Need guidance on moving forward to epoxy seal coat and color

M

MAKZ06

Newbie
When we made our last trip to our place in N GA in May I was finally able to complete the block sanding of the SPI epoxy on my F100. After a couple years of off-and-on sporadic work I’m now finally satisfied with the flatness and smoothness of the panels.

So it’s now been over 30 days since I had completed the blocking with 180 grit and then followed that with a couple unreduced coats of Epoxy. In those following days I tackled the roof drip rails and various body seams with dual-mix SEM sealer.

First question is whether I need another coat of unreduced epoxy over the seam sealer, or is a reduced seal coat adequate?

Keeping in mind that this is my first paint job and that I’m slow moving… I need clarification and advice on how to proceed. I know that before I spray my color I will have to spray reduced Epoxy within those prior 24 hours. However, I’m very confused about when and what sanding and abrasive grits come into play. Since it will have been well over 30 days before I am ready to do that seal coat of reduced epoxy, do I have to do another unreduced spray of epoxy first? If I have to do another unreduced first then I know I have to first sand again with 180. However, if I only need to do the reduced seal coat, what grit should be used prior? I’m just not clear on what grit I need to use when. I’ve seen msg threads that seem to indicate 320 is what should be used prior to a seal coat, but I’m not sure if I can sand my over 30 day cured epoxy with 320 and then go straight to the sealer…. That’s what I’m hoping I can do.

I will be spraying a blue single stage eventually. I think when I get back this month I will only have time to do a practice run on the interior and underside of the hood and save the rest of the truck for another trip.

Appreciate all the great info and good advice I get on here, and I apologize for the clueless newbie questions.
 
If It makes ya feel any better, I've got the same basic confusion, even after reading multiple threads about it.
 
DanMcG said:
If It makes ya feel any better, I've got the same basic confusion, even after reading multiple threads about it.
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Yeah, I’m sure we’ll both get some good answers now that I’ve asked the stupid questions. I always search and end as much as I can to try and figure out so I’m not asking the questions that have already been answered or should be obvious. Not sure I’m always successful…
I’ve got to do some searching and reading but I’m wondering if I need to spray some regular non-epoxy prImer at this point so that I don’t have to be stressed and dealing with the time restraints…
 
Ideally you would want to apply two more coats of epoxy over the seam sealer. It is acceptable however to seal over the seam sealer. Keep in mind that if it's 2 part seam sealer and it has been on the car for any length of time you would need to sand lightly it to ensure adhesion.

180 grit is recommended for maximum adhesion when applying more epoxy over existing epoxy. You can sand your existing epoxy with 320 and then seal over it. I would actually recommend you sand with 320 dry then 600 wet. 320 dry is rather coarse and if your color is a metallic 320 is too coarse. I see you are spraying a SS, you could get away with 320 scratches but I prefer going 320 dry then 600 wet. Then you are ready for sealer.

If I didn't answer all your questions, keep asking,:)
 
Thanks Chris. Is there a time limit on sanded epoxy? Say I have panels that have 2 coats of epoxy and have been sanded with 180 close to a year ago, are they good to go on to 340? or after that long should I hit them again with 180 and then proceed with another unreduced coat, then sealer.
 
Chris_Hamilton said:
Ideally you would want to apply two more coats of epoxy over the seam sealer. It is acceptable however to seal over the seam sealer. Keep in mind that if it's 2 part seam sealer and it has been on the car for any length of time you would need to sand lightly it to ensure adhesion.

180 grit is recommended for maximum adhesion when applying more epoxy over existing epoxy. You can sand your existing epoxy with 320 and then seal over it. I would actually recommend you sand with 320 dry then 600 wet. 320 dry is rather coarse and if your color is a metallic 320 is too coarse. I see you are spraying a SS, you could get away with 320 scratches but I prefer going 320 dry then 600 wet. Then you are ready for sealer.

If I didn't answer all your questions, keep asking,:)
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The sealer will be sanded just to get a little more uniformity and fix some areas in the drip rails.
Just to be clear, the proper procedure is for me to sand my cured over 30 day epoxy with 320 (then 600 for metallics)
before spraying the epoxy seal coat?
So the recommended 180 between coats of cured epoxy only applies to unreduced epoxy, but spraying the reduced seal coat of epoxy is done over 320/600 scratches even though that underlying epoxy has cured for over 30 days?
thanks and sorry I’m not getting it…
 
From what I understand, the epoxy is a mainly a mechanical type bond, so the first layer needs the scratch to adhere to. If the surface has been sanded and nothing applied over it, then clean it really well and the epoxy will bond.

When in the recoat window, it will bond to itself, so no sanding is necessary.
 
