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Old 05-06-2009, 03:10 PM
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biotex biotex is offline
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Join Date: Apr 30, 2009
Location: Alpine,Texas
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primer on bare metal questions

I have spoken with Dupont Technical Support, three body shops, and a few other people knowledgeable in painting, and I get conflicting information. I want to know what is the preferred way to prepare bare sandblasted metal for body work.
The Dupont guy said to apply the epoxy primer first, DA it with 180 grit to bare metal over the repair area, then bondo, then sanding primer. This method sounds like the correct way to me, but the bodyshops say not to put bondo over bare metal. Supposedly moisture can get between the bondo and metal. When I asked the tech guy about this, he said there was no way for that to happen as long as there are no holes in the metal.

Anybody know the correct procedure for applying Epoxy Primer, Bondo, Sanding Primer over bare metal?
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Old 05-06-2009, 03:42 PM
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rixcj rixcj is offline
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Location: RI
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One of my customers builds custom steamboats. He has done extensive research ( pretty much his own trial and error ), on the properties of different types of body fillers.

The typical Bondo that most everyone uses WILL absorb moisture, and could eventually bubble ( something about the talc content).

Apparently, some fillers are better than others. I don't know exactly which fillers are best, or what to recommend, but I just wanted to get this out there.

The next time I see him, I'll ask more about this (if I remember.... ).

Rich
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Old 05-06-2009, 04:50 PM
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If you follow the body shop's advice, you need to use an epoxy primer that allows filler to be applied over it. It's important which primer the body shops guys (that say to paint under the primer) are using. Everybody seems to like the PPG Deltron DPLF epoxy primer. The tech sheet for this primer specifically says that you can apply body filler over the primer. Note that epoxy primer will cure too hard for recoating after a week, so if you coat the metal with DPLF and then fill, you'll need to finish your body work and spray either primer-surfacer or color within the same week. Or else sand all the surfaces before you recoat.
https://buyat.ppg.com/refinishProduc...7-73f8653e2a34

My reading says that putting filler directly onto roughened metal is the common old-school way to do it. You then wipe down with degreaser and coat with epoxy primer. Your top coat will seal out any moisture, as long as there are no holes in the metal.
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Last edited by tgreese : 05-06-2009 at 04:58 PM.
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Old 05-07-2009, 04:41 AM
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OBX-AUTOMOTIVE OBX-AUTOMOTIVE is offline
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Join Date: Apr 10, 2001
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SAY YOUR FIXING A DENT,YOU DING IT OUT, THEN YOU GRIND IT WITH 24gt,THEN SKIM COAT BONDO,THEN SAND, THEN GLAZE, THEN SAND, THEN PRIMER ,THEN SEALER!!

THIS IS WHAT I USED DOING BONDO....1/2 ROUND CHEESE GRADER, 36gt/80gt

IFYOU WANT TO SHOOT CATALYST, WITH OUT A PAINT BOOTH,THEN,YOUR CRAZY!

The Dupont guy said to apply the epoxy primer first, DA it with 180 grit to bare metal over the repair area, then bondo...THAT GUY IS SMOKING SOMETHING!....

I BET YOUR ASKING YOURSELF,HOW DO I KNOW ALLLLLL THIS STUFF???

WELL.BECAUSE I'VE DONE BODY WORK ON THOUSANDS AND THOUSANDS, OF CARS/TRUCKS!

AND DON'T HAND ME ANY OF THAT "OLD SCHOOL" SHEET!!.... BASIC BODY REPAIR HAS NEVER CHANGED,ONLY THE PRODUCTS!

Last edited by OBX-AUTOMOTIVE : 05-07-2009 at 04:49 AM.
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Old 05-07-2009, 05:11 AM
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OBX-AUTOMOTIVE OBX-AUTOMOTIVE is offline
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OH! ONE/OTHER/THING!
AS FOR >>>> DEGREASER,YOU ONLY USE DEGREASER WHEN YOU FIRST WIPE DOWN THE PAINT,AT THE START!

YOU NEVER USE DEGREASER ON PRIMER,SEALER OR BARE METAL!....DO YOU KNOW WHAT "FISH EYES ARE"?

BUT!! HEY!! YOU DO WHAT YOU WANT!

Last edited by OBX-AUTOMOTIVE : 05-07-2009 at 05:15 AM.
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Old 05-07-2009, 05:02 PM
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obx2ack obx2ack is offline
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I'm restoring my 88 GW and ran into some of the same questions. Check out hotrodders.com forum. Here is a link.

http://www.hotrodders.com/forum/sear...archid=2596699

You will find that there are many different opinions on the process. Here is what I decided for bare metal (no rust, clean shiny bare metal). I used all Dupont products

1. Prep sol bare metal with white lint-free cloth until clean
2. DA 80 grit
3. Prep sol again
4. DA 120 grit
5. prep sol
6. final clean
7. epoxy primer
8. 180 grit
9. body filler
10. epoxy primer
11. 320 grit scuff
12. primer filler
13. block with 500
14. repeat primer filler and blocking until happy
15. primer sealer
16. base
17. clear
18. wet sand
19. buff
20. wax

It may be overkill. Probably is, being that I'm only on step 7 and havent driven it in two years.

Check out that forum. Great guys and a world of knowledge. Hope it helps and good luck.
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