i think there are now three aspects that we are now talking about:

1. galvanic corrsion caused by a perfectly functioning AC ground wire/ shorepower

2. grounding for the purposes of lightening protection/prevention

3. corrosion of metal parts that are not at all electrically connected to the boat. just grounded (that is, they are immersed in it.)

the first two make sense to me, but like someone else said, the third doesn't make intuitive sense. i am by no means denying that it happens, just trying to figure out the mechanism (so as to prevent it)

more confusion.....