The slow coat
Corrosion: metals are attacked by what is around them.
Shiny, then not
A new iron nail is shiny. An old iron gate left outside is covered with a reddish-brown powder. Copper vessels get a green coat. Silver turns black.
What is happening to the metal’s surface?
What this lesson covers
The idea
When a metal is attacked by substances around it such as moisture or acids, it corrodes; this process is corrosion, and rusting is the corrosion of iron into a reddish-brown coating.
Shiny, then not
A new iron nail is shiny. An old iron gate left outside is covered with a reddish-brown powder. Copper vessels get a green coat. Silver turns black.
What is happening to the metal’s surface?
- Substances around it (like moisture or acids) slowly attack it and make a new coating
- It is only dust sticking to it
- The metal is growing
Leave them outside
Press Play and watch what happens to each metal as time passes.
Attacked from outside
When a metal is attacked by substances around it such as moisture or acids, it corrodes. This process is corrosion. Rusting is the corrosion of iron into a reddish-brown coating.
Corrosion damages car bodies, bridges, iron railings and ships. Every year a huge amount of money is spent to replace damaged iron.
- Metal | Coating
- Iron | reddish-brown powder (rust)
- Copper | green coating
- Silver | black coating
Notes
When a metal is attacked by substances around it such as moisture or acids, it corrodes; this process is corrosion, and rusting is the corrosion of iron into a reddish-brown coating.
Check yourself
What is rusting?
A copper bowl gets a green coating. This is …
What can attack a metal and make it corrode?
- The corrosion of any metal. Corrosion is for any metal. Rusting is only for iron.
- Iron melting in the sun. Rust is a new coating, not melted iron.
- The corrosion of iron, which gets a reddish-brown coating — correct. Yes! Rusting is corrosion of iron.
- corrosion of copper — correct. Yes! The black coat on silver and the green coat on copper are corrosion too.
- rusting. Rusting is the name for iron only.
- paint peeling. The green coat is a new substance made from the copper itself.
- Nothing: metals never change. Metals do change when attacked by moisture, acids and the like.
- Substances around it such as moisture and acids — correct. Yes!
- Only the metal’s own weight. Weight does not corrode a metal.