Electropolishing of implants for medical technology
Electropolishing of medical products such as implants, stents and medical instruments decreases surface roughness. This process quickly and efficiently reduces roughness peaks, edges and angles. Another effect is fine deburring on the entire surface area, which inhibits the ability of dirt and germs to adhere to the processed component. We use this method to treat surgical instruments and implants in our Medical Surface Center. The smooth surface makes it easier to remove temporary implants after bone regeneration, for example. Electropolishing also increases the strength, corrosion resistance and therefore the service life of components that are subject to mechanical stress because it makes it possible to remove stress cracks and structural changes from the surface. On top of this, reducing microroughness creates a glossy surface.
Electropolishing – areas of application
How it works: Electropolishing for treating implants
Electropolishing is an electrochemical process, whereby the parts to be treated are anodically connected in a galvanic bath. Direct voltage is applied and electric field lines develop between the cathode and the anode (i.e. the parts). The electric field lines are most common at the surface peaks, where they attack the parts locally and flatten the surface.
This makes electropolishing an abrasive process. The chemical constitution of the electrolyte removes the metal, which remains dissolved in the electrolyte once separated from the surface. This process rounds sharp peaks, yet some surface unevenness remains and can even become more visible after electropolishing.
However, chromium, which is vital for stainless steel passivation, is harder to dissolve. It accumulates on the surface and, together with the oxygen on the anode, forms a thick layer of chromium oxide on the part, which increases the resistance to corrosion. Also known as electrolytic passivation. Electropolishing also removes foreign metal impurities, which is why electropolishing can be seen as a type of electrolytic cleaning too.
Electropolishing technology for implants and medical instruments
Electropolishing involves establishing a contact with the parts in the appropriate positions across a titanium anode rack that is then inserted into the electrolyte and energized in a direct current circuit. It can be carried out at a predefined current density, whereby the duration of the process dictates how much metal is removed. The process can also be performed by specifying a defined voltage and time. The advantage of this approach is that the surface of the parts does not need to be known. However, we do need to determine the required voltage and electropolishing duration for this process in pilot tests. As electric field lines for electropolishing need to develop between the surface to be treated and the cathode, shielded areas such as cavities can be treated only with additional cathode configurations.