Brass does not rust. Only iron and its alloys, such as steel, rust. Pure brass contains no iron and is resistant to corrosion. Brass can develop a red or green tarnish that may resemble rust.
Rust describes iron oxides that form when iron reacts with oxygen in the presence of air moisture or water. Metals other than iron can undergo corrosion, but the oxides formed are not referred to as rust.
Brass tarnish can be removed with household cleaning items like dish washing liquid. After the tarnish is cleaned, thoroughly dry and polish the item with an oil such as lemon to prevent the return of the tarnish.