Precious Metals: White Gold jewelry
White Gold
Source: Man-Made Alloy
The term "white gold" is a bit of a misnomer, as it is actually an alloy of gold combined with so-called "white" metals such as silver, palladium, or nickel. The "natural" color of white gold after it is alloyed is a light grey that is slightly yellow. Jewelry made of white gold is actually coated (electroplated) with highly reflective rhodium or platinum and palladium mixture which adds a brilliant shine, and "white" color to the metal's surface.
White gold is usually plated with a thin layer of rhodium, 0.05 to 0.5 micrometers in thickness. The purpose of plating the surface is to add luster to the white gold alloy, as well as to prevent oxidation of some of the metals found in the alloy itself. White gold is a less expensive alternative to platinum, and usually costs about 1/3 as much as platinum.
Creating the white gold alloy |
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Due to the thinness of this protective plating, wear will develop in the plating which could eventually cause oxidization to form. This will weaken the rhodium coating even more. For higher-quality jewelry the white gold alloy is typically plated with about 2.0 micrometers of rhodium for longer lasting, and more durable finish.
In the ancient world, the name "white gold" was used to describe the naturally-occurring free-metal alloy known as electrum, which is a combination of gold, silver, and trace amounts of copper.
Allergic Reactions to White Gold
About 12.5% of the population is allergic to the white gold alloy. This is due to a reaction to the nickel found in some white gold alloys. Reactions are typically mild and usually involve minor skin rashes. For people who are sensitive to white gold, palladium is a good hypoallergenic alternative.
White gold alloy is a soft metal which has a hardness of 2.5 on the Mohs scale, with a Vickers Hardness (VHN or HV) of 120. White gold has a melting point of around 1064.18 C (1947.52 F or 1337.33 K).
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