What's the oxidation process for brass?

[Jaybird62]

I was wondering about the dark-colored condition that brass cases turn to when left out in the weather for a long period. My biggest question: Is dark brass weaker than new brass, and can it be safely reloaded? Also, what are some home recipes for bringing brass back to new color? I've used ketchup to shine up dark copper bullets, and was just wondering if some other simple "home remedy" sources would work on brass.

Jay

[montana_charlie]

This is in my 'notes', so I will just copy and paste it into this post...

"Here is a recipe for cleaning grungy brass,

1 quart of water
1 cup white vinegar
1/2 cup lemon juice
1/4 cup liquid laundry or dishwashing detergent

I use a net bag to place brass in and dip it into cleaner and let soak for 20 to 30 minutes, aggitating every 5 minutes or so. Rinse with water and towl dry, I usually tumble for 2 to 4 hours after."

I have not had a need to try it myself...
CM

[Firebird]

I believe the dark color is caused by the formation of copper sulfide due to reaction with sulfur compounds in the air. It doesn't have any other effect on the brass other than changing it's color unless you let this process go much too long and lots of metal gets involved, then the case is weakened by the removal of the metallic copper as it changes to copper sulfide. Just like rust, keep it cleaned off and nothing is really changed, but let it go on a long time and you get pitting etc.

[JIMinPHX]

I believe that the oxide is harder, more brittle & more abrasive.

[kir_kenix]

Provided there is no pitting, I just tumble and reload the brass as if it were new. I've got hundreds of '68 '06 brass that is a brownish color, but I shoot cast out of them all the time with no problem. Most of my shooting is low pressure anyway, so ymmv if your hot-rodding it.

I'm sure a chemist will eventually be able come along and give us the scoop on this browning.

[StarMetal]

Worked at a chemical plant back in the 70's. One of the waste/byproducts vented to the atmosphere was a hydrogen sulfide gas. If you came to work with new pennies or a new cut house key for example, within 1 to 3 days those items would be nearly black. A lot of people would ask me what happen to my key when they saw my keyring full of keys. We had an industrial grade air conditioner in the control room mainly to cool the electronics. Well the copper coils in it kept leaking do to that vented gas working on them. The air conditioners company eventually epoxy coated the copper coils. I would say the oxidization does in time eat the metal away.

Joe

[FN in MT]

Isn't H2S gas EXTREMELY deadly???

The MT Guard used to shoot 7.62x51 mini guns in a LONG valley just east of Townsend. During the weekdays it was open and a Buddy and I once picked up several 5 gal buckets full of brass. At the time we had a couple of HK-91's and he had a Class3 FN-FAL. A lot of the brass was old and black. We tumbled and closely inspected....then loaded thousands of rds on his Dillon 1050. We never had a case split or any problems. At least none that we noticed.

Way back when 9mm was fairly tough to get (early 70's) I fell into a bunch of current 9mm brass , but it had laid on a range for a year or two. Same deal as above; cleaned and inspected,then loaded it, with zero issues. And a lot of it was reloaded 4-5 times too.

IF theres a problem with tarnished brass I've not encountered it.

FN in MT

[AZ-Stew]

The vinegar and lemon juice formula listed above should do a good job of cleaning tarnished brass. The organic acids in the ketchup you used to clean bullets do exactly the same thing (read the ingredients).

The brown patina on your cartridges is only a few molecules thick, so it doesn't affect the strength of the brass. If I'm not mistaken, the cleaning solution (above) simply removes a couple of chemicals from the patina, leaving the cartridge in, essentially, new condition. It doesn't remove the brass, it removes the other chemicals that have combined with it on the surface and changed its color.

Regards,

Stew