Rhodium is an element in the platinum family known for its resistance to tarnish and corrosion. Some people experience allergic reactions when they wear rhodium-plated jewellery, however. While rhodium is unlikely to cause an allergy, the fairly reactive white and coloured gold underneath may produce allergic symptoms.
Rhodium is bright and shiny under nearly all environmental conditions. Despite its high cost, rhodium is effective for plating because it preserves white gold and coloured gold pieces beyond their normal lifespan. Rhodium-plated jewellery is resistant to scratching and abrasion, and the metal is hyopallergenic.
While allergies to rhodium do not usually occur, allergies to coloured or white gold are common. These gold alloys generally include significant amounts of nickel, a metal to which many people are sensitive. According to the Better Than Diamond website, about 20 per cent of women have a nickel allergy. Since rhodium is porous, nickel may come into contact with the skin, causing itchiness, redness and rashes.
Rhodium plating can make jewellery that contains nickel wearable for some people. Not all pieces are suitable, though. Certain types of jewellery, such as earring posts and wedding rings, suffer from enough daily wear that the plating wears through quickly. Even though rhodium is abrasion resistant, it may eventually become thin enough to allow nickel to contact the skin. Necklaces, bracelets, and rings, which are worn less often, may be candidates for rhodium plating, though.
Rhodium is an extremely expensive material--four times the cost of platinum and nine times the cost of gold. Beware of inexpensive white or coloured gold jewellery, which may be non-plated or have a thin coating of rhodium, which allows more exposure to nickel. You should consider replating jewellery, or choose platinum jewelery over white gold if the cost of rhodium plating is too high.
Some people believe they can detect nickel in rhodium plated white gold using a magnet. This method is used when there's a concern about nickel passing through the rhodium plating. While nickel is technically magnetic, it is the least responsive of the three magnetic minerals, making this test ineffective. There is no sure test for nickel in jewellery alloys. The best option for those wishing to avoid nickel in rhodium plated jewellery is to shop only at reputable jewellers, or to choose metals which are never formulated with nickel.