Corrosion/preventative measures

Question 1

What is corrosion

Answer 1

Reaction of metal with its surrounding, such as air and water

Question 2

What happens when an object rusts

Answer 2

Iron+oxygen+water —> hydrated iron(III)oxide
Rusting is a redox reaction
It is called rusting when iron or steel is corroded

Question 3

What are the methods to prevent rusting/reduce it

Answer 3

Painting
Coating with oil, grease or plastic
Plating with zinc (galvanising)
Plating with tin

Question 4

How does Painting reduce rusting

Answer 4

Paint prevents air and water reaching the surface of the metal, but when it chips rusting starts on the exposed part of the metal

Question 5

How does coating with oil, grease or plastic reduce corrosion

Answer 5

Prevents the metal being exposed to the air and water, however if the coating is damaged rusting starts on the exposed metals

Question 6

What is sacrificial protection

Answer 6

Involves using a metal more reactive than iron such as zinc or magnesium. The more reactive metal will corrode first , protecting the iron/steel by ‘sacrificing ‘ itself.
This method is useful when painting is difficult.

Question 7

What is galvanising

Answer 7

Galvanising involves dipping the metal object in molten zinc. After it has cooled and solidified the thin layer of zinc stops air/water reaching the iron/steel below and acts as a sacrificial metal so the object is protected even if the zinc layer is damaged

Question 8

Disadvantage of tin plating

Answer 8

Tin is less reactive than iron, so if the tin layer is damaged the steel will act as the sacrificial metal and will rust faster than normal