Corrosion of active and passivating metals

Account for the differences in corrosion of active and passivating metals



  • Only a few metals exist in nature as uncombined elements, such as gold and silver.
  • Such noble metals do not corrode.
  • Active Metal: A reactive metal that forms a non-adherent and porous oxide layer.
  • The oxide layer of active metals can flake off, allowing continued corrosion.
  • Most metals are active metals and exist in nature as compounds.
  • Passivating Metal: A reactive metal that readily forms an unreactive surface coating with substances such as oxygen or water, thus protecting the metal from further reaction.
  • Passive metals therefore only corrode to a certain extent.