Yes, there is an electrolysis effect within the cooling system. I remember many years ago when the big rigs had HUGE brass radiators there were zinc plates inside as a sacrificial metal. You could put a voltmeter from engine to radiator and read a voltage. They then began using additives that would virtually remove this voltage.
If you don't see voltage when measuring as described, it may mean that there are additives present in the cooling system that are masking the electrolysis effect (laymen's explanation).
Some months back there was quite a discussion about antifreeze and additives for same. Someone, if my memory serves me correctly I believe it was Longston, works in the field and had a wealth of knowledge regarding the subject. Maybe he, or whoever it was, could comment.
Have a great day,