Quick question... Sealing up the body on my Model A because I've got to put it on a trailer and drag it across country. It's an epoxy primer/sealer. When I get the car to its new home I have some body work to finish up that I simply ran out of time to finish before loading it up. The plan was to simply protect it and then sand it off where filler is needed or maybe even take ALL the sealer off. I've always put filler directly to metal. Should I consider leaving it when I'm ready to get down to business and just hit it with 80 grit to give it a little tooth? Or just go ahead and take it all off? Some input would be appreciated! Thanks! S
Filler to bare metal is out of date. Applying filler over epoxy primer is now the preferred method. You should be good to go. Congrats on your move to Hill Billy Heaven by the way. It's a great place to live.
Body filler over epoxy is recomended, giving it a little tooth to grab after sitting for awhile is a good idea.
I "heard" it's the latest rage...putting filler over epoxy primer..... I prefer to get my body as straight as I can....with filler....before primer ever hits the surface....
Hey Scott, For eons, it was filler on bare metal. Now its filler over epoxy on bare metal- fresh 18-36 hour old epoxy to get a chemical bond between the epoxy and fillers then epoxy again. That's the stories anyway. It all sounds good and like the next best thing to sliced bread, that's how I chose to do it. I had a major failure with fresh epoxy first then filler. The reps did all sorts of testing and lab studies and could find no fault on my end and claimed to not be able to find any fault or more than likely didn't want to admit fault. The did cover the costs to redo the project with plenty of their core products. There's probably millions of jobs that didn't fail. In the end, the main tech guy told me to put the filler on the bare metal. Skim coat of waterproof first, duraglass or allmetal then my favorite fillers. Of course that eliminates them from exposure to a loss of body work and only to the finish right. Maybe epoxy first really is the best way, but it wasn't on that day for me or the manufacturer.
I've seen the results where filler has been put over paint and primers. It's fine if it's just a skim coat but other than that, no way. No frickin way. You still can't beat a fresh grind with a disc to give the bondo something to adhere to. It will last longer than it needs to.
Yeah I think the first time I saw it demo-ed was 20-25 years ago It's an expensive cure for a problem that doesn't exist
Filler over epoxy? I've always found that the primer tends to burn and then the lead just won't stick to the body no matter how hard I try. Doc
it depends on the filler you wanna use. older style evercoat or bondo i hit with 50 grit or 80 grit on bare metal. but they have newer filler like quatum1 that recommended over primer or paint sanded with 180 grit. both have draw backs but evercoat turns to concret damn near the longer you leave it on there and can be a huge pain to sand. as where quatum1 sands like butter as soon as it kicks off and hardens or 6 months later. most bondo cracks and fails because the of improper prep somewhere along the way, if your metal is not prepped well before you put the primer down everything on top of it is only as good as the layer it holding on too.
Filler is hydroscopic and absorbs water - the water then causes the filler to expand and you get the "bubbling or bursting" effect that you see when the rust and "bog" burst out on a improperly repaiered or finished panel. By repairing the panel with steel, using an expoxy undercoat and then the filler with another coat of expoxy filler over the top you are trying to "lock" the filler away from any moisture and thus stop any hydroscopic action and the resulting bursting/expansion of the filler. Here in New Zealand where we have a high huimidity this makes sense however to some guys who live in a low humidity environment then it may be not be as necessary. Some guys will even say you should use an etch primer first on the bare steel then the expoxy undercoat. All highly technical I suppose however when you are looking to do the job right the first time whether its in business or your own pride and joy I am a strong believer in following these steps - no come back and no repeat of a job a few short years down the track when the "bog" bubbles and ruins an otherwise fine job
I've had a "drop" of filler fall off the cardboard (not recommended) mixing plate and hit the concrete floor. I had to chisel that shit off the floor.
Wow! Quite a mix of responses... I'm using Rage Gold for filler. Quantum puddy for any fine skim stuff where needed. By the time I get the car to it's destination the sealer will probably be real dirty and need to be mostly, stripped, but it sound like a lot of you prefer to seal first. Interesting. I honestly wasn't expecting that. I've always gone straight to clean, bare, metal and applied it with the body being as close to ambient temp as possible. Maybe I'll be reconsidering. The thing I always wondered about applying filler over sealers is the tooth needed. If I'm not mistaken, once you sand a sealer product you break the sealing properties, don't you? But if you don't sand then you don't have the tooth and you're relying on a chemical bond. Seems risky. Some good info here. Keep it coming... Thanks guys!
I used to paint boats...boats that would sit in the water all the time. We put epoxy primer down first, then filler, then more epoxy, then topcoat.
Ive had to redo lots of bodywork that was done over epoxy . It just doesnt adhere as well as it does to just plain ol metal!
