Answer:
Rust is an iron oxide, formed by iron and oxygen reacting in the catalytic presence of water or air moisture. Rusting is an oxidation reaction. This means it involves oxygen reacting with something (in this case, iron in the presence of moisture).
The chemical formula for rusting:
4Fe + 3O2 + 6H2O → 4Fe (OH)3
Hope this helps!
- profparis