What is Rhodium Plating?
Rhodium finds use in jewelry and for decorations. It is electroplated on white gold and platinum to give it a reflective white surface at time of sale, after which the thin layer wears away with use. This is known as rhodium plating or rhodium flashing in the jewelry business. It may also be used in coating sterling silver to protect against tarnish, which is silver sulfide (Ag2S) produced from the atmospheric hydrogen sulfide (H2S). Solid (pure) rhodium jewelry is very rare because the metal has both a high melting point and poor malleability, making such jewelry very hard to fabricate — rather than due to its high price. Additionally, its typically higher cost assures that most of its jewelry usage is in the form of tiny amounts of powder, commonly called rhodium sponge, dissolved into electroplating solutions.
Rhodium has also been used for honors or to signify elite status, when more commonly used metals such as silver, gold or platinum were deemed insufficient. In 1979 the Guinness Book of World Recordsgave Paul McCartney a rhodium-plated disc for being history's all-time best-selling songwriter and recording artist.
The primary use of this element is in automobiles as a catalytic converter, which changes harmful unburned hydrocarbons, carbon monoxide, and nitrogen oxide emissions from the engine into less noxious gases. Of 30,000 kg of rhodium consumed worldwide in 2012, some 24,300 kg (81%) went into and 8,060 kg recovered from this application. About 964 kg of rhodium was used in the glass industry, mostly for production of fiberglass and flat-panel glass, and 2,520 kg in the chemical industry.
