Electroplating
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 cathode (negative) of the circuit while an electrode typicaly of the same metal to be plated forms the anode (positive). When an electrical current is passed through the circuit, metal ions in the solution are attracted to the item. The result is a layer of metal on the item however considerable skill and craft-technique is required to assure an evenly-coated finished product. 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 for functional and/or decorative purposes.
Some well known examples are chrome-plating of steel parts on automobiles. Steel bumpers become more corrosion-resistant when they have been electroplated with first nickel and then chromium.
Steel camshafts resist wear better when they have been electroplated with chromium.
Plain steel or aluminum parts in light fixtures become beautiful when they are electroplated with nickel and then decorative chromium or brass.
Steel bolts last much longer because they are sold with a coating of zinc that has been applied by electroplating.
Electroplating 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 radio frequency 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 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 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 Birmingham England from where it spread around the world.
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