What am I missing?

Doors were cleaned with soap and red Scotchbrite pad.
Gone over with 80 grit to provide scratch.
1 coat Epoxy primer mixed 1:1 shot with 1.4 tip.
Let cure for 60 minutes at 75 degrees.
Shot 3 coats of regular build 2k mixed 4:1 with a 2.0 tip and allow each coat to flash off.
Next day I guide coat and block sand with 150 grit. Repeat with 320 and then wet sand with 600.
Clean and dry thoroughly. Today I shoot a sealer coat of Epoxy reduced 25% and these show up.
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The only thing different was the primer gun. I just got it to replace my EVO4018 1.8 tip that finally quit on me.
My guess is there must be solvent trapped below but I am not sure how that could be.
Any help would be appreciated.
 
Sometimes a thick coat of epoxy has to dry longer than that before recoat. I am guessing that's where the solvent is, down at the bottom. Maybe that 2.0 is more of a hoser than you realized?
 
I think crash found the probable cause. When I first saw it I thought it was stress cracks in fiberglass bridged by the 2K, but being metal, it must be solvent trapped in the epoxy by the 2K, IMO. I wait overnight before spraying 2K over unreduced epoxy, but I have sprayed it over reduced epoxy after a couple hours. You were probably right at the limit, and that new gun pushed it over the edge.
 
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I've seen even worse things happen when putting poly primer on top of unreduced epoxy too soon. Laying epoxy down before our other coatings IS a best practice, but it also violates a basic refinishing rule, that you don't put faster drying materials on top of slower ones without taking some risks.
 
1 coat Epoxy primer mixed 1:1 shot with 1.4 tip.
Let cure for 60 minutes at 75 degrees.
Shot 3 coats of regular build 2k mixed 4:1 with a 2.0 tip and allow each coat to flash off.

That is pushing stuff pretty good time wise for the temp.

I also used the overnight or 8 hour cure as guideline when going to 2k, that was recommended to me by Barry when working with epoxy 1:1 at temps around 70.
 
Like all said, the 2K primer soaked up the excess solvents in the epoxy, like it is suppose to but could not get rid of them, so you have spots that tried to co2 gas and split that the 2K was overwhelmed.
 
I was following an old Epoxy Primer instruction sheet that I had saved. Just checked the date and it was 2009 when I saved it. :eek:

Spraying:
Spray two wet coats for normal applications. For special projects such as restorations
Spray one coat and let it flash about 10-30 minutes at 70° degrees or higher. Then spray
second coat for maximum corrosion protection. If one coat of epoxy is used wait 60
minutes before painting.


Lesson learned: replace old manuals when new ones come out!
 
I think that if you had sprayed the epoxy with a smaller tip it might not have been an issue. I have a 1.8 primer gun that I keep around only for poly primer. My LPH 440 is a 1.6 and it works okay for unreduced epoxy and other primers on large areas. But, I think the epoxy is actually intended to be sprayed through a 1.4, which is what I usually use if the epoxy is going to be used as a sealer. I'd be interested to see the tip size recommendation from 2009, I don't have any manuals that old! I guess it depends on what you are doing, typically if we are priming we will try to get epoxy on early in the day, then wait until almost the end of the day to spray urethane primer. It's safer.
 
Crash, I did use a 1.4 LPH400 to spray the epoxy. The iwata air gunsa az3 hte2 primer gun with the 2.0 tip was for the 2k build primer only.
This from the Old Tech Sheet:

EPOXY PRIMER
1:1

Product Numbers: Gun Tip: 1.4 or 1.5
#6600- White
#6610- Gray 1.4 if used as a sealer
#6620- Black
#6700- Activator
Available in quarts and gallons

Mix:
1:1 or 1 part SPI Epoxy to 1 part SPI Epoxy activator. This epoxy needs no induction
time, unless you reduce this epoxy with urethane reducer. If reduced an induction period
of 15-30 minutes is recommended.

Although this epoxy does not require an induction period unless you add urethane
reducer, we strongly recommend you activate the epoxy by first stirring very well and
then allowing it set 10-30 minutes. Stir once again before spraying and the longer in
between coats the better.

Uses for SPI Epoxy:
This epoxy is one of the finest available and it is great for use on any type of metal or
aluminum if properly cleaned. This epoxy eliminates the need for an acid-etch primer.
Use this epoxy on bare fiberglass or SMC before applying body fillers or 2K primers for
best long-term results.

Prepping the Surface:
Metal or Aluminum must be clean of all rust and oils and any films. Never clean metal
with lacquer thinner or reducers of any kind. Raw metal of any type is always cleaned
best with a waterborne wax and grease remover such as SPI’s part # 700-1. This is most
important for prepping aluminum and sand aluminum or metals with 80 grit DA paper.

Spraying:
Spray two wet coats for normal applications. For special projects such as restorations
Spray one coat and let it flash about 10-30 minutes at 70° degrees or higher. Then spray
second coat for maximum corrosion protection. If one coat of epoxy is used wait 60
minutes before painting.

Spraying Continued….
This epoxy does not need to be sanded if painted over within 7 days. Always paint or
primer over the epoxy within 7 days. After 7 days the epoxy should be sanded and recoated
with epoxy for best adhesion.

Body Fillers:
On any restoration it is always best to apply the body filler over the epoxy rather than
bare metal for best adhesion and corrosion protection. If one coat of epoxy is used then
the body filler can be applied in 60 minutes. When applying two coats of epoxy, wait
over night before applying the body filler. The epoxy does not need to be sanded before
applying the body filler.

Wet and Dry Sanding:
If for some reason you need to sand a large area of epoxy, the epoxy will dry sand best
after 12 to 16 hours. Wet sanding with moderate pressure can be done after 60+ minutes.

To use as a Paint Sealer:
To use the epoxy as paint sealer, reduce 10-50% with the proper temperature range
urethane reducer (this is very important). Spray one wet coat ONLY, let it set 60 minutes
and apply paint. For sealing of a potential problem paint job, apply two coats of epoxy
with proper flash times between coats and let it set over night before painting.

Pot Life:
24-48 hours depending on humidity and temperature (sealed container)

V.O.C.
4.6 ready to spray.
 
Like all said, the 2K primer soaked up the excess solvents in the epoxy, like it is suppose to but could not get rid of them, so you have spots that tried to co2 gas and split that the 2K was overwhelmed.

I believe my mistakes were multiple.
Not letting the epoxy cure long enough and also not allowing enough flash time between coats of 2k. With the new primer gun I was struggling to get it set up right and may like Crash suggested have been hosing it on.

If need be I will strip it all off and start over. I guess whether it will sand out or not will be the determining factor.
 
Sorry I did not re-read the OP, @'68 Coronet R/T ! I have noticed that @Barry neither provides a specific recommendation for recoating unreduced epoxy with 2K in the old tech sheet nor the new one, as far as I can tell. I have had some trouble over the year by going too fast, so we tend to wait quite a while. What I've seen in the past is that the 2K primer will crack and pull away from the outer edges of the part, but once it cures, it will sand out and be fine. I think the only thing you might need to do is feather and reprime those areas after a good long cure, and check all the edges, too.
 
With something like that Freightliner '68, in the future just reduce your epoxy slightly. 10-15% works well. That will allow you to re-coat with 2k within a few hours and give you most of the protection afforded by epoxy. Also with un-reduced epoxy I would consider 30 minutes between coats the absolute minimum amount of time. One hour between coats would be even better. Especially if doing 3 or more coats. For me, the rule I've always gone by for un-reduced epoxy is 24 hours minimum before 2k or body filler. 48 hours minimum before poly primer.
 
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