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Discussion Starter #1
I'm starting to paint cover for my engine with Duplicolor ceramic engine paint and the primer says 10 mins between coats, not less than an hour or you have to wait 7 days. Soooooooo since the topcoat color says the same thing, AND THE DAMN CANS DON'T SAY, can I swap to the topcoat color as long as it meets these time requirements?????? (Start topcoating as long as it's within an hour of the last coat of primer)? The clock is ticking.......................
 

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Probably. It might help to understand why. It all has to do with adhesion. Modern coatings use two mechanisms to make sure the various layers stay stuck to each other. One is 'mechanical' adhesion. This is where the paint flows into and hardens into the very small, almost microsopic surface irregularities and hardens so that it 'hangs on' to the surface. The other is a chemical adhesion (think 2 part epoxy). This is where each layer (coat) of paint forms chemical "atomic structure" bonds with the layers above and below it. It's this second chemical bond that has the time window limits. If you wait too long before applying the next coat, the previous coat will have chemically hardened (again, think epoxy) to the point where it will no longer bond to the fresh coat and you're likely to subsequently have adhesion problems. That's why the instructions say to either apply coatings within some specified time period OR you have to wait for it to completely dry (cure), then scuff it up some (to create some surface imperfections for the next coat to MECHANICALLY grab onto) before applying the next coat.

All of this is why it's important to learn about all the coatings you'll be using, understand their "recoat window" times, and really plan the whole process out before you start applying things. Different coatings have different compatibilities and different times, even between different vendors/manufacturers. (The latter is another reason to NOT mix manufacturers on a paint job but instead to use the same brand and even "product line" on everything from the bare metal primer all the way up through the final clear coat - that way you know all the various layers are formulated to be compatible with each other.)

Bear
 

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Discussion Starter #3
Understood. I spoke to Duplicolor today. They did confirm that within the 20-60 minute recoat time it was OK to switch from primer to topcoat. I told the CS guy that it might be nice to indicate that on the can. I have run into issues before (not with engine paint) where from primer to topcoat just requires dry primer to continue- not all primers require a "total cure" as with topcoats. Anyway, unless the finish left behind by the primer in a week has a profile I guess I'd be wise to hit the items with the scotchbrite prior to topcoating.
Once again, thanks for the input, Bear!
 
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