Questions on sea driven electrical production

hi please be gentle first thread and not a sciencetist but whilst meditating last night an idea popped in the old noggin, and before you ridicule there are quite a few sciencetists have claimed there break through's came to them whilst in a altered state of reality so

1 well some are aware that as a boat passes through water it generates a current this is known as electrolosis
2 they place nodes on the hull of the ship to stop the hull corroding

So my question is isn't there some way of harnessesing this current, say around the globe in tidaly active areas you would place large electrodes into the water to drain this current from the sea
surely there is some alloy that would react to sea water and allow the electrical current to flow from the sea into a useable form of electric for our technology
much like a primitive badghdad battery two electrodes into an acidict solution or like when they electro-coat objects (silver plating etc)
I am not a sciencetist or an electrician so do not fully understand and this is why I am asking, it is just an idea that popped out of nowhere please feel free to enlighten me
1 is this possible
2 why not and what prevents us from draining the naturely produced current of the oceans

just really fascinated by the idea of pulling free current from the world have watched a few things on tesla and this is probaly what inspired the notion please don't dismiss off hand and give it a thought if there is no validity to this fine I'm a dumb ass but what if this was possible ?

The electrolysis or to be more correct corrosion is independent of the water flow. The ship will corrode even if it is not moving due to impurities in the material. It is a pure chemical reaction which is accelerated by electrolytes(salt water). Of course you can use corrosion to generate electricity. This is how batteries work.

reply to post by moebius


so would it be possible on a large scale with no adverse effects to the ocean envoiroment ?

Well, if we had pure elements(iron e.g.) in abundance. The problem is that most metals are available as oxides only. They are already corroded. To get iron from iron oxides you have to put the same amount of energy you would be able to gain(theoretically) from its corrosion.

Originally posted by moebius
To get iron from iron oxides you have to put the same amount of energy you would be able to gain(theoretically) from its corrosion.

This is getting at the heart of the matter. It's feasible but not economical. I think the amount of energy you put in actually ends up being much more than you get out due to inefficiency and waste.

So why don't we do it? It's probably 10 times cheaper to get energy from burning coal.