Stainless steel is a special type of steel with a low carbon content, at least 10.5% chromium, and may also contain molybdenum, nickel, or nitrogen. When the metal is exposed to air, the chromium forms an oxide on the surface and will do so again if the original coating is damaged. This protective layer makes the metal resistant to rust and other corrosion, hence its name.

Stainless steels vary in their resistance to heat, scaling, and corrosion according to their grade and exposure. Many grades retain a durable metallic appearance in suitable environments. It is highly valued as a facade material, and because of its aesthetic and hygienic advantages it is a common material for instruments which handle food. Stainless steel is also 100% recyclable.

The chromium-rich surface film gives stainless steel its corrosion resistance. That resistance is not absolute: the alloy grade and exposure conditions affect its behavior.