What are stainless steels?

Stainless steel is a family of ferrous alloys containing at least 10.5% chromium. Chromium produces a thin layer of oxide on the surface of the steel, called a passivation layer. This prevents any further corrosion of the surface. Increasing the chromium content can improve corrosion resistance. Stainless steels have a unique feature due to the passivation layer: they are self-healing. Even if the stainless steel surface is scratched or damaged, this passivation layer, only a few atoms thick, will instantly reform under the influence of oxygen in air or water. This explains why stainless steel does not require any coating or other corrosion protection to stay bright and shiny even after decades of use.

In addition to chromium, stainless steel can contain other elements such as nickel or molybdenum.