Hi,
The chemical formula for rust is Fe2O3.nH2O.
Rust is the reddish brittle coating formed on iron especially when chemically attacked by moist air and composed essentially of hydrated ferric dioxide.

Fe(OH)3 dehydrates to produce Fe2O3.nH2O
Rust consists of hydrated iron oxides,iron oxides-hydroxide. It is the common term for corossion of iron and it's alloys.

Hello!

The chemical formula for rust is Fe2O3 .

Rust is formed when iron reacts with oxygen in moist air.

The following chemical equation represents the reaction: 4Fe + 3O2 → 2Fe2O3.

Hope this HELPED:)