Epoxy primer or SElf Etching - Team Camaro Tech
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post #1 of 12 (permalink) Old Apr 12th, 00, 12:52 PM Thread Starter
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I just got a new project car, and it has some serious surface rust. I am going to have the entire car blasted to get rid of the rust
and old paint. I am trying to decide what type of primer to use. Some people say the PPG DP90,while others say go with a full etching primer. Any input? Can the DP 90 be sprayed over putty like where I am going to weld in the new quarters? Also, whats DP90 cost a gallon?
Thanks
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post #2 of 12 (permalink) Old Apr 12th, 00, 03:00 PM
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The DP90 is a great primer and will adhere to putty and anything else just fine. Big problem, the DP40, DP50 & DP90 have been discontinued by PPG for some time now due to VOC regulations. The products that replaced them have an "LF" suffix on them. They are not nearly like the old formula. If (and it's a big IF)you can still find the old formula, you'll pay around $110 to $130 gallon. That would be more than enough to cover your car and then some. But you'll also need the DP401 catalyst. Again same problem with the DP90. That stuff is around the same price per gallon, maybe just a tad more.

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[This message has been edited by cardude (edited 04-12-2000).]
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post #3 of 12 (permalink) Old Apr 12th, 00, 03:56 PM
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I thought the DP-90 was a sealer, after the car has been worked with a builder (primer). It's been my experience that the sealer shrinks like paint. And after it's shot the car needs to be painted within 7 days, or you have to scuff, reshoot sealer, then paint. A secret I learned: go ahead and add a little shot of reducer to sealer & catalyst. It will spray smoother, and less chance of orange peel. Hope I'm on same page as you guys.
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post #4 of 12 (permalink) Old Apr 12th, 00, 04:45 PM
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When I went to a PPG training center they showed me some metal panels that were put topcoated, scratched, and run through salt tests. The panel sprayed with metel etch (wash primer) did better than the panel with DP 90 epoxy primer. I agree DP is a good product but a metel etch will give better corrosion resistance. Personally I would metal etch the whole car then follow up with DP, you can then grind the areas that need body work and do your repairs. This way the car is protected from the elements till it is ready for paint. As mentioned above it will have to be sanded before topcoating. As cardude mentioned the old DP has been discontinued and I agree the LF series in far inferior. I'm told we can still get DP in my area, but its not being produced anymore so its only while remainding supplys last.
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post #5 of 12 (permalink) Old Apr 12th, 00, 05:41 PM Thread Starter
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Do you guys have any part numbers that you recommend for the etching primer? Basically I hit the bare metal with etching primer. Do the body work and use a high solids sandable primer, then seal it with a DP90 type product before top coat. Any bare metal that appears in doing the body work should be sprayed with etching primer and not the high solids sandable. correct?
Thanks
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post #6 of 12 (permalink) Old Apr 12th, 00, 05:42 PM
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Wow, when did they quit producing DP 90? It's been over a year since my father or I purchased any. Wow, I hope we can still get it where I live. I think it would look great on some parts that we are doing for his 1948 Plymouth.

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post #7 of 12 (permalink) Old Apr 12th, 00, 05:42 PM
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Austin, I've been told there is a way of making the LF work better by mixing in some reducer such as Steve mentioned. Only by doing this, you are not VOC compliant. Have you run into this?

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post #8 of 12 (permalink) Old Apr 12th, 00, 06:19 PM
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When I did the body on my car I took it to bare metal first, cleaned it with a metal prep product and rinsed it with very hot water. Then I sprayed on a self-etching primer followed by a light coat (initially) of a primer-surfacer. The self etching primer really locks into the bare metal and gives it good corrosion resistant but it's not real tough - which was the reason for covering it with a layer of the primer surfacer.

When the body work in an area was finished I sprayed the self-etching primer on all bare metal followed again by the primer surfacer. When all the work was done and the entire car had been block sanded and was ready for paint, then we sprayed a sealer on prior to the paint.



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post #9 of 12 (permalink) Old Apr 14th, 00, 07:26 PM
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MikeDF80 If you are using PPG products use etching primer "DX 1791 & DX 1792" they are mixed 1 to 1. You can also add up to 10% of DT reducer to slow it down alittle (so it doesn't spray dry). You only need one light coat. According to my PPG rep this is the best performing metal etch PPG makes. I like to spray on DP about a half an hour after the metal etch just to seal it off. I then let it dry and in a day or two begin my body work. When done with body work I reapply metal etch to any bare metal areas and prime with a high quality primer. Metal etch has no filling quality it only helps prevent rust from accuring, so primer is needed over any body work that is performed.

cardude I only used DP LF a few times before we switched to PPG global which uses differant sealers, but the few times I used it I had some adheasion problems. The only things we use from the deltron line anymore is 1791&1792 metal etch, and we still have some DP for hitches, trailers (stuff like that). Global has its own metal etch, but my rep showed us how the 1791&2 out performed it, and also out performed DP in scratched panels put through salt tests. It etches the metal to prevent rust even if scratched or chiped. As far as reduction goes the regular DP it was not made to be used as a sealer, but when shops learned of its great adhesion they started using it for a sealer. If used as a sealer it SHOULD be reduced with DT reducer (1:1:1/2) other wise your paint can die back (loose gloss) after drying.
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post #10 of 12 (permalink) Old Apr 15th, 00, 06:46 AM Thread Starter
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Austin,
What primer do you recommend to use over the spots where body work is done?
Thanks
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post #11 of 12 (permalink) Old Apr 15th, 00, 08:47 AM
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Here in denver there's a shop call "ReinCARnations" that does resto work on all kinds of cars but specializes in Jags. I was up there with a neighbor (restoring an XKE) and saw a different approach to this issue of protecting metal.

This guy media blasts his cars to bare metal and then powder coats everything in a color very close to the final color. His reasoning is that the powdercoat can get in every little nook and cranny and forms a great corrosion resistant seal on the metal. The undercarriage is generally left alone after this, but he does body work right thru the coating - just sanding the area and working it normally. When he's all done he lightly sands the entire body and applies a conventional primer/sealer and then proceeds with a normal paint process.

He claims great long term success - and I suppose the extra grand or so for the coating gets lost in the overall cost to professionally restore a Jag. Not sure it's practical for the average guy but it's an interesting approach.

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post #12 of 12 (permalink) Old Apr 15th, 00, 08:06 PM
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Any good catalized high solids primer. The primer I use now is D822/D823 from PPG. I'm not trying to be a PPG pusher, its just what my shop uses so I know more about PPG. Other paint systems have similer products. Just make sure when you go to your paint jobber tell him you want high quality not "affordible" you'll be happier in the end. I actually prime the whole car, then block with a long block by hand, and reprime. This step might need to be repeated if your body work is shaky.
RockyMtnRacer, I haven't heard of this approch on auto sheetmetal. I can see the duribility of powdercoat, but you really have to bake that stuff. Our booth is capable of 200 degrees but we are told to keep it 160 or below so we dont damage anything on the cars. I'm not sure of the temps for powdercoat, but I thought they were much higher than that. If I'm right you would have to have your car striped to nothing but metal (I'll check into it we have a local powder coat buisiness). I'll let you know what I find out.
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