Polyester primer?

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PostPosted: Thu Oct 14, 2021 3:28 am
Hello and greetings from Norway!
I’m new to this forum, and I would appreciate some advice regarding my ongoing project.
I have a bmw E3 that I’ve strpped to bare metal and done alot of welding and bodywork to. The body was painted with black epoxy primer (SprayMax 2K spray cans) panel by panel as the stripping job progressed.
I’ve also spent many hours straightening panels using hammer and dolly and an angle grinder attached shrinking disc.
Now its time to do some filler work.. I have litle to none experience using body fillers and 2k primers. I’ve done alot of searching and reading on this forum earlier, and I’ve found alot of help in this.
So to my first question. How to proceed..
Starting with the roof of my E3:
8E9436F8-E43A-4BDA-AE16-241F3FDB67D1.jpeg

The roof was previously covered in a thick layer of filler, primers and paint.
Epoxy primer currently on the roof (1year old) is block sanded and there are some low spots as you probably can see.
None of the low spots are shallower than 0.3mm. I used a steel ruler and feeler gauge to check. Many hours with shrinking disc here.
Could I skip using body filler and use the following steps?:
1. A thin coat of epoxy primer
2. polyester primer - block sand
3. 2k high build primer - block sand
4. Epoxy primer as sealer
5. paint..

The rest of the car:
71BF4753-7314-48DF-91CB-D7551E161F59.jpeg



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PostPosted: Thu Oct 14, 2021 12:23 pm
first do you have a air compressor and a spray gun and maybe some air tools, D/A sander?
Jay D.
they say my name is Jay



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PostPosted: Thu Oct 14, 2021 12:48 pm
Yes I have a 7.5HP rotary screw compressor with air dryer. 200L air tank. :)
DA sanders 6" and 3"
3M accuspray HGP gun with 2.0, 1,8 and 1,4 tips
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PostPosted: Thu Oct 14, 2021 11:31 pm
good equipment. i don't really like the polyester primers that much, but your roof section is a good candidate. put it on good and wet it goes on heavy. be SURE you follow the user instructions, get the info sheet when you buy it. it will go off quickly ( start to harden) clean your gun immediately. you might want to sand the epoxy thats on it to clean it up some and provide some new tooth to it.
Jay D.
they say my name is Jay

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PostPosted: Fri Oct 15, 2021 10:10 am
My normal procedure when using poly primer is this:
1. 2 coats of epoxy. Let sit about 24 hours.
2. 2 coats of polyester primer using a 2.0 tip. (Poly primer is basically spray on body filler. Like filler it sets up by a chemical reaction and can ruin your spray gun if you are not careful and prepared.)
3. Apply guide coat a block sand with 80 grit to remove guide coat. (Here you can assess the condition of the panels and determine if more poly primer should be applied.)
4. If happy with the looks, apply 3 coats of 2k build primer, making sure to wait for each coat to flash off.
5. When cured, apply guide coat and block sand with 180 - 220 grit just to remove the guide coat.
6. At this point, more guide coat and then wet sanding with 600. The guide coat will help you to see when all the coarse grit scratches are gone.

Here's a quarter panel that needed a lot of work:
LH Quarter Filler Work Needed 1.JPG


Same quarter panel in polyester primer before sanding:
LH Quarter - Poly Primer.JPG
1968 Coronet R/T


ACTS 16:31



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PostPosted: Fri Oct 15, 2021 11:10 am
Great tips here. Thanks!
My 3M HGP gun is a pressure pot setup with PPS cups and disposable tips.
I think it would be perfect for poly primer.
6B70502B-F89C-4828-AC61-53E939AF500C.jpeg
6B70502B-F89C-4828-AC61-53E939AF500C.jpeg (11.58 KiB) Viewed 197 times



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PostPosted: Fri Oct 15, 2021 11:41 am
So you just block sand the polyester primer with 80grit and then go straigt to high build primer? No need for finer grit before high build?

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PostPosted: Fri Oct 15, 2021 12:01 pm
3 coats of 2k build primer will fill 80 grit scratches no problem.
Again the key is to make sure your surfaces are clean and dust free before spraying anything. And flash times are critical with 2k primer especially. Easy to trap solvent and get blisters if you rush things.
1968 Coronet R/T


ACTS 16:31



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PostPosted: Fri Oct 15, 2021 12:23 pm
:goodpost: I like to go over the 80 grit scratch with some 180 quickly just to knock the 80 grit profile down some then apply the hi-build primer.
Jay D.
they say my name is Jay

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PostPosted: Fri Oct 15, 2021 1:37 pm
badsix wrote::goodpost: I like to go over the 80 grit scratch with some 180 quickly just to knock the 80 grit profile down some then apply the hi-build primer.
Jay D.


Yeah, that is a good idea. Sometimes I just hate the thought of sanding it AGAIN!
1968 Coronet R/T


ACTS 16:31

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