Active metal


  • A corrosion resistant metal that has not been exposed to oxygen. Its protective oxide layer has not formed.
  • When the protective oxide layer is formed we say the metal has been passivated. The protective or passivated layer that forms on aluminum is aluminum oxide (Al2O3). Stainless steel forms chrome oxide (Cr2O3). These oxides are better known by their more common name “ceramic”.
  • You should never rub or polish corrosion resistant materials because you will remove this protective oxide layer and it will have to re-form to make the base material become corrosion resistant again
  • In a dry atmosphere this can take as long as 24 hours. In a wet corrosive atmosphere it can be almost instantaneous.