Hi Plum,

I doubt there has been any serious damage to your heads. A zinc anode on a boat usually lasts a pretty long time and that is submerged in salt water. As it sounds like the problem is caused by the dissimilar metals, which you can not change, I would go with the zinc anode or the coolants mentioned. You could also drain the system and refill using distilled water plus whatever antifreeze, water-wetter additives you desire. Distilled water is pretty much just H2O with no other ions so has less current carrying capacity. I know, it sounds as if I am talking about electrolysis again, but while not caused by an electrical current, galvanic corrosion is still an electrical phenomena. The worse of a conductor the fluid is, the less corrosion.

For fun sometime stick an aluminum nail and a copper nail into a lemon. Lemon juice is acidic, copper and aluminum are far apart on the galvanic scale. Put a voltmeter with one lead on each nail, completing the circuit. With the meter set on the lowest voltage DC setting you will be able to detect a current. Several of these in series will light up a flashlight bulb.

Okay, enough science. Now, go buy an anode and burn rubber.