[Bob Mulry]

Two completely different issues....

Rust is Iron Oxide (FE2O3) and is caused by Iron coming into contact with oxygen......

Adding a rust inhibitor and preventing air from contacting the cast iron, such as a coolant recovery system would help, but we dump the water to save the head gaskets and leave the block to air dry and that causes rust.

Galvanic Reaction is when 2 dissimilar metals are in contact in an electrolyte (water)...

The liquid allows the transfer of metal from the most active metal to the least active metal....

Copper radiator and cast iron block, using a zinc or aluminum sacrificial anode would work to save the radiator.

Aluminum heads, intake or radiator on a cast iron block would require a magnesium sacrificial anode to save the aluminum.

That's why they bolt "zincs" to the hulls of ships to save the bronze propellers and the hull...

Just my 2 cents...