Synthesis and Electrochemical Characterisation of Magnetite Coatings on Ti6Al4V-ELI

© 2020 by the authors.Titanium alloys have been widely employed in implant materials owing to their biocompatibility. The primary limitation of these materials is their poor performance in applications involving surfaces in mutual contact and under load or relative motion because of their low wear resistance. The aim of this work is to synthesis magnetite coatings on the Ti6Al4V-ELI alloy surface to increase corrosion resistance and to evaluate its electrochemical behaviour. The coatings were obtained using potentiostatic pulse-assisted coprecipitation (PP-CP) on a Ti6Al4V-ELI substrate. The preliminary X-Ray Diffraction (XRD) results indicate the presence of the magnetite coating with 8–10 nm crystal sizes, determined for the (311) plane. Using X-ray photoelectron spectroscopy (XPS), the presence of the magnetite phase on the titanium alloy was observed. Magnetite coating was homogeneous over the full surface and increased the roughness with respect to the substrate. For the corrosion potential behaviour, the Ti6Al4V-ELI showed a modified Ecorr that was less active from the presence of the magnetite coating, and the impedance values were higher than the reference samples without coating. From the polarization curves, the current density of the sample with magnetite was smaller than of bare titanium.This research was funded by Instituto Politécnico Nacional, Consejo Nacional de Ciencia y Tecnología (CONACyT), Proyecto SIP 20195816, and Centro Nacional de Investigaciones Metalúrgicas (CENIM-CSIC) Madrid, España supported this project.Peer reviewe

Characterization of modified Ti6Al4V alloy after fretting–corrosion tests using near-field microscopy

Fretting wear and corrosion of Ti6Al4V alloys at the bone/implant stem interface produce the release of wear particles and corrosive ions from the stem into the surrounding tissue that can induce bone resorption. In this work, oxidation treatments at 500° and 700 °C for 1 h have been studied for increasing the friction– corrosion resistance at these interfaces. The friction–corrosion process of thermally treated Ti6Al4V disks against pins of cadaver bone was evaluated in bovine serum medium for 1 million cycles of loading at 4 Hz with maximum contact pressures of 10 MPa. Cyclic displacement of 120 μm for pin-on-disk samples in a linear motion was applied. Samples were characterized, before and after the oxidation treatment, by atomic force microscopy (AFM), scanning Kelvin probe (SKP) and scanning electrochemical microscopy (SECM). The characterization of the Ti6Al4V samples showed the growth and the different morphologies of the oxides as a consequence of the temperature. SKP and SECM revealed that the surface of oxidized samples had lower electrochemical activity than as-received surfaces. After the fretting–corrosion test, the thermally treated samples showed low electrochemical reactivity; specifically oxidation treatment at 700 °C revealed that the rutile scale formed potentially improves the performance of Ti6Al4V in fretting–corrosion against bone.The authors acknowledge the financial support received through the MAT2011-29152-C02-01, MAT2009-13979-C03-02 projects and S-S2009/MAT-1585. E. Onofre would like to thank the financial support from the UNAM and the CSIC through the Scientific Cooperation Program UNAM–CSIC. Postdoctoral fellowships “Simon Bolivar” 2009–2010 and SNI-CONACYT are gratefully acknowledged.Peer reviewe

Synthesis and Characterisation of CeO2 Coatings on the AZ31 Alloy for Corrosion Protection and In Vitro Biocompatibility of MC3T3-E1 Pre-Osteoblasts

