Many jewellers rhodium plate their white gold as standard, but what is rhodium and why is plated over gold?
Rhodium is another type of precious metal which is part of the platinum group of metals. It has a higher melting point than platinum; it is as equally hard as platinum but is less dense so there for it is lighter. It is actually rarer than platinum, thus being more expensive, but it is only because it is used is such small quantities that rhodium plated gold is a cheaper option to platinum.
White gold is rhodium plated to make it look like platinum, as the natural colour of white gold is slightly different to that familiar bright white look. Pure gold is 24ct and a very rich yellow, this is then alloyed to make it more durable but also to change the colour. In the UK we tend to work with mainly 9ct and 18ct gold, to make the gold appear whiter it is alloyed with white metals such as silver and platinum. Both the 9ct and 18ct white golds have a warmer tone to them when compared to the cold bright white platinum or palladium. Historically the alloys used to make the gold whiter weren’t as successful as they are today so the gold was rhodium plated to look like the fashionable bright white of platinum. Rhodium plating therefore is an aesthetic option for those who do not wish to have a platinum ring.
It is worth mentioning that due to the hallmarking of palladium, another metal from the platinum family, there is now another alternative to having the bright white look of platinum without quite the same expense.
As the plating is only microns thick this means it will wear away, for an engagement ring this is generally first noticeable on the back of the ring as this is the area that will come into contact with more daily wear. The rate of how quickly it will wear away depends on the amount of wear that the plating comes in contact with; it may start to wear off in 3 months but could last for three years on a ring. Rhodium plating will last longer on something that doesn’t get that same amount of wear as a ring like a pendant.
It’s not only white gold that can be rhodium plated silver can also be rhodium plated , this makes the silver have a brighter white finish and the rhodium coating is also tarnish is resistant. Yellow gold can also be rhodium plated to make it look white but as the plating will wear off to reveal the original yellow colour of the gold, also its worth bearing in mind that the plating might not wear off evenly so could reveal patches of yellow.
The rhodium is applied by using the electro-plating process which involves using baths of chemical solutions, rhodium and the item to be plated, a chemical reaction occurs which fuses the rhodium to the surface of the item.