Aluminum is one of the worst for corrosion, so if you put a small amount of aluminum antifreeze in it should work for all those metals as copper/brass are higher up on the electrochemical scale.
http://en.wikipedia.org/wiki/Cathodic_protection has a table of metals and their voltage, lower will sacrifice to higher.
Now when we're talking antifreeze it's a little bit different that normal cathodic protection.
http://www.freepatentsonline.com/4873011.html:
"An antifreeze composition for use in aluminum internal combustion engines is disclosed. It is comprised of from 0.05 percent to 0.5 percent silicate, from 0.07 percent to 0.35 percent nitrate, from 0.2 percent to 2.0 percent phosphate, from 0.5 percent to 4.0 percent benzoate, from 0.1 percent to 1.0 percent molybdate, from 0.02 percent to 0.3 percent vanadate, from 0.05 percent to 0.3 percent triazole, and from 100 ppm to 5000 ppm organosilane stabilizer for the silicate. Organic amines and borates are excluded in the compositions and the pH of the compositions is from about 7 to about 9."
So basically you should get that type of antifreeze not the normal one for cast irons. As to amount, I can't really say but the less you use the more frequent it needs to be changed... but again, I don't have any numbers for you. Make sure when changing that you purge the system, tho... there can be small buildups.
(Just so you know, my knowledge is not in WC set ups, but I have taken classes in chemistry, thermodynamics, fluid dynamics, and hydraulics which is all very related to WC)