From my own experience living a mile from the Pacific Ocean and riding my bare polished 953 frame for around 12k miles over nine years in all kinds of weather, I can say that it shows absolutely no sign of corrosion or discoloration anywhere; it looks the same as the day I took delivery from the dealer in 2007.

The base material for Reynolds 953 is Carpenter Technology Custom 455® (UNS S45500) which is used for fabricating the landing gear on carrier based jet aircraft, and is exposed to salty seawater spray for extended periods. I don't use any protective coatings on the frame, but after riding for any significant time in the rain, I wipe the frame and components down with a damp terrycloth towel and then dry it with a clean towel.