Concept 5 of 8Foundation
Watch on YouTubeVideoRusting — a common chemical change
When iron is exposed to moist air, it slowly turns brown-red. This is rust (Fe₂O₃·xH₂O — hydrated iron oxide).
Rust needs:
- Iron
- Water (or moisture)
- Oxygen
Remove any one of these and rusting stops.
How to prevent rust:
- Painting (cars, gates, bridges)
- Oiling/greasing (tools, door hinges)
- Galvanization — coating with zinc
- Alloying — making stainless steel (Fe + Cr + Ni)
Example
A nail left out in the rain rusts in days. The same nail sealed in oil for years stays shiny.
💡 Tip:Rusting is slow but irreversible — it damages railway tracks, bridges, ships, cars worth billions yearly.
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5 questions to check what you just read.
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- Q1.Rust needs:
- Q2.Rusting is fastest in:
- Q3.To prevent rust on gates:
- Q4.Stainless steel resists rust because:
- Q5.Rust chemical form: