Thinking about rhodium plating for your engagement ring or other piece of jewellery?
Rhodium is a member of the platinum metals family – which includes rhodium, palladium, ruthenium, osmium, iridium, and platinum.
Rhodium is one of the whitest metals. While not that hard of a metal in its natural state, rhodium becomes extremely hard when the molecules are layered during the electroplating process. In fact it rates at around 475HV on the custom engagement rings Vickers Hardness Test, while 14k white gold unplated is 165HV.
Plating consists of dipping a ring or other piece of jewelry into a rhodium salts bath. The ring is then charged with negative ions. The bath is charged with positive ions. The rhodium from the salt bath is then able to be transferred to the surface of the ring/jewelry.
While it definitely has it’s uses, rhodium can wear off in a year or two since the coating is thin, so re-plating may be necessary. The proper thickness of plating is about 1 micron. In comparison, a strand of hair is 100 microns. Costs can be from $50-$100 to re-plate rhodium plate jewellery. There is no doubt that rhodium significantly improves the appearance and scratch resistance of 14k and 18k white gold.
Why is this important?
I want you all to know why certain rings are less expensive, and thus more enticing to the consumer. The nickel in lower karat white gold is what makes the gold harder, more brittle, and white. Nickel is also a known cause of allergies and skin irritation – but rhodium plating can create a shield to block the nickel from touching your skin..
Most mass produced white gold jewelry that has a lower nickel high copper content. The resulting alloy can be quite yellowish, but since it causes few problems with manufacturing and stone setting, it is tolerated. The resulting metal is also very ductile or easy to bend, making it easier to manipulate. So the question was how to market this somewhat yellowish metal to the consumer. A thin layer of the rhodium plating was the solution – turning these once yellowish rings to an ultra white. Nickle again can cause some skin irritations, yet rhodium is an inert substance. This means that the thin layer of rhodium forms a barrier that stops the chances of metal allergies(unless the rhodium wears off).
Some client’s tell me that their engagement ring is “turning yellow” at the bottom where the rhodium has worn off. We educate them about the difference between custom jewellery alloys and mass produced alloys. The cleaning process requires that all of the rhodium be sanded off. The ring must then be sized, re-polished, then re-rhodium plated for an added cost.
We are still happy to offer this service, but for those of you shopping for an engagement ring, 19k white is a little whiter than un-plated 14k white gold. Some clients still prefer that we also rhodium plate both 19k and platinum, because of the superior hardness and whiteness.