Pitted roof from rust under vinyl top repair

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68wssDartmmb

68wssDartmmb

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Hi, wanted to ask members how to go about tackling the pits in the roof from rust on a vinyl top car. Would very much like to put another vinyl top on which I already have from legendary in dark green.can I seal this and stop the rust from coming back? I thought metal filled filler. Can you skim it flat with lead fill like the seems are on the pillars? Any help would be great! Thanks Chuck

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Im suprised por-15 didnt seal it well enough. I would think a rust convertor of some kind first, then a skim of filler. Im facing the same issue, but im already accepting the fact its not going to stop it 100%.
 
I would use an acid wash to get into the pits and kill the rust.

Tel us, how is any filler going to stop rust?
 
I'm not surprised the POR15 didn't seal it. You cannot just paint over rust, it will return eventually. You have to chemically change rust with a rust converter and then you can seal it with a product such as POR15, Rustoleum and the like. You have to change the rust on a chemical level. I would treat that whole roof with a converter and then choose the sealer of your choice. Either that, or put a roof skin on it.
 
Phosphoric acid which Ospho is a diluted version. Soak in decent temps several times, scuff with scotch brite, and rince good with plenty of water. Neutralize!!!!!the acid!!!!! Some will say add baking soda. Remember most epoxy primers can react to OSPHO if not neutralized and it can react months LATER!!! I would then apply 3 good coat of a good epoxy primer, level with GOOD filler, I would use a fiberglass reinforced filler, and THEN a good general filler , block, and do a heavy urethane sanding primer, or a polyester primer, block seal and topcoat.. If any imperfection you know it will show in the topcoat!! Or replace that roof!!!!
Vinyl roofs were the worst auto invention...ever!!
 
RustyRatRod said:
I'm not surprised the POR15 didn't seal it. You cannot just paint over rust, it will return eventually. You have to chemically change rust with a rust converter and then you can seal it with a product such as POR15, Rustoleum and the like. You have to change the rust on a chemical level. I would treat that whole roof with a converter and then choose the sealer of your choice. Either that, or put a roof skin on it.
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The POR I was told stood for Paint Over Rust. But in my experience it didn’t work well and just peeled away anyways.
 
Dartsun said:
The POR I was told stood for Paint Over Rust. But in my experience it didn’t work well and just peeled away anyways.
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I've never had an luck painting anything over rust. It always comes back. I've used converter a few times and it stayed put.
 
The roof was stripped and acid treated to kill the rust and then the por15 was applied, done by a body shop 2 years ago, I took the car back and going to redo it myself, the rust did come back and bubbled the por15 coat
 
barbee6043 said:
Phosphoric acid which Ospho is a diluted version. Soak in decent temps several times, scuff with scotch brite, and rince good with plenty of water. Neutralize!!!!!the acid!!!!! Some will say add baking soda. Remember most epoxy primers can react to OSPHO if not neutralized and it can react months LATER!!! I would then apply 3 good coat of a good epoxy primer, level with GOOD filler, I would use a fiberglass reinforced filler, and THEN a good general filler , block, and do a heavy urethane sanding primer, or a polyester primer, block seal and topcoat.. If any imperfection you know it will show in the topcoat!! Or replace that roof!!!!
Vinyl roofs were the worst auto invention...ever!!
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I like this method, Thank You for the information.
 
barbee6043 said:
Phosphoric acid which Ospho is a diluted version. Soak in decent temps several times, scuff with scotch brite, and rince good with plenty of water. Neutralize!!!!!the acid!!!!! Some will say add baking soda. Remember most epoxy primers can react to OSPHO if not neutralized and it can react months LATER!!! I would then apply 3 good coat of a good epoxy primer, level with GOOD filler, I would use a fiberglass reinforced filler, and THEN a good general filler , block, and do a heavy urethane sanding primer, or a polyester primer, block seal and topcoat.. If any imperfection you know it will show in the topcoat!! Or replace that roof!!!!
Vinyl roofs were the worst auto invention...ever!!
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The op is not going to like this but, its way less effort to replace the roof section if you can find a good doner car. That roof is so bad , you will see it break out somewhere else anyway after repairing it. We estimated 40-60 hours to fix the original roof on this car. I decided to replace the whole roof from a good doner. Less than 8 hours from cutting the old roof off , replacing it with the doner. Make good measurements and reinforce the structure before proceeding.


