painting brass... gah!!

Discussion in 'Replica Props' started by Kaylee, Jan 26, 2006.

  1. Kaylee

    Kaylee Well-Known Member

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    so ONCE AGAIN.. when it's time to start the last phase of a paint job.. I take off the masking tape and... the paint comes off all the way down to the metal. Can you tell me what I'm doing wrong?

    1. Wash part.
    2. Use alcohol-based degreaser
    3. Spray on one coat automotive primer. Wait one day.
    4. Spray on second coat automotive primer. Wait one day.
    5. Spray on third coat automotive primer. Wait one day.
    6. Spray on one coat clearcoat. Wait one day.
    7. Spray on second coat clearcoat. Wait one day.
    8. Spray on one coat primary color. Wait one day.
    9. Spray one second coat primary color. Wait one day.
    10. Spray on third coat primary color. Wait one day.
    11. Wait one day, to make SURE it's all dry.
    12. Mask for 1st contrasting color (masking tape)
    13. Spray on first coat contrasting color. Wait one day.
    14. Spray on second coat contrasting color. Wait one day.
    15. Spray on third coat contrasting color. Wait one day.
    16. Removed mask. Big ol' section of the paint comes off all the way down to the bare brass.

    Aaack. As you can see, all this "wait one day" means I'm already two weeks behind where I wanted to be with this. How the heck does this work?

  2. wamser_e

    wamser_e Well-Known Member

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    Some metals require etching with an etching solution before painting or you can use a self-etching primer if local regulations allow sale/use of it.


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    I assume you're using paints of the exact same maker? (dumb question, but I had to ask) I know that water (or alcohol) based acylics can wreak havoc on enamels if applied over them. (such as Tamiya Acrylics over Humbrol enamel)

    I would never do a clearcoat between the primer and color... unless I've got it all wrong, the clearcoats purpose it to protect and seal. The primary will grip your primer better without it in between. But that will not solve your problem since I can't imagine the clearcoat weakening the primer.

    What kind of masking tape are you using? I have known some masking tapes to affect the paint if left on. (Almost destroyed my scratch built MK2 Viper when learning that lesson...) Try using a more expensive variety (like Tamiya) instead of general "harware store" tape. Just an idea.

    You could also try cleaning with pure acetone (not the oil based kind) instead of that degreaser.

    /Joe F

    FETTCLONE Well-Known Member

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    Perhaps you need an oil-based paint. They tend to leave a very durable coat on metals, although the dry time can be a little longer than latex-based. Failing the etching, maybe scuff it up a little with a fine sandpaper to provide a rougher surface for better adhesion? As always, test a small area or test scrap first...

    Low-tack painters tape (blue or green) is also a good idea if you're not already using it.

    Let us know how it turns out. I'm already curious to know what you're working on. :p
  5. steveday72

    steveday72 Well-Known Member

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    Same suggestion with the low-tack (blue) painter's tape, only don't leave it on for 3 days. The brands I've used say not to leave it on for more than 48 hours.

  6. DL 44 Blaster

    DL 44 Blaster Sr Member

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    First,....waaaaaaaaaaaaay too many coats of primer,clear,paint etc.... The problem is that your paint is building up and drying literally to the tape. That is why it is all coming off together. Plus it hasn't cured yet and that much paint would take weeks to cure...a day isn't even close.

    I'd strip it back down to bare metal with some pro-stripper and then clean again with alcohol. Shoot it with a couple of light coats of your finish color. Forget the primer unless you want to smooth and sand inbetween. Mask off areas you don't want painted and then remove masking after a day. If you're really concerned with lifting coming back off from the mask,I'd lightly score the edges of any masked areas with a No.11 X-Acto knife.

    Good luck :thumbsup

  7. RedTwoX

    RedTwoX Sr Member

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    Indeed. The purpose of the primer to provide a surface for the paint to bond to. If you spray your clear coat on the primer, then there is no point in having the primer there at all. Clear coat is the last thing you do.

    The exception to the above statement is that you may want to clear coat, use a surface treatment like rub 'n buff for weathering, and then another clear coat.

    If the primer is coming off them you need some better surface prep. You may need to go over the surface with steel wool or 600 grit grit sand paper first. The wash, dry, and prime.
  8. boatbuilder1

    boatbuilder1 Well-Known Member

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    ok guys listen up you all should know this by now.
    the only way to avoid this problem is to give you parts a dip in an acid solution.
    radio shack has what you need it is called pcb echtent. it is ferric chloride so be careful. I cover the work bench with cling wrap. then I put gloves on surgical latex or vinyl gloves. I use a disposable plastic tray half filled with water. I then poor a small amount (an once is all you will need if brushing it on) now uncap the acid. careful to not knock it over. I use a disposable brush from the soldering dept of the hardware store. simply dip the brush in the acid and brush it on the parts making sure to cover all areas once the metal starts to turn dark brown drop it in the water shwish it around making sure to get all the acid off. no cap up the acid and rinse the part in a sink,perferable porcelan the acid no matter how small the amount will stain the stainless steel yes you read that right. dump the water diluted acid from your tray in the toilet and flush it a few times.
    make sure to use protective eye wear, and gloves. during the entire process
    perform at your own risk
    I assume no responsability for this process
  9. Kaylee

    Kaylee Well-Known Member

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    Thank you thank you thank you.

    Looks like I shot myself in the foot, causing the problem I was trying to avoid. :)

    I don't believe I used clear between primer and primary, but between primary and secondary. Regardless, I'll try it over again with just a little paint this time.

    If all goes well.. cool pictures within the week. :D
  10. Kaylee

    Kaylee Well-Known Member

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  11. wuher da brewer

    wuher da brewer Sr Member RPF PREMIUM MEMBER

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    I recognize the symbol from Firefly/Serenity but otherwise am not sure what I'm looking at.
  12. Kaylee

    Kaylee Well-Known Member

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