In 1913, English metallurgist Harry Brearly while working on a project to improve rifle barrels, accidentally discovered that adding chromium to low carbon steel gives it resistance to damage and corrosion. In addition to iron, carbon and chromium, modern stainless steel may also contain nickel, molybdenum and titanium. Nickel, molybdenum and chromium enhance the corrosion resistance stainless steel. It is the addition a minimum of 12% chromium steel, which allows him to be corrosion resistant. Chromium in the steel combines with oxygen from the atmosphere to form a thin, invisible layer called "passive film".
Sizes of chromium atoms and oxygen are similar so neatly together on the surface of another metal, forming a stable layer only a few atoms thick. If the metal surface is scratched or in any other way damage the protective layer, more oxygen will in that place very quickly build up and form and recover the exposed surface, protecting it from further corrosion. It should be borne in mind that stainless steel has poor corrosion resistance in environments or environments with low oxygen circulation