Rhodium is a precious white metal that is often used to plate jewelry. It was discovered in 1803 by English chemist, William Hyde Wollaston in South America after his discovery of palladium. Rhodium is a by-product of platinum mining and platinum, copper and nickel refining. The main commercial use for rhodium is in catalytic converters for cars. It is also alloyed with other metals to improve thermo resistance and corrosion resistance. The name, "rhodium" comes from the Greek word for rose, "rhodon". This is because rhodium salts make a pink aqueous solution.
Since rhodium is brittle, extremely rare and expensive, it is not worked into jewelry by itself. Rhodium is used for plating (also called "flashing") and is extremely attractive because of its bright, white color and mirror shine. This makes rhodium plating popular for white gemstone jewelry, because the finish of the rhodium is almost as dazzling as the white gems, and therefore enhances the jewels. Rhodium plating can be used on silver and platinum jewelry. The surface layer of rhodium plating is not as bright as highly polished silver, but it remains bright where silver tarnishes over time. It is for this reason that silver is rhodium plated; to protect it from tarnishing. White gold jewelry is often rhodium plated to achieve a bright, white color.
An advantage of rhodium-plated jewelry is that it is hypoallergenic, so it prevents some of the problems caused by sensitivity to certain metal alloys, such as those containing nickel. But when the plating wears down, the metal beneath can irritate the wearer if it contains nickel. The downside with rhodium-plated white gold is that the plating will wear off over time, and the jewelry will become more yellow. Since white gold is an alloy that contains yellow gold, pure white gold jewelry is not as white as rhodium-plated white gold. This is why rhodium plating is used to gain brighter jewelry. The whiter the underlying metal, the less wear will show. The durability of rhodium-plated jewelry depends on the individual, the thickness of the plating and the amount of wear and tear. Once the plating wears away, the jewelry can be replated. The thicker the layer of rhodium, the longer the plating will last. However, if rhodium plating is too thick, it can render the metal brittle. Jewelry items like rings are likely to show signs of wear a lot sooner than pieces like pendants, earrings and brooches. Old jewelry is sometimes revived with rhodium plating, which can turn a discarded jewelry item into a more modern, wearable piece.
When it comes to rhodium-plated colored gemstone jewelry, to ensure that the plating adheres properly to the surface of the jewelry, the jewelry should be meticulously cleaned beforehand. The plating is best performed before the jewelry is assembled and the gemstones are set. This ensures that the rhodium coats every surface evenly. Also, some colored gemstones are sensitive to certain chemicals, acid and heat, therefore, it is advisable not to leave the stones in the jewelry when plating. To care for rhodium-plated jewelry, clean it with a soft cloth and mild detergent. Avoid scrubbing or the use of harsh chemicals, which can wear down the plating.
While rhodium is prized for its bright, white color, and mirror shine, like gold and other alloys, it can also be mixed with other materials such as tin sulfate, tellurium oxide and arsenic trioxide, to turn it black. Black rhodium plating is popular in modern jewelry because of its alternative look. Black rhodium plating is a good choice for gems such as boulder opal.
If you are planning to buy white metal gemstone jewelry, especially a wedding or engagement ring, it is worth learning about the different materials on offer and the advantages and disadvantages of all. Rhodium-plated jewelry is recommended for those who like bright, shiny white metal and are not adverse to having jewelry replated now and again to maintain its lustrous beauty.
- First Published: October-16-2015
- Last Updated: December-15-2017
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