brass getting dark right after cleaning?

[Unclenick]

Shadow9mm,

Your link is broken. If you just paste the text of the link into the body of your post, the system automatically shortens it. You have to go back and highlight the remaining link text and click on the little globe and link icon at the top of the window and paste the whole link into it.

The dezincification process is slow. I have a piece of LC brass that sat for months to maybe a year in a bag wetted with rain runoff. It has one pit under where it bloomed white with zinc oxide. It probed about 0.002" deep after all the oxide came off. It still shoots, but I wouldn't recommend shooting something like that, as you risk a gas jet that pits your chamber. I was running the experiment in a shot out barrel due for replacement.

There's a Canadian paper that used 0.1 molar hydrochloric acid (chlorine loves it some zinc) to demonstrate dezincification, but 24 hours later it still hadn't got deep enough that the affected layer couldn't be polished off. Also, it's action had slowed over that period, with most of the action in the first few hours. This is brass that was degreased and roughed up with a fine abrasive to insure good reactivity.

So it is hard to imagine much damage in normal cleaning time. Especially if the action slows as it progresses. Also, oxidation products tend to protect brass. Hatcher described putting polished brass and brass oxidized by the normal manufacturing and annealing processes on the roof of the Frankford Arsenal back in the 1920's sometime, when it was an industrial area with very corrosive air due to chemical plants (and probably from locomotive smoke). He wanted to see which could better tolerate that corrosive air and rain. A year later the polished cases were all eaten away, but the ones with an oxide layers were still intact. That's when the military stopped polishing cases.

So your darkening is probably protecting your brass. If your hot water is sixty degrees warmer than your cold water, figure it happens about eight times faster at that temperature.

[Shadow9mm]

Originally Posted by Unclenick

Shadow9mm,

Your link is broken. If you just paste the text of the link into the body of your post, the system automatically shortens it. You have to go back and highlight the remaining link text and click on the little globe and link icon at the top of the window and paste the whole link into it.

The dezincification process is slow. I have a piece of LC brass that sat for months to maybe a year in a bag wetted with rain runoff. It has one pit under where it bloomed white with zinc oxide. It probed about 0.002" deep after all the oxide came off. It still shoots, but I wouldn't recommend shooting something like that, as you risk a gas jet that pits your chamber. I was running the experiment in a shot out barrel due for replacement.

There's a Canadian paper that used 0.1 molar hydrochloric acid (chlorine loves it some zinc) to demonstrate dezincification, but 24 hours later it still hadn't got deep enough that the affected layer couldn't be polished off. Also, it's action had slowed over that period, with most of the action in the first few hours. This is brass that was degreased and roughed up with a fine abrasive to insure good reactivity.

So it is hard to imagine much damage in normal cleaning time. Especially if the action slows as it progresses. Also, oxidation products tend to protect brass. Hatcher described putting polished brass and brass oxidized by the normal manufacturing and annealing processes on the roof of the Frankford Arsenal back in the 1920's sometime, when it was an industrial area with very corrosive air due to chemical plants (and probably from locomotive smoke). He wanted to see which could better tolerate that corrosive air and rain. A year later the polished cases were all eaten away, but the ones with an oxide layers were still intact. That's when the military stopped polishing cases.

So your darkening is probably protecting your brass. If your hot water is sixty degrees warmer than your cold water, figure it happens about eight times faster at that temperature.

My apologies, link fixed.

[jetinteriorguy]

Originally Posted by MarkCO

Better, but there is as much in the primer pocket as in the primer cup, so don't be thinking you have no lead in your media because you do.

Hot water, given the proper metal ions WILL cause dezincification. Happens all over the US in potable water systems with some types of brass fittings on, or near water heaters. Cheers.

Interesting idea of lead in the primer cup, hadn’t thought of it that way. Makes me think it might actually be better to tumble with the primers still in place. Since the media probably doesn’t have much affect on cleaning the inside of the case it wouldn’t be as likely to release as much lead as if the primer pockets were exposed.

[MarkCO]

Did a but of reading on dezinkification. Granted this is related primarily to plumbing and copper it does cover brass as well. Apparently dezinkification can also happen in cold water. granted using hot water will speed up the process. But based on this it will most likely take a long time. I highly doubt the amount of time spent in the tumbler will effect things significantly.

