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Electropolishing is a process that uses an electric charge to finish or remove damage from a metal object. It's similar to electroplating, but is used to remove material from metal rather than adding it. This process may be used to polish metal, remove surface finishes, or prep the material for refinishing. Electropolishing is often referred to as the inverse of electroplating, and can even be used to remove metal coatings that were previously added through an electroplating process.
During electropolishing, a metal object must be placed into a barrel filled with an electrolyte-based solution, such as sulfuric acid. A metal cathode is also placed into the solution. When a direct current is run into the cathode, it acts as a conductor and sends a charge into the electrolyte solution. This electric charge leads to rapid oxidation of the metal. All finish materials on the surface of the metal dissolve, and are drawn to the cathode or left in the solution.
Electropolishing serves as an alternative to traditional blasting or grinding techniques. During blasting, sand or some other media is sprayed onto metal at high pressure to polish and remove finishes. Grinding require a great deal of labor to clean finishes off of metal using hand tools.
This process is often used to prepare objects for painting by removing impurities, rust, and existing coatings. It can also be used to add shine or polish to dull metal finishes. Electropolishing is also used to create a durable, long-lasting finish on tools, fasteners, and consumer goods.
One of the primary advantages to electropolishing is that it works on objects of many different shapes and sizes. By adding these objects to a large barrel, a large quantity of materials can be finished or polished at once, saving time and labor costs. This process is also beneficial because it leaves the surface of the material unchanged at the molecular level, allowing the object to maintain its natural strength.
Electropolishing tends to be more expensive than other processes in terms of upfront investment. This process also can't remove surface damage, such as seams, which can easily be removed through grinding. Finally, electropolishing may create an uneven finish or be ineffective on certain types of metal alloys. This could result in some dull surfaces on a polished object, or an object that remains unchanged after the process is complete.