About Rhodium Plating & 14K Gold Filled June 06 2013
Also called rolled-gold. These jewelry items are not actually filled with gold. They are made of a base metal (usually brass or copper) covered by sheets of gold in a mechanical bonding process. Effectively a thick coat of gold: the gold content is 5% or 1/20 of the total weight. Use gold-filled items for your top-of-the-line jewelry. Usually made with 14k gold, it is hard wearing. With reasonable care it will not peel or flake, and should last as long as solid 14k gold jewelry. It is safe for most people with sensitive skin
Rhodium, atomic number 45 on the periodic table, is a rare metal that is colored silver-white. Rhodium is 10 times more expensive than gold, which begs the question of why rhodium is used merely for plating instead of as a foundational metal for a piece of jewelry. The answer to that lies in another prominent characteristic of the element--the fact that it is extremely brittle.
The most common purpose of rhodium plating is to augment a piece of "white" gold jewelry to enhance the coloring and provide an added layer of protection against damage. The reason rhodium is so often paired with white gold is simple: White gold does not exist in fact. White gold is nothing more than gold mixed with another metal that has a white cast (usually silver, palladium or nickel). This results in a slightly yellow tint to the final product. As the buyer of white gold is looking for a brighter sheen, rhodium is used as a plating material to add that extra shine.
However, aside from its coveted reflectiveness, rhodium has protective properties that make it functionally useful as a plating metal. Rhodium will never discolor or tarnish. Aside from that, it is a harder metal than gold, which means it is more scratch-resistant and more able to survive the rigors of daily wear. Rhodium is also occasionally used on silver (primarily for its scratch-resistant properties) and platinum (to enhance shine).
Before buying silver, platinum or white gold jewelry, ask if it has rhodium plating to enable an accurate estimate of the cost of ownership, taking the necessity of replating into consideration. While it might be a shock to learn the coveted color and shine of that treasured white gold piece of jewelry is actually rhodium, it is better to understand that fact now instead of learning it for the first time at the jeweler, where that knowledge will undoubtedly be accompanied by a bill for replating.
From - eHow