Rust changes ACETONE. Genthin (GENERAL Thinner's in) ATF is Ok Best soaked with a sealed lid on it for GRUNGE . This best with things like Ball races. Rust is Fe2O3 or Fe304 and if there's moisture about it will be Hydrated. Lighter coloured. Phosphoric acid converts rust and doesn't remove the Base Metal. . Galvanic protection is the best Coating usually zinc based. Some rust is removed by High frequency Vibrations, Caustic bath with DC current or Molasses