New undercoating question

[Madman]

Going to start the body work on my 1970 F250 4x4 soon. The sheet metals is still pretty damn good, and I want to keep it that way. I wanted to ask what is a good undercoating to apply to the underside of the body to seal it and minimize rust, as I will be using my truck for elk hunting up here in the high Rockies, so I want to knock out the research now. I used to seal the undercarriage with primer (20 years ago) but figured there may have been some advancements in undercoating since then. Thanks.

[Bob]

Tectyl made by Valvoline. It doesn't get hard and when hit by stones and such it'll sort of repair itself. It's kind of like waxy grease but it does dry... but not hard. It is probably the main ingredient in most undercoatings offered? It's sort of orange-ish brown an stinks a little for awhile.

A buddy I know does an annual coating of old motor oil and then runs down a dirt road.

Or if you clean things up very well you could always go with the rubberized undercoating but if you ever need to remove it you're screwed. Also if it's not super clean and it detaches it'll store dirt and moisture behind it and make rot.

[69fordfan]

i just did the underside of my cab and inner fenders with bedliner. its tougher than undercoating and some brands you can even get in colors. i plan to do the bottom of the bed as well as the inside when i get that far. just something to think about. it goes on real easy and with a little tape you can get a neat job too.

[Madman]

i just did the underside of my cab and inner fenders with bedliner. its tougher than undercoating and some brands you can even get in colors. i plan to do the bottom of the bed as well as the inside when i get that far. just something to think about. it goes on real easy and with a little tape you can get a neat job too.

I did that on my 48 Willys, but I think it depends on the quality of the bedliner (of course). On the underside, so far, it seems to be hanging in there, but on the high traffic areas, it didn't do so well, peeling quite a bit. Saw some rust cover paint in the back of NPD (can't remember the name of it) and wasn't sure if anyone has used it for this application.

[69fordfan]

yea.. i was cautioned about that. its said that the prep is the key. i sandblasted everything and coated it with epoxy primer , scuffed it, and then shot it with some "raptor" brand bed liner. its a 2 part mix that you just mix, shake and shoot. real easy to apply. guess time and a few miles will tell.

[Bob]

We have a urethane spray system here at work and primer isn't really what you want under "bed liner" materials. Yes they scuff up a bed and shoot the stuff in there and it holds up well but technically it's not the best choice for a surface for two part urethane spray systems. Spray urethanes like rough bare metal covered with an runny glue made just for that purpose. The rough finish helped give a mechanical bond and the adhesive is what the goop sticks to best according to the folks making the stuff. Any paint is likely to lift or the goop will just be laying on it making a shell with next to no real adhesion. Also the better products out there (higher strength than bed liner goop) should be sprayed on warm parts with warm goop. Heated tanks and lines are required for an honest crack at doing it "top shelf." If you get it on there right... it's bulletproof stuff.

The Tectyl I mentioned comes in various grades (thicker or thinner... thinner being a little easier to wash off with thinner etc.) It's heavier form is typically called export crating fluid. It's designed to protect bare metal throughout a trip across the big ponds above deck with direct salt spray. If your stuff is clean before you put this stuff on it'll hang indefinitely. Same goes for the urethane except the application becomes more critical. The urethane lifting creates a holding spot for the wet mud. The Tectly if scraped off won't hold moisture against the metal. It can also be applied over paint so now you'd need to lose both the Tectyl and the paint to get rust going.

Then there's good old Ziebart...? Run it in and ive 'em a few bucks and bamm...

[Tpdaniels]

yea.. i was cautioned about that. its said that the prep is the key. i sandblasted everything and coated it with epoxy primer , scuffed it, and then shot it with some "raptor" brand bed liner. its a 2 part mix that you just mix, shake and shoot. real easy to apply. guess time and a few miles will tell.

I did exactly the same thing as "69fordfan", plus front inner fenders on the bottom side and underneath the cab from the frame rail to outside of the cab.

It looks great, took about $300 in "Raptor" material, but well worth it.