Despite the hardy protection it affords users, stainless steel is more "stain less" than "stainless." In other words, while the material is highly resistant to discoloration, blemishes and other imperfections, it is not completely impenetrable. Just look at the Gateway Arch, which is starting to show its age with rust and decay as it approaches five decades of welcoming tourists to St. Louis [source: Pistor].
The protective layer of film covering a stainless steel object can break down over time, leading to corrosion and pitting. In addition, chemicals like chloride, hydrogen and hydrogen sulfide often cause the film to stress and crack [sources: International Stainless Steel Forum].
The level of rust resistance provided by a particular steel depends largely on the materials used to create it. The more chromium, the more corrosion protection. The sturdier stainless steels also feature at least 8 percent nickel, which provides further defense against tarnish [source: International Stainless Steel Forum].
For household users, it is important to understand that many metals advertised as stainless steel are actually stainless steel plated. The plate is corrosion-resistant, but is susceptible to damage if cut or scratched deep enough to reach the underlying material. Because the plates can also wear off over time, buyers should clarify whether a particular product is made completely of stainless steel or simply plated [source: Qiu].
Whether plated or not, your stainless steel appliances and other products need to be cleaned. Most of the time good old-fashioned soap and water will do the trick. For tougher stains, professionals recommend a variety of household remedies. A couple dabs of olive oil or window cleaner can remove most of those pesky fingerprints and smudges, while white or cider vinegar will restore shine. Don't use steel wool pads or harsh cleansing powders as they will scratch the surface. If you need to remove burnt-on food from your stainless steel pan, let it soak in warm water and then clean it with baking soda and a nylon scouring pad [sources: Stainless Online].