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Thread: Epoxy Primer Sealer over bare metal

  1. #1
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    Default Epoxy Primer Sealer over bare metal

    I recently applied PPG DPLF50 epoxy primer sealer (mixed with 402LF catalyst and the appropriate amount of reducer to make it a sealer- 2:1:1/2 ratio) over bare metal with the thought that a sealer was needed to ward off rust during my restoration/ body repair of my 32 ford coupe. I can't get all the body work done in the 7 day window so the thought was to primer it with the ppg primer sealer and work on it a little at a time. Is there any issues with the primer sealer on bare metal? If I have to I will remove it and redo it with just the straight epoxy (no reducer) before going further.

  2. #2
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    I'm not familiar with PPG products but an epoxy primer mixed as a sealer should protect the metal while you work on the car. You can probably just scuff it when you're done and apply more epoxy primer when you're ready to apply fillers, filler primer or paint.

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    The tech sheet on DPLF will tell you to put 1-2 wet coats of DPLF mixed as a primer. When mixed as a sealer the sheet says you must maintain minimum build thickness which I would think would be a bit thinner since reducer was added. Now you didn't say how many wet coats you applied?

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    I put on 2 good wet coats of the primer sealer overlapping 50% on each pass. I have pretty good coverage as far as I can tell.

  5. #5
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    As tbm3fan said, The only difference between using it as a sealer and first coat is the reducer. It is optional on the first coat so you're good to go, really no difference at all. I still would keep moisture off it though. The only bad thing is you'll have to scuff sand it all (for adhesion)as the recoat window is 1 week. I would scuff if you leave itmore than 2 days just to be safe.

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    What do you recommend I scuff it with? Grey or red scotch brite or should I go with something more aggressive like 80 grit paper dry? Also since I'm already outside the recoating window of 7 days and I still need to apply filler do I sand/scuff, apply 1 more coat of epoxy primer and then do the filler or should I just grind to bare metal with 80 grit and then do the fill on those areas?

  7. #7
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    Quote Originally Posted by dpayne
    What do you recommend I scuff it with? Grey or red scotch brite or should I go with something more aggressive like 80 grit paper dry? Also since I'm already outside the recoating window of 7 days and I still need to apply filler do I sand/scuff, apply 1 more coat of epoxy primer and then do the filler or should I just grind to bare metal with 80 grit and then do the fill on those areas?
    Sheet says sand and respray with one coat. I'd go 80 so you get a good bite. Most here will tell you to do all your filler/body work on bare metal, THEN apply your epoxy. That is what I do now and saves you recoating epoxy. Paint companies want it before and after because you use more product

    On a side note. The only time reducer is required with DPLF is when painting flexible parts. DPLF IS a sealer whether you want it or not. I use put the optional reducer in it all the time as it sprays so much nicer. I have gone straight to topcoat numerous times with no problems

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    Kevininohio- thanks for your help. I spoke with PPG today and they are saying they would not recommend applying the DPLF as a sealer on bare metal but would have rathered I used the epoxy primer without the reducer. They are concerned that the product would not have enough film build with the reducer in it. We discussed sanding the current epoxy with 220 to 320 dry (ppg recommendation) and then applying another two coats of straight epoxy without the reducer. They were fairly uncommittal about doing this and just kept reiterating their recommendation would be to use straight epoxy on the bare metal in lieu of epoxy sealer. After reading the tech sheet (P196) I don't see anywhere that they state that a sealer should not be used on bare metal. There is a warning that when using it as a sealer the minimum dry film thickness must be maintained. The conclusion I'm reaching is that as long as I have the minimum DFT of primer I should be ok provided I apply another coat of epoxy prior to doing the filler work. My plan is to sand the car with 220 dry, apply 2 coats of epoxy, apply the filler, block sand the filler, spot prime the filler with epoxy, apply 3 coats of ppg k36 primer surfacer, block sand, apply 1 epoxy sealer coat of DPLF (with reducer), apply 2 coats of PPG DBU base and 3 Coats of PPG DCU2021. What do you think?

  9. #9
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    Quote Originally Posted by dpayne
    Kevininohio- thanks for your help. I spoke with PPG today and they are saying they would not recommend applying the DPLF as a sealer on bare metal but would have rathered I used the epoxy primer without the reducer. They are concerned that the product would not have enough film build with the reducer in it. We discussed sanding the current epoxy with 220 to 320 dry (ppg recommendation) and then applying another two coats of straight epoxy without the reducer. They were fairly uncommittal about doing this and just kept reiterating their recommendation would be to use straight epoxy on the bare metal in lieu of epoxy sealer. After reading the tech sheet (P196) I don't see anywhere that they state that a sealer should not be used on bare metal. There is a warning that when using it as a sealer the minimum dry film thickness must be maintained. The conclusion I'm reaching is that as long as I have the minimum DFT of primer I should be ok provided I apply another coat of epoxy prior to doing the filler work. My plan is to sand the car with 220 dry, apply 2 coats of epoxy, apply the filler, block sand the filler, spot prime the filler with epoxy, apply 3 coats of ppg k36 primer surfacer, block sand, apply 1 epoxy sealer coat of DPLF (with reducer), apply 2 coats of PPG DBU base and 3 Coats of PPG DCU2021. What do you think?
    That is HIGHLY interesting they would say that. My PPG rep RECOMMENDED DPLF over sandblasted and other sanded bare metal. As you state the sheets say it is fine. Look on the last page of 196 and it clearly states DCC and DBU can go right on top of it.

    My paint sequence is the same as you listed except I do the Body work/filler first, slick sand, 2 coats epoxy, K36, 3 coats DBU and finally 3 coats DCU 2021.

