I live in a small town in Montana where the roads get plowed in the winter and they put salt on the roads that practically eat your car. I have a '78 F150 and i bought like 8 or 9 cans of undercoating. should i undercoat the frame? or under the body (the cab) or anything else like that? i was just wondering because this truck is in great shape and i would like to keep it rust free and keep it from getting too corroded.

Thanks!!

 

I just did this last week, i undercoated almost everything...chassis, under the cab, bed, and i used semi-gloss black paint for the suspension parts and rear axle.

 

something else i might do is spray the backside of the front fenders and the inside bed sides

 

What brand of undercoating did you use? Also, what prep has to be done to the frame and inside fenders for the undercoating to stick?

 

I Used a scraper to get rid of the flacky stuff or mud or whatever-(if any). Also, take a wire brush to the frame rails and chassis stuff, floorboards, bottom of bed, ext....just to remove any rust or corrosin, use sandpaper if needed. You just want to make sure there is no rust or dirt that is going to get trapped in the undercoating because that would be bad...also it roughens up the surface a little to help it stick. Just dont go wearing a hole in something...HAHA. After preping it, if it isnt too cold, wash or at least spray it off with water. You can also use aceitone or even brake cleaner to make sure there is no contaminants that would stop the undercoating from sticking. MAKE SURE IT IS DRY before udercoating. As for what type or brand, i think it was 3-M or duplicolor, rubberized undercoating from advance auto. I would say my longbed, 2wd needed about 4-5 cans.

 

And i just lightly sanded and used the wire brush on the suspension and rear axle, washed and sprayed with semi-gloss for the axle, and low-gloss for the suspension parts.

 

I don't live in the Rust Belt and it never snows here in the flat lands of CA but after a thorough cleaning, I primered and rolled on two coats of gloss black Rustoleum in and on every nook and cranny under the cab and bed. IMO, undercoating holds onto grit and dirt - moreso than a slick surface like gloss paint.

Next on the to-do list is the frame but I've got stuff (lines/hoses/electrical/etc.) to move out of the way. No hurry on my part though.

 

I bought like 7 or 8 cans of Duplicolor rubberized undercoat. I'm not sure if I will need more yet or not

 

IMO undercoat SUCKS!!! I hate working on vehicles that just had cans of undercoat unloaded on them, especially once it gets warm and soft it sticks to everything. If you plan on keeping it do it right move lines/hoses/etc. out of the way sand and paint or use brush on bed liner( thats my plan) do it a lil at a time and before you know it your whole chassis will be coated. just my .02

 

I would do a little extra on the rust areas.
At the top of the rear fenders where the brace attaches.
The bottom of the doors. (you have to take the inside door panels off)
The lower rear cab corners. This is a hard on to coat. I crawled underneath and chiseled a three sided square about 2 inches by 2 inches and peeled the metal up so I could see the back side of the corners and sprayed them good.

 

Well I just finished last night. Took me awhile to just get out there and do it, but its done. 8 cans used. There is NO way without taking everything off that you can get every nook and cranny. BUT, I got 90% of it. Under the cab and the whole frame. I will post pictures in about 30 minutes.

 

 

 

I live in the upper mid-west. Yep snow salt and all that good stuff. My expeience with Rustoleum was exactly he opposite of yours. I sand blasted my frame and sprayed it with Rustoleum, over their primer. Six months later, it was peeling. Had to do it all over again. After cleaning the frame, I applied POR 15. I AM NOT advocating POR 15, I've had success with it, but also failures and it is expensive. But I've never had prolonged success with Rustoleum.

 

In my opinion rubberized under coating is the worst thing invented. Even properly prepped it don't stick good, it stays tacky forever, it will come off if you hit it with a pressure washer, it eventually peels in spots and traps water and dirt under it and actually causes more rust.

I clean the area well and spray on or roll on bedliner.