The OP is dealing with high humidity and probably sweat. Salt on the bike is a way of life in the southeast in the summertime. I even have stainless parts of my frame trying to rust if I don't remove the salt after every summertime ride. I wipe down the bike with a wet paper towel and then dry it. Also, the clear coat idea will only work short term. Rust will appear within a year or so. It'll be little spiders of rust that will keep growing year after year.
Edit: Sixty fiver posted about shellac while I was typing, go with that rather than the other options such as lacquer based clears.