Re: Brass corrosion question for the chemists

In article <f0dfis$6qm$1@xxxxxxxxxxxxxxxxxxxxx>,
"frank.logullo" <frankdotlogullo@xxxxxxx> wrote:

# "Robert Scott" <desmobob@xxxxxxxxxxxxx> wrote in message
# news:f0d4ip$15a$1@xxxxxxxxxxxxxxxxxxxxxxxx
# # I just found a canvas duffle bag in my cellar (sometimes damp, concrete
# # floor) that had some shooting gear in it. There were a couple of cheap
# # suede sandbag rests and a partial box of empty .223 cases from a long-past
# # shooting session.
# #
# # The parts of the suede rest bags that were in contact with the bottom of
# the
# # duffel were hard, leading me to believe they got wet at some point, then
# # dried. There were a half-dozen or so little mouse poops in there too;
# well
# # dried out.
# #
# # When I opened the .223 cartridge box, I was quite surprised to see the
# cases
# # were a beautiful light blue color and all bubbly looking! They looked
# like
# # they were dipped in some kind of ceramic glaze or something. Very
# # strange....
# #
# # I've never seen brass do that. Could plain water have done that? Or
# water
# # that had seeped through the concrete (changing its pH?)? Something to do
# # with the tiny bit of mouse droppings? Or did my damn cat pee in the
# duffel?
# # =:-0
# #
# I'd suspect carbonate formation such as you sometimes see on pipes. Copper
# carbonate, I believe is green. Not sure about zinc carbonate. Moisture and
# acidic conditions would cause this and there is enough carbon dioxide in the
# air for this reaction to occur.

I'd expect that the suspicion of the cat piddling on it is the simplest
and most likely explanation - Urine decomposition = ammonia.
Copper/copper-bearing alloys plus ammonia = pretty shade of blue scrunge.

Then again, acid rain = sulphuric acid (mostly - there are other fun
things in it as well) forming from reactions between loose
sulphur-bearing compunds and rainwater, and hitting
copper/copper-bearing alloys with sulphuric acid gives you copper
sulphate, which, in turn, is a rather pretty shade of blue. (the color
of the semi-precious stone turquoise is due to copper sulphate,
ferinstance)

--
Don Bruder - dakidd@xxxxxxxxx - If your "From:" address isn't on my whitelist,
or the subject of the message doesn't contain the exact text "PopperAndShadow"
somewhere, any message sent to this address will go in the garbage without my
ever knowing it arrived. Sorry... <http://www.sonic.net/~dakidd> for more info


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Relevant Pages

  • Re: Brass corrosion question for the chemists
    ... # I just found a canvas duffle bag in my cellar (sometimes damp, ... # floor) that had some shooting gear in it. ... Could plain water have done that? ... I'd suspect carbonate formation such as you sometimes see on pipes. ...
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