Stainless steels contain min 11% Cr and usually other alloy elements such as nickel as well. Due to these elements, these steels have corrosion resistance property. Although there are many different stainless steels, they can be divided into three categories. These categories are austenitic, ferritic and martensitic stainless steels. Stainless steels are used in variety of industries such as paper mills, chemical plants, water treatment and surgical instruments.