If used over a rusted steel surface will it prevent further rusting? I want to preserve the rust appearance while stopping further rust.

You've come to the right place, Jack! Rust-Oleum Stops Rust Crystal Clear Enamel can be applied over an existing rust and will help to prevent further rust from developing. Please keep in mind that prolonged exposure to humidity or moisture may contribute to premature rusting. - Rust-Oleum Product Support 4