It is a type of steel alloy known for its resistance to corrosion, containing a minimum of 10.5% or more Chromium and less than 1.2% Carbon in its elemental composition. The Chromium element in the composition of stainless steel reacts with the oxygen and moisture in the environment and forms a Chromium Oxide layer on the surface that provides resistance to corrosion and can repair itself. The thickness of this layer is between 1 and 3 mm. Stainless steel grades consist of five basic classes. 1. Austenitic stainless steels 2. Ferritic stainless steels 3. Martensitic stainless steels 4. Duplex stainless steels 5. Precipitation hardenable stainless steels