Then I am sure you have been painting over rust with it just as it is intended to be used that's what POR stands for ,not putting it on brand new metal that it will not stick too , ASK me how I kno..... it lasted about 3 months on my xj floors before it peeled , Also I work in R&D for the largest paint company in the world so that helps too lol . the product is utter rubbish ,it has no UV protection and will chalk badly unless you top coat it ,if you try to use it on new metal it peels off unless you make it rust first or use their acid etch first by the time you do all this you wer better off using something better that cost much less ,this is not my opinion these are facts Its up to you what you want to use tho. sorry if I sound harsh

 

 

Most that I have read turned out to be operator error. Sometime its best to read then do. Not starting a fuss or anything but this was my first time using it and I read their webpage and it pretty much clear cut on what to do and not to do..I thought anyway. Since its man-made its not perfect so I don't expect it to last for years (7 or more) but just figure what the hell done spent all this money anyway might as well give it a shot....hence also why I got the black bullet stuff too. Luckily this will be my last project like this as I just getting to old and everything hurts afterwards...But atleast I got me a new welder out of it! lol

 

Yes you weld in, then seam seal top and bottom.

I used this stuff.. works great.



This is my 95... It was a chore.

 

drivers side was gone.

damn with all my spot welds should of done solid beads. My welding still needs more practice. Had to go thru and touch up some of them.


2 coats of black bullet time to prime ,seal and paint. Started this project it was 92 degrees outside now its 58..lol what a difference 3-4 weeks makes!

 

That's my take too. Coming from years of autobody shop experience, and having used it a few times. But I personally don't care if someone wants to brush over-priced molasses on their car. People are going to do what they want to do regardless of what ya say. Those floor repairs look great BTW!!

BTW, back to seam sealing underneath, as an experiment, I went and applied seam sealer on our Grand Cherokee when it was fresh and clean from CA. Every seam underneath I sealed with a high quality urethane calk (after thoroughly washing with soapy water and drying). I wanted to see how covering the seams ...and preventing salt/water from getting IN the seams would look after about 10 salty winters ....compared to vehicles w/o. We're about 4 years into the test and so far so good. I also covered up with gorilla tape just about ever frame hole (not the drain holes). I have periodically hosed out the channels on dry days. My theory has been or many years that the open holes and seams do more harm than good. If you look under vehicles as they begin to rust, the rust often starts at the seams. I also oiled the bottom of the doors and other key areas.

 

I kinda disagree on the POR 15. On rusty metal even without proper prep it holds up. Jury is still out with cleaner metal though. When I first discovered it I bought one of the little starter kits. Prepped some rust under the Jeep, mostly where floor pan seams meet, and applied it. Having a little left over I slapped some around. Did not even prep or even wire brush. On cleaner metal it just peeled right off. As expected. On the rusty metal held up pretty good. Below is a shot of my gas tank heat shield. This is where I slapped it on. I reached up there best I could. No prep what so ever. 2 years later I took it off to hang a gas tank skid. And I live in New England where they use that crap on the roads. Now on cleaner metal I have been wire brushing it, using more Metal Prep, and letting it sit for a longer then the instructions say. For the most part it seems to be holding up pretty well. But time will tell.

 

I advocate removing the rust via blasting or chemical process (that completely 'eats' away the rust), then apply a couple coats of high-zinc self-etching spray primer. That, or replace the affected rusted metal with new metal (and apply self-etching zinc primer on the new metal).
...WAY beyond POR15. Problem with aftermarket replacement panels is the e-coat is ****-poor. Once it starts rusting (below POR15), it creates an even BIGGER mess. But POR is better than nothing. I remove the cheap e-coat and use self-etching when the repair is done.

That said, there's a time and place for POR15 too. If ya don't have the means to remove the rusts, it's probably an ok approach. You might as well use a couple coats of cheap (hardened) enamel paint at a fraction of the cost. Basically you're just putting an 'tough' oxygen barrier over the rust. Or, try the molasses trick!

 

I'm glad I don't have to worry about salty winter...I just made a mistake of buying a XJ that spent 4 years up north.

 

I’ve never worked for any paint company let alone the largest in the world. I just follow the instructions on the label. I use POR on rust … because that’s what POR stands for. Why would I put it on “brand new metal”? I guess you found out the hard way that it peels off. Etching clean metal is what you would want to do for most paint coverings. I do it and then apply paints that are cheaper than POR15. If you think it’s rubbish because it has no UV protection … apply a top coat, just like the instructions say. Fact is that it works just fine for me.

 

well by the looks of the NEW floor pans this guy is putting in they are NOT RUSTY!! and that is my point! do not use this on NEW floorboards did you even look at what he did all the rust is gone and you are telling him to use this crap !!! PAY ATTENTION even the name of this thread says NEW PANS WELDED IN...... , not rusty old crap I wanna hillbilly up with por 15 so it will last 10 minutes longer

 

Actually this thread is about seam sealer and whether it should be applied on the underside. At least that’s what the OP asked about. You use 3M – I use Dominion which works just fine. If you think POR15 is “crap” … no problem … use what ever you want, knock yourself out. As for hillbilly work, I’ve been restoring cars since the late ‘60s and I’m no stranger to rust repair. I’ve used many products over the years and POR15 on rust works fine for me as it does for many others. As country2 said, a lot of the problems with it are due to operator error.

 

What about 3M 5200 for seam sealer?

 

If you are talking about mine that's NOT POR-15. I mentioned in the post what it is...Black Bullet which can be used on clean metal unrusted metal. Since mine were not rusty I did not use POR-15 ...since its paint over rust!

 

OK..back on topic....If you have both the urethane and the regular brushable sealer is one better suited for underneath?