Re: restore rusty roof 1972 charger
[Re: DynoDave]
#277403
04/05/09 08:50 AM
04/05/09 08:50 AM
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Joined: Oct 2005
Posts: 708
Mechanic Falls, Maine
4BBodies
mopar addict
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mopar addict
Joined: Oct 2005
Posts: 708
Mechanic Falls, Maine
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It probably rusted from the inside, around your repair areas. I see it all the time in Maine, you cut out the rust, weld it, and it bubbles where the seam was. It is usually because I didn't cut back/repair far enough, also, you shouldn't put bondo over paints or primers, if you have to fill pits, use fiberglass. (Fiberfill) Bondo is porous, and like a spong with water. Sandblast, weld, Fiberfill, THEN Encapsulator, or POR 15. And paint/seal the back side if at all possible.
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Re: restore rusty roof 1972 charger
[Re: 4BBodies]
#277406
04/05/09 10:38 AM
04/05/09 10:38 AM
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Joined: Mar 2005
Posts: 390
pacific northwest
wings471
enthusiast
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enthusiast
Joined: Mar 2005
Posts: 390
pacific northwest
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Quote:
It probably rusted from the inside, around your repair areas. I see it all the time in Maine, you cut out the rust, weld it, and it bubbles where the seam was. It is usually because I didn't cut back/repair far enough, also, you shouldn't put bondo over paints or primers, if you have to fill pits, use fiberglass. (Fiberfill) Bondo is porous, and like a spong with water. Sandblast, weld, Fiberfill, THEN Encapsulator, or POR 15. And paint/seal the back side if at all possible.
Would "All Metal" be a good/better choice if the rust was completely removed? 
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Re: restore rusty roof 1972 charger
[Re: 4BBodies]
#277407
04/05/09 12:18 PM
04/05/09 12:18 PM
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Joined: Feb 2003
Posts: 21,318
Manitoba, Canada
DaytonaTurbo
Too Many Posts
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Too Many Posts
Joined: Feb 2003
Posts: 21,318
Manitoba, Canada
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Quote:
It probably rusted from the inside, around your repair areas. I see it all the time in Maine, you cut out the rust, weld it, and it bubbles where the seam was. It is usually because I didn't cut back/repair far enough, also, you shouldn't put bondo over paints or primers, if you have to fill pits, use fiberglass. (Fiberfill) Bondo is porous, and like a spong with water. Sandblast, weld, Fiberfill, THEN Encapsulator, or POR 15. And paint/seal the back side if at all possible.
I would not bondo directly over bare or partially rusted metal, not if you want it to last for any length of time. Because bondo does not provide you with any kind of a seal is why you want to coat the metal with something before using it.
But either way, you did a patch job over a rusty surface, you should not be surprised it bubbled up on you. Really, unless you are going to cut out the entire rusted section and replace with good metal from a donor car, the rust will always come back. If you are welding onto metal that has been 'thinned' by rust, it is only a matter of time. These rust-stopper products don't prevent this permanently, the best they can do when properly applied is to delay it somewhat. This means cleaning the surface of rust as best you can, then coating it from both sides. Honestly I would only do this kind of repair on a roof I intended to throw a vinyl top on to hide the evidence...
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Re: restore rusty roof 1972 charger
[Re: DDDDDD]
#277409
04/06/09 04:39 PM
04/06/09 04:39 PM
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Joined: Oct 2005
Posts: 708
Mechanic Falls, Maine
4BBodies
mopar addict
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mopar addict
Joined: Oct 2005
Posts: 708
Mechanic Falls, Maine
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It's because the air got to it from behind the repair. I doubt it is the Rust Bullet's fault. After I weld, I sandblast the metal, then fiberglass, then bondo. THEN you can Rust Bullet, Encapsulate, Rust-oleum, or pray to the Sun God. Whatever helps keep the rust from coming back! It has to be sealed, either by completely being welded SOLID, or by a combination of that and painting/sealing behind the repair. Good luck, I have delt with this countless times, and doing it right doesn't always guarantee it will last. But is does help your odds! 
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Re: restore rusty roof 1972 charger
[Re: DDDDDD]
#277412
04/09/09 12:47 AM
04/09/09 12:47 AM
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Joined: Jan 2003
Posts: 5,449
Woodbridge,CA
NAS Backyard
master
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master
Joined: Jan 2003
Posts: 5,449
Woodbridge,CA
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I am currently using/testing Rust Bullet on a GM car floorboard and inside an evaporative "swamp" cooler. Short term results look really good. If you are using it on a roof like that you will have to get it on the backside of the rust also. Maybe by drilling a few holes in the inner roof frame and squirting it in with a pump oil can. It is very spendy but a cheaper alternative to complete replacement. My Olds floor pans are 60.00 for 1 section,I used a 60.00 quart on the whole floor. A new swamp cooler was 500.00 I used another 60.00 quart on that. I will see how this stuff holds up.
1970 Challenger Ragtop 426 4 speed
1961 Olds 88 2 dr Sedan 394 4 speed GVOD
1968 Pontiac Firebird 428 4 speed
2000 Ford F-150
2002 HD Roadking
1961 Licence Plate collection
1995 Buick Roadmaster
www.nogreenautolaws.com
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