[Hbond]

If we look at the theory of the earth having a solid iron(nickel) core, should such a metallic core set up a chemical potential to the surface, i.e., oceans and atmopheric oxygen, which will cause the earth to act as a galvanic cell? The mantle is ionized and full of oxygen and other ions, such that electron transfer should not be inhibted from the core through the upper mantle. While the critical state of water should be able to dissolve its way from the surface into the upper mantle, while picking up small ions along the way, due to extreme the pressure and mantle heat. This should allow electron transfer within the crust.

[Bystander]

I'll paraphrase your question, "Is the earth at a state of chemical equilibrium?"  And, the answer is, "Obviously not."  Temperature and concentration gradients, and heat flow continue to drive differentiation processes.  "Do those processes include short circuited galvanic cells?"  Yes, plus a whole lot of other chemistry.

For your homework, estimate the equilibrium pressure of oxygen over an iron oxide melt at 10,000 K.  Should give you a "feeling" for the chemical potential gradient across the mantle.

[Hbond]

The problem is how does one take into consideration pressure and the dense fluid state of the mantle? There is probably not a vapor gap between the mantle and core, but rather contact between the core and a dense fluid continuum of ionized oxygen and other atoms. The fluid aspect of the earth's core should be a solution that is rich in ionized oxygen due to the free movements of ions within dense fluid and the calculated abundance of oxygen within the mantle. The oxygen should continue on and reach the solid core.

The critical state of water, by allowing water to reach the mantle, also implies that the flux of ionied hydrogen protons flowing into the upper mantle will see a concentration gradient to the core. This is not a gas but is also part of a dense ionized solution. Just like acid protons do not jump out of water. The hydrogen protons, when they reach the iron core, are small enough to permeate the metallic core tying up electron density. This weakens the metallic matrix of the outer surface, allowing oxygen to also diffuse into the iron. The corrosion of sorts, should conduct the electrons to the oxidizing surface.

The iron core theory is not beyond question. It, like all theories of the earth's core, can not be directly proven with hard data. The basic assumption of a phase separation of metallic iron from a hot primal state of the earth does not make a lot of chemical sense. In other words, if one took all the ingredients of the earth on a small scale heated and pressurized it, where would the reduction potential come from to make metallic iron with so much oxygen present. If there was a very high percentage of hydrogen present during the gravity based phase separation of iron, this might explain it, but the hydrogen would become oxidized and ionic and not a gas. It would therefore remain within/on the earth. With the iron core 1000 times larger than the oceans, and with so little proportional fixed hydrogen within minerials and within the surface water, compared to the giant volume of the iron core, there could not have been enough reduction potential within the earth for an iron core to phase separate. The galvanic cell may not occur because there may not be an iron core.