Recently got four boxes containing 77 fired cases. Three of the boxes were somewhat worn and had reloading labels attached, the near new one did not. As I cleaned the brass I noticed that around 16-17 of the m were much darker, almost a pewter look compared to the others. Since I knew it was possible (probable) that some of the cases had been fired at least twice and maybe more, I wondered if the color of brass is affected by the heat and pressure of firing and that the darker ones were those from the near new box originally and had just been fired once? Or if that might be the case, but different batches of cases might just vary a lot in color.

No big deal to me one way or another I just wondered why the difference in appearance. All the brass is same make and of the type listed on the boxes.

corroded ?

quote:

Originally posted by hivelosity:
corroded ?

Not t all, just a different color which was really noticeable
only after not polishing as well as the others in my tumbler.

Brass was exposed to chemicals in the powder or some other chemical in the environment that the untarnished brass wasn't.

Contact with ammonia or vinegar will make brass dark over time. Also may make brass weak. stress corrosion cracking or dezincification happen.

Corrosive primers?
Nasty things going on in them!

Tarnish? There's a difference between tarnish (very, very, early stages of corrosion) and corrosion. Try some steel wool on a couple to see if the coloring comes off. Pics?

does it look like this?
I have brass look like this after it was polished and shiny brass .set in a plastic bag for a while after handling with my hands

I polish cases that show marks like these with Nevr Dull and a Lee Case Trimmer Shell holder in a electric drill. I only takes 5-8seconds of spinning and they are looking as new.