Undercarriage Detailing Epoxy Question(s)

C

Chris

New Member
Hey guys. New here. I’ve tried to read a lot before asking something that’s been addressed, but I can’t quite find the answer I need.

Working on a ‘65 Mustang. It’s been in 2 coats of SPI red oxide for about 2 years. Now, I want to do the factory overspray, etc. on the undercarriage. I’ve read the epoxy needs to be sanded with 180, resprayed in red oxide and then the “overspray” needs to be applied in the 7 day window. BUT, I’ve also read that you can see the 180 scratches under the new epoxy after you recoat. As the red oxide will be the final finish on the undercarriage, what are my options? I do my want the 180 scratches to show, but I also don’t want 5 coats of epoxy either. This is an important car to me and I want it to be the best I can make it.

Should I sand with a finer grit?
Shoot the “overspray” without sanding?

I’m including photos of what I’m trying to achieve for reference. The factory primer on my example is black and my car is red oxide, but you get the idea. Your help is greatly appreciated.
 

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In the photos you provided, it looks to me like it was sprayed with a 2k then sanded and the over spray was applied.

As far as you seeing 180 grit scratches, you're either not applying wet enough coats, or you're applying to much pressure when sanding and not letting the sand paper do the work. I've had that happen to me, lesson learned.
 
I'm assuming you are working with car on a rotisserie. If not you'll need one to do what you want to do.
Easiest way is to get the body ready, including the underside. Have the car on the rotisserie, when you are ready to spray shoot two coats of unreduced red oxide epoxy on the underside areas. If you are confident in your ability to spray it without cratering then don't reduce it. You can reduce it slightly to help with the catering. 1:1:10%.
Then flip it and proceed.
320-400 grit as your final before this on the underside would be sufficient.
 
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I should clarify that it would be best practice to go over all your 2 year old cured epoxy with 180 and re-epoxy and proceed from there. Then prep as normal and do what I outlined above in order to get the overspray to stick on the red oxide.
 
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You've come to the right site for advice. Many experts here that know SPI products. Too many to mention. As a new member here they have helped me considerably.

As a lover of the 60 and early 70s Fords I'd like to see how your project progresses. Please post some pictures of your Mustang going forward?
 
Thank you for your replies, guys. I truly appreciate it. I think I have a plan because of your help.

Yes Dean, that was a typo. I definitely DO NOT want my 180 scratches to show, so I’ll go easy.

MJM, I’m not seeing 180 scratches on my project. I’ve just read about seeing them on the forum. If I was going over the epoxy with high-build it would be fine, but the red oxide is the finish coat on the undercarriage, etc, so I don’t want to see them. I’ll shoot unreduced.

Chris, thanks for your response. In the photo I’ll attach the car is on a body cart, but now it’s on the rotisserie to make all the undercarriage (and Lizardskin) work easier.
 

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Just to be clear, the best way to do this is to first go over all the epoxy with 180 and shoot 2 more coats. Then proceed with prep. I say this because two year old epoxy is fully cured and the adhesion of your subsequent coats relies purely on mechanical (sanding scratches) adhesion. To ensure max adhesion ideally you want to go over all the 2 year old epoxy with 180 and spray 2 more coats unreduced. Then prep that. 320 dry then 600 wet for example, Then you can spray the red oxide again on the underside, either unreduced or very slightly reduced and seal as normal on the topside.

You can text Barry on the Tech Line for more guidance. He'll probably be able to better explain what I'm trying to explain here.:)
 
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