If you ever pass thru west Texas, I can show you an aluminum radiator that is about 15 years old that has straight water plus and additive run at least six months a year for more than ten years of the 15 and it has no corrosion. I continue to think this is a "problem" that was created to justify a magic part instead of promoting good maintenance.
At this point in time, I suspect I potentially have more problem with the fin bonding on the tubes than I do any interior problems. People often don't realize that the quality of the bond between the fin and tube deteriorate with time and the cooling efficiency of the radiator suffers as a result.
But the corrosion can be occurring at other locations other than the radiator. Aluminum components like heads can perhaps result
in block corrosion, due to dissimilar metals. Also, the quality of engine grounds might affect corrosion rates. If you install this zinc anode,
and in a few years it is corroded, then that shows its working. We use to strap large zinc blocks on the hull of our submarine, which was continually
generating a lot of electricity, similar to a car alternator.