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Advanced Biomaterials and Devices in Medicine
December 2014, Volume 1, Issue 1, pp 46-52
Corrosion resistance of silicon-modified nitinol in artificial physiological solutions
A.I. Lotkov1*, S.G. Psakhie1,2, L.L. Meisner1,3, A.V. Korshunov4, S.N. Meisner1,3, V.M. Diamant5
1 Institute of Strength Physics and Materials Science, Siberian Branch, Russian Academy of Sciences, Tomsk, 634021 Russia
2 Skolkovo Institute of Science and Technology, Skolkovo, 143025 Russia
3 National Research Tomsk State University, Tomsk, 634050 Russia
4 National Research Tomsk Polytechnic University, Tomsk, 634050 Russia
5 Lithotech Medical Ltd., Katzrin, 12900 Israel
* Corresponding author: Prof. Aleksandr I. Lotkov, e-mail: lotkov@ispms.tsc.ru
Abstract
Electrochemical methods were used to investigate the corrosion resistance of nitinol specimens modified with silicon by ion implantation (fluence 2  1017 ions/cm2). After ion beam treatment, nickel concentration in the surface layer is significantly reduced up to 20 nm deep and a silicon-containing layer is formed at the depth of 10...80 nm with the maximum concentration of 30 at % at the depth of 30...35 nm. The breakdown (pitting) potential Eb of such NiTi–Si specimens in 0.9% NaCl physiological solution and in artificial blood plasma is ~0.9 V (Ag/AgCl/ KCl sat.) which is much higher than Eb of test specimens subjected to mechanical, chemical or electrochemical treatment. It is shown that under potentiostatic conditions at Eb the NiTi–Si specimen surface is stable to failure and does not exhibit pitting, spotting or microcracking. The comparison of corrosion test results with the cyclic voltammetry data for NiTi, Ti and Ni as well as with thermodynamic calculations demonstrates that the surface of the modified NiTi–Si specimens has enhanced stability with respect to the release of nickel ions into solutions.
Keywords: nitinol, ion implantation, silicon-modified surface, artificial physiological solutions, corrosion
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