Question

the reddish brown coating of rust formed when iron reacts with oxygen and moisture is made of
iron oxide, iron sulphide, hydrated iron oxide, hydrated iron carbonate​

Answer 1

Rust is an iron oxide, a usually reddish-brown oxide formed by the reaction of iron and oxygen in the catalytic presence of water or air moisture. Rust consists of hydrous iron oxides and iron oxide-hydroxide, and is typically associated with the corrosion of refined iron.