The Gearbox's are definitely coated, but whose to say the coating won't crack over time and allow moisture in? etc.
If you are an operator, visually inspecting your gear boxes (be it daily, between flights, or weekly) to detect flaws in the coatings (and subsequent touchup) is what many people call "good maintenance practices." Likewise, sometimes a flaw/crack in a coating leads you to inspect for cracks in the base metal.
Yes indeed, as you point out, coatings can be compromised over time.
The second part of my post was questions to Grunt92, rather than yourself, but perhaps I failed to make that clear. Apologies for any confusion.
