I have gotten conflicting info about this. I did bare metal bondo last time and it didn't work as well IMO. I was thinking prime then bondo then prime again...
Sounds good??
Sounds good??
Prime bare metal before bondo?
- Thread starter dieselcruiserhead
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ya prime
primer/sealer then scuff alittle for adhesion purposes then bondo..
bondo has a premium product that is designed to go over primer.
Check the specs on whichever product line you decide to go with. Evercoat, a good quality brand of filler, states to use the product on bare metal.
From Evercoat's FAQ:
Q. Can Evercoat fillers be applied over bare metal? Can they be applied over paint?
A. Our fillers are designed to work over bare, properly prepared substrates such as: steel, aluminum, galvanized, stainless steel, fiberglass, and SMC. Some people prefer applying an epoxy primer over bare substrates to enhance corrosion protection. Our products don’t need to be applied over an epoxy for corrosion protection as long as the bare surface area is clean and no surface rust or contamination is present. However, some auto manufacturers do require body technicians to coat the bare metal surface with an epoxy before applying fillers. If you are performing warranty work, you should consult the manufacturer of the automobile for the recommended procedure. Fillers and putties will normally work OK over properly sanded (80-180 grit) cured OEM paint. However, with so many different types of aftermarket paint available (lacquer, enamel, urethane, water-based). We recommend that all paint be removed where filler is to be applied.
http://www.evercoat.com/faq.aspx
From Evercoat's FAQ:
Q. Can Evercoat fillers be applied over bare metal? Can they be applied over paint?
A. Our fillers are designed to work over bare, properly prepared substrates such as: steel, aluminum, galvanized, stainless steel, fiberglass, and SMC. Some people prefer applying an epoxy primer over bare substrates to enhance corrosion protection. Our products don’t need to be applied over an epoxy for corrosion protection as long as the bare surface area is clean and no surface rust or contamination is present. However, some auto manufacturers do require body technicians to coat the bare metal surface with an epoxy before applying fillers. If you are performing warranty work, you should consult the manufacturer of the automobile for the recommended procedure. Fillers and putties will normally work OK over properly sanded (80-180 grit) cured OEM paint. However, with so many different types of aftermarket paint available (lacquer, enamel, urethane, water-based). We recommend that all paint be removed where filler is to be applied.
http://www.evercoat.com/faq.aspx
- Thread starter
- #7
I have done that before and had bondo crack and fall off. But also related to wheeling damage. What I have seen for thin layers is primer, then bondo, then primer again. Then several coats of primer with block sanding between. Then several coats of final paint. I was a really bomber but good looking and super solid paint job...
- Thread starter
- #8
Also, I know more primers will absorb some level of moisture. But I feel like a layer of primer before bondo would provide an extra seal to protect the bondo from any internal moisture from the metal as well.. Curious on thoughts on this...
The bodyman (buster congdon) that showed me the ropes insisted that bondo and not much be incapsulated between sealer coats not on bare metal, Always had good luck with his method.But more than a 1/16 bondo was to much for him.
I've worked in a few body shops and not a one would allow bondo to be applied to anything but bare metal. Cracking and popping out can be related to how you apply or mix your hardener vs temp outside & thickness.
read here, one of these is for over primer. I used it that way too.,
http://www.bagdel.com/Bando/Bando.html
http://www.bagdel.com/Bando/Bando.html
old school method was to use 36 grit crosshatch pattern to bare metal for lots of "tooth", a very rough surface. when the metal was slightly flexed it wouldn't pop off... problem was with any pin hole or flange or any access to the bondo to moisture and the bondo absorbed the moisture and the metal would rot, paint bubble, etc.
this method is probably okay if you have access to back of the metal panel and can apply thick undercoating or other.
metal should be very clean and non oxidized.
new school is to try to isolate the bondo from any moisture with sealing surface all around it. I have had good luck and good adhesion when good brand like RAGE was applied to fresh primer like DP that was only few hours old.
some of the newer fillers like metal to metal supposedly have less talc and are considered waterproof. they usually don't sand well or leave as smooth of a finish.
this method is probably okay if you have access to back of the metal panel and can apply thick undercoating or other.
metal should be very clean and non oxidized.
new school is to try to isolate the bondo from any moisture with sealing surface all around it. I have had good luck and good adhesion when good brand like RAGE was applied to fresh primer like DP that was only few hours old.
some of the newer fillers like metal to metal supposedly have less talc and are considered waterproof. they usually don't sand well or leave as smooth of a finish.
