Easily prevented with a drip pan connected to a suitable drain. They
install these under AC air handlers all the time for exactly the same reason.
I'd strongly advise against an aluminum radiator. See how long
this stuff lasts in a closed car system.
You can usually find car radiator rebuild outfits that will use
nothing but a brass or similar alloy core - because they don't
want the angry returns. You can probably have them rebuild
something that is more suitable for your purposes, maybe a truck
To avoid using corrosion inhibitor in the entire storage tank,
you could set up a water-water heat exchanger, basically two
coaxial pipes. You can get them with ribbed inner pipe for
better heat transfer. Or, you could run the radiator loop as a
coil of pipe in the storage tank.