painting under the truck

[jcfuzzdog29]

Was thinking of doing some kind of undercoating on my 01 f350 was wondering what you guys have done or used how its holding up.Did you grind away any rust or just paint over it. Not looking for the most expensive paint out the also. thanks ahead of time for posting

[zrain25]

I did por 15. Bought a pint. Thinned it a little put it in a spray gun and went to town. I scraped loose stuff off and washed it then after it dried I painted it. I did everything. The whole front suspension area. Both differentials, frame. And the body underneath... It cost me about 80 bucks to do 30 for a cheap gun and then the paint and other stuff. The por 15 is amazing my truck looks like new underneath And will not rust anymore il try to find a pick


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[Lilfarmrboy]

I Bought a couple of bottles of that stuff that eats rust (a few of them out there) and used a brush to put it on then I followed that with a couple of cans of spray on undercoat that I got from ACE Hardware. Works good so far.

[zrain25]

Don't put undercoating on it I heard that if you put undercoating on a frame that already has rust on it. It will trap all the moisture and make it worse. Undercoating is for new vehicles with no rust


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[Lilfarmrboy]

Zrain, although you may be right, I have done this method with other pickups and to my fathers 18 wheelers with nothing but good results. I should point out that usually we scrape as much of the rust off as possible, powerwash off the frame with a powerwasher powerfull enough to blast rust off of the metal, let it dry then hit any hard areas with sand paper or sandblaster. I have never noticed any metal rusting faster because of rust already being on the metal and then undercoating. Rusting occurs when water in the air attacks it, by undercoating you are stopping any other rusting from occuring but it shouldn't make it worse IMO.

[zrain25]

Ya but most people don't do that much prep work Lol. Thats why more often people say undercoating makes it worse unless it's a new car. Which if you do the prep work that you and ur dad do the frame will be almost like new any way lol


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[Tj Krawler]

It's not cheap, but I've always heard great things about POR-15. That's what I'll be using. ($100 for a gallon of the stuff is a LOT cheaper than a new cab or bed...) Make sure to do the proper prep, or nothing will stick. I'm going to see if I can get a local place to blast the frame/under side of the cab. I don't know if they will with the brake lines and stuff.


There is a major body shop near me that does a complete undercoating for under $100. It's an oil spray. They even get inside the doors. I thought of this, but you need to do it every year, and if you ever need to work under there... well, it's all going to be coated in oil...

Originally Posted by zrain25

I did por 15. Bought a pint. Thinned it a little put it in a spray gun and went to town. I scraped loose stuff off and washed it then after it dried I painted it. I did everything. The whole front suspension area. Both differentials, frame. And the body underneath... It cost me about 80 bucks to do 30 for a cheap gun and then the paint and other stuff. The por 15 is amazing my truck looks like new underneath And will not rust anymore il try to find a pick


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Any idea how much you had to thin it? I would rather brush mine (thicker coating, should be better), but there is so many small gaps under the cab and bed, spraying it would be 10x easier. Plus, spending 12+ hours under the truck isn't real fun trying to reach up to paint every little spot.

[rmb1393]

Id recommend port 15 as well and if you can spray it then spray it! I used a brush and its a PITA!!

[spdracer71]

Originally Posted by zrain25

Ya but most people don't do that much prep work Lol. Thats why more often people say undercoating makes it worse unless it's a new car. Which if you do the prep work that you and ur dad do the frame will be almost like new any way lol


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I do know that if you remove either the water OR air rust can't form. I needs both to make the chemical reaction of rust. So as long as you know that whatever coating you use in not breathable may help ones decision in hoping not to make things worse..............

[TooMuch03]

Originally Posted by zrain25

I did por 15. Bought a pint. Thinned it a little put it in a spray gun and went to town. I scraped loose stuff off and washed it then after it dried I painted it. I did everything. The whole front suspension area. Both differentials, frame. And the body underneath... It cost me about 80 bucks to do 30 for a cheap gun and then the paint and other stuff. The por 15 is amazing my truck looks like new underneath And will not rust anymore il try to find a pick


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After you spray the Por-15 on it, how hard is it to remove things underneath, like if you need to service diffferentials or brake lines or whatever?