Did you ever hear of a product called Rust Bullet? This stuff is as hard as nails and resists rust returning. I have a friend that did his frame on his truck, after they shortened it and now they are using the truck as a mud bogger. This stuff stood up to all of the dragging and banging that was in the shop as they built the truck and it still is standing up to water and abuse.
http://www.rustbullet.com/?source=ad...FZaCaQodvHcAMQ