Rhodium plating is a chrome-like finish normally applied to gold rings to create what is called "white gold," but is actually yellow gold that is plated. Gold is always a yellowish color and for those who prefer jewelry to be silver-colored, they can choose gold-plated with rhodium. You can easily tell if a ring is rhodium-plated by a few simple techniques.
Perform the light test. Under a bright light look at the underside of the ring where your finger comes in contact with table surfaces. If the ring is rhodium-plated, the yellow gold will show through slightly due to the everyday wear of the ring.
Check for rhodium plating on a new ring. If the ring has not been worn, your jeweler will tell you if the ring is plated or whether it's a more precious silver-colored material like platinum. If you do not have access to a jeweler, you can check the underside of the ring with a magnifying glass. There should be a stamp such as "14k" or "10k" to signify what type of gold the ring is made of. If you see this stamp, and the ring is silver-colored, it's rhodium-plated.
Check for rhodium plating using the the "wear test." If the ring maintains its chrome/silver finish for multiple years, without showing any wear back to a gold color, the ring may not be plated and is most likely platinum, which is a more valuable material than gold.