I spray bare metal with self etch then grind back to do filler then primer, block, primer paint but i'm no expert
More food for thought.....http://www.autobodystore.com/filler_&_epoxy.shtml Personally, I have been using plastic filler directly over clean metal for 25+ years. No failures so far. The key is having solid, sound metal and applying as little filler as possible. I also wipe down the metal with solvent first to remove fingerprints, etc
Claiming better adhesion and durability, in recent years it has become popular to put filler over epoxy primer. I have done hundreds of jobs where fasteners had to be tightened on surfaces that were filled and show finished. Having tried both ways, this is what I can pass along: - Metal is not porous. If you are painting rusted through metal, that needs to be addressed. Although filler is damaged by moisture, filler applied to metal and covered with primer/paint is protected from moisture just as well whether or not the filler is applied directly to the metal or over primer. - Primer adheres to metal, filler, and itself, better than filler adheres to metal, primer, or itself. - Filler adheres to bare metal better than it does to epoxy primer. So what's the bottom line? Filler adhesion is the weak link. Because filler adheres to bare metal better than it does to primer, the higher adhesion/mechanical strength is achieved when filler is applied to bare metal, then coated with epoxy primer. We aren't talking about a small difference, it's major. While either seems to be adequate for a quarter panel, there is a big strength difference between the two alternatives. It is very important that filler be applied to a rough, clean surface. A sandblasted surface is ok, a rough sanded surface is good.
You have the right idea, stripping the epoxy off before you start doing the body work at your new location. Epoxy primer is just that, primer... It will soak up moisture and deteriorate without a top coat. Good luck on the move and put it on bare metal.
I usually put filler over bare steel, but on occasion, I have done it over HOK epoxy primer, and do quite a bit of tiny touch ups with catalyzed glaze on top of the epoxy. Haven't had a failure with either. Just do it RIGHT!
I have over 30 yrs experience as a body man. The idea of putting filler over epoxy is not new, was recommended by some paint companies at least twenty years ago. I did it that way (filler over epoxy) for a while, but have had some problems with filler adhesion. The other thing about this method that I do not like is that when you sand your filler, you break through the epoxy around the edges of the filler. Unless the epoxy is very well cured, it is hard to feather edge nicely. I have gone back to putting filler on freshly ground, clean metal only. Never had an adhesion problem with filler over bare metal! Not saying using epoxy is wrong, just telling you what works for me.
I have restored and repaired many, many cars using either method. Never had a car come back with any problems. If you are worried about the filler seperating from epoxy/or even paint do a test of your own, test filler on bare metal and do a test on an epoxied,primed or painted panel. I garauntee you that if you use quality products and sand the surface with attleast 180, you will have a hard time removing the filler... or telling a difference after paint is applied. Many newer/replacement panels use a special coating that is even better than primer (can't remember the name off it) but why would you want to strip it all off just to apply filler... Also primer wether epoxy or high build is NOT a sealer, their is primer sealer that is the last coat before paint . So the idea of losing the sealing capabilies is not an issue concerning filler over epoxy,or high build primer. I have to say that 62 chevy does have a point... you need to let the epoxy cure for a good while before applying any filler.
As 35Desoto said, it depends on the humidity in your area. Here in NZ, where we can have 100% humidity its is suicidal to bog over bare metal. Your exspensive paintjob wont last more than 3-5 years before it starts to bubble up. Of course the customer then comes back complaining that his paint is blistering and expects me to repaint for free or else legal action!! ( this is the cars that came to me already primed). Every single time, it has been that the car was bogged over bare metal and there is a browny orange rust stain under the outer edges of the bog over the bare metal!!! It seems that the bog, being porous, absorbs moisture from the air, and then when it is sealed in by the 2 pak paint, it then sweats against the steel. It doesnt happen in the centre of the bog patches where it is thicker, but only around the thinner edges of the feathered out bog, where the moisture doesnt have to travel far before it hits the steel. It never used to happen as bad in the lacquer days as lacquer must be more porous than 2pak and allows it to "breath" and not sweat. There are epoxy primers especially designed to go under bog, ONLY use those if anyone is going to bog over epoxy. We use a PPG epoxy primer that can be bogged over after only about 1/2 hour. And, as a side note, some companies like porsche or audi, that have/had galvanised bodies, the factory recommended method was to epoxy prime the car before you did any bog work.
No question that adhesion is adequate for most situations, people do it successfully all the time. But there is no question that filler/primer/paint results in better adhesion than primer/filler/primer/paint. While many say what you have, if you read the product sheets and application instructions for DP primer, it is IS a sealer. And, all the paints I have used over DP primer do not recommended using a primer over DP primer. Changes were made when DP primer switched to the LF series. The primer is no longer 100% impervious to moisture as it once was. In spite of that PPG still doesn't recomend a sealer coat.
If the filler is absorbing moisture from the air, that moisture would cause paint failure. Not doubting your observations, but I believe we are missing a piece or two of the puzzle.
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