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Corrosion

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  • 1. CORROSION Corrosion is a reaction which takes place on the surface of a metal
  • 2. During corrosion:
    • The metal element changes into a compound
    • Magnesium metal + oxygen in air
    • 2Mg + O 2
    • The metal atoms loose electrons to form metal ions
    • Mg
    • This loss of electrons is called OXIDATION
    Magnesium oxide 2MgO Mg 2+ + 2e -
  • 3. WHAT IS RUSTING?
    • The corrosion of iron is called rusting
    • For iron to rust you need
    • Water (H 2 O)
    • Oxygen from air (O 2 )
    • 2Fe (s) +2H 2 O (l) + O 2 (g) 2Fe 2+ (aq) + 4OH - (aq)
  • 4. The battle against corrosion
    • Materials
    • Beaker
    • W tube
    • 3 nails
    • Magnesium ribbon
    • Copper ribbon
    • Ferroxyl indicator
    • Sodium chloride
  • 5.
    • Ferroxyl indicator is a pale yellow-coloured solution which turns blue when Fe 2+ ions are produced.
    • Sodium chloride (common salt) is an electrolyte, rusting occurs faster when an electrolyte is present.
  • 6.
    • Procedure
    • We take three iron nails:
    • 1)Nail with Mg ribbon attached to it
    • 2)Bare Nail
    • 3)Nail with Cu ribbon attached to it
    • We place the nails in the Sodium chloride solution and we add some drops of ferroxyl indicator solution
  • 7. What is about to happen?
  • 8.
    • 1)No B lue , no corrosion of iron
    • Mg loses e - more readily than iron.
    • Mg Mg 2+ + 2e -
    • 2)Some Blue , corrosion of iron
    • Fe Fe 2+ + 2e -
    • 3)More intense Blue , corrosion of iron.
    • Fe loses e - more readily than copper.
    • Fe Fe 2+ + 2e -
  • 9. QUESTION 1
    • Attaching a metal that is higher in the ECS Magnesium (Mg)
    • A) Protects iron from corrosion
    • B) Speeds up corrosion
  • 10.
    • Attaching a metal that is lower in the ECS Copper (Cu)
    • A) Protects iron from corrosion
    • B) Speeds up corrosion
    QUESTION 2
  • 11.
    • Attaching a metal that is higher in the ECS (Mg)protects iron from corrosion, but attaching one that is lower down (Cu) speeds up its corrosion.

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