Trailer
I have a freshwater trailer, so I'm probably not the best person to ask for advise on the freshwater rinse. Can't harm it. My hunch is that the trailer has spent it's share of time in the weather and the elements have finally caught up with it. If you find that the corrosion is so bad in some of the other key areas as mentioned it may be cost effective just to look for a different trailer. Using the borrowed slip, as mentioned earlier, will make repaires somewhat easier. Start tapping with a mallet---if you go through the metal, it's time to replace Or you may want to take it to a marina or trailer center for an inspection. They may try to sell you a new trailer--at worse. But they should be able to tell you other areas that may need attention. Maybe you could use that borrowed slip while having this done, as well. You cold also get it repaired at a nominal charge if needed. Knowing the trailer is sound should be a priority. Not only for you, but others on the road.