Originally Posted by jimrafford
POR15 will do the job.
The problem with undercoating is that it never really dries. You will end up with nasty tar like stains on what ever you set the tank on. POR15 will really do the trick. it is basically and epoxy paint, and is available in small containers as well. So one can will do a couple of tanks, and perhaps a few other things too. It is very tough and good at preventing rust. Not sure how it would effect getting the tank re-certified when the time comes. They may not allow repainting, I am not sure about that. I am sure they would not like a thick tar like paint that would prevent you from seeing the rust.