Ummm, why do they use copper as a base plating for chrome? Chrome doesn't stick well to plain steel, so they first coat it with copper. It also helps level the surface of the steel for a nice smooth finish, as it's easy to polish.
Aluminum on the other hand is something I would avoid. Anti corrosives such as antifreeze are nice and all, but I find it best to not go there in the first place.
The alternative would be an aluminum waterblock to match the aluminum 'core. Not as good as copper in performance, but not bad.