miked
02-23-2001, 10:24 AM
found this while searching for rust repair help for my roof, thought i'd post it in for those interested.
Joe,
While alot of the suggestions here are great, and will work just fine- I don't understand the mentality that abounds that "Fiberglass and Bondo" are to be avoided at all costs. And that replacing "rusty areas" can only be corrected by welding in new metal. I have been in the antique auto restoration business since 1990 and have worked on my own cars since 1974 (at age 14). I have made my mistakes over the years- but (surprisingly) I have been able to learn a few things. The following is what I do when faced with a situation similar to yours.
Let me explain a few things about RUST then cover some of your options for your roof.
First off- RUST (i.e.: oxidation) can ONLY occur in the presence of oxygen. Any metal or material subject to corrosion such as this, can be treated with a number of coatings that prevent "oxygen" in any form- from ever reaching the base material- therefore- continued corrosion CANNOT reoccur. In your case- oxygen can be transferred to the base material from the atmosphere, moisture from humidity, and any exposure to water (rain, dew, washing). Your ex-vinyl roof is proof of that. That vinyl-once the surface was broken (or creeping in from the edges)- absorbed and held moisture in those areas where you now have rust. You may notice, that the nicely painted areas under the vinyl (though manufacturers seldom did a good job of painting a roof destined for a vinyl-top) are still intact and in good condition- Why? Moisture and other oxidizing agents were prevented from reaching the base metal.
Fiberglass and especially "bondo" (though I prefer the words "body fillers")- are porous materials and absorb moisture when in their raw (uncoated) state. So, it is imperative that they be sealed in some way to prevent moisture absorption. Also, while it is easy to seal the "outside" of these- many people fail to seal the base metal before applying the Glass or Filler. This is why failures of these products is common. I have removed fillers and glass from many cars where the applicator just slapped bondo over a gaping hole and old rust- then complained that the bondo was at fault- when it bubbled and flaked off in sheets....and therefore was unworthy of it's intended use. It's not the products fault- I have NEVER seen these materials fail when properly applied.
So, What does this have to do with your roof? (or anyone else dealing with rust-through)
If the largest hole you have is only the size of a half dollar, it should be a fairly easy repair.
No cutting- no welding... Let me suggest some pretty non-invasive surgery that any home based car nut can do simply. Unless the holes are in a critical structural area- you can follow the following procedure. I'm assuming (if you planned on welding and doing this yourself) you at least have a compressor and typical body-shop tools. I will talk about a great product called POR-15. I have been using this product for several years- believe me their claims are true! If you are not familiar with this- check out their website: http://www.POR15.com/
Or check out a recent project I have at my shop. Just follow the links to the frame/suspension and body pages (phase II pages 5-6). http://lee.cosw.sc.edu/
1) Remove all existing rust by using any of several methods- be sure to do BOTH sides of the areas wherever possible: A wire brush on a drill, sandblasting, or even a grinder (40 grit). Pay particular attention to the "pits" where rust remains even when the surface areas are clean. (which is one reason I prefer sandblasting). Remove all you can from these areas inside and out (if possible).
2) Blow off the areas with high pressure air then apply an automotive "Metal Prep"- follow the instructions. On the perforated areas- you can mix the metal-prep 50-50 with denatured alcohol- and apply with a mixture-soaked shop-towel. Avoid rags that catch fibers easily on the jagged edges.
Wipe the area clean with a towel soaked in plain water- while using your blowgun to help keep it dry.
3) Prime the areas (both sides) with POR-15 (very rust-preventative coating). On the places where the rust has perforated the metal, or created a hole- bridge the holes from the inside with fiberglass mat (not cloth)-using the POR-15 as the resin (do not use fiberglass resin- it absorbs moisture *not talking gel coat here folks- that's different*). Bridge the holes with the first layer 1" out, then put a second layer 3" outside of the edge of the holes. Let this cure overnight.
4) On the surface areas that can be seen, and will eventually be painted- You will need to "scuff" the POR-15 with 100 grit paper- primer/paint/filler will not stick to it unless you do. It may come off in several areas where the base metal was nice and shiny before treatment... BUT- leave it to fill in the pits. POR-15 relies on having texture, rust or other oxidation present for adhesion.
