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Improvement of the Corrosion Resistance of NiTi Stents by Surface Treatments

Published online by Cambridge University Press:  10 February 2011

C. Trépanier
Affiliation:
GRBB, Biomedicai Engineering Institute, École Polytechnique de Montréal, CANADA
M. Tabrizian
Affiliation:
GRBB, Biomedicai Engineering Institute, École Polytechnique de Montréal, CANADA
LH. Yahia
Affiliation:
GRBB, Biomedicai Engineering Institute, École Polytechnique de Montréal, CANADA
L. Bilodeau
Affiliation:
Institut de Cardiologie de Montréal, CANADA
D. L. Piron
Affiliation:
Department of Material Engineering, École Polytechnique de Montréal, CANADA
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Abstract

Because of its optimal radiopacity, superelasticity and shape memory properties Nickel-Titanium (NiTi) is an ideal material for the fabrication of stents. Indeed, these properties can facilitate the implantation and precise positioning of those devices. However, in vitro studies on NiTi report the dependency of the alloy biocompatibility and corrosion behavior to surface treatments. Oxidation of the surface seems to be very promising to improve both the corrosion resistance and the biocompatibility of NiTi. The present study investigate the effect of electropolishing, heat treatment (in air and in a salt bath) and nitric acid passivation to modify the oxide layer on NiTi stents. Techniques such as potentiodynamic polarization tests, Scanning Electron Microscopy (SEM) and Auger Electron Spectroscopy (AES) have been used to develop relationships between corrosion behavior, surface characteristics and surface treatment. Results show that all surface treatments improve the corrosion behavior of the alloy. SEM results indicate that treated stents which exhibit a smooth and uniform surface show a higher corrosion resistance than non treated stents which possess a very porous oxide layer. AES results, indicate that the best corrosion behavior was observed for the stents which exhibit the thinnest oxide layer (electropolished and passivated samples).

Type
Research Article
Copyright
Copyright © Materials Research Society 1997

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