I forgot to mention, after having soaked your metal, and leaving it in the open air. DO NOT DRY IT. You want the water to force the metal to oxidize. If you dry the metal, it will not show rust. Placing it on a water soaked foam pad will do the same thing to it.

Note: Chrome plated items wont rust until the coating is worn off.

As NatalieD mentioned nickel plating or nickel filler is a problem, check for metal content, you can do that through the manufacture. The stores don't usually list this information.