Corrosion resistance of aluminium

1
Corrosion resistance of aluminium
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Corrosion resistance (???) of aluminium

• Chemically, Al is more reactive than Fe.
• However, Al articles (??) corrode more slowly in
  air.
• Al is protected by alayer of impermeable(???)
  oxide Al2O3 from the attack of air.

Air
Al
Al2O3(s)
3
Formation of impermeable aluminium oxide
4
? Why is aluminium resistant to corrosion while
iron isn't ?
5
? Why is aluminium resistant to corrosion while
iron isn't ?

• The aluminium oxide layer formed at the surface
  of aluminium is very dense and stuck firmly (?)
  onto the metal which protects aluminium from
  further corrosion.
• The rust formed at the surface of iron fakes off
  (??) easily and exposes the iron to further
  corrosion.

6
Anodisation of Aluminium article
The oxygen gas evolved reacts with Al to form a
thicker layer of Al2O3(s)
7
? Write the equation(s) for the reactions
involved at the anode of anodisation process.
8
? Write the equation(s) for the reactions
involved at the anode of anodisation process.

• At anode4OH-(aq) ? O2(g) H2O(l) 4e-
• 4Al(s) 3O2(g) ? 2Al2O3(s)

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Corrosion of aluminium
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Reaction of aluminium with air (with HgCl2(aq))