from a hot rodders standpoint is he might strip a fender then you cant leave it or it will start rusting so he epoxy primes first then he can do his filling later..If everybody works like me i strip one part at a time (BE IT A FENDER OR DOOR) then epoxy prime then using filler which is never right the first time it allows him to avoid the dreaded rust gremlin.mike

GalaxiGuy,
First of, Dang you got your Christmas tree up and still have time to spot primer. Your my idol. I need to get up on the roof and fall of a couple of times to make sure the lights are working LOL. But Seriously thanks. I was trying to figure out should I get all the weld lines and beads done at once then primer. But You provided exactly what I needed to know. Also I shot my ever first line of paint mp170 epoxy primer and it was a rush. I'ts been two days and I'm still peeking on the inside of the truck to see it. But I'm going to have to first get all the spot welds done on the top seam then grind them down and epoxy prime the spot. then get back to filler which I'm using the evercoat rage product. Then someday get that tree up....

I really don't see how either way would really make a huge difference. Applying the Epoxy first will only add an extra step. I don't see how it offers any more protection. This is why; If you apply the filler directly to scuffed metal and then epoxy over it, How will moisture get to the filler or metal under the filler? It can't since it is potected by the epoxy, correct? What more protection does apply epoxy first and then filler offer?

I am not saying one way is better than the other I just want a clear cut answer as to why some think one way is better. This is a question I have had for years and as you can see it all depends on who you ask.

Now if you were going to apply filler over bare metal and NOT use an epoxy primer or sealer over it. I can see how problem could occur. Once the work is sealed (epoxy or sealer) the metal should be protected, correct?

How do you get enough bite for the filler if you apply it over epoxy? I was always taught to apply to cleaned and scuffed (36 grit) metal, to give the filler something to bite into. So if you have an area to fill, do you grind, then spray epoxy and then fill? Just seems to me the filler would have more of a chance to lift if it doesn't have a good tooth.

Just something to think about. Not argueing either way.

Royce

Actually what I see in the Hot Rod, Custom Car and restoration area is that the guys try and massage the metal until it is smooth and good and so very little filler is required any way..If tha tis done then any minor scratches can be taken care of with a high build sanding primer or one of the thinner fills.

Actualy we are trying to en-courage folks to learn the metal finishing skills as I have found that for myself that I can take out a dent or crease in pretty short order using the slapper and dolly and the shrinking wheel and then not need to use any or very little filler to get a nice job.

That is instead of doing the "cave and pave" routine and winding up with a lot of bondo on a car..

Just a different approach to doing the work..I do think it does make a difference in the quality of the finished job..

By then using the epoxy the piece is then rust proofed and can be set aside while I work on the next piece..

This is just what I have learned to do..

OMT

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I would rather make it work than make it popular..And if it does not work it will not be popular..

How do you get enough bite for the filler if you apply it over epoxy? I was always taught to apply to cleaned and scuffed (36 grit) metal, to give the filler something to bite into. So if you have an area to fill, do you grind, then spray epoxy and then fill? Just seems to me the filler would have more of a chance to lift if it doesn't have a good tooth.


Royce[/QUOTE]


Yeah, years ago I was also taught to rough up the metal with a coarse grit grinder using a crisscross pattern for the ultimate texture for the filler to stick to, but with todays fillers this isn't necessary-they stick well to bare metal with minimal texture. But they stick even better to epoxy primer-try it. Think of the filler adhesion to epoxy primer being similar to that of urethane primer applied to epoxy primer and you won't be far off base-can't seperate them if applied properly. Bob

[QUOTE=camaroman7d]I really don't see how either way would really make a huge difference. Applying the Epoxy first will only add an extra step. I don't see how it offers any more protection. This is why; If you apply the filler directly to scuffed metal and then epoxy over it, How will moisture get to the filler or metal under the filler? It can't since it is protected by the epoxy, correct?
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Either way is great and its not about filler not sticking. Filler sticks to ground metal just fine and great for everyday work.
The filler for one is porous (air) and never totally drys or all the solvents leave if it did it would crack, so now you have air and solvent and it can start a rusting process.(ever sanded filler 5 or more years old, the metal is turning yellow)
Lead, nothing lasts long term over lead except epoxy, so instead of grinding out the lead as a lot of restorers do, coat with epoxy and than lay the filler or glaze coat over the epoxy and the epoxy will work as an insulator.
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I am not saying one way is better than the other I just want a clear cut answer as to why some think one way is better. This is a question I have had for years and as you can see it all depends on who you ask.
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There are a number of benefits, first after a week or two filler gets brittle and filler sticks so good to epoxy it will give the filler a fair amount of flexibility.
This is most important on Fiberglass, SMC and other plastics for long term life.
Best example I can give is the endure bumper on the 69 Judge, it was shot and you cannot find a replacement that is any better, so I epoxied it and than sprayed two coats of polyester primer and blocked smooth. It will be good for years but if I had not used the epoxy it would have cracked first day in sun or just setting in the showroom, only a matter of when!



