Electromagnetics question - magnetic field and electrolysis

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Hi everyone,

I am most likely the least scientifically minded person to ever have visited these forums! I'm here with a question that I hope someone more scientifically minded can answer for me.

If a pair of plastic coated axial neodymium magnets are installed either side of a sheet of alloy, will the electromagnetic field from the magnets cause electrolysis on the alloy sheet? The alloy sheet will often in contact with salt water.

Thanks in advance for any answers or information on this.
 

Answers and Replies

33,579
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An alloy of what, and what else is in the salt water?
A static magnetic field won't cause electrolysis of anything, but the salt water might cause corrosion on its own.
 
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Sorry I probably didn't explain it very thoroughly. The material in between the magnets is aluminum and the salt water is sea water.

The sea water on its own won't corrode the aluminum. My concern is around whether or not a magnet on either side of the aluminum in the sea water will introduce an electrical current into the aluminum, an eddy current, which could cause elecrolysis on the aluminum. Or does the aluminum actually have to be moving in between the two magnets for this to happen? And if the aluminum was moving between the magnets and an eddy current was created, could this cause electrolysis?
 
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33,579
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A static magnetic field doesn't induce any current. Where would the energy come from?
In addition, a current in a metal doesn't mean there would be electrolysis.
 
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I'm not scientifically or technically minded at all, to be honest I don't really understand it.

So if the magnets are static, there's no way that this could cause electrolysis in the aluminum which is also in contact with salt water?

Apologies for my lack of understanding - I really appreciate your responses & help :)
 
33,579
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Correct.

There might be reactions that have nothing to do with the magnets.
 
1,392
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Static relative to what?
If a conductor (the salt water) flows through magnetic field, this can also set up electromotive forces... causing anodic corrosion.
 
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Snorlack thanks for your response.

Imagine two magnets either side of the aluminum hull of a barge. The barge is in sea water and the barge will move through the sea regularly. The magnets will be above the water line and inside of the hull but salt water will come in contact with the area directly around the magnets.

I'm not sure exactly how big the magnetic field will be, but the magnets I will likely be using are neodymium 40mm x 5mm round N45 strength.

Are you saying that this setup has the potential to cause anodic corrosion?
 
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The voltage of electromotive force due to magnetohydrodynamics scales as ∫B×v⋅dL
Note that the voltage does not depend on the conductance of the fluid (the current does).
Can anyone estimate the orders of magnitude for B and voltage involved?
 
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Any takers?? Would love to get to the bottom of this
 
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I interpret it that you want to hold something on the outside of a boat with a magnet inside and out, to keep from drilling a hole.

You don't need to worry about the magnets inducing a current and driving electrolysis, but you do need to worry about a currents generated from the two metals in contact ... the neodymium magnet metals and the aluminum hull. I'm not sure how much corrosion that might cause.

You might be able to coat the magnet with a rubber paint. Or paint the hull.

But you won't generate electricity in the aluminum with the static magnets, if my interpretation of your setup is correct.
 

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