Rhodium plating is used over sterling silver to toughen it up and add resistance against daily wear and tear. Rhodium is harder than silver and has a high level of light reflectivity, creating a smooth, shiny surface that's highly resistant to corrosive acids. Rhodium isn't invincible; however, the best way to protect it is to keep it away from the acids and chemicals you encounter in your daily life.
Take off your rhodium-plated rings when you sleep. According to ArtisanPlating.com, constant contact with body oils can eventually lead to discoloration.
Apply lotions and perfume before you put on your ring. The chemicals in these products can help erode the rhodium plating over time. Make sure the products have dried on your skin before you put your ring back on.
Remove your ring before you exercise or do any sort of activity that will make you sweat. Just like body oils, sweat can be corrosive to rhodium over time.
Avoid exposing your ring to household chemicals. Take it off before you do dishes in the sink or use liquid household-cleaning products.
Take off your ring before getting in a chlorinated pool or hot tub.
Monitor the rate of wear to the rhodium. Most jewelry is plated with anywhere from .1 to .5 microns of rhodium states ArtisanPlating.com. If, after several months of wear, you see sections of sterling silver showing through, it's possible that the initial plating wasn't thick enough. A reputable jeweler can apply a second, thicker coating of rhodium to your ring.