    With your plan you'll do fine. What would they prefer you use on bare metal? Was it just not have the reducer in it. It's so little, I don't see how it effects the end result enough that they wouldn't put a warning in the sheets. Amazing.

  10. #10
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    Kevininohio- Thanks again for your interest and help. I'm new to all this so every little bit of info helps. All PPG was saying was that they didn't recommend the DPLF epoxy as a sealer over bare metal, ie with the reducer in it. They fully recommend using the DPLF epoxy mixed as a primer(no reducer) over bare steel (sanded or sandblasted). My original thought was that the DPLF mixed as a sealer would be better because it would seal out any moisture until I had time to do all the bodywork. That's why I sprayed it as a sealer instead of just as a epoxy primer. I had stripped the entire body by DA and by sandblasting and didn't want it to flash rust so I primed it with the DPLF sealer ( with reducer) to allow me time to get all the body work done. It's hard to believe that the small amount of reducer would make much of a difference. Like I said in my previous post I think PPG was only concerned that the proper film build (0.75 to 1.5 mils) would be obtained using the DPLF epoxy sealer because the reducer in it thins it out causing thinner film builds. If I had to do it over again I would do all the body work before applying the epoxy primer, as you currently do, and then give it 2 wet coats of spraight DPLF epoxy Primer.

    You said in an earlier post that you use to apply the DPLF with the optional thinner (ie as a sealer) and then go straight to top coats with no problems. What was your sequence then? Was it 2 coats of reduced DPLF followed by filler, high build primer surfacer, more DPLF sealer, 2 coats of base color and finally 3 coats of clear?

  11. #11
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    Sanding the cured epoxy with either 320 or 400 should be more than enough. The guy I go to who has sold PPG a long time says that is what he would do and everybody in the store nodded their heads. I did what he said and with those grades it is easy enough to go right through the epoxy to bare metal if aggressive.

  12. #12
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    Quote Originally Posted by dpayne
    You said in an earlier post that you use to apply the DPLF with the optional thinner (ie as a sealer) and then go straight to top coats with no problems. What was your sequence then? Was it 2 coats of reduced DPLF followed by filler, high build primer surfacer, more DPLF sealer, 2 coats of base color and finally 3 coats of clear?
    I used to work at an agriculture fertilizer outfit. We'd sandblast the rigs bare, 2 coats epoxy and 2 coats of topcoat. No base clear there We did it for durability and it did better, longevity wise, than factory paint. Fertilizer is like salt only worse for metal.

    I've never done base/clear directly after epoxy. Here is my current project. I did the leaf springs using this method. Sandblasted, smoothed bare steel down to 150 grit, resandblast lightly, 2 heavy coats of DPLF, 2 coats of DCC color with no sanding after DPLF. Used the thinner as these ARE flexible parts. Picture doesn't do it justice on how smooth it is. Would I do it on body panels? NO, but for certain things it works great.

    MVC-024S.JPG

    MVC-025S.JPG

  13. #13
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    Kevininohio- I talked to PPG again later today and got a different technician. He said their only concern with putting on reduced DPLF was that insufficient film build might result depending on how many coats were applied and how heavy each coat was. He said to fix this issue I should sand the car with either 320 dry or a red scotch brite and then apply two coats of the DPLF epoxy without reducer. So I came home from work and went out to the shop to start sanding. I had originally applied duraglass on the welded areas so I began sanding those areas first. I put this duraglass on the welded areas of my coupe after doing the original 2 coats of the reduced epoxy primer. I applied the duraglass after roughing up the surfaces with a scothbrite even though I applied the filler within the recoat window. It's been a week since I put it on. That stuff if pretty tough to sand! I knocked it down with 40 grit then 80 grit. I was going to sand the entire car with the 320 as PPG recommended and then top coat it with two more coats of the DPLF epoxy, then do the rest of the body work. But after sanding the duraglass I would only have to sand a little more with the DA and 80 grit paper to be down to mostly bare metal in the areas needing further filler. I'm thinking of doing the bondo work on bare metal and then sanding the entire car with 320 and then the 2 coats of epoxy on everything. What do you think?

    Man do those springs look great! So does the chassis!

  14. #14
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    Quote Originally Posted by dpayne
    Kevininohio- I talked to PPG again later today and got a different technician. He said their only concern with putting on reduced DPLF was that insufficient film build might result depending on how many coats were applied and how heavy each coat was. He said to fix this issue I should sand the car with either 320 dry or a red scotch brite and then apply two coats of the DPLF epoxy without reducer. So I came home from work and went out to the shop to start sanding. I had originally applied duraglass on the welded areas so I began sanding those areas first. I put this duraglass on the welded areas of my coupe after doing the original 2 coats of the reduced epoxy primer. I applied the duraglass after roughing up the surfaces with a scothbrite even though I applied the filler within the recoat window. It's been a week since I put it on. That stuff if pretty tough to sand! I knocked it down with 40 grit then 80 grit. I was going to sand the entire car with the 320 as PPG recommended and then top coat it with two more coats of the DPLF epoxy, then do the rest of the body work. But after sanding the duraglass I would only have to sand a little more with the DA and 80 grit paper to be down to mostly bare metal in the areas needing further filler. I'm thinking of doing the bondo work on bare metal and then sanding the entire car with 320 and then the 2 coats of epoxy on everything. What do you think?

    Man do those springs look great! So does the chassis!
    Sounds like a good plan. In the future do the filler work first. You can do a panel/side at a time, Body work and filler, epoxy, then shoot your K36 and let it sit. Go to the next panel/side and repeat. That way no bare metal for extended times and when All the body work is done you can just sand. As long as it's inside you do fine thuis way. Kevin

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