The action of coating or the state of being coated; a layer or covering applied to a surface.
From coat (from Old French 'cote') plus -tion (Latin suffix forming nouns of action). Related to Middle English 'coten' meaning to cover.
Coation is surprisingly rare despite being perfectly logical—we say 'coating' instead—but it appears in some technical and historical texts as the formal noun for the process of applying protective layers to materials.
Complete word intelligence in one call. Free tier — 50 lookups/day.