Keep the rust away

The idea

Rusting of iron can be prevented by painting, oiling or greasing it, or by applying a protective layer of zinc on it, which is called galvanisation.

The painted gate

Iron gates and railings are painted. Bicycle chains are oiled. Why do we bother?

We just learned that rust needs both air and water. How could we stop an iron nail from rusting, even in moist air?

• Cover it so that air and water cannot touch the iron
• Leave it out in the rain to wash the rust away
• Nothing can be done

Which coat protects?

All five nails sit in moist air. The first one stays bare. Pick a coat, tap a nail to cover it, and try all four coats. Then slide the days forward.

Preventing rust

Rusting of iron can be prevented by painting, oiling or greasing it, or by applying a protective layer of zinc on it. Coating iron with zinc is called galvanisation.

Each coat covers the iron so that air and water cannot reach it. And without both, there is no rust.

• Coat | Result after a week in moist air
• None (bare nail) | brown rust
• Paint | stays shiny
• Oil | stays shiny
• Grease | stays shiny
• Zinc | stays shiny

Notes

Rusting of iron can be prevented by painting, oiling or greasing it, or by coating it with a layer of zinc (galvanisation).

Check yourself

Applying a protective layer of zinc on iron is called...

Which one is NOT a way of preventing iron from rusting?

Why does a coat of paint stop an iron gate from rusting?

Which coats did we use to protect the nails?

• galvanisation — correct. Yes! Galvanised iron is iron coated with zinc.
• corrosion. Corrosion is the spoiling of metal surfaces.
• conduction. Conduction is the transfer of heat along a material.
• Painting it. Paint is a way to prevent rusting.
• Greasing it. Grease is a way to prevent rusting.
• Leaving it bare in moist air — correct. Yes! A bare iron object in moist air will rust.
• It keeps air and water away from the iron — correct. Yes! Rust needs both air and water.
• It makes the iron softer. Paint does not change the iron.
• It makes the iron heavier. Weight has nothing to do with it.
• Paint, oil, grease and zinc — correct. Yes! Four ways to keep rust away.
• Only paint. There are more ways: oil, grease and zinc too.
• Water and air. Water and air are what cause rust, so they cannot be the protection.