Stainless steel is a generic name commonly used for that entire group of iron-based metal containing at least 10% chromium as an alloy metal. The name 'stainless' was derived from the fact that the material does not 'stain', rust or corrode easily.
Over 150 stainless steel grades are produced commercially with about fifteen stainless steel grades being the most common. Alloy elements, notably nickel (Ni) and molybdenum (Mb) are sometimes added to the basic stainless composition to produce both variety and an improvement in properties.
There are five main classes of stainless steel: