had just finished sizing some brass and decided to degrease them in a chemical we use in the smokehouse, after washing them in the neat solution we tipped them out and rinsed them in hot water they turned black. It doesn't say what the chemical is apart from 7%sodium hydroxide.
I like the look of these and wondered if any one has any experience of this and is there likely to be a detrimental effect on the brass using this degreaser.
thanks in advance

griff

I think we would need a little more info on what chemicals you are playing with. At least I would. some of the chemists on here can probably answer your questions though. It's obviously a chemical reaction, personally I would be worried about hardening the brass or making it too brittle. - Dan

When you guys find out if it is same, let me know. I have often thought of color coating my brass for easer identification. This would be an easy way to Identify calibers or bullet weights.

Are you guys aware that NaOH is the main ingredient in drain cleaners, oven cleaners, and lye?

In addition, it is incompatible with a wide variety of materials including many metals, ammonium compounds, cyanides, acids, nitro compounds, phenols, combustible organics. Hygroscopic. Heat of solution is very high and may lead to a dangerously hot solution if small amounts of water are used.

Just to put everyone mind at ease, the chemical used is a water based degreaser called spotlight made by a company called dy-chem.have contacted them to find out what other chemicals are in this, and will post as soon as I get them!

Griff

I've been looking for ways to blacken brass for use in making dummy rounds. I bought a small bottle of blackener at a jewelry supply house; it seems to be a mixture of sulfur and hydrochloric acid (HCl). HCl will eat brass alive, going after both the zinc and copper; sulfur, under some conditions, can convert to mild sulphuric acid (H2SO4) which will also eat brass. Anyway, I got mixed results with this mixture and am planning on making up a small batch of my own out of flowers of sulfur and toilet bowl cleaner containing HCl (The Works). I certainly wouldn't try to shoot any brass that had undergone such a treatment.

Have spoken to dy-chem
spotlight conists of: 1-5% sodium hydroxide,and non ionic surfactants.
they listed the only hazardous material as sodium hydroxide.
dont know if this is any help

griff

Any acid will harm ( etch ) brass. I once got blackening after we cleaned some equipment with NaOH ( 2% solution ) and adding "Wasserstoffperoxid" H2O2, to remove organic dirt.

So I�m quite sure its an oxidizing reaction, perhaps helped by the alkaline solution.

Cleaning can be done by detergents, acid, alkali or oxidizing, mostly a combination. ( Or by elbow grease ). Oxidizing may be done with Hydrogen Peroxide ( or other Peroxides ), chlor or chlordioxide, or Bromium and the like.

Ask them about oxidizers, Hermann

Griff,

I know you're Scottish but surely you can spend a couple of pence for some washing up liquid

1894
there will be no invites deer stalking for you this year!!
But you have to try these things, or how else would we find out?
Also not Scottish by a long chalk,Lancastrian and proud of it!!
Just Exiled to Scotland!!!
just kidding "is that really your year of birth"

Griff

Zinc (30% of brass) is soluble in sodium hydroxide solution. You might have depleted the surface of the brass of zinc, leaving a porous surface layer of copper (with a wee bit of zinc left in it) that tarnished especially well.

What you did to the cases may be harmless or it may be bad. I use stainless steel high pressure equipment at work, and one common type (316) gets actually cracks in it from exposure to sodium hydroxide. That makes the exposed piece less able to hold pressure without failing.

I'll see if I can find brass in a materials of construction manual at work and get back to you.

H. C.

http://www.birchwoodcasey.com/antiquing/antiquing-9719.html

There is a discussion of "antiquing" brass here. To blacken really well, they de-zinc the brass surface with caustic (sodium hydroxide) and then put the brass in a second oxidizing bath containing sodium nitrate.

The black coating is cupric oxide.

Were your cases pink before you rinsed them with hot water? I just ask because B-C says that is the color of de-zinced brass.

Haven't found anything on stress corrosion cracking of brass yet, but I haven't looked very hard. According to my reactor manual (which doesn't include brass), austentitic steels such as 316 stainless are subject to stress corrosion cracking when exposed to hot caustic.

H. C.

[ 06-13-2002, 07:43: Message edited by: HenryC470 ]

Hi Henry,
the cases were already black when I tipped them out of the solution, when I say black it was like a multi coloured finish with lots of rings where the bubbles had popped in the solution, physchodelic effect.
when I poured the hot water over them this just blackened them further! the case head is a dark blue very similar to when you grind metal.
the thinner parts of the case are black.

griff

I think you did a low-tech antiquing job, with air acting as the oxidizing agent. I don't know whether I'd shoot them, but it sounds like a nice way to identify dummy rounds as Rezdog suggested.

You can get lots of nice photographs of stress corrosion cracking of steel and brass by using that phrase as a search term. This happens with brass exposed to ammonia as most already know. The list of hits is just so long. I supposed "de-zincing" or "dezincing" could be added to a search to narrow it.

Brass is not a recommended material of construction for equipment that is going to be used to handle caustic (sodium hydroxide), but the reference I consulted is concerned with long-term exposure. I guess in air, you could have a situation where the caustic de-zincs the surface, the air oxidizes the de-zinced surface to cupric oxide, the cupric oxide sloughs off, and the newly exposed brass gets de-zinced again. That process would erode the brass, and eventually the caustic would eat through, although one tiny layer at a time if it happened as I described. If that was all that happened, the whole process would probably be innocuous to a piece of brass used in high stress applications. I don't have any evidence that this is all that happens. What would be worse is stress corrosion cracking, because in that case the caustic is damaging that brass deep below the surface, and you can get failures (cracks, breakage) even before much of the metal is actually oxidized or eaten away.

As I said, I still don't know whether they're safe to shoot.

It sounds safer to just color all over the outside of a case with a marking pen to identify it. I've done this with black markers, and the brass gets black enough to tell the difference. I don't see any good reason not to use green, red or blue markers, for that matter.

H. C.

[ 06-13-2002, 16:53: Message edited by: HenryC470 ]

Considering the cost of bulk brass at $30.00 per hundred give or take, I would just dump the lot and start over....I'd feel a whole lot better knowing I wasn't risking my rifle and my face. Just speaking for myself.

I repeat myself. In Breweries they used brass fittings. They were cleaned with alkali ( NaOH, 2% solution ) all the time. Perhaps some decolouring, but hardly noticable. Add Hydrogen Peroxide ( H2O2, for better cleaning effect )( or any other oxidizing agent ( Cl ) , air will not do! ) and the brass gets black.

If its not a thin layer which easily scratches off, I would discard the lot.

Hermann

Griff,

I prefer the hinds after Xmas so no harm done

1894 year of birth of the 6.5x55