Black Oxide on UNS C36000 Brass

I have several questions regarding a Black Oxide Finish on UNS C36000 Brass...

First off...I'm used to hearing about black-ox on steels but recently saw it can be done on brass...is it doable on C36000?

#2 I've heard that black oxide finishes need to be oiled (Don't know if that's true or not). Is this true for Black Ox on Brass, or can they be done oil-free?

#3 Is the surface coating on Brass a reaction with the iron on the brass, or is it an oxide of the copper? In my application that's important for legal purposes.

#4 Is Black Ox on threads subject to chipping or flaking on threads when assembled?

Thanks for any help.

There are many ways to obtain black colour on brass-ammonia/copper carbonate ⇦ on eBay or Amazon [affil link] ,potassium persulphate, copper nitrate ⇦ on eBay or Amazon [affil link] and copper sulphate/potassium permanganate ⇦ on eBay or Amazon [affil link] processes(there are many other processes too). All that finishes are only decorative(there are no any corrosion protection). Try to find old Fishlocks book on metal colouring (D.Fishlock:Metal Colouring,Teddington 1962.).Good luck!

adv.