You know I was kidding with you about the bag, right?
Another thought... the new one is going to do the same thing - I know what you're talking about with the bare magnet. Clean up the one you have with muriatic acid and coat it with poly or epoxy resin. Or coat the new one to keep it from happening again. Poly is less expensive but still way more than adequate for the job. Boats are made of poly. Epoxy is less smelly and easier to work with (and stronger, but that doesn't factor in here).