Been using my home brew setup for a bit now and using antifreeze has prevented any signs of corrosion on the blocks. The biggest draw back I've found is what appears to be cavitation on the pumps, 1 swiftech and 1 alphacool 24v @ about -30c .

submerging rads in a closed loop into the evap bath with a sharp temp change could cause contracting and expanding within the loop and I'd guess cause some fitting to break loose or blocks to crack. Just a noob shot at it.