Chris,
In office tower air conditioning systems, the chillers (which use a refrigeration cycle to produce the chilled water for the air conditioning) have dissimilar metals in contact with water, which always causes corrosion. In this case, copper and steel, forming a weak "battery". To counter this you can install a passive system which has sacrificial anodes. Sacrificial, in that you use a material with an electrochemical potential such that IT corrodes before the material you are protecting. Similar to the protection you get by hot dip galvanizing steel. Or you can go a step better and use impressed current cathodic protection. This uses a power supply and applies a potential difference to prevent metal ions moving in the corrosion direction, to put it simply. Works very well. This is similar to the system you are referring to. However in a piece of equipment in a building which always has water, to act as the electrolyte, and has power readily available, it is easy. In a motor vehicle I think it is less effective as the steelwork often isn't wet, and it is absorbing battery power all the time. My 2c worth.
Dalton
