As Dockhead says, galvanic
corrosion can create serious issues with a
steel or
aluminum 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.