copper protection

Consider plating a barrier coating of nickel to prevent corrosion. Pore free layers can be quite thin.

What considerations do you have? e.g., cost, temperature, environment, size of tubes, any other technical concerns about a coating on tubes.

I suspect that this might be a type of heat exchanger that requires good thermal conductivity.

Would the nickel plating affect the electrical conductivity?
This part needs to be resist the temperature!

I don't think the nickel would harm the conductivity, but a charming solution could also be to add a polymer coating and to create small openings where you want to make electrical contact. On these places a gold layer could be added by spot-plating. The small holes in the coating can be achieved by lithography.

This is a quite common technique for circuit boards (a so-called solder-mask) and could be usefull unless the copper plates are not too large.
Edwin Muller
KEMA Power Generation & Sustainables
Arnhem, The Netherlands
E-mail e.f.muller@kema.nl
Internet:

Nickel is used for electrical contacts to improve the initial and long term contact resistance of copper. For higher current densities, you might consider silver, but nickel is quite good.