A compact tension Electropolishing, also known as electrochemical polishing or electrolytic
polishing (especially in the metallography field), is an electrochemical process
that removes material from a metallic workpiece. It is used to polish, passivate,
and deburr metal parts. It is often described as the reverse of electroplating.
It may be used in lieu of abrasive fine polishing in microstructural preparation.
Typically, the workpiece is immersed in a temperature controlled bath of electrolyte
and serves as the anode as it is connected to the positive terminal of a DC power
supply, the negative terminal being attached to the cathode. A current passes from
the anode, where metal on the surface is oxidized and dissolved in the electrolyte,
to the cathode. At the cathode, a reduction reaction occurs, which normally produces
hydrogen. Electrolytes used for electropolishing are most often concentrated acid
solutions having a high viscosity, such as mixtures of sulfuric acid and phosphoric
acid. Other electropolishing electrolytes reported in the literature include mixtures
of perchlorates with acetic anhydride and methanolic solutions of sulfuric acid.
To achieve electropolishing of a rough surface, the protruding parts of a surface
profile must dissolve faster than the recesses. This process, referred to as anodic
leveling, is achieved by a mass transport limited dissolution reaction.[clarification
needed] Anodic dissolution under electropolishing conditions deburrs metal objects
due to increased current density on corners and burrs.
