Steve is correct about the fasteners,, nowdays most connectors and fuse panels are made with brass or stainless, i would coat all connectors and fuse lugs with NOLOX. you can buy it at the electrical supply store. Its a protected required on all connections on the incoming wires into a home by federal code. On all of the other exposed threads of bolts and things you can apply some anitsez to them to help protect them. There is NOTHING that will 100% keep the saltwater and salt air from corroding things, even doing all you can to protect things in time you will see the salt take a effect on something.