I have been working on dezincification cases in plumbing and cartridge brass for well over 20 years. You are correct that it takes longer in cold and longer in buffered waters. In testing, I have detected the initiation in under an hour with several "home brew" recipes suggested when hot water is used. In most cases (pun intended) it does take a while, but once started, each subsequent wet tumbling furthers the process. In almost every instance I have checked my own solution, after tumbling, and in the many cases I have worked on professionally I have found zinc levels in solution and the initiation of the process by testing of the cases in the SEM.

The Woolite Dark, Lemi-Shine and no pins with cold water was the least amount and was comparable to the solutions sold by the various manufacturers. So that is what I use when I wet tumble, which is maybe half of the time.

[pete2]

Are ya'll sure wet tumbling is better than dry??????

[Shadow9mm]

Originally Posted by MarkCO

I have been working on dezincification cases in plumbing and cartridge brass for well over 20 years. You are correct that it takes longer in cold and longer in buffered waters. In testing, I have detected the initiation in under an hour with several "home brew" recipes suggested when hot water is used. In most cases (pun intended) it does take a while, but once started, each subsequent wet tumbling furthers the process. In almost every instance I have checked my own solution, after tumbling, and in the many cases I have worked on professionally I have found zinc levels in solution and the initiation of the process by testing of the cases in the SEM.

The Woolite Dark, Lemi-Shine and no pins with cold water was the least amount and was comparable to the solutions sold by the various manufacturers. So that is what I use when I wet tumble, which is maybe half of the time.

Very interesting. It helps to have a good understanding of the why behind the system you use. How do you test for dezinkification? What "home brews" have you tested?

I would be very interested in doing some testing myself.
Control with distilled water no pins
distilled with pins
tap no pins
tap with pins
tap with dawn/lemi shine
tap with frankford packets
tap with mcguiars ultimate wash n wax
tap with woolite dark/lemi shine

With that said I am not sure of what benefit testing the water for zinc would be. Seeing as tumbling the brass is basically removing the powder residue and generally the top oxidized layer of metal whether wet or dry. To me this means metal is removed from the casing while polishing. I would think it would be hard to isolate whether it was dezinkification of the case itself, or the zinc in the oxidized brass that had been removed during cleaning/polishing.

[RC20]

Are ya'll sure wet tumbling is better than dry??????

My brother loves it. But he is both setup for it with water in his garages and a place to the fluid down the drain.

I am badly setup for doing it and I am fine with the Vibratory.

The wet gets the inside clean and that has some affect on anneal timing and may get a bit better anneal as you do not have the coat of carbon (though I just test and time it and have had no issues annealing). He did get a time change when he went to wet.

Nothing wrong with either one, its really a preference thing.

[MarkCO]

Shadow9mm.

When I do a test for a case I am working on, I run a control with some passivated steel cases. So same powder and primer and bullet as the brass cases. The wet chemistry is done in a lab to isolate all of the elements present, cases weighed and SEM analysis done. In the SEM I can get a surface compositional analysis and compare that against a few pieces of brass held out for control, and what I see in the water. The benefit of testing the water for zinc is for me to be able to tell if zinc is being pulled out of the brass cases, that is it.

The "home brews" I have tested are what individuals in cases claim they used. I have been able to find most of them pretty easily by internet searches. Lemi-shine is a common component usually, some folks have added vinegar, different dish or laundry soaps, lye, etc. I am not going to give you exacts, because some are protected case docs. Also, the water one uses, the temp, etc. are all variables.

[MarkCO]

Originally Posted by pete2

Are ya'll sure wet tumbling is better than dry??????

There are pros and cons to both.

Wet gets the cases cleaner inside, almost eliminates inhalation of dust with lead compounds. Dezincification is, for most, a minor concern that can be mitigated.

Dry, if you want clean primer pockets, involves a little more work to make sure primer pockets are clear of media.

I use different methods based on what I am after for the specific hand loads I desire.

[Unclenick]

RC20,

Metal is removed by polishing, but the amounts are really small. I've yet to be able to measure it with a micrometer that resolves 0.05 thousandths. I ran some with just citric acid for another post, and it worked fine, but of course, the brass darkens afterward as there is no protective film. I'll be interested to hear how your water-only test goes. It may get all the crusty carbon.

Also, there is the problem of distinguishing between actual dezincified metal and red copper oxide. The military brass has red oxide as part of its annealed oxide coating, so a number of the cases I did with only citric acid came out with highly polished and smooth pinkish necks, but no sign of pink anywhere else on the brass, including the shoulder, from which I concluded the annealing flame made the necks hotter than the shoulder (no surprise). The red oxide (cupric) is just not very reactive with the citric acid, so it stayed behind.

