Electropolishing

Permanently implantable medical devices such as stents and filters use electropolishing as a critical final surface finishing step.

While mechanical processes may polish and chemical processes may passivate, electropolishing does both. When electropolishing, the metal work piece is connected to the positive terminal of a DC power supply and immersed in a temperature controlled bath of electrolyte. The negative terminal of the power supply is attached to a separate electrode in the bath. When voltage is applied, current flows through the bath removing material from the work piece. It is this material removal that polishes the work piece.

The imperfections inherent to micromachining nitinol may negatively affect the performance and reduce the service life of a particular device. Subsequently, electropolishing is often critical to the functionality of the final Nitinol device. In nitinol this process removes surface imperfections while creating a thin uniform titanium oxide layer (TiO2) that improves biocompatibility and reduces corrosion. The nearly nickel-free TiO2 layer of electropolished Nitinol has been shown to be an excellent source of corrosion protection.

Electropolishing benefits stainless steel parts in ways similar to nitinol, but the mechanisms are different. Instead of a titanium oxide layer being formed, the corrosion improvements come from the removal of free iron from the surface of the material.

Our experienced engineers understand that there are different electropolishing requirements for different medical devices. We work with our customers on their unique electropolishing needs, which range from minimal material removal to micro-polished surfaces. Minimal material removal may refer to as little as 10% material removal, while micro-polishing the surface of a part may exceed 40% material removal. However, both of these values may vary greatly depending on the type of material and geometric configuration of the device. Please contact Pulse Systems and let our experienced engineers work with you on your specific needs.

Materials:

• + Nitinol, Stainless Steel, Cobalt Chromium

Tolerance:

• + Exceptional repeatability and predictability

Benefits:

• + Removes slag, machining artifacts, and heat affected zones (HAZ) that result from thermo-cutting processes (e.g., laser, and EDM machining)
• + Eliminates surface irregularities
• + Rounds sharp edges
• + Improves performance characteristics of Nitinol parts
• + Dramatically enhances corrosion resistance
• + Improves surface reflectivity and brightness
• + Provides the most superior form of passivation of Stainless Steels and Nitinol
• + Removes metallic and non-metallic inclusions introduced by manufacturing