Stainless steels are iron alloys with an additional component, to improve corrosive resistance.
The additional components are usually chrome, nickel and manganese - either separately or in various combinations.
The chrome is the most important component, since it provides extra corrosive resistance. Whilst the nickel is responsible for improving the mechanic characteristics and the processing capacity.
Passivation for stainless steel is a chemical procedure that removes the iron from the surface of the stainless steel, and prevents, as a result, any potential corrosion.
The corrosive resistance of the stainless steel is for two hours after the passivition process at the salt chamber (ASTM B117).
Different kinds of stainless steel undergo different passivation procedures, according to the AMS-QQ-P-35 or ASTM A 967 or AMS 2700.