Corrosion Flashcards
(8 cards)
What is corrosion
Where metals react with substances in their environment and are gradually destroyed
What does iron need in order to rust
Oxygen and water, found in the air
Equation for rust
I… + oxygen + w… = h… iron o…
Iron + oxygen + water = hydrated iron oxide
What happens to the layer of rust on iron
It flakes away leaving the iron expose to corrosion again
What happens to the layer of rust on aluminium
It doesn’t r… away, but rather forms a p… layer that sticks to the a… and stops any further r… from happening
It doesn’t flake away, but rather forms a protective layer that sticks to the aluminium and stops any further reactions from happening
Iron rust experiment
Nail in boiled water with oil on top:
(water, no air)
-the nail … rust
—>water is b… to remove …
—>o… stops a… getting in
Nail in tube with just air:
-the nail … rust
Nail with air and water:
-the nail … rust
Nail in boiled water with oil on top:
(water, no air)
-the nail won’t rust
—>water is boiled to remove oxygen
—>oil stops air getting in
Nail in tube with just air:
-the nail won’t rust
Nail with air and water:
-will rust
What are the 2 main ways to prevent rusting
- -p…/coating with p…
-e… (electrolysis to r… metal i…)
-o…/greasing - S… method
—>placing a more r… metal with the i…, so oxygen and w… will react with the more r… metal than the i…
- -painting/coating with plastic
-electroplating (electrolysis to reduce metal ions)
-oiling/greasing - Sacrificial method
—>placing a more reactive metal with the iron, so oxygen and water will react with the more reactive metal than the iron
What is galvanisation
-where an object is s… with a coat of x…
-this initially p… the object, but if its s… the zinc around the site of the s… works as a s… material
-where an object is sprayed with a coat of zinc
-this initially protects the object, but if its scratched the zinc around the site of the scratch works as a sacrificial material
