Even reels that are designed for saltwater will eventually be destroyed by saltwater. Unless of course you spend lots of $ on a VS or Zbass. Saltwater is just so brutal and destructive to metal. The average saltwater reel will resist corrosion. It is possible to get about 5 seasons out of some of the better ones. This is about all you can really expect. If you get 5 seasons, consider yourself lucky. However, if you use a freshwater reel, you will be very lucky to even get one season out of it. The metals used in their mechanical components are very low quality, making them very susceptible to corrosion. I have used freshwater reels for salwater fishing. I have always washed them with soap and water after each use, and sprayed them with WD-40. Some of them survived, most of them did not. They soon became very hard to crank, and made a grinding noise. Some freshwater reels are better than others in holding up to saltwater use. I have had some very good luck with some shimano baitcasters. For example, I have a Coriolis that I have used for many years in saltwater and have never had a problem. Most of the Shimano spinning reels I have used in saltwater however, only lasted about one season. Even the Stradic, which many consider to be a saltwater reel, last about 2 or 3 seasons.