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Corrosion of metals
Metals corrode when they are
left in contact with air or water.
Which metals corrode quickly
and which corrode slowly?
When iron corrodes, it is called rusting.
Rusting is the oxidation reaction of iron
with oxygen in the presence of water.
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iron
+
oxygen
➨
iron oxide
2Fe
+
3O2
➨
Fe2O3
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Does salt make iron rust faster?
People who live by the seaside often claim that their cars go
rusty faster.
Does salt speed up the rate of the rusting reaction?
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What is needed for iron to rust?
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Preventing rust
Rusting destroys a huge amount of iron and steel every day.
People spend a lot of money making sure that their iron and
steel buildings, engines, lorries and ships do not rust.
What methods could you use to prevent things rusting?
painting
galvanising
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plastic coating
oiling
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Rusting: sacrificial protection
Sacrificial protection is another way of preventing rust.
This involves attaching big blocks
of magnesium or zinc to the iron
hull of a ship or water pipe.
Because magnesium is
more reactive than iron,
it corrodes first, leaving
the iron intact.
Eventually the magnesium
blocks have to be replaced
because they have
corroded completely away.
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reactive
metal
iron
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Rusting: true or false?
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