Anodes are not really that expensive. But I don't have a solution for protecting the whole car. You would have to treat with something the metal before painting. I guess covering the car in some "anode juice" (for the lack of a better term) Even then, I think the industry has come a long way from when cars would rust. But seeing as how your location is Ontario, I imagine that you see the problem more than I do in Dallas. Still a neat idea.
Go to
West Marine: Home Page and search "anode" to see some real products.