Corrosion

• What is the general term that refers to the process by which metals are slowly broken down?

  Corrosion
• What is rusting specifically an example of?

  Rusting is an example of corrosion.
• What substances are involved in the rusting of iron?

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

  Hydrated iron oxide
• What happens to iron atoms during rusting at the atomic level?

  Iron atoms lose three electrons to become iron three plus ions.
• What do oxygen atoms do during the rusting process?

  Oxygen atoms gain two electrons to become oxygen two minus ions.
• Why is the rusting process considered a redox reaction?

  Because both oxidation and reduction are taking place.
• What conditions are required for rusting to occur?

  Both oxygen and water must be present.
• How can you demonstrate the conditions required for rusting using test tubes?

  • Test tube 1: Contains water but no oxygen (boiled water with oil layer).
  • Test tube 2: Contains air (oxygen) but no water (calcium chloride).
  • Test tube 3: Contains both air and water.
  • Only the nail in test tube 3 will rust.
• Why does only the surface of a metal corrode?

  Because only the surface is exposed to substances like water and oxygen.
• What happens to rust that forms on the surface of iron?

  It flakes off, revealing new metal underneath.
• How does corrosion differ in aluminum compared to iron?

  Aluminum forms a protective layer of aluminum oxide that prevents further corrosion.
• What are the two main categories of methods to prevent rusting?

  1. Barrier methods

  • Painting
  • Oiling or greasing
  • Electroplating

  1. Sacrificial methods

  • Adding a more reactive metal (e.g., zinc or aluminum)
• What is the purpose of barrier methods in preventing rusting?

  To prevent oxygen and water from touching the iron.
• What is one example of a barrier method for preventing rusting?

  Painting the iron.
• What is electroplating?

  Using electrolysis to cover iron with a thin layer of another metal.
• What is the sacrificial method of preventing rusting?

  Adding a more reactive metal to oxidize instead of the iron.
• What is galvanizing?

  Coating iron with zinc to protect it from rusting.
• How does galvanizing serve as both a barrier and sacrificial method?

  It forms a protective coating and reacts with oxygen if scratched.
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