As Dockhead says, galvanic corrosion
can create serious issues with a steel
boat. The problem of rust in a steel
boat is secondary.
You have to be extremely cautious with every component of the boat. On an luuminum boat, forget about bronze components, must use non-ferrous fasteners, etc. They say that the new aluminum
alloys are more resistant to galvanic corrosion
, but no metal boat is immune.
IMHO the electrically inert qualities of fiberglass
(and wood) are a huge advantage.