The electrochemical surface modification of nitinol for inhibition of nickel elimination

• A.I. Shcherbakov, I.V. Kasatkina, I.G. Korosteleva, V.E. Kasatkin, L.P. Kornienko and V.N. Dorofeeva

A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Leninsky pr. 31, 119071 Moscow, Russian Federation

Abstract: Nitinol, an alloy with a shape memory effect, is used in many high-tech developments, in particular in medicine as self-expanding material for vascular endoprostheses, stents, etc. However, a high nickel content in the alloy may be undesirable for biocompatibility and therefore requires the use of certain processing products to reduce the rate of formation of Ni²⁺ as a result of corrosion processes in the presence of alloy with body tissues. To solve this problem, the possibilities of Nitinol electrochemical treatment based on the different rates of dissolution of the alloy components from the surface layer were investigated. The processes of potentiostatic etching of NiTi in sulphate solutions, which provide selective dissolution of one alloy component and accumulation of another one in the surface layer, have been investigated. Using the polarization curves methods and the electrochemical impedance spectroscopy, it has been discovered. The possibility of selective etching of nickel from the surface layer of Nitinol with the simultaneous formation of titanium dioxide is shown. The high insulating properties of TiO₂ film formed on the alloy surface as a result of oxidation at a controlled potential, inhibits the release of nickel from the surface layer and the accumulation of Ni²⁺ ions in a corrosive, like the physiological solution.

Keywords: Nitinol, selective dissolution, passivation, impedance, protection

Int. J. Corros. Scale Inhib., 2019, 8, no. 3, 726-732 PDF (521 K)
doi: 10.17675/2305-6894-2019-8-3-19

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