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This is a mouthful! I have a copper pipe fixed with zink coated (galvanised) saddles.

  1. I want to ascertain what the voltage would be in the dissimilar metal galvanic reaction between zinc and copper? Looking at the tables is confusing to me because the values given for copper is +0.34V but 0.34V in relation to what? is that the voltage relation between copper and Stainless steel or Copper - Tinanium or Copper - Zinc, I dont know?
  2. Would the surface area influence the voltage or potential difference between the metals?
  3. If so, how would I determine the voltage produced per square surface of the metal faces. I have 10 sq cm surfaces of the metals in contact with each other.
  4. How would I then calculate the current strength between the two metal surfaces?

Thank you for any help with this!

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  • \$\begingroup\$ Consider the tempreture difference at the junctions. (thermocouple) Junction cross section allows for more current, as it does for any conductor. \$\endgroup\$ – Optionparty Mar 17 '14 at 13:17
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This probably belongs on a chemistry site, but

  • Looking at the tables is confusing to me because the values given for copper is +0.34V but 0.34V in relation to what?

You need the difference between the copper and zink potentials, which nicely removes the question about what they both are relative to :)

  • Would the surface area influence the voltage or potential difference between the metals?

no

  • How would I then calculate the current strength between the two metal surfaces?

That is very complex, depends on temperature, fluid composition, fluid movement, metal area, metal surface properties, and the ohmic resistance between the two metals (probably very low to start, but it might corrode) and probably a lot more. Designing a battery is not easy.

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Half-cell voltaic potential is measured relative to the hydrogen/proton reaction. Note that this is distinct from the hydride reaction, which itself has a potential of -2.23V.

The surface area does not affect the voltaic potential, but it does affect the reaction rate which will influence both the internal resistance as well as the instantaneous available current.

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