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
• What happens to iron nails in three different test tubes regarding rusting?

  • 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
• Why does only the surface of a metal corrode?

  Only the surface is exposed to the environment
• 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
  2. Sacrificial methods
• What are the three main types of barrier methods to prevent rusting?

  • Painting
  • Oiling or greasing
  • Electroplating
• How does painting prevent rusting?

  It prevents oxygen and water from contacting iron
• Why is oiling or greasing necessary for moving parts?

  It prevents rust while allowing movement
• What is electroplating?

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

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

  Coating iron with zinc for protection
• How does galvanizing work as both a barrier and sacrificial method?

  Zinc protects iron and oxidizes if scratched
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