Stainless steels contain at least 10% chromium which gives them superior corrosion resistance compared to other steels. There are three main groups of stainless steel: austenitic, ferritic, and martensitic. Austenitic stainless steels are non-magnetic and contain nickel, making them heat and corrosion resistant. Ferritic stainless steels do not contain nickel but have good heat and corrosion resistance, while martensitic grades can be heat treated but have lower corrosion resistance.