Simple Simon wrote:

The positive pole of a battery is where electrons congregate.
Electrons will follow a circuit to the ground side of the battery

No.

Are you really so stupid or are you trying to stir things up again?

Electrons have a NEGATIVE charge.

Exactly. That's why wherever they congregate you'll find the mood
very negative. The battery's negative terminal is so called because
there is a lot of negativity at it. There's a crowd of electrons
waiting for their chance to leap out and do work.

There are two models for explaining how electric circuits work.
On posits that units of positive charge travel from B+ through
your lightbulb to B-, the other that there are units of negative
charge going in the opposite direction. The two models are
equally valid. Sometimes the "units of positive charge" are
called "holes", i.e. gaps into which electrons can go.

Do you remember those puzzles which consist of X*Y-1 square bits
of plastic or wood, each of which has a unique number or letter
on it, or maybe a fragment of picture, and you can shift them
around in a X*Y frame, to get the numbers/letters/picture into
the right order/place? Well, each time you move a square left,
the hole "moves" right, etc. Electricity works the same.

If you make the steel hull the
positive pole the hull will have a net NEGATIVE charge.

No, this is wrong. And even if you had said the opposite,
that the hull would have a net POSITIVE charge, that would
also be wrong.

The hull has no charge. What you need to set up is a CIRCUIT.
Just ONE electrode is NO USE, you need TWO.

Any metal
with a negative charge will draw positive ions to it and will build
up and not waste away. It will take metal from any source and
actually plate it to the hull. This is how zinc plating of an anchor
or chain works, btw.

In solution, metal ions are positive. Different metals differ in
their eagerness to dissolve, and so if you immerse two electrodes
of different metals WHICH ARE CONNECTED TO EACH OTHER into an
electrolyte, then whichever is more eager (e.g. zinc than iron)
will emit Metal+ ions (and absorb electrons) and will be the anode.
The other will be the cathode, and will emit electrons.

If you want to discourage the hull and/or its fittings from being
an anode, you have to make it be a cathode, so you have to make
it negative. But there is no absolute positive or negative, and
choosing to wire your on-board electrical system as positive
earth or negative earth has no influence whatever. What you need
is to set up an electrolytic cell. One way to do this is with a
sacrificial anode. I suppose it may also be possible with a
non-sacrificial one, but I'm not sure. The point of sacrificial
zincs is that they automatically form a battery which "generates"
the power to let the electrons and holes flow, but the work which
is done causes the zinc to dissolve. When the "battery is empty"
the protection stops. I dare say that instead of using a zinc,
you could use a non-dissolving anode but drive it from a real
battery (of the appropriate voltage) but if you do this, then
the hull or whatever fittings you want to protect will need to
be connected to the negative terminal of that battery. The battery
WILL do work, so will need to be kept charged.

S.Simon - electrically neutral

Intellectually neutral?