Stainless Steel is defined as that steel which when correctly heat treated and finished, resists oxidation and corrosive attack from most-corrosive media. The different types of stainless steels are as follows:

1. Martensitic stainless steel. The chromium steels containing 12 to 14% chromium and 0.12 to 0.35% carbon is called martensitic stainless steel, as they possess martensitic structure. These steels are magnetic and may be hardened by suitable heat treatment and the hardness obtainable depends upon the carbon content. These steels can be easily welded and machined.

2. Ferritic stainless steel. The steels containing greater amount of chromium (from 16 to 18%) and about 0.12% carbon are called ferritic stainless steels. These steels have better corrosion resistant property than martensitic stainless steels.

3. Austenitic stainless steel. The steel containing high content of both chromium and nickel are called austenitic stainless steels. The most widely used steel contains 18% chromium and 8% nickel. Such a steel is commonly known as 18/8 steel. These steels are non-magnetic and possesses greatest resistance to corrosion and good mechanical properties at elevated temperature.