Evaluation of the Physicochemical Properties of Passive Layers Produced on NiTi Alloys for Use in the Cardiovascular System

Implants made of NiTi alloy for use in the bloodstream should be characterized by good biocompatibility and hemocompatibility, understood as not exerting a harmful effect on blood morphotic components, and prevention of clot formation. Due to the small size of the implants, electropolishing was used. Next, four methods of NiTi alloy passivation were applied: in boiling water, in boiling $$H_{2}O_{2}$$ , in the autoclave, and in air at temp. 450 $$^{\circ }$$ C. Potentiodynamic impedance, EIS, and wettability tests were used to assess the surface. The results of corrosion resistance tests in the environment of artificial plasma show that there are no significant differences in the methods of passivation compared to electropolishing. Therefore, it can be concluded that already during the electropolishing process a passive layer with very good biocompatibility is produced spontaneously and the use of additional passivation methods does not improve but also does not deteriorate the properties tested.