Brass corrosion


I recently checked some cartridges at the back of my storage cabinet and found an 8mm Lebel, which I’ve had for many years, with the centre of the case almost encircled with large, circular patches of pale blue corrosion. None of the other cases in the drawer is affected.

What causes this to happen to just one case in a drawer (which incidentally is steel, lined with corrugated cardboard), and what’s the best way of cleaning it off?


For such coorosions I usually make use of “rust converter” (as far as I remember orthophosphoric acid). You may use a small tampon soaked with it and just wipe out the corroded spot (fortunately not too big in your case) and then wipe out the acid and other remnants with wet cloth. Then thus treated spot may be pollished with woollen cloth. Here I post the pics of a cartridge about 130 years old extracted from a river, which was treated this way.


I also had observed such corrosions on cartridges saved in a cardboard box, but I can’t tell what is the reason of their appearance.

Good luck!


As powder breaks down, the residual nitric acid reacts & can sometimes even leave a small hole in the case.
Doc AV had a better, more correct answer in a post awhile back.

I usually carefully , gently (with the aid of a glass) scrape the effected area with a piece of square edged brass (no nicks on the edge otherwise it may scratch the case) until the residue is completely gone. Then your better off if you pull the bullet & dump the powder as it will continue. Some also add the step of boiling the case in water as I understand it.


As per my experience such problem may caused because of powder decomposition, which is clearly describe PetedeCoux. Nitrocellulose deteriorates with time, yielding acidic byproducts. Such problem is common for calibers like 8 mm Lebel loaded with not stable powders or powders made by simplified technology during war. May be powder was not dry completely, or may be it containe insufficient quantity of stabilizers, such as Diphenylamine.

Of course, I can’t except the action of the water together with corrugated cardboard. May be cartridge was damp (I mean something like one drop of water). Paper and cardboards cotain a lot of components harmful for brass. Water help to activate these components. I saw a lot of digged cartridge boxes where cartridges had a good condition, but the parts of cases directly contact with box paper or cardboard had a considerable corrossion, even deep grooves.

As for me, in your case is better to use mechanical cleaning first of all. Chemical cleaning need very careful removing acid reminders from the case surface. For this purpose is better to use neutralizer, for example soda water solution. Otherwise you will get red copper spots on the cases during time, because acid reminder will continue to etch the brass of the case.


I also pull the bullet and dump the powder as Pete mentions. After that I rinse the case inside and out with hot soapy water to disolve the corrosive salts that have formed on the inside (as explained above). Then I scrub the inside of the case with a Q-tip and rinse again until the water comes out clear. I then set the case upside down so it drains and dry for a good day. My favorite way to dry is stick a thumb tack in a piece of wood and stand the case up on it. This leaves the case upside down and allows air circulation up into the case to ensure it dries. Last step is a touch of 3 in 1 or some other light oil, applies on the inside with another Q-tip. This is basically the same procedure I use after shooting corrosive ammo and my bores stay shiney.

One thing I also really like is using extra fine bronze wool to clean crud off cases. It leaves no scratches and does a great job cleaning. I’ve also noticed that if you are gentle with it, it will not damage lacquer or other washes like copper or brass applied to steel cases.

Being a collector of German steel cased ammo, which has terrible corrosion issues, this method has proven itself over 25+ years to stop corrosion for me. It is unusual with brass, but I’ve been left with no choice on a few and they have also held up very well over time after this process.


Thanks for your responses, gentlemen.

Bearing in mind that the cartridge is common and inexpensive, it may be simpler just to replace it.


Yes, it is absolutely essential to remove all of the remaining acid after applying my method either by neutralilzing the acid with soda water solution or with soap water and the just clean water!

Also, for the mechanical method, it is essential that the material of the cleaning tool is no harder than the cleaned surface (fine brass wool works splendid). I’ve seen so many ruined specimens treated with sandpaper, that I’m on the verge of tears just remebering them…

I’m usually (in a worst cases) applying these two methods in a succesion.

Wish you all the best, Gentlemen!



I use a brass scraper made by flattening the mouth of a large rifle case, such as the .30-06 (it gives you something to hang on to). A Q-Tip with white vinegar works wonders on staining, but must be followed with water to neutralize. My blackpowder shotshells ooze crud from between the paper hull and brass head, although, I just bought a full box of WRA Co. New Rival 10 gauge shells that show no signs of deterioration. Indeed, storage conditions play a big part in breaking down of elements. Good luck. Cheers!


The advantage of using a small piece of brass (with the aforementioned handle) that the cleaning can be localized to just the affected area & not outside it, which is what may well happen with brass wool or larger tools, because it is hard to apply (for me) just to the affected area, & will perhaps give the area around the ‘spot’ a different patina. So unless one does the complete case with it, your left with two different colored areas.
To my eye I’d rather see a dark stain on a case with original patina, than one cleaned. Plus cleaning sometimes / often removes things like the annealing color or tool marks.

Dave notes that being gentle with the extra fine bronze wool leaves this patina.

All that said, it’s your round(s) & however it looks good to you, works for me.

As to the cardboard used in lining the shelves I don’t think it is the case of the powder breakdown. treshkin is correct, acid paper will stain the brass if it absorbs moisture & quite badly, but it is different kind of corrosion. A finely grained grey colored stuff & hard to remove.

Your right Tony it’s easier to find another 8mm Lebel, unless you want that exact lot, date, metal supplier & case maker… So dig out that case in the basement!

I have a once nice .303", headstamped " C.T 7.70 (over) A.PX . 17 " that the powder went south in & split the neck. That one will be very hard to replace. So powder dumped & such.


I have had good results at removing that grey grainy corrosion with a brass bristled brush. The patina was left largely intact when I have tried this on small arms rounds.


I have rescued some heavily corroded brass cases using a weak citric acid solution. It does not do much on dark stains, however. There is a product sold in supermarkets (at least in my area) for use in automatic dishwashers to prevent water spotting on glassware called “Lemi Shine,” which is simply citric acid crystals with an anti-caking additive.

I make up a solution of about two tablespoons per quart of water, and it can be re-used indefinitely, even after it turns green. It’s not very aggressive and won’t damage the brass itself no matter how long the cases are submerged. I usually let cases soak for at least an hour.

I used the citric acid solution several months ago to clean up a batch of over 2000 .38 Special empties, many of which were dirty and corroded range pickups. They came out looking very good, even if not just like they left the factory. Awhile back, I came into about 40 rounds of WWI-era (1918) .45 ACP ammo that was so badly corroded it would not chamber. After a dip in the acid, they looked pretty good and chambered OK. Most even fired.