5.3.1 Rusting

Last updated at April 25, 2026 by

What is Rusting?

It is a chemical change where iron reacts with air and water to form rust .

Key Facts and Examples
  • Iron objects develop brown deposits when exposed to moist air .
Example: Bicycle handles, iron gates, car bodies show brown rust
  • Rust formation requires both oxygen and water to occur.
Example: Iron nails in dry air don't rust quickly
  • Rusting is an undesirable change that weakens iron structures .
Example: Rusted bridges need repair, old cars have holes
  • New substance formed is iron oxide which has different properties .
Example: Rust is brown and flaky, iron is grey and strong
Rusting Process Iron meets air Oxygen contacts iron surface Water present Moisture from humid air Chemical reaction Iron + oxygen + water react Brown rust forms!
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