2)flow based pH control.For all the materials,the organic medium accelerates the corrosion process.Constant pH maintained by CO_(2)flow through the medium results in considerably higher corrosion rates for all alloys.The impact of pH is lesser on the as-cast alloys due to the barrier effect of the secondary phases,particularly pronounced in the Mg1Zn1Ca alloy which showed the lowest corrosion rate.The wrought Mg0.5Zn0.2Ca alloy that lacks the refined secondary phase network and exhibits high number of twins undergoes accelerated uniform corrosion under constant pH conditions.

关键词： MgZnCa Magnesium Biomaterials Characterization Corrosion

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Quasi-in vivo corrosion behavior of AZ31B Mg alloy with hybrid MWCNTs-PEO/PCL based coatings

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Journal of Magnesium and Alloys 2022年第11期10卷 3217-3233页

作者： Morteza Daavari Masoud Atapour Marta Mohedano Hugo Mora Sánchez Juan Rodríguez-Hernández Endzhe Matykina Raul Arrabal Aboozar Taherizadeh Department of Materials Engineering Isfahan University of Technology84156-83111 IsfahanIran Departamento de Ingeniería Química y de Materiales Facultad de Ciencias QuímicasUniversidad Complutense28040 MadridSpain Institute of Polymer Science and Technology(CSIC) Polymer Functionalization GroupMadrid 28006Spain

This study investigated the effects of multi-walled carbon nanotubes(MWCNTs) and polycaprolactone(PCL) on the quasi-in vivo corrosion behavior of AZ31B Mg alloy treated by plasma electrolytic oxidation(PEO). Thin(~2 μm, PCTPCL4) and thick(~60 μm, PCTPCL6) PCL layers were applied only onto the MWCNTs-PEO coating(PCT) as it showed better corrosion performance. Findings reveal that incorporation of MWCNTs induced several structural and functional modifications in the PEO coating, such as increased roughness, a thicker inner barrier layer, and reduced hydrophilicity.Quasi-in vivo corrosion testing was carried out under controlled temperature, p H, and fluid flow in simulated body fluid(SBF) by electrochemical impedance spectroscopy(EIS) and hydrogen evolution experiments. EIS results revealed that, after 48 h immersion, a diffusion process controlled hydration of the ceramic coatings. Comparison of the collected hydrogen after 15 days of immersion in the quasi-in vivo environment revealed that the PEO and PCT ceramic coatings decreased hydrogen generation by up to 74% and 91%, respectively, compared to non-coated alloy.PCTPCL6 coating exhibited the lowest amount of collected hydrogen(0.2 m L/cm^(2)). The thick PCL layer delayed the onset of substrate corrosion for at least 120 h, reducing the corrosion rate by 85% compared with the PCT.

关键词： AZ31B Mg alloy Plasma electrolyte oxidation(PEO) Multi-walled carbon nanotubes(MWCNTs) Quasi-in vivo condition Polycaprolactone(PCL)

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