Coal tar epoxy ?
 

Does anyone have any experience using this stuff on trucks? I used it this last summer on a boat bottom and it was the toughest finish I have ever sanded on. I'm thinking it would be real good for undercoating and maybe a bed liner material. Any thoughts?

Never heard of the stuff. Now I gotta look.
For bedliner, I've had Rhino on my '99 since it was new and other than a little fading and one ding where I hit it hard with a sharp shovel, You can't beat it

Just do an online search for coal-tar-epoxy. It probably would not do for most people's bed liner cause it is so hard it would be slick. It's main attribute is that it's tough and it would inhibit rust.

We used it in oil refineries on cold service pipes.
Paint the pipe then insulate over it, great rust inhibitor
for that application. I know guys who used it for
undercoating, painted frames, rearends, leaf springs with
good results. When mixed together there is a time limit
that you need to use it by, it will "kick off" and get hard
in the can. Not real fast, you had all day or so to
use it. I want to try it on hydraulic valves.