primer coat vs coat of paint

primer coat and coat of paint both are nouns.

Word	Noun	Adjective	Verb	Adverb
primer coat	Yes	No	No	No
coat of paint	Yes	No	No	No

As nouns, coat of paint is a hypernym of primer coat; that is, coat of paint is a word with a broader meaning than primer coat:

primer coat: the first or preliminary coat of paint or size applied to a surface
coat of paint: a layer of paint covering something else

primer coat (noun)	coat of paint (noun)
the first or preliminary coat of paint or size applied to a surface	a layer of paint covering something else