The ASTM F2129 test standard is used to assess the corrosion resistance of small metallic implants or components. Devices which might be evaluated by this test method include endovascular stents, clips, filters, and other metallic implants.
Passivation of stainless steel is a chemical process for the removal of iron contamination from the surface. This process does not significantly affect the bulk of the stainless steel but provides for the formation of a passive protective film. Passivation is commonly utilized to improve the corrosion resistance of stainless steel components used in medical devices.
Passivation of Nitinol, like that of stainless steel, also alters the surface of the material without significantly affecting the bulk material properties. However in this case, passivation is achieved through formation of a protective oxide layer.