Galvanic Anode CP vs ICCP

[xda]

if we choose galvanic anode CP system for protecting old cs pipe, is there any max possible economical current output that is supplied by total anode than using ICCP system? What is other relevant considerations?
thx

 

[mshimko]

More info is needed, including (1) are you trying to protect the inside or exterior of the piping?, and (b) what is the environment that is causing the corrosion.

I suspect you've got a buried steel pipeline, but that's just a WAG (wild ass guess) on my part.

 

[xda]

yes, we're considering to protect 20,000 meter external burried pipeline; the environment is soil (onshore) with 7000 ohm-cm resistivity and pH = 5.
For galvanic anode system, may be many anodes required to protect it, but untill what total current output of total anodes are considering to change protection system by using ICCP?