Harley engines are uncoated, and often times the fins are "Diamond Cut" with a Dremel on each single fin. It creates the illusion of each fin having "jewels" or "Diamonds" going all the way around the cylinders and the heads. No trouble with oxidation that I've heard of. It is a very common finish that has been used for decades.
I am aware that certain aluminum alloys will oxidize, of course it all depends on the alloy and the way the surface is finished.
The only thing better than one red head; twin red heads. Thanks for the compliments The heads are stock. Just got them back from a valve job. I’ve never had issues with corrosion on fins on my other motors.