I am getting ready to work on the underside of a 2004 Tj. After I get it cleaned of rust and painted can I then use a waterproofing membrane like Flex Seal on it?
Rust Proofing and Paint
- Thread starter midland
- Start date
I am not in the rust belt but anything you can do to keep moisture and seal helps. Product that does not absorb or traps moisture is the key. I have opted to clear coat with rattle can enamel. Once you got it clean you can indiscriminately spray everything without the need of masking and the exhaust will burn it off. Might be some better options offered but this is what I have done
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I would get off any flaky rust, use some type of good rust treatment (converter, encapsulator, or remover (or a combination), top coat, and then apply some type of oil undercoating. I use Woolwax and have had very good results with it in the rust belt. I would not use anything that has a rubber base like a undercoating product or something like flex seal. It will seal in the moisture and rot under the barrier without you even knowing it.
CreepinDeth
TJ Addict
Remove all oxidation (wire wheel on drill, etc)
Sealcoat it with a high zinc paint like Rustoleum pro
Then buy black cosmoline RP-342 , 4-5 cans (amazon)
Military grade rust preventative used industrial
Comes in black or translucent (wax seal)
https://www.cosmolinedirect.com/cosmoline-rp-342-heavy-spray-military-grade-rust-preventive/
Sealcoat it with a high zinc paint like Rustoleum pro
Then buy black cosmoline RP-342 , 4-5 cans (amazon)
Military grade rust preventative used industrial
Comes in black or translucent (wax seal)
https://www.cosmolinedirect.com/cosmoline-rp-342-heavy-spray-military-grade-rust-preventive/
CreepinDeth
TJ Addict
Fwiw I also bought a similar product sold in high end luxury cars like Land Rover called WaxOyl
https://www.waxoyl-usa.com/
https://www.waxoyl-usa.com/
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Terrible idea. Moisture gets underneath coatings like Flexseal, rubberized undercoating, etc and any new rust will spread undetected. Use an annual oil or lanolin based treatment.
Coating the INSIDE of the frame is the #1 thing to do (drilling drain holes #2). I cleaned mine out, used 4 cans of Eastwood internal frame coating, then sprayed Blaster Surface Shield inside.
For what they're worth, my notes are here.
If you can be sure the inside of the frame has dried out well after cleaning, then I'd go with a more permanent product like Eastwood. If not, I'd go with something like FluidFilm, even thought that requires periodic reapplication.
I used Fluid Film on everything underneath my Jeep for the winter salt. I sprayed that crap off after the "salt" season, because you can't work on anything with the greasy crap getting all over you. It reminded me of my leaky grease gun.
No. Anything flexible and rubberized is an albatross for rust. It's a messy salt/water trapping membrane that accelerates rust similar to GM frame wax. If you really want to rot out a frame, spray it right over rust.
Grind it all down, paint it with a good frame paint (I used Krylon Rust Tough in flat black) and use surface shield, woolwax, or even fluid film (fluid film doesn't last quite as long) and you'll be fine. You can even use your used motor oil, but this is obviously a bit thin and not the best choice (although it is free and better than nothing). These "creep" as the coating gets knocked off by road debris, which helps shield the metal. Paint and rubberized coatings, especially the latter, will just chip and expose metal.
These oil based coatings are not permanent, and people who really keep up with them (at least once a year, some do it twice) frequently have "rust free" vehicles even after 10-15 years in the rust belt. I put rust free in quotation marks because there will always be at least some sort of surface rust beginning in the rust belt, because salt gets everywhere. Undercoating usually can't, but it's pretty damn close if you do a good job.
You really do need drain holes. 2 5/8" holes on each frame rail. A few inches before the bend of the frame works fine. Most TJ's that have been sent to the boneyard are due to the absence of frame drains from the factory.
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