Take care with your analysis. If you have chemically induced corrosion,
this will generate a voltage, typically 1 to 2 volts dc. Chicken/Egg!
As Greg says ph is the key. All metal corrosion involves electrical phenomena, not all of which may be measurable, due to closed-loop circuits.
Water softening creates potential corrosion scenarios.
Hard salt ions like calcium replaced by sodium ions reduce limescale deposition, but this also prevents protective layers of lime being deposited on the copper.
The softener resins are occasionally backflushed with common-salt brine to remove the calcium from the system. Any brine getting back into the pipework would cause corrosion, although that's unlikely.
Another common problem is cement or concrete. A copper pipe in contact with, or cast into, concrete or cement mortar will probably perforate in less than 10 years. This corrosion will induce local voltage, which in turn can induce copper salts to form in the pipe bores, if the ph is not neutral.
