Electroplating is the coating of an electrically conductive item with a layer of metal using electrical current. The result is a thin, smooth, even coat of metal on the object.

Process

The process used in electroplating is called electrodeposition. The item to be coated is placed into a container containing a solution of one or more metal salts. The item is connected to an electrical circuit, forming the anode or the cathode of the circuit. When an electrical current is passed through the circuit, metal ions in the solution are attracted to the item. The result is an evenly-coated layer of metal around the item. This process is analogous to a galvanic cell acting in reverse.

The plating is most commonly a single metallic element, not an alloy. However, some alloys can be electrodeposited, notably brass.

Industrial use

Electroplating is used in many industries. It can be used to silver plate copper or brass electrical connectors, since silver tarnishes much slower and has a higher conductivity than those metals. The benefit of the silver is lower surface electrical resistance resulting in a more efficient electrical connection. Silver plating is also popular for RF connectors because RF current flows primarily on the surface of its conductor; the connector will thus have the strength of brass and the conductivity of silver.

History

Modern history

Modern electroplating was invented by Italian chemist Luigi V. Brugnatelli in 1805. Brugnatelli used his colleague Alessandro Volta's invention of five years earlier, the voltaic pile, to facilitate the first electrodeposition. Unfortunately, Brugnatelli's inventions were repressed by the French Academy of Sciences and did not become used in general industry for the following thirty years.

By 1839, scientists in Great Britain and Russia had independently devised metal deposition processes similar to Brugnatelli's for the copper electroplating of printing press plates. Soon after, John Wright of Birmingham, England discovered that potassium cyanide was a suitable electrolyte for gold and silver electroplating. Wright's associates, George Elkington and Henry Elkington were awarded the first patents for electroplating in 1840. These two then founded the electroplating industry in England from where it spread around the world.

Prehistory

A number of artifacts known as the Baghdad Battery were found near Baghdad, Iraq, and were speculated to have been crude galvanic cells used for electroplating. The exact age of the artifacts is not known, but they are believed to be either Parthian or Sassanian. The theory that they were used for electroplating is not widely held today, even by those who believe that the artifacts were in fact electrical devices.

Miscellaneous

One of American physicist Richard Feynman's first projects was to develop technology for electroplating metal onto plastics. Feynman successfully developed this technology, allowing his employer to keep commercial promises he had made but couldn't have fulfilled otherwise.

On June 28, 1988, four workers at an electroplating plant in Auburn, Indiana were asphyxiated by hydrogen cyanide gas produced when muriatic acid was mixed with zinc cyanide in a cleaning operation. A fifth victim died two days later.

Related topics

• gilding
• electropolishing
• anodization

External links and sources

Electrochemistry Encylclopedia article