ABSTRACT
Metals in the passive state (passive metals) have a thin oxide layer on their surface, the passive film, which separates the metal from its environment. Metals in the active state (active metals) are film free. Most metals and alloys that resist well against corrosion are in the passive state: stainless steel, nickel-chromium based superalloys, titanium, tantalum, aluminum, etc. Typically, the thickness of passive films formed on these metals is about 1-3 nm.
