Blast it and if the weather holds epoxy it but rather than putting two coats of this and two coats of that order this from Amazon:
http://www.kilz.com/hammerite/v/inde...008a05d103RCRD it comes in many colors but the real reason to use it isn't printed on the label anymore. It contains ground glass and aluminum and once fully cured is a very tough industrial enamel. Rustoleum is a fish oil based product and can only be coated with other Rusto products. I have been using Hammerite for well over 15 years in both the fence business [where it was subjected to saltwater mist] and the car business painting all suspension part. If there is any rust it traps it in place and seals it away. Its so tough that on a budget I painted a whole truck with it, let dry, sanded it and cleared it. You can't even tell its not automotive grade paint.