How do you get enough bite for the filler if you apply it over epoxy? I was always taught to apply to cleaned and scuffed (36 grit) metal, to give the filler something to bite into. So if you have an area to fill, do you grind, then spray epoxy and then fill? Just seems to me the filler would have more of a chance to lift if it doesn't have a good tooth.
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As the open-coat goes away the adhesion will take care of itself.
Just like paint over epoxy, the adhesion goes from poor to great in a couple of days. Sanding the epoxy first does not hurt or help adhesion before applying filler or glaze.

Like I said, either way is great but if your doing high dollar rods or restorations, its not a bad idea to do the filler work over the epoxy.

Thinking about it, I have not put filler over bare metal since 1976. Reason I know the date is that is when I was sent to Mercedes so I could be qualified to do warranty work. Its been so long I just cannot bring myself to do it no matter what I'm fixing.
Hope this helps, without writing a book.
Barry

Barry.
That was a real good explanation.
Question, Is it better to apply the filler within the specified time limit, or let it cure or whatever solvent evaporate before applying filler, what would be the best time if you could please give it in hours. I am thinking wait over a week then scuff, it then body filler, in case of evaporation or shrinkage if this happens. Also can you wait a year or two then scuff epoxy and paint it, this is ppg dp
Thanks Rob
http//www.2manitowoc.com/paintroom.html

http://webpages.charter.net/2manitowoc

An overkill and a good rule to follow is at 75 degrees let the epoxy set over night 6-12 hours.
However, most tech sheets say an hour or two.

The LF is a little slower cure than most if its a custom job where time allows I would give it two day before applying the filler or like you said hand sand with 180 down the road first. I'm a little afraid to say "that down the road" with the LF as I have not tested it in a long time. So I would unless PPG can give you an answer feel better to say after seven days scuff the epoxy and re-coat than apply the filler in day or two.

edit
Hey I was just looking at your frame pictures. Now that is a frame job, I want to tell you!

Barry, thanks for the information and the compliment
Rob

Ok I think I see where you are coming from with the 'bond". You are saying the filler will have a chemical bond to the epoxy. When applied to vare metal the filler has a mechanical bond, that's where the difference is. I will give it a shot and see how I like it. I don't do it for a living, I just do all my own work.

Now that that part is answered, I still would like to know how epoxy under the filler offers more protection? Like I stated above with epoxy over the filler there is no way for moisture to get to the filler and metal under it. Are we saying that with the filler over epoxy the bond is stronger? If so, that's the added benefit?

Thanks for the clarification so far. This is good information.

Royce

When doing patchwork where there is a great chance of pinholes being overlooked in the weld area and this also goes for plug welds there is always a chance these pinholes or even smaller voids will leave an open channel for moisture to wick into the bodyfiller from the backside of the panel. When this happens the moisture will be held within the filler and create rust on the surface of the metal below the filler. By applying epoxy to the metal surface it will protect the metal no matter if any amount of moisture is absorbed by the filler. This is just one example of potential problems and the benifits of using epoxy. Another example like Barry said is to use epoxy to seal fiberglass before any filler work. Now in the case of fixing a dent using filler over bare metal then sealing the repair with epoxy, that's just fine and it will hold up as long as the seal isn't broken, but once that area get's a chip or scratch that compromised the protection the filler will absorb moisture and start the rusting process. In this situations it's still a plus to use epoxy though for the extra adhesion and flexibility offered. Using filler over bare metal is still a right way to do it, but using filler over epoxy is the better way IMO

This discussion has been added to the Body - Exterior Discussions category of the Hotrodders Knowledge Base.

Also, the Wikipedia.org article on rust has been added to the Body - Exterior Articles category of the Knowledge Base. Thanks OneMoreTime for posting the link .


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Body filler on rough, bare metal will outlast the owner. I've had some on my 62 Chevy for over 20 years and it's still holding. I don't see the need to put filler over epoxy.

in my auto body class we've been taught to use filler direct to metal. And I will still continue doing so. Over filler I can use epoxy

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