Investigation of the corrosion resistance of a Ti alloy functionalized with silver nanoparticles.

Titanium and its alloy, specifically, are extensively used in particular applications such as dentistry, orthopaedic devices and bone fixation systems. Ti-6Al-4V is a principal titanium alloy used in implants for its good mechanical properties, high flexibility and strength, biocompatibility, and corrosion resistance. Despite the really high corrosion resistance of the material, implant failures due to corrosion problems are presented. Since physiological liquid is not an environment to consider welcoming for an implanted metal alloy, in the biomedical field, corrosion represents a big issue as it leads to the release of ions and particles in peri-implant tissue which may result in inflammation, material degradation until the necessary extraction of the prosthesis. In addition to the corrosion, bacterial infections represent another critical factor which could affect the success of the implant. The use of silver like alternative solution has been taken into consideration, as it ensures antimicrobial properties of the material to avoid infections and the necessity of a prolonged antibiotic therapy. It could however also influence the good corrosion resistance of Titanium in a negative way, by a galvanic coupling. Therefore, This thesis has the aim to study the corrosion behaviour and the metal release of this alloy, with a surface treatment to improve the biocompatibility and a functionalization with nanoparticles of silver. To mimic the physiological environment samples were exposed in a physiological solutions based on PBS with varying H2O2 and bovine serum albumin concentrations at a constant temperature of 37°C. Electrochemical, metal release tests have been carried out, accompanied by a careful analysis of surface characterization. The results were as follows: The electrochemical test demonstrated that Ti6Al4V treated superficially had a higher corrosion resistance than Ti6Al4V not treated and the presence of nanoparticles of silver could affect the corrosion behaviour in the more corrosive ambient. The metal release test demonstrated that a big amount of Aluminium was released from the samples treated superficially and the release of Silver was not controlled but it happened all at once, things that could have toxic effect for the body. The surface characterization shew that functionalization of silver have not been successful since the surface presented agglomerated of the order of micrometers and unevenly distributed.