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Thread: Self-etching primer under Urethane Finish

  1. #1
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    Default Self-etching primer under Urethane Finish

    Is it okay to use Eastwood self-etching primer under PPG Concept DCC acrylic urethane topcoat?

    Thanks,

    Steve
    just passin' thru

  2. #2
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    Steve, although we attempt to test every combination of products that we can collectively think of to test thier compatability with Eastwood products, it is impossible to test every combination.
    Knowing what I do about the chemistry of both products, it certainly SHOULD be fine, however, I would advise test spraying a coffee can or something with the combination first to be sure. Let us know what your results are.

  3. #3
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    Thanks for the reply, Cloud59...I have already tried it on several parts and it seems to be fine. Certainly no chemical reaction. The urethane lays down just fine and adhesion seems to be okay too.
    The reason I made the post was I thought I read (maybe mistakenly) that it was not to be used under an epoxy type paint. I know it can't be used under chassis black.
    The PPG Concept urethane is a catalyzed mix, so it is in effect an epoxy I would think.
    I guess I have concerns over nothing, as it seems to be fine.

    Steve
    just passin' thru

  4. #4

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    Quote Originally Posted by steve392
    I guess I have concerns over nothing, as it seems to be fine.

    Steve

    I think you were right to question the use of E.W. etch primer under your DCC. Anytime you use a two-part paint over a physical-drying paint you need to test it out first.

    I know that you haven't had any reaction and rattle-can Etching primer usually doesn't react to catalized products but let me tell you a horror story.
    About 5 years ago I painted my dad's Mustang. Know matter what I told him, he knew better. He used Rustolium under the primer surfacer I supplied him with. His mentallity (and that of alot of "old dogs") was that Rustolium stops rust, prevents rust, and lord knows what else they think it can do to rust.
    Fast forward to last summer. His 'stang started blistering. And I am not talking about rust blisters or bubbles. This was some strange looking stuff! This winter I dug into it and the primer (rustolium) was seperating from the metal. No rust, just lifting.
    My point is not to scare you but to just keep in mind that chemicals should never be mixed and matched unless the company says it is ok to do so. I've used many of Eastwoods paints and had no ill effects, but their products are designed and sold with re-coating in mind. The hardware store stuff is made for park benches.
    Chris'
    Autobody
    Restoration
    Service

    www.carsofcomfrey.com

    Comfrey MN

    William McCormick "I am not an expert, but I do know some basics that are often not known by many."

  5. #5

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    I agree that testing first is always best.
    Rustoleum's primer for rusty metal actually contains fish oil (that's the original recipe) and should only be used on actively rusting metal. If used on metal that is not rusted the oil will not penetrate and will wick back out at some future date. They (Rustoluem) have a separate clean metal primer product. I'm not saying these are automotive grade products, but it sounds like he may have used the primer product incorrectly which led to this specific failure.

  6. #6
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    Thumbs up

    If I may add some other items to your discussion,
    First of all a urethane is not an epoxy. those are two different resins. PPG urethane may be fine, the reason self etch primers are not always recommended to be directly topcoated with color is that 1) the etch pigment could bleed into the topcoat and discolor it and 2) if the etch primer is too thin, there is not enough film build for the total film of color and primer to protect the metal substrate. There are several companies that do NOT recommend directly topcoating for those reasons.
    If you look at the ppg web site,they do have a self etch primer and it is like most if not all self etch primers, a single component with an acid reducer. I did not look it up but they will tell you what PPG topcoats will work over the etch primer. Apply the same recommendation to the Eastwood primer as the PPG tech sheet says. If it states to prime or seal first, then I suggest doing it.
    If you seal or use a 2K primer over the etch, you will also get a better final gloss in your topcoat color.
    Also, if you use an aerosol can of primer, the film build is typically less and requires more coats then if you use bulk from a quart can and reduce it and spray it out of a paint gun.
    Just wanted to add some things for future readers.
    Freerider

  7. #7
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    http://www.Rockwelder.com/GeneralCad...airprimer1.jpg

    This was my first adventure using 3M chromium etching primer. I have to say it is hard stuff. In fact it was my first etching primer ever. I did not even know Eastwood had such a thing. Do they sell it by the gallon?

    The only problem I noted is that if you scrape the finish paint that is on top of it with a falling object. Instead of the etching primer yielding to the object and allowing it to dig into the metal stairs and come to a stop like regular primer would allow it to do, what ever hits the staircase, kind of just skims along the etching primer. Taking the finish paint off as it goes. I am not complaining I am sure the finish paint is working great and it is holding on just fine.

    I love the fact that this thing will never rust. Because that etching stuff just does not come off.

    In old swords, they used to put a piece of soft brass into the back spline of the sword so if someone hit your blade, instead of his blade just glancing and following your sword down to your hand, arm or body, it would get caught on your sword. This also tired out the opponent.

    But you have to see how the etch protects the metal. It is a hard surface.

    I was just wondering if the etching primer you are talking about is of the same variety.


    Sincerely,

    William McCormick
    Last edited by William McCormick; 03-12-2006 at 08:43 PM.

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