If you’ve ever needed to treat metals and metal surfaces, you may have had to choose between mechanical polishing or electropolishing, especially for stainless steel. At that time, you might have asked yourself: what are the differences between mechanical polishing and electropolishing, and in which cases is it better to choose one treatment over the other? Let’s start from the beginning and try to understand how these two treatments work to provide an answer.
Mechanical Polishing or Electropolishing? The Differences
Mechanical polishing, also known as mechanical finishing, and electropolishing or electrochemical polishing are two completely different treatments despite the similarity in their names. Mechanical finishing, whether in the process of polishing or satin finishing, involves the use of abrasive cloths on a surface to remove (mechanically, of course) part of the material to achieve the desired surface roughness. Electropolishing, on the other hand, is a chemical and not a mechanical treatment that removes a superficial layer from a material, eliminating every tiny imperfection through the principle of electrolysis.
These treatments can also be performed sequentially on the same piece, but it all depends on the goal: mechanical polishing aims to achieve a mirror finish (and, if required, a well-defined surface roughness), while electropolishing is a treatment that makes every surface cleaner and more protected by improving the roughness profile and helping to form a protective passive layer: the treated surface becomes extremely resistant to biological and chemical attacks. For this reason, electropolishing is an excellent treatment for stainless steel.
Mechanical Polishing and Electropolishing, Application Sectors
There are some sectors where both electropolishing and mechanical polishing treatments are used together. An example? The pharmaceutical field, where there is first a need to achieve a very low roughness starting from possibly very rough sheets (thus with significant material removal) and then the need to intervene with electropolishing to make the surface even more hygienic and protected thanks to the chromium oxide that naturally forms on stainless steel surfaces. Electropolishing indeed accelerates the production of chromium oxide to create it in abundance for a thicker layer. This passive layer also results homogeneous and uniform through this process, preventing the formation of iron oxides in aggressive environments that could lead to corrosion even in alloys with high chromium and nickel content.
Some other examples? Mechanical polishing is common in the industrial manufacturing or furniture sectors where it is essential to achieve an aesthetically pleasing result. In the ice cream machine industry, for instance, electropolishing can be done without any prior mechanical treatment and serves to make the surface of the machinery resistant to corrosive attacks from chlorinated components (in this case, salt) harmful to stainless steel. Another example is the aerospace industry, where vacuum chambers for satellite testing need extreme cleanliness and reflectivity that only electropolishing can provide.
Electropolishing, the Advantages
There are various reasons or situations for preferring electropolishing over mechanical polishing:
- Cost-effectiveness: Sometimes electropolishing is preferred over mechanical polishing for economic reasons.
- Suitability for complex artifacts: The electrochemical treatment is also used when the tools and abrasives for mechanical polishing cannot reach areas of the artifact that are fully accessible by the electric current.
- Protection against aggressive agents: A perfectly smooth surface benefits and protects any artifact, from railings to fences, from urban furniture elements to a pharmaceutical tank.
In short, the advantages are many: the key is perfect coordination between the company producing the artifact and the company performing the treatment, perhaps already in the engineering or design phase, to avoid problems. We can help you with this: contact us for a consultation!
