This video explains what electropolishing is and how electropolishing equipment works to remove burrs and polish parts.
Electropolishing is an electrochemical finishing process that removes a thin layer of material from a metal part, typically stainless steel or similar alloys. The part is immersed in a temperature controlled bath of electrolyte (typically mixtures of sulfuric acid and phosphoric acid) and the part serves as the anode as it is connected to the positive terminal of a DC power rectifier, and the negative terminal of the rectifier is attached to the cathode which is typically made from titanium or other alloys which do not dissolve during the electropolishing process.
As the rectifier applies current, it passes from the anode to the cathode by way of conduction through the part. Throughout this process, the part surface area metal is dissolved in the electrolyte. This process can be tightly controlled to dissolve extremely small amounts of part surface area resulting in micron level thickness of part surface area.
Since the electrical conduction occurs evenly over the entire part surface area, the electropolishing process typically removes the most surface area per unit volume which is typically burrs and other scratches.
The electropolishing process may improve a surface finish by up to 50% and sometimes more. The electropolishing reaction removes material while it improves surface roughness, but since it removes material, electropolishing process runtimes are minimized to maintain dimensional tolerances. Since electropolish systems improve a surface on the microscopic level, macroscopic textures or surface scratches will only result in a smoother texture or smoothed scratch. Mass finishing is utilized to remove macroscopic surface imperfections.
How much material is removed by electropolish systems?
The amount of material that is removed by electropolish systems is directly proportional to the runtime / cycle time and the amp-minutes that pass through the surface area of the part. All of these variables can be controlled to create a very consistent, reliably controlled surface finish. Material removal is commonly only to 0.0003″ to 0.0007″ for most deburring and polishing applications after machining operations. For an electropolishing process with longer cycle time and amp-minutes, as much as 0.003″-0.005″ of material may be removed depending on process conditions. It is always important to review the dimensional tolerances of a component before it is electropolished and either machine the part oversized to accommodate material removal or dimensionally tolerance the part with electropolishing material removal rates in mind.