C6.2 Corrosion

• What does corrosion refer to?

  The breakdown of metals by environmental reactions
• What is rusting specifically?

  Iron reacting with oxygen and water
• What is the chemical name for rust?

  Hydrated iron oxide
• What happens to iron atoms during rusting?

  They lose three electrons to become ions
• What do oxygen atoms do in the rusting process?

  They gain electrons to become ions
• Why is rusting considered a redox reaction?

  Both oxidation and reduction occur simultaneously
• What conditions are required for rusting to occur?

  Presence of oxygen and water
• Why does only the surface of a metal corrode?

  Only the surface is exposed to the environment
• What happens to iron nails in three test tubes with different conditions?

  • Test tube 1: Water, no oxygen - no rust
  • Test tube 2: Oxygen, no water - no rust
  • Test tube 3: Both oxygen and water - rust occurs
• What happens to rust that forms on iron?

  It flakes off, exposing new metal
• How does aluminium corrosion differ from iron corrosion?

  Aluminium forms a protective oxide layer
• What are the two main categories of rust prevention methods?

  1. Barrier methods

  • Paint
  • Oil or grease
  • Electroplating

  1. Sacrificial methods

  • Adding more reactive metals
• What is one barrier method to prevent rusting?

  Painting the metal surface
• How does oiling or greasing prevent rusting?

  It prevents oxygen and water contact
• What is electroplating?

  Covering iron with a thin layer of metal
• What is the sacrificial method of rust prevention?

  Adding a more reactive metal to iron
• What is galvanizing?

  Coating iron with zinc
• How does galvanizing work as a rust prevention method?

  It provides a protective zinc layer
• What happens if the zinc coating in galvanizing is scratched?

  Zinc reacts with oxygen, protecting iron
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