Effect of ePTFE sintering post processing steps on surface quality and pitting corrosion behavior of NiTi stents

Expanded polytetrafluoroethylene (ePTFE) as a bio-inert barrier cover on NiTi stents has been broadly used in recent years at medical industries. Using ePTFE prevents or delays the tissue ingrowth within the stent and therefore maintains luminal patency for longer periods after initial stent deployment. ePTFE cover normally sinters on the electropolished NiTi bare stent via applying pressure/heat. However, effect of sintering process on the surface quality of NiTi stent and consequently pitting corrosion behavior is not fully understood. In the present study, effect of different sintering temperature (250-550 C), times (10-60 min), strain and furnace atmosphere (air, Ar and vacuum) on the corrosion behavior of the electropolished NiTi stents will be investigated. The surface quality of the stents will be also characterized using scanning electron microscope. Preliminary results show that sintering the stents in the air furnace degrades the corrosion behavior (lower breakdown potential) compared with as-electropolished NiTi stent.