You can buy your way out of it somewhat. Pricier bike components are usually anodized, stainless, or nickel plated, or at worst chrome plated and powder coated. Cheaper ones might be black oxide coated or galvanized. Better components also have better ball bearing seals, especially for MTB parts. On the other hand leather saddles and grips and luggage are more susceptible than plastic. Waterproof luggage is made from waterproof fabric, but if it's leather or heavy fabric like a book bag it needs wax.

Kind of depends on the water too. Coastal areas are going to get salty corrosive moisture