Shipwrecks and Salvage > 2. Corrosion of Iron >
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.