from my experience with hv pole mounted switchgear near the nth Wales Coast it don't really matter what materials you use, the salty atmosphere will win, stainless, galvanised or whatever, stand back n watch it corrode, hence my comment about rinsing it off after recovery, I've seen very expensive stainless powder coated gear that's survived all sorts of test lab conditions destroyed in two to three years up a pole near Caernarfon, it's don't half make the switchgear manufactures cringe when they see their once lovely kit returned looking like it's been sprayed with rust