Electroplating is widely used in industry and decorative arts to improve the surface qualities of objects—such as resistance to abrasion and corrosion, lubricity, reflectivity, electrical conductivity, or appearance. It may also be used to build up thickness on undersized or worn-out parts, or to manufacture metal plates with complex shape, a process called electroforming. It is also used to purify metals such as copper.
The term “electroplating” may also be used occasionally for processes that use an electric current to achieve oxidation of anions on to a solid substrate, as in the formation of silver chloride on silver wire to make silver/silver-chloride electrodes.
Electropolishing, a process that uses an electric current to remove metal cations from the surface of a metal object, may be thought of as the opposite of electroplating
The strength of polished products can be higher than their rougher counterparts owing to the removal of stress concentrations present in the rough surface. They take the form of corners and other defects which magnify the local stress beyond the inherent strength of the material.
Electroplating changes the chemical, physical, and mechanical properties of the workpiece. An example of a chemical change is when nickel plating improves corrosion resistance. An example of a physical change is a change in the outward appearance. An example of a mechanical change is a change in tensile strength or surface hardness which is a required attribute in tooling industry. Electroplating of acid gold on underlying copper- or nickel-plated circuits reduces contact resistance as well as surface hardness. Copper-plated areas of mild steel act as a mask if case hardening of such areas are not desired. Tin-plated steel is chromium-plated to prevent dulling of the surface due to oxidation of tin.