Corrosion Flashcards
What is corrosion
Process by which metals are slowly broken down by reacting with substances in their environment
What 2 components are needed in order for a metal to rust
Oxygen
Water
When iron rusts what happens to the iron
It’s being oxidised
Because it’s loosing electrons
When iron rusts What happens to the oxygen
It’s being reduced because
oxygen is gaining electrons
What type of reaction is rusting
Redox reaction
What does oil rig stand for
Oxidised is loss (of electrons)
Reduction is gain (of electrons)
Why does only the surface of a metal corrode
Because only the surface is exposed
What happens when iron rusts
The rust flakes off revealing new metal
That then rusts and the process is repeated
If left long enough entire chunk of metal can break down
What happens when aluminium corrodes
Only the surface atoms are affected
The aluminium oxide forms a protective layer
protecting the rest of the metal from the environment
What are the 2 methods to prevent iron from rusting
Barrier methods
Sacrificial methods
How do barrier methods work
Prevent oxygen or water from ever touching the metal
3 types of barrier methods
1) paint it, works well for big pieces (side of ship)
2) oil or grease it, necessary if object has moving parts (bike chains)
3) electroplating, using electrolysis to cover the iron in a thin layer of another metal (protecting underneath)
What is the sacrificial method
Adding a more reactive metal on top of the iron
An object is added to oxygen the more reactive metal will be oxidised
Therefore won’t rust.
What method is both a sacrificial method and a barrier method
Galvanising
How does galvanising work
Coating an iron object in a layer of zinc
If the zinc gets scratched the O2 from the surroundings will react with any zinc
In a rusting reaction, what can remove any water vapour from the air?
Calcium chloride
