coating vs overcoating

coating and overcoating both are nouns.

Word	Noun	Adjective	Verb	Adverb
coating	Yes	No	No	No
overcoating	Yes	No	No	No

As nouns, overcoating is a hyponym of coating; that is, overcoating is a word with a more specific, narrower meaning than coating:

coating (noun)	overcoating (noun)
the work of applying something	an additional protective coating (as of paint or varnish)
a thin layer covering something
a heavy fabric suitable for coats
a decorative texture or appearance of a surface (or the substance that gives it that appearance)