The use of bioabsorbable metals as temporary medical implants has attracted considerable research interest as they do not require a second surgical operation for removal after the healing process is completed. However, magnesium (Mg) and its alloys have a degradation rate that is too high in biological environments. Therefore, it must be controlled using various strategies. In this study, an AZ31-Mg-based alloy coated with CeO2 is investigated to analyse the effect of the coating on its corrosion protection and biocompatibility. The AZ31 alloy is anodised with NaOH solution, before coating to stabilise the alloy surface. The CeO2 coating is deposited on anodised AZ31 by chemical conversion treatment. The electrochemical properties of samples are evaluated using electrochemical impedance spectroscopy and cyclic polarisation curves using Hank’s solution. Structural and morphological characterisation of the samples are performed using X-ray diffraction and scanning electron microscopy–energy dispersive X-ray spectroscopy. Additionally, biocompatibility is determined by live/dead assay using MC3T3-E1 pre-osteoblasts. The preliminary results indicate that CeO2 coatings exhibit higher electrochemical properties. Additionally, an increase in the ratio of live/dead cells of the AZ31OH-CeO2 surface is detected, in contrast with AZ31, thus indicating improvement in biocompatibility upon CeO2 coating

Materiales metálicos biodegradables en el campo biomédico.

El campo de los biomateriales ha experimentado un importante cambio de mentalidad durante los últimos años, viéndose impulsada la investigación en nuevos materiales biodegradables y reabsorbibles para la sustitución y regeneración de tejidos. Así, si bien hasta el momento se trataba de sustituir el tejido dañado por un biomaterial que cumpliera con las exigencias del tejido sustituido, actualmente se persigue el desarrollo de nuevos materiales capaces de interactuar con el tejido dañado mediante la estimulación de diferentes respuestas celulares en función de las características superficiales de los mismos, a la vez que son lentamente degradados y reabsorbidos por caminos metabólicos hasta su total desaparición en el organismo, una vez restablecida la función del tejido.Peer Reviewe

Optimisation of the phosphate conversion treatment for generating protective coatings

[ES]En el presente trabajo se estudia el fosfatado como tratamiento de conversión química (TCQ) libre de cromo, partiendo de un estudio básico del fosfatado comercial aplicado por inmersión en soluciones al 100 % y diluciones 1:2, 1:5 y 1:10. Para conseguir un buen recubrimiento de fosfato se determinó el tiempo óptimo de inmersión mediante curvas de potencial a circuito abierto. Las propiedades de protección contra la corrosión se evaluaron mediante medidas de resistencia a la polarización e impedancia electroquímica. La adherencia al sustrato se determinó por ensayos de tracción (pull-off). Los resultados en inmersión continua mostraron que la aplicación de un recubrimiento orgánico sobre el sustrato previamente fosfatado en una dilución 1:5 (10 min) aumenta la resistencia a la corrosión en, al menos, un orden de magnitud con respecto al sustrato no fosfatado, incrementando la adherencia y el tiempo de vida del sistema recubrimiento-sustrato debido a que la película de conversión forma parte integral del sustrato y la superficie generada incrementa el área y número de sitios activos.[EN]This paper evaluates the phosphate treatment as a chemical conversion treatment (CCT) free of chromium, from the basis of the study of a commercial treatment applied in phosphoric solution at different concentrations (100% and dilutions 1:2, 1:5 and 1:10). The optimum immersion time for the phosphate conversion treatment was established from the evolution over time of the open circuit potential. Protection against corrosion of the conversion layers was evaluated by polarisation resistance and electrochemical impedance measurements. The adhesion to the substrate was evaluated by pull-off tests. Results have shown that the application of an organic coating on the substrate with a previous phosphate treatment in 1:5 dilution (10 min.) increases the corrosion resistance in, at least, one order of magnitude with respect to the non phosphate-coated metal and improves the adhesion to the substrate, since the conversion layer obtained is part of the substrate and the surface generated increases the number and area of active sites.Los autores agradecen el apoyo económico del proyecto MAT2008-06719-C03-01. E. Onofre agradece también la ayuda recibida de la UNAM y el CSIC a través del programa científico de cooperación UNAM-CSIC, “Simon Bolivar" postdoctoral 2009- 2010, DGAPA-UNAM. M. Carboneras agradece la concesión de un contrato JAE-Doc otorgada por el CSIC.Peer reviewe