Treat any exposed bare metal again with "metal prep".
5) Be sure the areas are now thoroughly dry and treated- and all perforations are "backed-up" with fiberglass/POR-15.
6) Prime any exposed bare metal (from sanding)with self-etching EPOXY primer (lots of manufacturers have this available).
7) The first layer of "fillers" for the pitted and perforated areas should be done with a special
"metal-based" filler. I use USG's "Metal-Fill", or Marson's "Alumafill II".
8) Roughly shape the Metalfill with 80 grit sandpaper
9) Reseal the Metalfill with self-etching primer
10) Begin application of your "regular" body fillers. I like Marson's "Platinum" body filler for the major filling and shaping, and Evercoat's "Metal Glaze"- epoxy final glazing compound for filling pinholes and deep sand scratches. Avoid using the "spot-putty" in a tube- it is lacquer-based, and absorbs moisture should you ever get a break in the surface paint (or if you topcoat with lacquer).
11) When you are happy with the results of your bodywork, Sand everything at least 12" outside of the areas you've done bodywork to- with 180 grit sandpaper. In your case, you are going to paint the whole roof, so seal all exposed fillers with etching primer- or a pre-paint sealer. and topcoat the entire roof with 3 coats of high-build EPOXY primer. Personally, I like Dupont's K-200, and BASF's DP-20 (Diamond Prime).
12) Now you are ready for your routine block sanding.... and finishing of the roof.
If you have questions about specific areas of your roof (such as the windshield and back-glass channels) e-mail me and I'll try to answer promptly.
Ray
Ray-Lin Restoration
North Carolina
------------------
Mike D'Ambrogia - San Ramon, CA
69 Custom Wagoneer - The Firetruck (http://www.tworock.com/mjd/firetruck.html)
Built 350 w/ Buick 4 barrel manifold, 600 cfm quadra-jet, RV cam, 10:1 - Pertronix ignition - 8mm plug wires
MSD coil - rebuilt TH400 w/ B&M shift kit - Powr-Lok rear end - Factory A/C - Herculiner over new floorboards - Complete rewire with American Autowire Power Plus kit - LPG/Propane install coming soon!
Joe,
While alot of the suggestions here are great, and will work just fine- I don't understand the mentality that abounds that "Fiberglass and Bondo" are to be avoided at all costs. And that replacing "rusty areas" can only be corrected by welding in new metal. I have been in the antique auto restoration business since 1990 and have worked on my own cars since 1974 (at age 14). I have made my mistakes over the years- but (surprisingly) I have been able to learn a few things. The following is what I do when faced with a situation similar to yours.
Let me explain a few things about RUST then cover some of your options for your roof.
First off- RUST (i.e.: oxidation) can ONLY occur in the presence of oxygen. Any metal or material subject to corrosion such as this, can be treated with a number of coatings that prevent "oxygen" in any form- from ever reaching the base material- therefore- continued corrosion CANNOT reoccur. In your case- oxygen can be transferred to the base material from the atmosphere, moisture from humidity, and any exposure to water (rain, dew, washing). Your ex-vinyl roof is proof of that. That vinyl-once the surface was broken (or creeping in from the edges)- absorbed and held moisture in those areas where you now have rust. You may notice, that the nicely painted areas under the vinyl (though manufacturers seldom did a good job of painting a roof destined for a vinyl-top) are still intact and in good condition- Why? Moisture and other oxidizing agents were prevented from reaching the base metal.
Fiberglass and especially "bondo" (though I prefer the words "body fillers")- are porous materials and absorb moisture when in their raw (uncoated) state. So, it is imperative that they be sealed in some way to prevent moisture absorption. Also, while it is easy to seal the "outside" of these- many people fail to seal the base metal before applying the Glass or Filler. This is why failures of these products is common. I have removed fillers and glass from many cars where the applicator just slapped bondo over a gaping hole and old rust- then complained that the bondo was at fault- when it bubbled and flaked off in sheets....and therefore was unworthy of it's intended use. It's not the products fault- I have NEVER seen these materials fail when properly applied.
So, What does this have to do with your roof? (or anyone else dealing with rust-through)
If the largest hole you have is only the size of a half dollar, it should be a fairly easy repair.
