1 Ton Flatbed

I have built a new flatbed with sides and wheel wells. I want to protect the the under side from the previous problem (RUST).It’s all new tubes and cold rolled steel exept for the original chanel frame.The cold rolled sides and wheel wells are really smooth. I need to know what would be best to cover the under side of the bed. I’ve been told that I need to sandblast the smooth steel (ICK). You won’t be able to see any of it but I want it to be protected. What do you suggest. THANKS!!!!!