In vitro corrosion behaviour of Ti-Nb-Sn shape memory alloys in Ringer's physiological solution

Area of Science:

• Biomaterials Science
• Materials Science
• Electrochemistry

Background:

• Nitinol (Nickel-Titanium) is widely used in medicine for its shape memory properties.
• High nickel content in Nitinol raises concerns regarding allergic, toxic, and carcinogenic reactions.
• There is a need for biocompatible alternatives to Nitinol in biomedical applications.

Purpose of the Study:

• To investigate the in vitro corrosion behavior of Ti-Nb-Sn alloys.
• To compare the corrosion resistance of Ti-Nb-Sn alloys with Nitinol.
• To evaluate the potential of Ti-Nb-Sn alloys as biomedical materials.

Main Methods:

• In vitro corrosion resistance assessment in Ringer's solution at 37°C.
• Electrochemical measurements including corrosion potential, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization.
• Analysis of EIS spectra using an equivalent electrical circuit model for oxide film structure.

Main Results:

• Both Nitinol and Ti-Nb-Sn alloys form spontaneous passive oxide films in Ringer's solution.
• Ti-Nb-Sn alloys exhibit lower anodic current density and no breakdown of passivity compared to Nitinol.
• EIS studies reveal high impedance values for Ti-Nb-Sn alloys, increasing with exposure time, indicating improved corrosion resistance.
• The passive film on Ti-18Nb-4Sn alloy shows the highest resistance, suggesting superior corrosion protection.

Conclusions:

• Ti-Nb-Sn alloys demonstrate superior in vitro corrosion resistance compared to Nitinol.
• The enhanced corrosion resistance is attributed to a stable, duplex-structured passive oxide film.
• Ti-Nb-Sn alloys are promising candidates for biomedical applications, offering a safer alternative to Nitinol.