Galvanic currents and electric fields...

[Externet]

Hi .

Does galvanic protection under seawater by the use of dissimilar potential metals create an electric field and electric current in the water?

 

If yes, to what extent ?

 

A mile apart chunks of zinc and iron, will there be an electric current between them ?

 

Miguel

[Tartaglia]

You get two electrochemical reactions

 

Fe -> Fe2+ + 2e (Anodic reaction)

 

1/2 O2 + H20 +2e -> 2 OH- (Cathodic)

 

This will give rise to current due to electrons moving through the metal from the anodic region to the cathodic region and presumably the OH- move the other way through the water completing the circuit. (Or Fe2+ move through the water the same way)

 

Fe2+ +2OH- -> Fe(OH)2

 

There is then a subsequent further oxidation to give Fe (III)

 

The cathodic equation tells you why both O2 and H2O are required for rusting. The fact that salt speeds up rusting so quickly tells you there must be movement of ions through the water involved. Salt increases the conductivity of water considerably

 

Although anodic and cathodic regions are distinct I doubt there would be miles between them