Stainless steel is the generic name for a number of different steels used primarily because of their corrosion resistance. All stainless steels share a minimum percentage of 10.5% chromium. Chromium is always the deciding factor, although other elements, particularly nickel and molybdenum, are added to improve corrosion resistance. In many applications, stainless steel competes with coated carbon steels and other metals such as aluminium, brass, and bronze. The success of the material is based on the fact that it has one unique advantage: the chromium in the stainless steel has a great affinity for oxygen, and will form a film of chromium oxide on the surface of the steel at a molecular level. The film itself is about 130 Angstroms in thickness, on e Angstrom being one millionth of a centimetre. This layer is described as passive (does not react or influence other materials), tenacious (clings to the layer of steel and is not transferred elsewhere) and self-renewing (if damaged, more chromium from the steel will be exposed to the air and form more chromium oxide). This means that over a period of years a stainless steel knife can literally be worn away by daily use and yet will remain stainless.
The initial investment cost of producing a component or fabrication in stainless steel will always be more expensive that using ordinary steel, not just because of the higher cost, but also because it is more difficult to machine. However, it is the better life cycle costs of stainless steel that make it more attractive, both in terms of a much longer service life, less maintenance costs, and high scrap value on de-commissioning.
Austenitic, or 300 series, stainless steels comprise over 70% of total stainless steel production. They contain a maximum of 0.15% carbon, a minimum of 16% chromium and sufficient nickel and/or manganese to retain an austenitic structure at all temperatures from the cryogenic region to the melting point of the alloy. The balance of the composition of each grade is iron. All of our stainless steel alloys are dual certified to the standards indicated.