Preventing corrosion

• Corrosion

  A corrosion process in which iron or steel reacts with oxygen and water
• Preventing corrosion

  1. Keeping oxygen or water away from the iron or steel

  2. Storing metal in an atmosphere of unreactive nitrogen or argon

  3. Using a desiccant to absorb water vapour
• Physical barriers to oxygen and water

  • Painting
  • Oiling and greasing
  • Coating with plastic
• Electroplating


  Using electrolysis to deposit a thin layer of metal onto another metal, usually to improve its appearance or corrosion resistance
• Electroplating process

  • Cathode is the iron or steel object
  • Anode is the plating metal
  • Electrolyte contains ions of the plating metal
• Sacrificial protection

  Iron can be protected from rusting if it is in contact with a more reactive metal, such as zinc
• Galvanising


  Coating iron or steel with a layer of zinc to prevent rusting

  This protection still works even if the zinc layer is scratched
• Tin layer on steel food can is broken

  Iron oxidises more readily than tin, so the damaged can rusts very quickly