Sam, my question was rhetorical. My point was that corrosion can be addressed in a number of ways and tailored to attack the mechanism that one is faced with. Specifically, that sacrificial anodes won't work in the case of a dry-stored boat and that isolating and minimizing the exposed surface area of the cathode might be better options.

jimbo, one problem with the mica or other insulating sheets is that it doesn't prevent conduction and possible corrosion at the rivets, nor does it seal the mast at the same time. At several hundred or thousand volts per mil of dielectric strength, some of the insulating compunds don't need a goopy, shifting mess in order to work. Again, not that we can find them at the local auto parts store. Maybe an electrical supply house?