I have highly corrosive sweat, and the mainspring housings of both of my hard-chromed 1911s show rust as a result.
In order to stop the rust from forming, I've resorted to a baked-on enamel coating over the hard-chromed mainspring housings.
So much for the "imperviousness" of hard chrome. But I must admit that it does a very good job of protecting the rest of the guns.
And it's not very reflective, either, since it was applied over a bead-blasted surface.