Just for grins let's start from the beginning.



The problem is caused by galvanic corrosion. In real simple terms, the stainless steel (SS) and the Aluminum (AL) have different potentials. Whenever you have a electrically conductive path in addition to the contact point, there is a current between the Al and the SS. To support the current the Al corrodes. To stop the corrosion you must stop the current. To stop the current you can break the path (insulate one or both of the materials) or replace the materials with something that will not support galvanic corrosion.



The easiest way is to break the path. You can either stop the metals from touching or prevent a conductive path from forming. The easiest way to do this is to wash the salt away and keep it dry. This is tough if you life near the ocean. There are chemicals that you can spray on that insulate the metals but they wear off easily. You can paint the SS bolt and nut with epoxy and use plastic washers You can put a plastic bushing in the hole in the mast. If you can keep the different metals from touching, you can prevent galvanic corrosion. Don't forget about the inside of your mast. Salt water on the inside of the mast can produce fabulous corrosion



A harder and more expensive solution is to replace the materials with ones that do not support galvanic corrosion. What about a Tornado style Al or carbon rotator with an Al bolt or no bolt at all.





With all of this said, my current solution is to use a bushing and keep the exterior clean. Putting a bushing in the holes and using Duralac would be even better. You would have to wear out your bushing and wear away the Duralac, to have a problem.