Rusting
Iron reacting with oxygen and water to form hydrated iron oxide, a flaky orange-brown solid. Both oxygen and water are needed.
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Analogy
Rust is like iron slowly getting eaten by the air and damp around it.
Example
iron + oxygen + water-> hydrated iron oxide (rust)
In practice
Painting, oiling, galvanising (coating with zinc) and plating all keep oxygen and water away.
Practice
Flashcards
- What two things does iron need to rust?Oxygen and water.
Questions people ask
How can rusting be prevented?
Stop water and oxygen from reaching the iron. Painting, oiling or coating with plastic act as barriers. Galvanising coats iron with zinc, which also protects by sacrificial protection because zinc is more reactive and corrodes first. Alloying iron with chromium makes stainless steel.
What is sacrificial protection?
A more reactive metal such as zinc or magnesium is attached to iron. The more reactive metal reacts with oxygen and water in preference, so it corrodes instead of the iron. Ships have blocks of zinc on their hulls for this reason, and these blocks are replaced when worn.