What is rhodium plated sterling silver ?
It is common to see rhodium silver jewelry for sale online.
Unfortunately, internet users often don't know what rhodium silver is.
So here is a definition and an explanation of what rhodium is and why we use it in jewelry.
Rhodium plating with a brush
Definition of rhodium plated
18-karat white gold signet ring (vivalatina collection)
The rhodium-plated jewels are rings, chains or bracelets having been covered with a thin layer of rhodium, a precious metal having the property of protecting the silver of the chemical agents responsible for its blackening, namely the sulfur compounds present in the air and on the skin.
The thickness of the deposited layer can vary from 1 to 5 microns according to international standards and the manufacturer. It will be impossible to control for the buyer.
Example of electrolytic bath surface treatment (Source: Cookson-clal)
Rhodium is electrolytically deposited on silver and gold jewelery to protect them and maximize their brightness in light, thanks to the reverberation properties of this metal.
What is rhodium ?
Left, rhodium ore. Right, chemical symbol and physical data of ore
Rhodium is a rare and extremely expensive platinum-group metal discovered in 1803.
We produce about 20 tons a year worldwide and its price was around 30,000 euros per kilogram in 2013.
We find it only in mines in the Urals, in Canadian Ontario or South Africa. It is mainly used by the automotive industry (90% of global consumption) in catalytic exhaust systems.
Silver rhodium jewelery is therefore brighter and whiter than the classic silver jewelry that interacts with its environment and darkens over time.
However, the rhodium layer is not eternal and changes with frictions, friction and shocks, leaving the silver naked. The lifespan of the rhodium layer on a jewel depends on the thickness of the deposit and the care given to the jewel.
Extra cost of a jewel due to its layer of rhodium
A jewel in rhodium silver costs more than a classic silver jewel. The density of this metal is 12.4. Take the example of a single silver ring size 8 and 8 mm wide, 19 mm inside diameter and 21 mm outside.
The ring has a surface of 1000 mm2, so a volume of 1mm3 of rhodium to treat the ring with a layer of 1 micron of this metal. This corresponds to 0.08 g of this metal which costs nearly 30 euros per gram.
Therefore, it will cost 2.41 euros of rhodium to cover the ring of this precious metal. If the rhodium layer was five microns, it would cost 12 euros rhodium
This calculation does not take into account the industrial cost of the treatment but it gives you an idea of the price that can represent the rhodium of your jewelry.
What to choose, rhodium plated or bare silver ?
Electronic machine for rhoding
It depends on your tastes.
The rhodium treated jewel will stay with a new look without much longer than an untreated jewel.
If you like to maintain your jewelry and see them evolve over time, to see them take contrasts of different colors depending on the hollows of your jewelry, then natural silver jewelry will completely satisfy you.
The ancient jewels have evolved from a gleaming silver aspect to an aspect of glare tarnished silver but just as beautiful.
Otherwise you can also get in touch with your jeweller and ask him to rhodium plate your silver jewelry.
More information :
- Check this article about rhodium plating and white gold
- Article on how to recycle silver to pure silver
- Article on silver melting
- Article on 999 silver in Mexico