I'm reinstalling a cleat ripped out during Irma. The cleat is aluminum, fasteners are 316 stainless. I want to isolate the fasteners from the cleat. Hunter did a great job on the original fasteners, as there was some sort of white caulk-ish substance between the fastener head and the cleat. That same material was all the way down the body of the bolt, around the threads, inside the nut, and all over the washer. I would use it if I knew what it was. It held up for 30 years, and there was no galling between the two dissimilar metals.
What would you use to prevent galling, and to seal this properly?
What would you use to prevent galling, and to seal this properly?