Increasing overall chip resistance

When restoring and painting vehicles I have found some of my paint jobs seems to chip easier than others. The only thing done differently that I can think of is some have reduced epoxy as a sealer and some the color is applied directly over the 2k.

I would like a standardized plan that gives me maximum chip resistance on every paint job.

Right now I am adamant that two coats of epoxy is the first thing applied to bare metal.
Filler work follows that and then I have been going straight to 2k.
 

Chris_Hamilton

Trying to be the best me, I can be
Just my opinion but max chip resistance would be epoxy on bare metal, filler work on top of epoxy, no more than 1/16" of filler. No urethane primer, epoxy only, epoxy when sealing and a UV clear. Urethane primer, filler greater than 1/16", and no seal coat all contribute to higher incidences of chipping. As does the clear you use.
 

EddieF

Top Banana
My red car chipped tiny spot on quarter/door jam when wheelchair hit it.
Close inspection shows original primer still there, base & clear gone.
I didn't prime or seal & used light grit to not break through to metal.

68, what coating let go should give clue.
Like Chris said epoxy before base i've read 1000x here is the way to go.
 

sprint_9

Rookie
From what I've read the two things that could help you are always using epoxy sealer and activating your base. I don't remember when or where I read it but on here somewhere I saw it mentioned that epoxy sealer cuts down on the chips by a lot.
 

John Long

Member
I believe doing your final blocking on 2-3 coats of epoxy also helps. There is no reason you can't do a sealer coat on top of epoxy if you go over the seven days. Epoxy not only has fantastic adhesion, it has just a shade of resilience that helps preventchipping..

John
 

Chris_Hamilton

Trying to be the best me, I can be
Base and clear chip showing 2k primer.

Chris, you are saying the best scenario is all epoxy?
IMO for maximum chip resistance eliminate the 2k urethane. Use epoxy instead. That would be the ideal. Urethane primer is the weak link in terms of adhesion and chip resistance. That being said, I think the first thing I would do '68 would be to seal with epoxy any job where you are concerned about chip resistance. That will help alot toward eliminating any chipping versus spraying over prepped 2K. That and watch how much build you have with urethane. Especially on the edges. If you are going all out on something, epoxy as your build/filler primer would be the ultimate solution. That and controlling the total amount of millage on the panel. The more millage regardless of what it is the higher the chance for chips.
 

jcclark

Oldtimer
I switched to epoxy for all my bumpers years ago, the increased chip resistance has been incredible.
I think it has reduced road rash over 90% compared to when I used only urethane primer.
I do have to usually let it cure 2 days before sanding.
 

Jim C

Oldtimer
like others have said, epoxy all the way through the process would be "maximum" BUT if you cant do that and you keep with a 2k primer surfacer then you need to do epoxy as a sealer. 1 reduced coat 10-20min before base then activate your base. your chip resistance and adhesion should be extremely good.
 
Thanks for the help. I am looking down the road to painting my '68 Plymouth GTX and wanting it to be as perfect as I can get it.

The '62 Chevy that I painted in SPI Dark Red was supposed to be a "driver" paint job so I went epoxy, 2k and then base. The owner made the mistake of covering it with a tarp in windy Arizona and the hold down buckle chipped the paint. He tried to fix it but . . .
IMGP0055.JPG


It is obvious that the chip went to the 2k level. There were others as well especially on the tailgate where he mounted a flag and the pole was hitting.
 

John Long

Member
I have posted this picture before but I found this very interesting.

This is a plug I cut out of the firewall to mount a brake booster. As you can see the weapon of choice was a chassis punch.

The firewall had three coats of epoxy, maybe 1/8" of body filler, more epoxy, then base/clear.

if you look closely, you will see the paint never lost adhesion. The punch actually fractured the body filler and pulled it apart through the middle of the film. Underneath that gray body filler is more epoxy. I found that to be really amazing. This really demonstrates how body filler ( or 2k primer) would be the weak link in the paint job and the most prone to chip.

John

 

Barry

Paint Fanatic
Staff member
Epoxy wins the chip contest HANDS DOWN!
This is why restro shops always seal in epoxy before base.
Insurance shops usually don't use epoxy but I have number of the higher end shops that do because of cars coming back with chips, epoxy is far better than activating the base as far as chips but activating the base helps in its own way.
Urethane sealers test no better than 2k primers for chip resistance.
 

cmfisher4

Active Member
I'm reading this with great interest and have planned on using epoxy as my sealer. However, why? There are two paint products (in varying coats) between the stone and the epoxy. Does the epoxy provide a cushion or some sort of non-brittle base that allows the base and clear to flex, instead of crack, when the stone hits it?
 

Barry

Paint Fanatic
Staff member
I'm reading this with great interest and have planned on using epoxy as my sealer. However, why? There are two paint products (in varying coats) between the stone and the epoxy. Does the epoxy provide a cushion or some sort of non-brittle base that allows the base and clear to flex, instead of crack, when the stone hits it?
I am speaking of SPI epoxy only.

First the adhesion to the substrate is excessive and the base-coat adhesion the epoxy is also greater.

The next big factor is the SPI epoxy is flexible at the 4 inch thick level, that is the thickest I have tested cause it take about a year to perform the test BUT that with the adhesion give the base more flex where as most bases get brittle as they dry.
 

John Long

Member
I think the picture of the plug I punched out shows why more and more high end builders are replacing 2K primer with all SPI epoxy when circumstances allow. Granted, it does not build as fast as 2K but with the extended pot life and recoat window, it is much more versatile and easily used in place of a medium build primer surfacer. It obviously is a stronger more durable product.

John
 
I have been sold on SPI epoxy for many, many years now and I always activate my base coat.
With the red paint I decided to shoot over the 2k because it was gray and the epoxy I had on hand was black. A mistake I won't make again!
 

metalman

Oldtimer
I have been sold on SPI epoxy for many, many years now and I always activate my base coat.
With the red paint I decided to shoot over the 2k because it was gray and the epoxy I had on hand was black. A mistake I won't make again!
What I do is keep white and black epoxy (SPI) in stock and I mix if I want grey to whatever value I need. Write down the ratios so if more is needed it will be very close.
 
Top