Recently painted a side skirt piece i got for my truck. I used all Dupli color Laquer. I have used it several times and never had any issues before. It is the brand the local parts store carries so it is most convenient. Not the best choice but it works.
These are the steps i took-

Step 1: wet sand it just to rough it up a little and get any scratches or marks off of it prior to paint.

Step 2: adhesion promoter then primer followed with a light wet sand.

Step 3: sprayed my base. Let it dry over night until the next evening. Looked great and dried nice and flat.

Step 4: Sprayed my clear and it looked even better. Go to check it the next evening and i find these cracks all over it.

You can see the primer (white)





What was the cause of this? Base coat not fully cured?

What steps should be taken to repair. Wet sand to roughen up the clear and respray my base color?

Pretty frustrated when i saw that since it was going so smooth but it happens i guess. Help is appreciated so i can fix it the easiest/most effective way to prevent this again.

What did you clean the part with before using the adhesion promoter? Modern plastics come from molds and can have mold release agent still on them from the factory or as in the case of SMC fiberglas the mold release is actually IN the plastic which requires some special prep. And that brings up another point here.... what is the base plastic material here? Lacquers are much more sensitive to things like that than modern paint systems. You could also have just put too much primer on at one time and it needed a few more days to completely off gas before your topcoats. Could be other things, too.....
Best advice?.... get it all off back down to plastic, thorough cleaning with soap and water, dry, hit it with water based degreaser, reprime....., light coats of primer, allow extra dry time, and finally topcoats again. If it happens again, I would suspect some type of plastic that is reacting with the solvents in the lacquer.... past that you'll have to go into SSU or base/clear systems.

It was sanded before anything went on and wipe down with soap and water. Its weird because this only happened when the clear dried. While it was wet and in the process of drying it was fine. But in a day it turned to those cracks.
Could it be possible that the base did not dry enough and the clear separated it? If it was metal i would know for sure but painting plastic is a different game

For moving to bc/cc is hopefully a short time ahead. Been researching prices and where to get paint matched paint for a good price.

Always try to do your cleaning before you sand any part like this. If there are any traces of mold releases they can get pushed into the plastic so that cleaning after the fact does not remove it all. With lacquer over plastics you never quite know when things have dried enough for recoat. The solvents in the lacquer soften the plastic and can actually migrate somewhat into the plastic.
See back in prehistoric times when lacquers were the thing, we had bunches of shiny chrome on cars and lacquers went over metals only. By the time plastics were becoming popular paint had evolved further.....

Was that piece of trim new, or second hand?

If new, was it already primed, ex factory?

Reason I ask is that I've seen that before. It's a reaction (only mild) between the thinners in acrylic lacquer based products and a two pack primer. When the primer is sanded the scratch marks from sanding open up the surface and the thinners gets in and reacts, just like it does on feathered edges of old paint, but much less since less is exposed. It generally comes from over wet coats and insufficient drying times. Can also happen on substrates which have been previously painted.

Some factory primers are very susceptible to it, others are not. The worst are those that use an iso-free hardener.

It came like this



Do you think i should sand out the cracks smooth and re spray the color then clear. i will let it dry multiple days before clearing it.

I got it sanded down today. I tried not to go to the plastic but it happened in some areas.




Am i going to need to apply adhesion promoter to those areas again? Can i just tape off and hit those spots directly or can i go over the whole piece with it?

After that should i prime it again before paint? I will at least spot prime the areas i hit through to the plastic.