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hopwrangler 05-03-2009 08:53 PM

underbody coating
just got my jeep 3 days ago and it has some rust underneath it....what is the best stuff to get under there and spray the entire underside with to stop rusting?

KBR97 05-03-2009 09:12 PM

alot of people throughout the auto world are using truck bedliner these days, on all sorts of vehicles.
I would remove the rust first though.

Unless you dont feel like doing that then look up POR-15. Its a whole system of products that work really well, but it can get costly $$$.

hopwrangler 05-04-2009 05:43 AM

Are people doing the entire underbody with it? You talking about the bedliner you can get from walmart and just getting under there and painting everything?

meyers 05-04-2009 06:19 AM

You want to make sure you clean up the rust and treat it with something like POR-15 or Extends. If not you will be just trapping the rust under the coating and cause you more problems.

KBR97 05-04-2009 09:37 AM

yea alot of people use the bedliner on the whole underside...floor pan, frame, all that. Just make sure you remove the rust.

hopwrangler 05-05-2009 06:09 AM

what about spraying rust converter or rust oleum, instead of por-15....thats expensive! Would that be ok? Then coat with bedliner or rubberized undercoating....

dweilmd 05-05-2009 07:00 PM

You can get a good rust converter from Advance Auto (or probably any auto parts store) called "The Right Stuff". It converts ferric oxide (rust) to iron phosphate. A whole bottle is about $4. I just pour it into a spray bottle and spray it on the rusted parts. Wait a while and it will start to turn a black color. Wipe it down and you can primer/paint right over it. Just remove as much of the heavy/loose rust that you can before using it.
As for undercoating, I did the whole underside of my FJ40 Land Cruiser with Duplicolor Professional Undercoating/Sound Dampener. It is a rubberized undercoating and a can sells for about $5. I was really happy with the results. Get the "professional", not the regular, its worth the slightly higher price. Just remember to shake the can very well and be careful because it sprays really fast. I have used POR-15 in a few areas, no doubt it is a great product, but it is really messy and had to be painted on. If you buy the POR-15, don't buy the $$$ rust coverter that they try to sell you. Get the Right STuff -- they are almost identical products.

603TJ 05-05-2009 09:55 PM

I just did this project last weekend....

I noticed a lot of surface rust on the outer most visible portions of my frame. I got underneath my jeep and noticed more on the underside of the frame and on some of the factory skid plates. This is what I did:

Buy a wire brish attachment for your drill. Hopefully your drill has some balls, and a good battery or two...

1.)Take off your wheels, and go to town on the frame, skid plates, and any other non moving parts under the body.
2.) Get a bucket of water and some mild dish soap, and wash all the parts that you just sanded. This gets all the rust-dust off, and will help the undercoat to stick.
3.) I used the aforementioned Duplicolor Professional Undercoating. It does spray out fast, and I can't stress this enough: SHAKE THE HELL OUT OF IT. If you don't, it will not come out evenly or stick to the surface well, which results in it flaking off easily and you having to re-do the job. I know- because I didn't shake my first application, and had to re-do the entire passenger side of my jeep. Waste of time and money.
4.) The undercoat eventually dries and becomes hard, after that you can paint it. I used some rustoleum flat black spray paint. This step is probably unnessesary, but I had the time and the paint, and it came out real nice.

I am really happy with the result. Goodluck, post pics!

hopwrangler 05-06-2009 05:51 AM

will you post some pics of your job please, a couple so I can kind of get an idea what it should look like. how hard was it to watch out for lines, hoses? thanks!

603TJ 05-06-2009 07:03 AM

If it ever stops raining I will post pics....For prep, I wrapped the brake lines with masking tape, and used disposable shop towels to cover my shocks. And don't worry if you get some on your paint, I used 409 before it dried and it came right off.

dweilmd 05-06-2009 10:17 PM

1 Attachment(s)
Here's a pic of the Duplicolor professional undercoating I used on my Fj40. I used in on the frame after de-rusting and also the entire underside of the vehicle. The undercoating is black so I did not feel a need to paint over it. I used 3M adhesive and wax remover to get it of of the paint. Use a tarp because it is hard to it get off of the garage floor.

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