Cracking SEM High-Build Primer

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PostPosted: Fri Sep 13, 2019 9:57 pm
I am in the process of painting the dashboard of my '66 Beetle. It is my first project car. There were some holes from the previous owner, so I weld-filled the holes, ground the welds down, put some Bondo on and sanded it down, and sprayed some 2X Rust-Oleum primer down. At this point, everything looked okay, except I could see the where the Bondo was, so I went and got some SEM high-build primer to put over the Rust-Oleum primer (after wet sanding). As the SEM dries, it starts to crack. I am thinking either 1. I just didn't let all the moisture dry enough after wet sanding, 2. the surface was contaminated before spraying the SEM, or 3. the SEM is not compatible with the Rust-Oleum.

Also, does the high-build primer help eliminate very minor surface bumps, or if I feel something, do I need to add more Bondo?

I'd appreciate any advice. Thanks.



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PostPosted: Fri Sep 13, 2019 10:44 pm
i'm thinking your Rust-Oleum is enamel based and your SEM'S is a lacquer based and enamel doesn't like lacquer being put over the top of it. it usually wrinkles.
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PostPosted: Fri Sep 13, 2019 10:50 pm
Second vote on that incompatibility. :goodpost:
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PostPosted: Sat Sep 14, 2019 12:09 am
Thanks. I reckon I should re-sand and put down a lacquer base coat on the metal, then SEM.



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PostPosted: Sat Sep 14, 2019 4:35 am
Andy66 wrote:Thanks. I reckon I should re-sand and put down a lacquer base coat on the metal, then SEM.

dashboards take a beating.lacquer isnt a good choice.

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PostPosted: Sat Sep 14, 2019 8:22 am
There is a sticky post at the top of this forum that will guide you in the proper prep and painting techniques.

You will need to determine what quality of a job you want to do on this car. Rattle cans and experimenting will only cost you money in the long run and produce poor quality results that won't last very long.
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PostPosted: Sat Sep 14, 2019 12:41 pm
I definitely need to do more research. I would like to do the best job I can do working on this in my driveway. I probably need a bigger compressor and a paint gun, for starters. I was using cans because I figured it wash just the dash and I need to get it done so I can finish putting the interior together, but obviously I want it to look good.

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