Ceramic coating also does a good job of keeping the heat in the pipe too, rather than in the engine bay. Worth looking into if the discolouring of the headers bothers you.
As said, powder coating is simply epoxy powder attracted to the surface by a static charge, then oven backed to melt into a smooth coating. Great for the chassis, but would happily melt in the first few seconds on a header.
Here is a link to a supplier's FAQ
Zircotec high temperature coatings, ceramic coatings, engine, exhaust and mainfold coatings.