The most corrosion resistant (and wear for that matter) would be a composite coating - such as a high phos electroless nickel with a good barrier coating, such as Cerakote, applied over it.
I haven't experienced any corrosion, but carrying a Glock 22 in a CCC Shaggy AIWB, it accumulates an incredible amount of lint. Disproportionate amounts in the ejection port, muzzle, around the sights, basically everywhere the holster covers. It's not an issue as long as I wipe it down regularly, but I never experienced this with a traditional IWB rig.
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As long as it's integral, sure. When a coating like that gets violated, a medium like sweat provides a really good catalyst for galvanic corrosion ebcause of the differing metals involved. If you are one of those people who have very corrosive sweat (a friend of mine wears the stippling off of backstraps pretty routinely), a straight polymer directly over the base metal is probably better. Of course, high phos EN is plenty hard and non-porous, so I usually only get nervous about violation if there's a deformation involved, like a buckling beam.
Corrosion pitting on my P2000SK, this part of the slide is in direct contact with my skin.
Even the much vaunted H&K "Hostile Environment" finish can't stand up to daily AIWB carry in New Mexico.
"For a moment he felt good about this. A moment or two later he felt bad about feeling good about it. Then he felt good about feeling bad about feeling good about it and, satisfied, drove on into the night."
-- Hitchhiker's Guide to the Galaxy --
A tidbit the FCN/Melonite/etc crowd fails to recognize when discussing corrosion - that system is attacked quite aggressively with acidic (even mildly acidic) solutions.
...and the acidic, chloride containing sweat will do a real number on hard chrome too.