Stainless steels are chromium containing steel alloys. The minimum chromium content of the standardised stainless steels is 11%. Chromium makes the steel 'stainless' this means improved corrosion resistance.

The better corrosion resistance is due to a chromium oxide film that is formed on the steel surface. This extremely thin layer, under the right conditions, is also self-repairing.

Besides chromium, typical alloying elements are molybdenum, nickel and nitrogen. Nickel is mostly alloyed to improve the formability and ductility of stainless steel. Alloying these elements brings out different crystal structures to enable different properties in machining, forming, welding etc.

The four major types of stainless steel are:

Austenitic
Ferritic
Austenitic-Ferritic (Duplex)
Martensitic

Austenitic is the most widely used type of stainless steel and still represents 80% of the world market. It has a nickel content of at least of 7%, which makes the steel structure fully austenitic and gives it ductility, a large scale of service temperature, non-magnetic properties and good weldability. The range of applications of austenitic stainless steel includes housewares, containers, industrial piping and vessels, architectural facades and constructional structures.