Lesson 5 of 14
Why iron goes orange
Show on a big screenOne cycle chain turned orange. A spare chain stayed bright. Why?
Step 1 of 3
- Three nails in three places.
- The sealed dry tin has no water. The boiled water under oil has no air.
- Only the damp, open nail rusts.
Iron turns orange when it meets air and water together. The spare chain missed one of them.
The rule
Rust needs air and water together. Take either away and iron stays bright.
Iron left in the open turns into orange rust. Plain water has air mixed in it. Boiling pushes that air out. The oil stops new air getting back in.
| Where | Air | Water | What happens |
|---|---|---|---|
| Damp courtyard | Yes | Yes | Rusts |
| Sealed dry tin | Yes | No | Stays bright |
| Boiled water, oil on top | No | Yes | Stays bright |
Keeping iron bright
- Zinc is a grey metal. A coat of zinc keeps air and water away.
- Paint blocks them too, until bits of it break off.
- Oil does the same job, and must be put on again.
Now try it. Switch air and water. Does the nail rust?
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