Poodle is right. As long as you apply the right amount of voltage and current, and everything is connected together electrically and is kept fully submerged in an electrolytic solution (the ocean for example), it will work okay.
Great for boat hulls, maybe not so great for your car, unless you own James Bond's Lotus Esprit.
I bought a electric rust protection kit last year, never got round to installing it. Just went out to the shed to get it to install, but the kit itself is all rusty, so, no, it doesn't work.
One of our FIFO friends used to stash her car in my shed when she was away pretending to work real hard, in less than 2 weeks the electrons in the wheat silo type battery were knackered.
disconnect the rust preventer thingo and even with the original elcheapo ancient battery the electrons were happy enough to start 'er up at first go - even after two weeks of taking up valuable shed-space.