Study Notes
Corrosion of metals occurs when a metal reacts with water and air, leading to oxidation. Rusting is the formation of hydrated iron(III) oxide when iron reacts with oxygen and water. Example: Iron railings rusting when exposed to rain and air.
- Galvanising — coating a metal with a more reactive metal to prevent rusting. Example: Coating steel with zinc to protect it from rusting.
- Sacrificial Protection — using a more reactive metal to corrode instead of the protected metal. Example: Zinc anodes on ships to protect the iron hull.
- Barrier Methods — techniques to prevent rust by blocking water and oxygen. Example: Painting or greasing metal surfaces.
Exam Tips
Key Definitions to Remember
- Rusting: The formation of hydrated iron(III) oxide from iron, oxygen, and water.
- Galvanising: Coating a metal with a more reactive metal to prevent rusting.
- Sacrificial Protection: Using a more reactive metal to corrode instead of the protected metal.
Common Confusions
- Rusting is specific to iron and steel, while corrosion can occur in other metals.
- Galvanising is not the same as painting; it involves a chemical reaction.
Typical Exam Questions
- What conditions are necessary for iron to rust? Water and oxygen are necessary for iron to rust.
- How does galvanising protect iron? Galvanising protects iron by coating it with zinc, which corrodes instead of the iron.
- What is sacrificial protection? Sacrificial protection involves using a more reactive metal to corrode in place of the protected metal.
What Examiners Usually Test
- Understanding of the conditions required for rusting.
- Knowledge of different methods to prevent rusting.
- Ability to explain the process and benefits of galvanising and sacrificial protection.