[MarkCO]

Pinkish and Reddish coloration is an indication of dezincification. Over-annealing with flame alters the matrix and or burns out the zinc.

[RC20]

RC20

Metal is removed by polishing, but the amounts are really small. I've yet to be able to measure it with a micrometer that resolves 0.05 thousandths. I ran some with just citric acid for another post, and it worked fine, but of course, the brass darkens afterward as there is no protective film. I'll be interested to hear how your water-only test goes. It may get all the crusty carbon.

Not what I do or plan. I do dry and will stay with it. I loose cases over loose primer pockets over time but none to wearing down so far.

As noted, nothing against wet, whatever process my brother uses he does not get tarnish fast. How long he gets I have not asked.

I also have a bit of a personal laugh about dust. I had serious asthma on top of random asthma. Upshot (pun not intended but not avoided) is when I quit work (100 conveyors) it went away, now is back to random.

Have to wonder what that did to my lungs..............

[Unclenick]

So, to settle some of this for practical purposes, I did an experiment. I took one of the cases I had wet-tumbled with 0.7% citric acid and nothing else (left in the photo). You can see how pink the annealed area is. I then increased the citric acid concentration to 5% as recommended by Frankford Arsenal long ago and left the same case in it for 72 hours.

What you see in the case on the right is that not only did the citric acid produce no dezincified pink during the long soak, it actually slowly removed some of the pink from the neck and shoulder of the case. You can see the surface has become matte in appearance from slight etching. The solution became faintly blue, too, from the copper it picked up. But there is no sign of it taking out zinc preferentially.

I was expecting, if the pink was cuprous oxide, that it would dissolve faster, which scores a point for Mark's contention that it is copper. But I still don't know why I have observed no tarnishing of the pink as I would expect on pure copper (showing a fingerprint, for example). Perhaps it has an oxide protective layer. But I would need analytical equipment I don't own to sort that out.

The bottom line is that citric acid solution as used in case cleaning and even stronger does not produce visual evidence of dezincification of brass. The pink color observed after citric acid cleaning is something that was already present under the oxidation removed by the citric acid and is not cleaning damage. That's the main thing of importance to folks using citric acid for case cleaning. This tends to agree with the comments in the long thread on citric acid case cleaning the castboolits forum where it was suggested the reaction is self-limiting. At least it seems to slow greatly after initial oxide removal.

[Shadow9mm]

great example. thank you. No pink, just tarnishing/getting dark quickly as they dry. Running a batch now. making sure I have a good rinse and testing a dish washer drying aid.

[Unclenick]

The one on the right was at least a day old when I took the photo. But I worked entirely with cold or room temperature water, so I still think it is heat that is whacking you.

The dishwasher drying aid will be a bit like Kodak Photo-Flo and other wetting agents. I should make the water sheet and prevent water spots. I would expect a car wash wax to do better about preventing color change. Some of them have wetting agents in them, too, so you don't have to go over the car with a chamois.

[MarkCO]

I was expecting, if the pink was cuprous oxide, that it would dissolve faster, which scores a point for Mark's contention that it is copper. But I still don't know why I have observed no tarnishing of the pink as I would expect on pure copper (showing a fingerprint, for example). Perhaps it has an oxide protective layer. But I would need analytical equipment I don't own to sort that out.

Copper oxides go from bright aqua blue to dark blue to brownish to dark brown to pink. All dependent on the amount of oxygen, other oxidizers and metal ions present. The pink is most common in cartridge brass, but it is not only coloration that signals dezincification. If 50% or less of the zinc is removed, you might not get any color change at all, just the dull appearance.

What you have shown is the the copper oxide on the surface is removed (expected)as the acid concentration increases and that the dezincification has moved deeper into the case. In most of the cases I have worked on where dezincification has fully penetrated and resulted in fracture, the surface looks brassy and dull with a light pink or brown tint. The pinkish layer, in some cases, is deep into the structure. I know it is fun to try and beat a subject matter expert, so you can go with your test if you want. But what you proved is that you have over annealed and burned off zinc leaving a ruby red color. Sure, that copper oxide will be easily removed, but that does not mean the zinc has not been removed, in fact, in that case it was removed by flare off and acidic attack.