CORROSION OF NITINOL IN HANKS` SOLUTION AND SODIUM CHLORIDE AT ROOM TEMPERATURE

Nitinol is a superelastic and shape-memory alloy having various applications including production of vascular stents and surgery implants¹. Since a device inserted into a living body is impacted by corrosion, a study of its corrosion behavior in physiological liquid media is of the great importance.

Nitinol wires were immersed into Hanks` Balanced Salts Solution² and into 3% NaCl at room temperature until stable corrosion potentials were achieved. After that Electrochemical Impedance, Small Amplitude Linear Sweep Polarization and Large Amplitude Linear Sweep Polarization measurements were performed and Impedance Spectra, Linear Polarization Resistance plots and Tafel plots were built. Corrosion parameters, namely corrosion potentials and current densities were calculated. Surface morphologies before and after a corrosion test were compared.

It was found that nitinol is more noble in Hank’s solution that in sodium chloride. On the other hand, corrosion current densities are similar in both kinds of media and the average corrosion current density is 0.09 μA/cm². Plausible equivalent circuit hints that the metal surface is covered by a non-continuous layer of corrosion products.

1. T. Duerig, a Pelton, and D. Stöckel, Mater. Sci. Eng. A, 273–275, 149–160 (1999).
2. J. H. Hanks, J. Cell. Comp. Physiol., 31, 235–260 (1948).