Effect of added porosity on a novel porous Ti-Nb-Ta-Fe-Mn alloy exposed to simulated body fluid

Abstract

Porous titanium materials have gained interest as prosthesis materials due to their similar mechanical propertiesto the human bone, biocompatibility, and high corrosion resistance. The presence of pores in the metal matriximplies a decrease in the elastic modulus and an increase in the active area, perhaps improving the osseointegration.Corrosion resistance is a critical consideration as corrosion may lead not only to mechanical failure butalso the release of ions and/or particles to the bloodstream. In this work, a novel Ti-Nb-Ta-Fe-Mn alloy withvarying percentage of porosity (25, 31 and 37 v/v%) was exposed to simulated body fluid (SBF) at 37 °C and itscorrosion resistance was investigated using electrochemical techniques and surface analysis as a function ofexposure time. Open circuit potential and polarization curves revealed that the effect of porosity was mainly onthe shift of the corrosion potential to more negative values with a slight increase in the anodic current. A passiverange was also observed, which was not influenced either by increased exposure time or increased porosity.Therefore, a change in the surface specific area could have taken place during the exposure, which is not necessarilyrelated to a corrosion process. Moreover, a typical porous electrode behavior was identified by electrochemicalImpedance spectroscopy, without any significant change over time. No release of metal ions wasdetected by on line ICP-AES, either at the open circuit potential or upon polarizing the samples up to 2 V vs. SCE,whereas only traces elements (Fe and Mn 1 nmol/s cm2) were detected in the electrolyte accumulating allreleased ions during 30 days of exposure. Additionally, the surface analysis showed thickening of the oxide layerwith exposure time. Therefore, the stability of the passive layer and low release of ions indicate that the porousalloys are suitable for further study as prosthesis materials.