No cutting- no welding... Let me suggest some pretty non-invasive surgery that any home based car nut can do simply. Unless the holes are in a critical structural area- you can follow the following procedure. I'm assuming (if you planned on welding and doing this yourself) you at least have a compressor and typical body-shop tools. I will talk about a great product called POR-15. I have been using this product for several years- believe me their claims are true! If you are not familiar with this- check out their website: http://www.POR15.com/
Or check out a recent project I have at my shop. Just follow the links to the frame/suspension and body pages (phase II pages 5-6). http://lee.cosw.sc.edu/
1) Remove all existing rust by using any of several methods- be sure to do BOTH sides of the areas wherever possible: A wire brush on a drill, sandblasting, or even a grinder (40 grit). Pay particular attention to the "pits" where rust remains even when the surface areas are clean. (which is one reason I prefer sandblasting). Remove all you can from these areas inside and out (if possible).
2) Blow off the areas with high pressure air then apply an automotive "Metal Prep"- follow the instructions. On the perforated areas- you can mix the metal-prep 50-50 with denatured alcohol- and apply with a mixture-soaked shop-towel. Avoid rags that catch fibers easily on the jagged edges.
Wipe the area clean with a towel soaked in plain water- while using your blowgun to help keep it dry.
3) Prime the areas (both sides) with POR-15 (very rust-preventative coating). On the places where the rust has perforated the metal, or created a hole- bridge the holes from the inside with fiberglass mat (not cloth)-using the POR-15 as the resin (do not use fiberglass resin- it absorbs moisture *not talking gel coat here folks- that's different*). Bridge the holes with the first layer 1" out, then put a second layer 3" outside of the edge of the holes. Let this cure overnight.
4) On the surface areas that can be seen, and will eventually be painted- You will need to "scuff" the POR-15 with 100 grit paper- primer/paint/filler will not stick to it unless you do. It may come off in several areas where the base metal was nice and shiny before treatment... BUT- leave it to fill in the pits. POR-15 relies on having texture, rust or other oxidation present for adhesion.
Treat any exposed bare metal again with "metal prep".
5) Be sure the areas are now thoroughly dry and treated- and all perforations are "backed-up" with fiberglass/POR-15.
6) Prime any exposed bare metal (from sanding)with self-etching EPOXY primer (lots of manufacturers have this available).
7) The first layer of "fillers" for the pitted and perforated areas should be done with a special
"metal-based" filler. I use USG's "Metal-Fill", or Marson's "Alumafill II".
8) Roughly shape the Metalfill with 80 grit sandpaper
9) Reseal the Metalfill with self-etching primer
10) Begin application of your "regular" body fillers. I like Marson's "Platinum" body filler for the major filling and shaping, and Evercoat's "Metal Glaze"- epoxy final glazing compound for filling pinholes and deep sand scratches. Avoid using the "spot-putty" in a tube- it is lacquer-based, and absorbs moisture should you ever get a break in the surface paint (or if you topcoat with lacquer).
11) When you are happy with the results of your bodywork, Sand everything at least 12" outside of the areas you've done bodywork to- with 180 grit sandpaper. In your case, you are going to paint the whole roof, so seal all exposed fillers with etching primer- or a pre-paint sealer. and topcoat the entire roof with 3 coats of high-build EPOXY primer. Personally, I like Dupont's K-200, and BASF's DP-20 (Diamond Prime).
12) Now you are ready for your routine block sanding.... and finishing of the roof.
If you have questions about specific areas of your roof (such as the windshield and back-glass channels) e-mail me and I'll try to answer promptly.
Ray
Ray-Lin Restoration
North Carolina
------------------
Mike D'Ambrogia - San Ramon, CA
69 Custom Wagoneer - The Firetruck (http://www.tworock.com/mjd/firetruck.html)
Built 350 w/ Buick 4 barrel manifold, 600 cfm quadra-jet, RV cam, 10:1 - Pertronix ignition - 8mm plug wires
MSD coil - rebuilt TH400 w/ B&M shift kit - Powr-Lok rear end - Factory A/C - Herculiner over new floorboards - Complete rewire with American Autowire Power Plus kit - LPG/Propane install coming soon!