Current through seawater

[Davey]

Is it possible to send current through seawater without electrolysis, including corrosion of electrodes and the production of H2O and Cl gas?

 

Im thinking about using AC or alternating-DC polarities.

[Externet]

Yes, AC and DC current flows very well in seawater. And kills all life in its path, quickly.

 

Once I put into the sea the ground (work) electrode from an arc welder machine on a pier just to see if the metal hulled boat having welds done with only the rod terminal passed on board. Was not strong enough, but performed without rising the amperage control.

 

Electrolytic corrosion/erosion will happen anyway.

[Fuzzwood]

It only works if the voltage is well below the redox potentials required for electrolysis.

[studiot]

Yes seawater is conductive is the simple answer, if you want more detail, you will have to supply more detail of the application.

 

Electrolysis of water starts at about an impressed voltage of 1.24 volts, but external heat from the surroundings is also required for significant action at this level.

 

Electrolysis of the chloride ion does not start until the impressed voltage is above 1.36 volts.

 

If you keep below these values you are pretty safe to use the seawater as a conductor.

 

This limits the available current and very large electrode areas can be required if much current is to be passed, but this is not a problem for low current applications such as measuring resistivity in a seawater fishtank.

Edited June 18, 2017 by studiot

[Davey]

Yes seawater is conductive is the simple answer, if you want more detail, you will have to supply more detail of the application.

 

Electrolysis of water starts at about an impressed voltage of 1.24 volts, but external heat from the surroundings is also required for significant action at this level.

 

Electrolysis of the chloride ion does not start until the impressed voltage is above 1.36 volts.

 

If you keep below these values you are pretty safe to use the seawater as a conductor.

 

This limits the available current and very large electrode areas can be required if much current is to be passed, but this is not a problem for low current applications such as measuring resistivity in a seawater fishtank.

"Very large electrode areas can be required"

What do you suggest is very large? I want as much current to be passed as possible.

[John Cuthber]

 

 

Electrolysis of water starts at about an impressed voltage of 1.24 volts, but external heat from the surroundings is also required for significant action at this level.

 

 

No it isn't.

[studiot]

"Very large electrode areas can be required"

What do you suggest is very large? I want as much current to be passed as possible.

 

For the same reason you require thicker wire in power circuits in your house than you do for lighting circuits.

 

 

That doesn't hardly describe you application as I asked ??

[Externet]

Seawater presents about 0.25 ohms per metre. (cubic?) or 4 mho/m

[John Cuthber]

Seawater presents about 0.25 ohms per metre. (cubic?) or 4 mho/m

No.

Seawater presents about 0.25 ohm .metres

It's ohms times metres not ohms divided by metres.

Edited June 18, 2017 by John Cuthber

[Externet]

Thanks for educating me; again. I was reading the following a few days ago and perhaps got it wrong. Only the reciprocal is per m. ?

 

Is this accurate ? :

 

Edited June 18, 2017 by Externet

[John Cuthber]

IIRC the mho is a bit out of fashion, having been replaced by Siemens.

The conductance would be measured in mho per metre.

 

The variations with temperature and salinity look plausible. I'm not really in a position to check.

[studiot]

No it isn't.

 

 

I would be interested to learn what comment you have about this more detailed article from London South Bank University..

(Where the information you objected to came from.)

 

http://www1.lsbu.ac.uk/water/electrolysis.html

 

 

To clarify:

 

The minimum necessary cell voltage to start water electrolysis is the potential 1.229 V

The potential necessary to start water electrolysis without withdrawing heat from the surroundings is

-ΔH°'/nF = 1.481 V.

This results in at least a 21% unavoidable loss of efficiency. Normally further heat is generated, and efficiency lost, from the overpotentials applied.

Edited June 19, 2017 by studiot

[studiot]

Although it is not clear what ions were in the water, here is a tragedy that demonstrates the conductivity of water with ions.

 

http://www.bbc.co.uk/news/world-europe-40388161

[Davey]

I understand that there are non-metal materials that are "better" to use in this case, such as carbon and graphite for example. Due to these materials are more resistant to corrosion i assume.

 

What would be my best choice of material for creating a long lasting circuit with the most power possible, through seawater?