priming coat vs flat coat

priming coat and flat coat both are nouns.

Word	Noun	Adjective	Verb	Adverb
priming coat	Yes	No	No	No
flat coat	Yes	No	No	No

As nouns, priming coat and flat coat are synonyms defined as:

priming coat and flat coat: the first or preliminary coat of paint or size applied to a surface

Other synonyms of priming coat include ground, primer, primer coat, priming, undercoat.

priming coat (noun)	flat coat (noun)
the first or preliminary coat of paint or size applied to a surface	the first or preliminary coat of paint or size applied to a surface