Ask me how I know LOL !!


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Finished result...


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The ONLY way to do the repair correctly is to re skin it. Anything else is a lesser quality repair.
 
Kill the rust with acid. Use etching primer, then filler, sealer, then paint it. You don’t need filler with metal or fiberglass in it. It’s not any better than anything else. It’s the prep and what you put it over the top of that makes it work. Don’t cheap out on any of the materials.
 
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I like the fiberglass reinforced filler as it is wtaerproof and adds strength. A ***** and nasty to dry to sand any at all. Ya I agree it needs a new roof but many guys are not able to do such.
 
Even putting fiberglass over it, that rust must be converted. If it's not, it's going to come back.
 
Thanks guys for all your advice, I’m setting this car up to drag race with very little street driving and use. Will be garage kept and it will live in Lake Havasu city AZ. With that I’m going to do my best to kill off the rust and use converter, then epoxy primer inside and out on the roof then use a good filler. I’ll be back at it on Friday so I’ll keep you posted posted on my progress. Happy Thanksgiving everybody
Chuck
 
Thats some deep pitting and even phosphoric wont treat it well enough to rid it. You would be well ahead to replace the roof skin on that car.
If roof skin replacement is out of the question I would suggest media blasting the pitting and sealing it with epoxy prior to any body work. The problem with filler on a roof anywhere away from the edges is the roof expands and the filler can break free.
 
Looks like you have more than pits, do I see holes? I also see rust through in a section you posted that should require metal patching.
My process was to blast pits clean, rust converter sanded flush, epoxy primer/sealer, then high fill primer, then urethane base.

Overkill? maybe...
I`ll be going through this with my vinyl top cuda some day too. I don`t even look forward to that mess:(
 
Dartsun said:
The POR I was told stood for Paint Over Rust. But in my experience it didn’t work well and just peeled away anyways.
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There is a love/hate relationship with POR 15. Some swear by it, and other say it's useless. Most of the failure arguments (I have READ) say that surface prep is the key to using POR 15. That is, follow their instructions to the letter including using their prep products........Who knows?
 
@413 why do you disagree with what I said? I realize there are many different ways to fix a pitted, rusted roof but the only correct way is to replace the bad metal. Not fill it with something.
 
TT5.9mag said:
@413 why do you disagree with what I said? I realize there are many different ways to fix a pitted, rusted roof but the only correct way is to replace the bad metal. Not fill it with something.
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Yes I disagree with that. You don’t need to replace the metal to have a lasting repair.

kill the rust with chemicals
etch prime the metal
fill the pits, seal the filler
prep and paint.

where is the problem here?
The pitted metal is strong, there are no holes.
Rust won’t return, it’s killed with chemicals
metal is covered.
filler is in between primer/ sealer.
paint is over a properly prepared surface with quality materials.
 
413 said:
Yes I disagree with that. You don’t need to replace the metal to have a lasting repair.

kill the rust with chemicals
etch prime the metal
fill the pits, seal the filler
prep and paint.

where is the problem here?
The pitted metal is strong, there are no holes.
Rust won’t return, it’s killed with chemicals
metal is covered.
filler is in between primer/ sealer.
paint is over a properly prepared surface with quality materials.
Click to expand...
I just think that is a lesser quality, sub standard way of repairing rust/pitted sheet metal. I’ve built a handful of vehicles and almost every one starts with un doing poor workmanship from previous owners. And most of the time that is body work and electrical.
 
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