Corrosion

Question 1

Corrosion

Answer 1

Chemical reaction
Coating is produced as metal reacts and forms compound
I.E magnesium + oxygen -> magnesium oxide
Oxidised
Over time metal becomes weaker and eventually all of it becomes metal oxide

Question 2

Rusting

Answer 2

Found on iron
Needs oxygen and water
Hydrated iron oxide

Question 3

Word equation

Answer 3

Iron + oxygen + water = hydrated iron oxide (rust)

Question 4

Which metal protect iron from rusting

Answer 4

Magnesium

Because it’s more reactive metal than iron, reacts with oxygen and water first (in preference to iron)

Question 5

Which metal speeds up appearance of rust?

Answer 5

Copper

We used agar gel

Question 6

Physical barrier

Answer 6

Grease on bike chain
Painting railings
Plastic lab tap

Question 7

Sacrificial protection

Answer 7

Magnesium block (in railway lines)

Question 8

Galvanising

Answer 8

Coating applied by dipping metal in molten zinc
Zinc keeps out air and water
Motorway crash barriers
Buckets

Question 9

Physical barrier + -

Answer 9

Cheap easy quick

Not long lasting must be repaired

Question 10

Sacrificial +-

Answer 10

More long lasting in inaccessible places
Expensive
Has to be replaced every so often
More reactive metal oxidises more readily than iron, sacrifices itself so iron does not rust
Has to be replaced once corroded away

Question 11

Galvanising +-

Answer 11

Long lasting good for inaccessible
Not quick and easy
Expensive