Hello Capt. :) - I stand corrected on the getting the 2 methods confused - quite right. But I still see the "capacitive protection" concept as less than convincing :D The only real references I can find to these systems are from the producers of such devices, like this one...
CounterAct Electronic Rust Protection System - Corrosion Control
Be that as it may, allow me to make a few observations (and remember, I'm a Geophysicist, not a chemist!) ...
From what I can gather, it is supposed to work like this - An electric current is applied to the metal object to be protected - in this case, our vehicles, by treating the metal object as the negative plate of a capacitor. This is achieved by a capacitive coupling between the metal object, a dielectric material and a positive plate. Pulses of direct current are provided to the positive plate. The vehicle acts as a common ground with the means for providing the pulses coming from it's battery.
If this is exactly how it works, then there is no net DC current generated - that is the nature of an insulator. Therefore, during the pulse, there would be protection, but during the absense of the pulse, the bias is opposite. At best, this would cancel the effect of the pulse phase,; at worst, it might even be sufficent to cause corrosion beyond that driven by oxidation differentials in the metal - actually encouraging rust! :eek:
I'd use lanolin!