Saturday, February 22, 2014

Rhodium Plated Sterling Silver: What Is Rhodium?

A lovely etsian sent me an email today and said they were confused, because I described a bracelet as Sterling Silver but also Rhodium plated.

Rhodium plated fine jewelry (like Sterling Silver) is SO common  that I never realized that there could be any confusion. It never occurred to me!  I know I've seen Rhodium plated (and gold plated) base metal chains and hydrangea leaf charms and things all over etsy (which are given a "flash" of Rhodium or gold), but I never really thought that people might not realize that fine PRECIOUS metals are also Rhodium plated. So I thought I'd explain it here.

Rhodium is the most expensive metal on Earth.  It is used to plate high-end jewelry made of Sterling Silver, White Gold and even Platinum.  It provides a very high, and very lustrous finish and helps prevent oxidation (tarnish) on Sterling Silver.

Some lower-end jewelry such as brass is sometimes Rhodium plated to give it the look of high-end jewelry.  Rhodium plated brass will look just like white gold or Sterling Silver, but will not be hallmarked.  Sterling is always hallmarked "925" or "Sterling" by law, and gold is hallmarked by karat (10k, 14k, 18k, etc.).

What is Rhodium?

Rhodium is a chemical element that is a rare, silvery-white, hard, and chemically inert transition metal and a member of the platinum group. It has the chemical symbol Rh and atomic number 45.  It has a very high melting point at 3,565°F. 

It is one of the most expensive metals, at almost twice the price of platinum and three to four times the cost of gold. Rhodium has an extremely high reflectivity and doesn't normally form an oxide, even when heated.

Because rhodium is a "noble metal" and inert, it withstands corrosion and makes Sterling Silver and White Gold more durable as well.

Additionally, rhodium is hypoallergenic. White gold and even sterling silver employ nickel to provide the whiteness of white gold, however, approximately 20% of women will have some form of allergy to nickel. Thus, by rhodium plating, a possible allergen is removed from contacting your skin. 

Why Is Sterling Silver Often Rhodium Plated? 

Pure silver (99.99% silver) is very soft and scratches easily and is too soft to hold gemstones. Other metals, mostly copper, is alloyed with pure silver to form Sterling Silver.  Sterling is hallmarked .925 indicated that it is, by law, 92.5% pure silver, and 7.5% copper (or occasionally nickel). 

Rhodium plating can dramatically increase the long term durability, brightness and luster of the finish.  Rhodium plated sterling silver will remain tarnish-free for a longer period of time than unplated sterling silver.

Why Is White Gold and Platinum JewelryAlso Rhodium Plated?

White gold is an alloyed metal--mixing yellow gold with nickel or other metals to achieve a whiter look.  However, it still has a slightly yellow cast.  To achieve the brightest finish, particularly on engagement and wedding rings, all white gold is Rhodium plated.  This also enhances the diamonds or gemstones set in the white gold, and provides a hypoallergenic finish (since a large number of people are sensitive to nickel).  Platinum jewelry ils also Rhodium plated.  That seems strange, but platinum is rough-looking and more grey, a little bit like a new nickel, and plating it with Rhodium gives it that very shiny and bright, smooth look.

Does it Wear Off?

Yes, Rhodium will eventually wear off, especially on everyday rings like a wedding or engagement ring.  However, it's easily re-plated and jewelers recommend replating jewelry every 3 or 4 years.  The cost is about $45 to replate with Rhodium, and the original luster is returned.  Keep in mind that Rhodium plating will not eliminate dents and scratches but it will  make the jewelry more shiny and bright and more expensive looking.