Corrosion resistance of TiN coated biomedical nitinol under deformation

The corrosion resistance of nitinol with and without a titanium nitride coating is electrochemically investigated at 37 °C in artificial plasma. The electrochemical experiments show that the titanium nitride (TiN) coating can increase the stable potential from 0.95 to 1.5 V versus a saturated calomel electrode and reduce the corrosion current density from 0.20 to 0.10 mA/cm2. The valence of the dissolved titanium and nickel ions is plus two. At deformation less than 6%, no significant negative effects on the corrosion resistance of the TiN coated nitinol is observed. More deformation causes cracks in the TiN coatings and consequently, the corrosion resistance degrades slightly, but it is still better than that of the uncoated nitinol since no galvanic corrosion is observed from the broken areas.