What is Electropolishing? – Process, Advantages and Applications

An electrochemical process that removes material from a metallic workpiece is known as electropolishing. It is also known as electrochemical polishing or electrolytic polishing.

Electro-polishing uses a combination of rectified current and a blended chemical electrolyte bath to remove flaws from the surface of a metal part. Electropolishing is often described as the reverse of electro-plating.

Process of Electropolishing

The schematic arrangement for the electropolishing is shown in the figure.

In electro-polishing, the metallic 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 of the DC power supply is connected to the cathode. An electric current passes from the anode to the cathode and the metal on the surface of anode is oxidized and dissolved in the electrolyte. At the cathode, a reduction reaction takes place which generally produces hydrogen.

Normally, the electrolytes used for electro-polishing are concentrated acid solutions having a high viscosity like mixtures of sulfuric acid and phosphoric acid.

Once the process is completed, the metallic part is run through a series of cleaning and drying steps to remove the clinging electrolyte. The resultant surface is clean and bright.

Advantages of Electropolishing

Following are some of the advantages of using Electropolishing −

  • It increases the resistance to corrosion.

  • Provides attractive appearance to the metallic surface.

  • It provides improved surface finishing.

  • Reduces the product adhesion and hence provides ease of cleaning.

  • Electropolishing simultaneously deburrs and polish the surface.

Applications of Electropolishing

The major applications of electropolishing are listed below −

  • Electropolishing is widely used in the metal finishing industry because of its simplicity and it can be applied to objects of complex shape.

  • Electropolishing is used for polishing of ultra-high vacuum components in order to have a smoother surface for improved vacuum pressure and pumping speed.

  • Electropolishing is also applied to the preparation of thin metal samples for transmission electron microscopy.

  • The stainless steel drums of washing machines and the stainless steel surgical devices are typically electro-polished.