galvanic corrosion will happen but
cars have aluminum heads and copper rads why arent all those cars stopt dead in thier tracks ?
well antifreeze has aditivs that mostly prevent galvanic corrosion if u chnage the fluid every yr
why are so many ppl hit with galvanic corrosion ?
1 they buy snake oil water cooling aditivs that containe ither harsh soaps
strong sulfurs or oxides to kill bacteria wich they doo but they will eat ur rad and block too
2 rads are made by soldering a buncha small pices together do do that they use flux and lots of flux , that flux is left inside long after its made and when u buy a new rad and hook it up to ur loop the flux disolves in the water and makes the water slightly acidic wich againe eats ur rads and blocks , so even if its new wash it out with plenty of water or chnage the water in ur loop a few times after puting in a new rad
so wash out ur new rads and use antifreeze it will kill bacteria and prevent galvanic corrosion some will say water works best for cooling maybe soo but 10%-40% of antifreeze in ur loop will kill all the swampy monsters
and keep ur loop from rusting away
and brass and copper will not react with eachother no matter what u doo