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Old 08-27-2007, 08:12 AM
tx_jayhawk tx_jayhawk is offline
Join Date: Mar 2005
Location: Olathe, KS
Posts: 368
Default Does Polyurethane Paint Stick Over Self-Etching Primer?

Like many before me, I am using the Napa 7220 self-etching primer on the outside of many skins so that it offers a little protection and looks acceptable prior to being painted on down the road.

A composite builder friend of mine suggested that painting polyurethane paint (or any other good aircraft paint) over the self-etching primer was a no-no, as the primer could cause the paint to lift.

For those that have gone this route, is that a problem? In general, I'm trying to understand if there will be any problems down the road when it comes time to paint if I use the 7220 now. Obviously, I do not want to have to remove all of the self-etching primer later on.

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Old 08-27-2007, 08:48 AM
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frankh frankh is offline
Join Date: Jul 2006
Location: Corvallis Oregon
Posts: 3,547
Default As far as I remember

The instructions on the Valspar automotice polyurathene suggested using self etching primer to promote adhesion.

I didin't paint he outside with self etch but then again I was not careful in removing it either.


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Old 08-27-2007, 08:58 AM
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atreff atreff is offline
Join Date: Jan 2005
Posts: 215
Default Epoxy under urethane

PPG suggests an epoxy primer under acrylic urethanes. Self etching primer is an attempt to eliminate the etch/alodine step prior to priming. Urethanes will lift anything other than an epoxy primer.

My suggestion is to pick your topcoat brand, and use products in their product line and address your questions to their dealers and technical help lines. I used PPG because there are many dealers in my area.

Art in Asheville.
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Old 08-27-2007, 09:01 AM
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Allen231ah Allen231ah is offline
Join Date: Apr 2007
Location: Cleveland Ga. (0GE5)
Posts: 123

Don't need to use acid etch primer for the fiber glass parts . I am using PPG K36 for fiberglass and Sherwin Williams wash primer for the metal . My top coat is PPG Concept urethane . I have only topcoated my fiberglass parts so far and the results have been excellent . The only recommendations I'm aware of concerning topcoat over wash primer is to spray the topcoat b/4 24 hours to get a good chemical bond .

RV-8 N231AH 300+ hrs
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Allen Holcombe VAF962
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Old 08-27-2007, 11:17 AM
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Köhler Köhler is offline
Join Date: Jan 2007
Location: Northeast WI
Posts: 72

Advice for aspiring painters... When you buy any primer/topcoat product, ask the jobber for the technical sheet for each product as you buy them. It will list all the info you need to select compatible systems and correctly use the products.
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Old 08-27-2007, 11:32 AM
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Radomir Radomir is offline
Join Date: Jan 2005
Location: Charlotte, NC
Posts: 1,518

You'd hope that a good painter will remove/strip that stuff you put on... Proper prep is 90% of a good paint job, so I'm not sure how he can rely on your work... He won't know how well you prepped the surface for that 7220, so even if "compatible" with top coat, I'd expect him to strip it all off and re-do prep. Call a painter or two and ask what their procedure is...
RV-7A sold
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Old 08-27-2007, 02:49 PM
kcpgm kcpgm is offline
Join Date: Jan 2005
Posts: 59

on my -7 i used the 7220 primer All the places on the outside that was being painted it was sanded off then primed with an epoxy primer then i caovered it with the final paint I used RM paint The supply Co that i use sells RM and spies hecker I did have a lifting issue but it was caused by the reducer that was given to me by the supplier a rep came over and gave me something else to try and it worked well

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