I've got to admit, I'm still skeptical. At least in theory, the radiator is not electrically connected to anything (3 rubber mounting bushings). To get galvanic corrosion, you need dissimilar metals immersed in a conductive medium that are electrically connected. Now aluminum heads would certainly qualify and what about aluminum intake manifolds? Both are through bolted to the block and have coolant going through them. I have never heard of anyone suggesting cathodic protection for them.