Several years ago Practical Sailor evaluated several common solutions to preventing the problem of S/S fasteners from interacting with the aluminum into which they are threaded. The best solution, at that time, was (oddly enough it might seem) Locktite. Use the kind which allows refitting unless you don't want to ever take out the fastener (then use the red stuff).
Since that time Ultra Tef Gel [ The Corrosion Eliminator and Anti-Sieze Lubricant]
came along (expensive) and works well. What makes these very different solutions to work is their ability to prevent any egress of oxygen into the space separating the two materials under any condition.
I have successfully used 3-M mylar tapes to isolate S/S from the mast
or boom using an Exacto knife to carefully form the proper outline of the part. Still working well after 26 years.