Does this have anything to do with keeping the copper pipes from corroding from the inside?
In order to prevent corrosion. In many cases water pipes were and is made out of cast iron and steel. Rust on ferrous metals is in fact result of electrochemical reactions. In presence of humidity, kind of primary batteries form on the surface of the metal, and small currents flow between iron and the surrounding materials. By connecting a low voltage current source with opposite polarity these currents can be prevented to flow, this way the corrosion (well, the wast majority of it, caused by the above-mentioned phenomenon) can be stopped. Corrosion inside the pipes is many times slower because clean freshwater is a poor electrolyte.
This is called active corrosion control. It causes corrosion to 'reverse' direction. Passive corrosion control would involve attaching a easily corrosive metal (tin for example) and it would corrode before the pipes. This is also called sacrificial corrosion control. Funny thing about active corrosion control - if other pipes near by are not protected by active corrosion control, they will corrode even faster than normal.