Don't use "Bondo". Use Evercoat or other professional type products. Evercoat's metal to metal is a great product as is their Rage Gold. I wouldn't prime first. Most Evercoat products can be thinned with glaze. Use a guide coat and if you have pin holes or other tiny imperfections, use some glaze.
Heere are some good links:
http://www.autobodystore.com/class.htm
http://www.autobody101.com/forums/
Heere are some good links:
http://www.autobodystore.com/class.htm
http://www.autobody101.com/forums/
Saw this recently and figured I would add it. Some interesting results for those who normally insist on using epoxy primer before any filler:
http://www.autobodystore.com/filler_&_epoxy.shtml
http://www.autobodystore.com/filler_&_epoxy.shtml
Cant get any better than that!
I know what im going to do, now.
I know what im going to do, now.
ya what they said
Nice link.. still wonder about corrosion resistance.
kief, doesnt that go back to preperation and location? If doing the bodywork in a humid environment, there will be moisture present in the filler. The brand name Bondo product was notorious for popping when i lived in fl. problem was due to 5 main factors.
1. Crappy product...(enough said)
2. ineffective surface prep.
3. improper mixing(too much hardener, not enough hardener, or not mixing enough)
4. Applying the product too late in the kick cycle, and/or working it too much after its been applied...working it as its hardening injects airpockets into the filler.
and #5. layering a 3/8 inch thick glop of the stuff to fill a hole or cover crappy metalwork.
If youre concerned with moisture coming from behind, then weld up any holes, or seal them from behind with some metal tape, and undercoat over that to lock the tape in place.
1. Crappy product...(enough said)
2. ineffective surface prep.
3. improper mixing(too much hardener, not enough hardener, or not mixing enough)
4. Applying the product too late in the kick cycle, and/or working it too much after its been applied...working it as its hardening injects airpockets into the filler.
and #5. layering a 3/8 inch thick glop of the stuff to fill a hole or cover crappy metalwork.
If youre concerned with moisture coming from behind, then weld up any holes, or seal them from behind with some metal tape, and undercoat over that to lock the tape in place.
Kief,
This is an interested thread.
What I was taught is that you get flash rust forming in 45 minutes of cleaning the metal and similarly with aluminum you get corrosion with in 45 min as well.
Either way, if your going to put filler, paint or whatever on bate metal, you need to clean it before you go to work. RIGHT before. Metal wash is a often done with a mild acid solution but mechanical removal of rust - even rust that you can't see can be done right away.
Take a coupon, clean it off and then let it sit for a day. Wipe down with a clean rag and thinner and you'll see a slight bit of rust of the rag.
Real life example: I once restored an old motorcycle. It was 21 years old when I got from the original owner who had dented the tank when it was brand spanking new. Who ever fixed it back in 74 did such a good job that not only did the filler did not want to come off but the metal was really clean beneath it 20 years later on a bike that was ridden DAILY out in the rain in DC and had 100,000 miles on it. This dent was right next to the gas tank filler and had gas spilled on for years with no lifting or popping and it was about 1/8th thick. This may be key as I have heard this is the max thickness for filler.
I had to use a grinder to take that stuff off as I could not sand it off.
Clearly it was something other than good old bondo. Moral of the story, not all body filler is created the same. EVEN if the same company that makes bondo makes it. Go to the autobody store and get some good stuff that the pros use.
Also, don't mix it incorrectly, if you fold it over when you mix it, it traps bubbles of air in there. And, put it on in many thin layers vs. on thick layer. I find that sanding bare metal is best but that bead blasting/sand blasting/media blasting also makes a good foundation for bondo (and paint).
-Stumbaugh
Good to know, sounds like anything is better than letting my rigs rust to death, as the paint is thinning and the surface rust spreads....