Corrosion and its prevention

Question 1

When does corrosion occur

Answer 1

when metals react with substances in their environment and are gradually destroyed

Question 2

When does iron rust

Answer 2

when it is reacts with water and oxygen and the hydrated iron (III) flakes off

Question 3

Rate of iron corrosion increases because of

Answer 3

sea water (salt increases rate of rusting) and acid rain

Question 4

Why does aluminium corrode

Answer 4

oxygen causes a thin layer of aluminium oxide to form, this acts as a barrier preventing the oxygen reacting with the aluminium underneath

Question 5

Examples of prevention

Answer 5

barrier, sacrificial. galvanising

Question 6

Barrier protection definition and examples

Answer 6

covers the metal preventing the environment reacting with the metal, e.g. painting, oiling, plastic coating, electroplating (POPE)

Question 7

Sacrificial protection definition and examples

Answer 7

a more reactive metal is bolted to a metal you want to protect, the more reactive metal will corrode before the other one (this is usually magnesium and iron)

Question 8

Galvanising protection definition and examples

Answer 8

uses both barrier (cover the iron in zinc) and sacrificial protection (zinc corrodes fist as it is more reactive)

Question 9

Iron oxidation half equation

Answer 9

Fe - 3e- -> Fe3+

Question 10

Why do iron nails rust

Answer 10

there is oxygen and water present in the air