I have a 68 Mustang coupe with a vinyl top that I plan or putting back on. The car was rust free except for the severe rust that developed under the vinyl.

I originally sanded and treated it with a phosphoric acid mix and then coated it with Por-15. Unhappy with the looks of it I stripped all of the por-15 off and reapplied it but then read Randy’s dent removal article. Off it came again.

I also read Rand’s Secrets of Rust Removal article and decided to leave the Por-15 off. I used the navel jelly and even left it on over night with plastic wrap on there to keep things moist.

It looked like I did everything by the book except that I painted the roof with a Dupont Variprime self etching primer and their URO Primer/Sealer. I used filler right over the metal to fill the pits. Topcoat was Nason Ful-Thane 2K Urethane.

It is now two years later (where did the time go) and I’m thinking of installing the vinyl roof. I removed some boxes off the roof and the blanket that was there to protect the paint. I then noticed what looks to me as small rust bubble forming. The only way to know for sure is to poke at the bubbles but if it is rust how should I fix this? Would the use of an epoxy primer have stopped this from happening or would the rust have come through anyway? I wish I had noticed this two months ago when a scraped a perfect roof. It this rate it would have been easier to remove the roof and weld another on there.

I just coated my camaro frame with "rust bullet", comes with alot of recommendations. It went on smooth and easy, seems to cover well and the prep was minimal. I can't tell you about longevity yet though, I'll repost on that in a few years! (God willing!)

How bad was it to begin with? Given that you may already looking at at least a partial repaint if you want something that will last, I'd consider changing roofs, getting one from a non vinyl top car. You certainly don't want a re-occurrence once the vinyl is on. I changed roofs on a '70 Cuda a few years back (originally a vinyl top car) and it was well worth it as the rest of the body was completely solid and rust free, except for a little trunk rot. In my case I had no intention of reinstalling a vinyl top anyway. So other than filling the seams where it's welded on, it actually eliminated a lot of other work and of course made it a better car.

It had a lot of pitting with a few pin holes. The thing that stinks is that the entire interior is back in the car including a new headliner along with new front and rear glass. I wish I used that roof I just got rid of instead of messing around with trying to remove the rust. I was thinking of sand blasting of using black beauty to blast the roof and start over again. I don’t think the use of soda will work too well.

Hi,about 1 year ago,i blasted the chassis of my 48 ford coupe (body and suspension off) i put 2 coats of por-15 on it,it looked great.i have been working on the body,(body is still off chassis) i had covered the chassis with a plastic tarp (not covered tightly) it never left the garage,. i just finished the body,and was getting ready to put the body back on,when i removed the tarp,i notiiced the por - 15 flaking,i pulled a flake and a piece about 2 in x 10 in came off,then i got to pulling more,and a lot more came off. that por 15 is JUNK,now im going to blast the chassis AGAIN,and prime (epoxy ) and recoat WITH URATHANE paint. forget that POR 15,i wouldnt use it again if it was FREE...

Epoxy before any filler work would have made a world of difference on the success rate with that job IMO.
You mention there were some pinholes so I imagine the rust was pretty severe in some areas, did you weld the pinholes shut or just fill over them? Filler absorbs moisture over time, and most primer surfacers will also absorb moisture over time, variprime offers little corrosion resistance by itself. Epoxy primer provides the best metal protection and if applied before any fillers and surfacers it really doesn't matter if these other products absorb moisture or turn to dust in the wind for that matter the metal will not corrode with epoxy protecting it.

POR15 has it's uses, I use it sometimes on inner panels where cleaning light rust is impossible and on these areas that are protected from UV light it works just fine. On areas that can be cleaned well I see no reason to use POR and would never use it on the exterior or frame. The project I'm working on right now was started by the vehicle's owner, he POR'd the floor inside and I just removed about 75% of it with an airblower-poor adhesion...

All of that POR crap is off and I went with the paint instead.

The rust was severe and I thought I got all of the rust out with navel jelly. I think I applied the filler directly to the metal but it was two years ago and can't remember now. I might have sprayed it with the self etching primer first but that doesn't really matter now.

Sprayed the roof a few times with the URO as a filler and got everything smooth. From there I sealed it with the URO and sprayed the roof with the Nason urethane. I think between the URO Filler/Sealer and the topcoat I did this over a week period.

Looks like I'm going to blast the roof with some black beauty and hit it with an epoxy primer and go from there.

Just be aware of warping that roof as it is thinner from rusting. Try to do an angle insead of pointing it straight on. Maybe a super fine quartz sand would be less destructive? It'd be slower but safer??

How are you going to blast with headliner still in and pinholes? Guess you are taking out the headliner....again.

I think the warping is the least of my problems considering that the metal was pretty pitted. Do you think the sand would be better than fine black beauty?

Believe it or not the underside of the roof looked perfect and was covered in red oxide paint. The pinholes seemed to develop after I was poking at the rust to get some of the scale off. Between scraping, sanding, steel wool and using a wire wheel two pinholes developed. This stuff was real heavy in the areas of the seams in the vinyl. Most likely this was the original roof and was cooked by the California sun.

I wish I could find the before pictures after I pulled the vinyl.

I'm not a blasting pro; but white quartz sand is very sharp and the finer the grade, the better it does on cleaning out the pits IMO.

Finer grades take longer, so maybe it would need more time per square inch which might be a bad thing? ...as far as warping?

I'd take my time with the pressure set real low, it gets really slow & boring but why risk a bigger problem.

As far as filling the pinholes without welding them all up; I have used a product made by Bondo called "Fiberglass Gel". It does not have strands in it; it is just like a stiffer type of resin that spreads like filler, but is waterproof. I use it on weld seams on patch panels on junker daily driver work to prevent the typical bubbling later. It comes in a pint can. It does not feather-edge as well as a normal good body filler, but if you don't get agggresive with coarse DA paper, it works Ok. I've even used it on lawn mower steel gas tanks, so I know it must be totally waterproof?

Sandblasting is not the answer as you will most likely destroy that roof if you blast it even with Black beauty and sand will certainly be a disaster. Lightly blasting to remove paint is one thing but in order to remove rust it will require aggressive use of the media which even a solid roof could not stand up to and that rusted one will warp much easier. Those pinholes you discovered were already there whether you could see them or not and became apparent when the rust filling them was removed and if the coating on the underside of the roof is removed (even though it may appear to still be good) you will most likely find a lot more that you missed. It would be a lot less work just to replace that roof and you would have a much better repair since it sounds as if the rust is so extensive that you have little left to work with. I hate to be discouraging but I think you would be doing yourself a big favor if you just replace that thing with a structurally solid piece since it is not all that difficult and I have done this a couple of times, once on a rusted '68 Mustang and on a '67 that had been damaged.

Pretty much is already between the pits and what looked like somebody walking on the roof! Had it looking pretty nice and was thinking of leaving the vinyl off.

Is that the way it is now? You need a roof.

This is with hitting the roof with fine sand and 60psi. Some of the areas were so badly pitted that the metal was paper thin or thinner.

Anybody in the New Jersey area have or know of somebody with a 67-68 Mustang parts car with a good roof for a reasonable price?