would be simple enough to employ a
sacrificial anode
zinc would likely be the best choice, with a cooler at least its relatively easy to "flush" the system and swap out coolant.
Of course cobbled together chip chillers are a pain in the butt, your cutting corners.
1. youve already invested considerable effort and money you might as well "try it"
2. for the first runs, provided the dewpoint is low enough, no insulation required, galvanic corrosion generally takes some time, if you employ an inhibitor (water wetter) you fine for testing
3. if its looking good insulate and employ a sacrificial annode, or determine the effectiveness of your inhibitor and how long till you need to swap out coolant
4. upgrade with the help of a local AC Tech to a
convoluted counterflow wort chiller ($110)
5. once your new friend the AC Tech is fascinated with your insane plans, have him help you build a cascade chip chiller
with another AC unit and refrigerant to refrigerant heat exchanger cooling the first (which you again swap out refrigerant on to a lower one),
then toss it into a case of sorts with wheels
