Atomic Layer-Deposited Al2O3 Coatings on NiTi Alloy
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Atomic layer deposition is introduced as a method suitable for preparation of Al2O3 layers on the surface of NiTi medical devices such as stents because of the excellent thickness control and conformal protective coating on complex structures. The corrosion properties of NiTi plates with Al2O3 coatings of various thicknesses in an environment similar to that occurring in the human body were studied using open circuit potential, potentiostatic electrochemical impedance spectroscopy, and cyclic polarization tests. It shows that the layer thickness plays a key role in the inhibition of corrosion. The thinner layers are more diffuse and make it easier for anodic reaction of passive NiTi with protective TiO2 underneath of Al2O3, while the thicker layers have the barrier effect with local pores initiating pitting corrosion. The results of our electrochemical experiments consistently show that corrosion properties of thick Al2O3 coatings on NiTi plate are inferior compared to the thin layers.
KeywordsALD Al2O3 coating corrosion NiTi
The authors from Institute of Physics of the ASCR acknowledge the support of SmartNets project of the 7th Framework and the support by the Grant Agency of the Czech Republic Under Contract No. 101/09/0702.
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