If there are doodads out there that can prevent electron transfer( which is what need to happen) then the thing would have to run 24/7 365,,,,to do the job.
I would think you'd have to plug the car in every night to keep the unit running.
I do know how to De-Rust parts using washing soda, water, and a battery charger,,,but this other gizmo strikes me as a good intention,,but short on proof.