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Old 05-17-2009, 07:07 AM
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How long do epoxy primers last? (uv fade)

I want to shoot my Nova project in Gray PPG DP epoxy and leave it as a topcoat for awhile. I know questions surrounding this subject have been beat to death as this appears to be "trendy" right now. For me, I'm getting older (and nostalgic) and gray primer reminds me of all my old Novas I had as a kid (typically, couldn't afford real paint). How long does it take DP to "chalk up" when exposed to UV? The car will be kept in the garage and only really come out on dry weekends. If I get a few years out of it like that before I have to scuff and reshoot, I'd be happy. Any thoughts?

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Old 05-17-2009, 07:54 AM
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it's not really the UV protection that's the problem ( it's part of the story ) but the main concern is that primer absorbs moisture causing rust you can't see.. the top coat is needed to seal it up.... possibly shooting a flattened clear over top would make it permanent.
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Old 05-17-2009, 08:58 AM
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Quote:
Originally Posted by matt167
it's not really the UV protection that's the problem ( it's part of the story ) but the main concern is that primer absorbs moisture causing rust you can't see.. the top coat is needed to seal it up.... possibly shooting a flattened clear over top would make it permanent.

So that particular epoxy absorbs moisture? If so, what is the reason to use it over other waterproof epoxys?

I've left bodywork in epoxy for months on drivers with no problems. I always sand it good before topcoating and usually shoot another coat of epoxy before topcoating. I realise it won't last forever, but the Kirker epoxy I use holds up great in the short run when exposed to the elements.
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Old 05-17-2009, 09:02 AM
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I was always under the impression that catalyzed primers (with hardeners) like PPG's DP series were water proof. I know the old spray bomb primers did indeed suck up moisture like a sponge leading the futher corrosion issues.
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Old 05-17-2009, 09:42 AM
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Quote:
Originally Posted by matt167
it's not really the UV protection that's the problem ( it's part of the story ) but the main concern is that primer absorbs moisture causing rust you can't see.. the top coat is needed to seal it up.... possibly shooting a flattened clear over top would make it permanent.
I have never heard of a (true) epoxy primer absorbing moisture.
Why do you think it will?
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Old 05-17-2009, 10:32 AM
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as the primer breaks down, it becomes vulnerable to absorbing moisture.. there truly only waterproof when first applied
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Old 05-17-2009, 10:35 AM
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I could see that happening I suppose. After its left outside for some time, epoxy primer will get chalky much like the way cheap spray bomb primer is from the get go. I just wondered how long that takes (getting chalky), especially when the car is garaged and kept out of the rain.
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Old 05-17-2009, 10:43 AM
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I think a real test of UV stability will be shown by black primers. I have parts painted with PPG DP90 black for a long time...

Model T Ford frame and undercarriage painted in 1994 or so. Used for day (and week) trips is showing some light greying. NO RUST.

Garden tractor blade was painted with DP90 in about 1996 and sits out in the sun 100%. This has noticeable greying, but still NO RUST.

The same cannot be said for all brands of epoxies. I have some jack stands that were painted with Kirker grey primer about 18 months ago. They have been sitting outside 100%. They are chalky, and some rust is showing in areas where the paint is a little thin.

Stick with the PPG product. It is good stuff.
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Old 05-17-2009, 07:53 PM
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dp proimer.......

Hi,i have my 48 ford coupe inside a metal garage, in the winter, in the mornings, it is covered in moisture (until the sun heats up the garage) i stripped the car to bare metal, and I painted it with dupont dp 90 about 4 1/2 years ago. 3 coats,there is NO RUST anywhere.
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Old 05-17-2009, 08:25 PM
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Quote:
Originally Posted by matt167
as the primer breaks down, it becomes vulnerable to absorbing moisture.. there truly only waterproof when first applied
This does not apply to high quality epoxy primers. If you have proof, please post it. Otherwise, many people can still use black epoxy to finish chassis parts (no UV exposure) with excellent waterproof, long lasting results...
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Old 05-18-2009, 06:18 AM
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My experience is 100% in line with Crashtech. Stick with the QUALITY epoxies and you will be very happy. In general, I have found that three coats of PPG DP series epoxies will provide fair uv resistance and excellent rust protection. My experience with the Kirker (cheap) epoxy is that both uv and rust protection when stored outside is not nearly as good.
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