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Thread: Sealing primer

  1. #1

    Default Sealing primer

    I am currently working on the sheet metal for my 26' JD. My plan is to get everything fitted, body worked, and into primer then run the bike for a few months to work out all the bugs. Then come back and paint all the sheet metal at once. My question is how (or do I need to) do I seal the 2K primer. I have always been told that primer can absorb moisture and want to avoid this if possible. Also I'm sure in the process of running the bike some gas/oil will end up on the prime red surfaces. I have a many hours into the body work and don't want to have to redo it all.

    Thank you!
    Mike
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  2. #2
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    You are correct. Self etching primers like Dupont Vari-Prime are not waterproof. They need to be covered with a workable primer. A little gas once and a while is not going to work it's self under the primer unless it's lifting to start with. Bob L

  3. #3
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    The two part "2K primer" is used on top of the self etching primer which is used over bare metal. I used RM Diamont system back when I used to do bodywork/paintwork. If you leave the 2 part primer sit without topcoating (color) longer than 12 hours, you will just need to sand it with some paper, then coat it again with the 2K primer, THEN put the topcoat on. I am pretty sure that you can leave the 2K primer alone for a long time but you would need to sand it and then coat it AGAIN with a 2K primer before topcoating. Just do some reading on the product that you are using...

    http://www.refinish.basf.us/rm_diamont
    Jim

    AMCA #6520

  4. #4
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    Jim, from a practical side, you know you're going to be doing a lot of block sanding, and spot filling when you do old dented sheet metal. It seems a bit impractical to use something like 2K after every round of block sanding. How would you go about getting fenders and tanks in primer before the top coat.
    Eric Smith
    AMCA #886

  5. #5
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    Since I've done body work all these years, I would straighten the metal out the best I can first. Fenders and "flat" areas I would use a body hammer and a dolly (not the kind of dolly that says mama). When I have it as smooth as possible, I then use a high quality body filler (we used to call it body plastic or just plastic). As for the gas tank, I worked mine with a rod or anything else that I could use to push out any dent in the tank and then use body filler. After I apply my first coat of body plastic I would start with a 40 grit paper and finish the body plastic (filler) with something around 100-180 grit. As for the sand scratches, if they are really heavy or deep, I would apply a THIN skim coat of plastic and avoid heavier grit paper, and start sanding with a finer grit paper such as maybe 100 grit. Then I would apply the etching primer over the bare metal and bodywork and top that with the 2K primer. The Diamont DP20 which is what I used is a HIGH FILL primer which can easily fill minor sand scratches. I would AVOID using putties such as the old fashioned "NITROSTAN" filler which was OK for Lacquer paints. Nowadays, IF NEEDED they use a 2 part "epoxy putty" filler that you can apply over primer for those DEEPER sand scratches. Most times I would just use the DP20 and then sand that down and use that to fill the small sand scratches. Materials can vary with manufacturers. So, I also recommend that you pick a supplier and stay with that. So, if you used BASF RM Diamont, start and finish with that product. Diamont is VERY VERY EXPENSIVE now...

    Block sanding (with a block of course) is OK for flat areas, but doesn't work as well on curved areas. For rounded areas I would wet sand the primer with a 400 grit using my hand, but never sanding in one area in one direction as that could show 'grooves" from your fingers.

    I hope this helps!
    Jim

    AMCA #6520

  6. #6
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    Thanks to Obmie and his homie main crew at the EPA. Every brand of paint is astronomically expensive. Bob L

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    Thanks for the tips, and advice Jim. It is always good to get help, and knowledge from someone who has done it professionally, and for a living. I think an amateur can do anything a pro can do, but it will take more time, money, and skin, and most people aren't willing to pay that price.
    Eric Smith
    AMCA #886

  8. #8
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    Quote Originally Posted by Robert Luland View Post
    Thanks to Obmie and his homie main crew at the EPA. Every brand of paint is astronomically expensive. Bob L
    You are trying pitifully to preach to the choir, duh.

    Back to paint, I have finally found a P4gas resistant black 'paint' for carburetors, but it is just as fragile as the rattle-can stuff that previously seemed best.

    Carl Olsen suggested SEM primer, but it was too flat of a finish for my tastes, yet I hope it will support the butyrate gloss finish over it.

    Has anyone else any experience with this combination?

    ....Cotten
    Last edited by T. Cotten; 09-15-2016 at 05:54 PM.
    AMCA #776
    Dumpster Diver's Motto: Seek,... and Ye Shall Find!

  9. #9
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    Tom, the only thing I can offer you is eat **** and die already. How many times have some one said this to you this week? Your pal, Bob

  10. #10
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    I wouldn't do any filler or primer now. I would do all the metal work and hammering, put the bike together as raw metal and run. Then when your ready, pull it all apart, sandblast, bondo, primer and finish paint.

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