Actually, scientificly,...the patina action stops further oxygen from comming into contact with the Bronze by building up a coat too thick for Oxygen to penatrate. This is not so for Iron Oxide, Oxegen will continue to ventilate through Rust !!
If you look at the Patina on the big old brick Catholic churches roofing,..you see the green with black spotting,...the green is the second stage of Patina action and the black is the final stage,..both stages stop oxegen from getting through but the lead is drawn out of the Copper by Barimetric pressure changes, very slowly leave`n the black color !!
With cymbal grade Bronze, there is Phosphorus added for strenghth instead of lead to make it harder,..Lead makes copper or Bronze more malable and castable so you may never see black patina on a cymbal !!
I like the first phase brownning look myself and if you clean a good Ziljian to a shine, in just a few months it will be that brownning stage for quite some time !! Fingerprints are acidic and invite oxegen into the metal !!