Characterization of roughness and pitting corrosion of surfaces modified by blasting and thermal oxidation

The blasting process generates a renewed surface on the surface of metallic biomaterials with a different topography and a different chemical composition. The impact of particles on the metallic surface increases both the surface roughness and susceptibility pitting corrosion. The aim of this work is to smoothen the sharp edges of blasted Ti6Al4V alloy surfaces by means of oxidation treatment and the evaluation of their susceptibility to pitting corrosion after this thermal oxidation. Oxidation treatments were performed at 500 and 700°C for 1h on samples blasted with SiO2/ZrO2 and Al2O3 particles. Compositional, microstructural and topographical characterization of the blasted surfaces were carried out by scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDAX), and atomic force microscopy (AFM). The surface reactivity and corrosion behaviour of the samples were assessed by scanning Kelvin probe (SKP) and by anodic polarization curves. The susceptibility to pitting corrosion of the Ti6Al4V blasted surfaces becomes higher as roughness increases. The oxidation treatment of the Ti6Al4V blasted surfaces causes the presence of nuclei of oxides that cover the area free of particles, especially in the samples treated at 700°C, giving rise to a higher micro-nano roughness. The presence of the oxide, covering the blasted Ti6Al4V, decreases the surface reactivity leading to a lower passive current and wider pasivation region, decreasing the susceptibility to pitting corrosion. © 2010 Elsevier B.V.Peer Reviewe

Electrochemical Assessment Of Steel Concrete Reinforced System Modified whit Natural Fiber for ITS Anticorrosion Protection

The deterioration in the steel-concrete structures is mainly due to chloride contamination, which causes corrosion problems that occasionally leads its partial or total destruction. In this work we propose adding fibers bagasse of sugar cane to the steel-concrete reinforced system. with the objective of provide the corrosion protection. Meanwhile, the sugar cane bagasse is the residue fibrous lingo-cellulosic remaining after grinding stalks the sugar cane at the mill to extract the juice

EVALUACIÓN ELECTROQUÍMICA DE RECUBRIMIENTOS BIOCOMPATIBLES OBTENIDOS POR CONVERSIÓN QUÍMICA SOBRE LA ALEACIÓN Ti6Al4V UTILIZADA COMO BIOMATERIAL

El campo de los biomateriales ha cobrado gran importancia, debido a que este tipo de materiales sustituye y/o modifica la anatomía del ser humano. Sin embargo, los implantes metálicos que actualmente son utilizados se ven mermados debido a que en presencia de fluidos biológicos pueden desencadenar reacciones de oxidación, provocando la liberación de iones agresivos para el cuerpo humano disminuyendo el tiempo de vida del implante y en la mayoría de los casos se requiere de una nueva operación para remplazar la pieza dañada. En este trabajo se evalúan las propiedades anticorrosivas de recubrimientos de óxido de lantano generados a partir de tratamientos por conversión química sobre la aleación Ti6Al4V. Un tratamiento térmico de recocido se aplicará para obtener TiO2 con una estructura rutilo, la cual debido a su estabilidad brindará una protección extra antes de aplicar el recubrimiento; la película de La2O3 se obtendrá haciendo inmersión de la muestra en una solución de LaCl3. El recubrimiento obtenido se evaluará mediante la técnica de difracción de rayos X, para corroborar que sobre la superficie esté presente el La2O3 y mediante técnicas electroquímicas (resistencia a la polarización, potencial a circuito abierto e impedancia electroquímica) se determinará la velocidad de corrosión de estos materiales. Resultados preliminares de DRX, demuestran que sobre la superficie del Ti6Al4V sin tratar se encuentran el TiO2 con una mezcla de estructuras rutilo y anatasa; por otra parte, la muestras fueron sometidas a tratamientos térmicos a temperatura de 800° C, obteniéndose sobre la superficie solo TiO2 en su fase rutilo