Abstract
The objective of the present study was to evaluate the corrosion resistance of the experimental alloy Ti-35Nb-7Zr-5Ta, modified by laser beam, in a physiological solution of 0.9% NaCl. This evaluation was carried out by open circuit potential analysis (EOCP), potentiodynamic polarization curves and cyclic polarization curves. The open circuit potential curves show the specimen irradiated by laser beam at 35 Hz presented a more stable and corrosion resistant surface. It was observed in the polarization curves, low current densities in the order of nA /cm2, for all specimen indicating an expected passive behavior for the investigated alloy. The cyclic polarization curves show that for specimen treated with laser, the potential for repassivation (Er) is greater in relation to the potential for corrosion (Ecorr), which indicates greater resistance to corrosion of metal alloys when treated with laser.
Highlights
For dental and orthopedic applications, titanium has a successful history for use in biomaterials due to its biocompatibility
Considering the metallic components used in implantable devices are constantly subjected to aggressive means, the study corrosion is fundamental importance for the understanding its performance and functionality, when applied clinically.(Lopes et al, 2016; Paital & Dahotre, 2009) Corrosion resistance is evaluated as a vital property for these applications, considering corrosion products are responsible for biocompatibility, since they can produce undesirable reactions to the organism.(De Assis et al, 2006; Trivinho-Strixino, F; Santos, J S; Sikora, 2017) Studies carried out by Chai et al and Lopez et al, showed the development of new low-toxicity, vanadium-free Ti-based alloys, such as Ti-7Nb-6Al, Ti-13Nb-13Zr and Ti-15Zr-4Nb, for use as biomaterials, demonstrating the spontaneous formation an oxide layer in contact with air.(Chai et al, 2008; López et al, 2001)
It is observed in the untreated specimen - there is initially a decrease in the open circuit potential attributed to the dissolution of the native oxide layer on the alloy surface, adsorption of chloride ions, dissolution of alloy elements and changes in ion concentrations on the surface and oxygen. (Silva et al, 2017) After 20 min the Eocp value starts to rise, due to the formation of a passive layer of titanium oxide
Summary
For dental and orthopedic applications, titanium has a successful history for use in biomaterials due to its biocompatibility. Considering the metallic components used in implantable devices are constantly subjected to aggressive means, the study corrosion is fundamental importance for the understanding its performance and functionality, when applied clinically.(Lopes et al, 2016; Paital & Dahotre, 2009) Corrosion resistance is evaluated as a vital property for these applications, considering corrosion products are responsible for biocompatibility, since they can produce undesirable reactions to the organism.(De Assis et al, 2006; Trivinho-Strixino, F; Santos, J S; Sikora, 2017) Studies carried out by Chai et al and Lopez et al, showed the development of new low-toxicity, vanadium-free Ti-based alloys, such as Ti-7Nb-6Al, Ti-13Nb-13Zr and Ti-15Zr-4Nb, for use as biomaterials, demonstrating the spontaneous formation an oxide layer in contact with air.(Chai et al, 2008; López et al, 2001). The modification the surface can promote improvement the corrosion resistance the material, increase of the bioactivity characteristic of the titanium oxides formed spontaneously on the surface, presenting promising results in the interaction with the tissue, since the biocompatibility (inertiality or bioactivity) is determined by chemical processes occur at the interface between the prosthesis and the living tissue.(Capellato, 2020; Chen et al, 2013; Geetha et al, 2009; Mohammed et al, 2015; Rungsiyakull et al, 2010) One of the most promising surface modifications is laser beam irradiation, a technique that consists of providing a large irregularity on the surface the material in a '' clean '' manner to create a morphology with a large specific area and physical properties-chemicals suitable for promoting the interaction of apatites and providing the formation of a great diversity of oxides aiming induce the phenomenon of osseointegration more effectively and satisfactorily.(Queiroz et al, 2013; Valente, 2017) Some researchers, in a study using Nd; YAG lasers, found that implants with surfaces modified by laser beam, present better and more stable fixation to the bone in relation to the machined ones, and attributes this characteristic to the oxidation process of the surface contributing to a favorable way for the osseointegration process, providing increased hardness and corrosion resistance, as well as improved wettability and increased free surface energy.(Filho et al, 2011; Laurindo, Lepienski, Amorim, Torres, Soares, 2018)
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