MAKZ06 said:
Just to be clear, the proper procedure is for me to sand my cured over 30 day epoxy with 320 (then 600 for metallics)
before spraying the epoxy seal coat?
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Yes.

MAKZ06 said:
So the recommended 180 between coats of cured epoxy only applies to unreduced epoxy, but spraying the reduced seal coat of epoxy is done over 320/600 scratches even though that underlying epoxy has cured for over 30 days?
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Yes. 180 is used when re-coating existing epoxy with more epoxy to ensure max adhesion.

An example say two coats over bare metal, then filler work is done. Doing so takes it over the 7 day limit. You would then need to scuff all the epoxy with 180 to ensure max adhesion before re-coating. It is recommended as "best practice". It does not mean that anything finer in grit will not stick to cured epoxy.

Using 320- 600 grit (anything in that range) is the proper procedure in order to proceed with topcoating. Every car done with epoxy eventually needs to be topcoated and what I described above, is a "correct" way to do it.

What you are doing now is refining the scratches or in other words, putting a refined finer scratch on the epoxy to facilitate applying your topcoat. You need a coarse enough scratch to allow the top coat to stick, but refined/fine enough to not show through. the range of 320 dry to 600 wet is what is needed. Whether your epoxy has cured has no bearing on this. It is really very simple.
 
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Chris_Hamilton said:
Yes.


Yes. 180 is used when re-coating existing epoxy with more epoxy to ensure max adhesion.

An example say two coats over bare metal, then filler work is done. Doing so takes it over the 7 day limit. You would then need to scuff all the epoxy with 180 to ensure max adhesion before re-coating. It is recommended as "best practice". It does not mean that anything finer in grit will not stick to cured epoxy.

Using 320- 600 grit (anything in that range) is the proper procedure in order to proceed with topcoating. Every car done with epoxy eventually needs to be topcoated and what I described above, is a "correct" way to do it.

What you are doing now is refining the scratches or in other words, putting a refined finer scratch on the epoxy to facilitate applying your topcoat. You need a coarse enough scratch to allow the top coat to stick, but refined/fine enough to not show through. the range of 320 dry to 600 wet is what is needed. Whether your epoxy has cured has no bearing on this. It is really very simple.
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Thanks so much for setting me straight on this and taking the time to explain. Finally seeing some light at the end of the tunnel.
 
Chris_Hamilton said:
When I say topcoat that would include the reduced epoxy sealer.
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One question on the same subject Chris. Working on a C3 Vette. Stripped to bare glass. Doing all priming and blocking with SPI epoxy. No Bondo, 2K primer, or polyester primer. Paint will be SPI black SS. Once I'm done with all blocking and sanded out to 600, is the reduced epoxy seal coat necessary or is that only required when there's material variations such as some areas are epoxy and others have broken thru to hi build 2K or polyester when products like that have been used? I'm unclear whether the sealer coat provides better adhesion for the paint or if it just used to provide uniform color and texture prior to paint.
 
metlmunchr said:
One question on the same subject Chris. Working on a C3 Vette. Stripped to bare glass. Doing all priming and blocking with SPI epoxy. No Bondo, 2K primer, or polyester primer. Paint will be SPI black SS. Once I'm done with all blocking and sanded out to 600, is the reduced epoxy seal coat necessary or is that only required when there's material variations such as some areas are epoxy and others have broken thru to hi build 2K or polyester when products like that have been used? I'm unclear whether the sealer coat provides better adhesion for the paint or if it just used to provide uniform color and texture prior to paint.
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It's not neccesary but sealing it will give better adhesion than going straight over sanded epoxy. Epoxy reduced 1:1:1 (1:1:50%) would work well and allow you to shoot over it in as little as 30 minutes.
 
I can’t say I’ve ever shot basecoat over fresh epoxy. If I use high build primer, once my final block with 220 is done I shoot one more coat and then sand that 400. It fills in all the 220 scratches.

Then I do one final coat of epoxy unreduced. I always wet sand this 600 to give a perfect substrate for base; removes any peel and especially any dust, trash, bugs, etc.

Then I base.
 
Jim C and TexasKing explain why you should seal in this thread.....think of sealer mxed as I described above as an adhesion promoter of sorts. Especially with cured epoxy.


Sanding Epoxy "Outside" the Window

So a little background - several years ago after completely stripping my car I sprayed 3 or 4 coats of SPI epoxy primer. I blocked this with 180g dry sandpiper and sprayed another 2 coats of epoxy primer. The blocking and next 2 coats were within the 7 day window. I knew I would have to stop at...
www.spiuserforum.com
 
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