Affiliations: Biomedical Engineering Institute, Biomechanics/Biomaterials Research Group | Department of Engineering Physics, Groupe des Couches Minces | Department of Metallurgy, École Polytechnique de Montréal, P.O. Box 6079, Succ. “Centre-Ville”, Montreal (Quebec), Canada H3C 3A7
Note: [] Corresponding author: L'Hocine Yahia, Biomedical Engineering Institute, Biomechanics/Biomaterials Research Group, École Poly technique de Montréal, P.O. Box 6079, Succ. “Centre-Ville”, Montreal (Quebec), Canada H3C 3A7. Tel.: +15143404378; Fax: +15143404611; E-mail: [email protected].
Abstract: NiTi Shape Memory Alloys (SMA) are potential biomaterial candidates for medical devices such as osteosynthesis staples. However, Ni dissolution induced by uniform or localized corrosion could lead to toxicity. In this work, plasma polymerized tetrafiuoroethy1ene (PPFTE) coating is used to improve the corrosion resistance of NiTi plates and corresponding NiTi staples. The scratch test indicates a good surface adhesion of the film but that it lacks cohesiveness. Potentiodynamic tests in physiological Hank's solution show that PPTFE coating improved the pitting corrosion resistance. The passivation range is increased from 35% to 96% compared to the untreated sample and the pit diameter is decreased from 100 μm to 10 μm. The uniformity of the deposited film is a very important parameter. When the film is damaged, the corrosion seems to increase in comparison to the untreated samples. Otherwise, if the staple is carefully manipulated, the coating follows the large deformations induced by the memory effect of the alloy without cracking, and then, protects efficiently the staple from pitting.
