RE: Crock Pot
If your corrosion is white (aluminum oxide which will collect dirt and look dark), it will not be removed with antifreeze. It will remove castor stains but caution is necessary. If there is any water mixed with the antifreeze, it will discolor the aluminum darker. If the engine is not fully submerged, a dark line will be made where the air/antifreeze meet.
I've fount thie antifreeze method to be not worth the risk to the engine.
I have taken up cleaning with ultrasonic in a bath of Branson MC-3 which works very well on all stains.
I still don't know of anything short of mechanical means that will remove the aluminum oxide.