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Thread: Pink discoloration on brass

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  1. #1
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    Pink discoloration on brass

    I have been reading the pros and cons of using citric acid for cleaning brass. The opinions seem evenly split. Some of the posts that I read claim that using citric acid will cause de-zincification of the brass and thereby weaken it. Others say that this occurs only on the surface and will not cause any serious harm, and in addition it will create a passive layer on the brass which makes it more resistant to corrosion in the future. Any opinions from anybody here?

  2. #2
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    Don't know about citric acid on brass, but if it does indeed "de-zincify" the brass, what's left is copper - and really clean pure copper is pink.

    I'd advise against its use. Brass doesn't need to be that clean anyway.
    When you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind. [Lord Kelvin]
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    MuyModesto (5th April 2020)


  3. #3
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    What got me reading about it is I had some Remington brass stored for years. It was stored in a dry location but some pieces were pretty tarnished. I cleaned them in a solution of citric acid and Dawn. Some pieces came out with pink splotches. These spots cleared up reasonably well when I tumbled them. Was this pink discoloration only on the surface? I am trying an experiment...I filled a small glass with water, Dawn and a heaping teaspoon of citric acid. I put in a new case and a fired case and I am going to let it sit a day and see what happens.

  4. #4
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    No idea what the pink splotches actually were. All I know is that really clean copper is pink based on my experience with cleaning printed circuit boards (PCBs) prior to soldering. But PCBs need to be really clean for a good reliable solder joint. Cartridge brass doesn't need to be really clean prior to reloading, unless your not using a carbide resizing die.
    When you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind. [Lord Kelvin]

  5. #5
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    I know that if you have dissimilar metals submerged in salt water, the weaker metal will be eaten away and protect the stronger or more noble metal. That is why zincs are used on metal boat rudders, shafts etc. With bronze fittings for example, a greenish corrosion is just normal corrosion, however, reddish or pink discoloration is a bad sign and it indicates that zinc is being eaten out of the fitting and thus weakening it. A REALLY bad sign is if the bronze fitting becomes very shiny, a sign that stray current is in the water near the boat. In any event, I was thinking of this when I noticed the pink splotches on the brass I cleaned. What got me to wondering is that they were stored dry and were not submerged with any amount of dissimilar metal unless when cleaning them unless you count the primers, plus fresh water was used and not salt water. I have found brass at the range that lay in the soil for quite a while and I noticed that they had an overall pink appearance. I guess the chemical makeup of the soil is helping to corrode it in that manner. In any event, looking at different sites and reading what I could about it, it seems the opinions are evenly split on this subject. I just like to try to understand completely whatever it is I am doing. I think the thing to do is if the discoloration is minimal and consists of a few splotches, I will keep it. If it is extensive, toss them.

  6. #6
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    You haven't stated what the concentration (pH) of your citric acid solution was or how long you let the cases soak. The grocery store vinegar (acetic acid) in my pantry is diluted to 5% when bottled and has a pH of about 3. Birchwood Casey case cleaner is a mixture of phosphoric and other acids and when diluted 20:1 with water has a pH of about 2. Howsomever, the instructions on the bottle say to soak cases for 2 to 3 minutes, remove and rinse. Then use fine steel wool if you want them shinier.

    I soaked old 1960's vintage R - P many times fired cases in both solutions and couldn't tell the difference. Both were a nice brassy color with minor blemishes and much cleaner than they really need to be for reloading on my bench. No pink spots before or after soaking either.

    While this doesn't answer your questions about de-zincification or what the pink spots might be, it does lead me to think you may be soaking them too long.
    When you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind. [Lord Kelvin]
    Last edited by niemi24s; 6th April 2020 at 11:33.


  7. #7
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    Hello Niemi: Thanks for replying. I used 2 1/2 teaspoons of citric acid in 2 1/5 quarts of water along with a few squirts of Dawn dish detergent. I soaked them for 20 minutes. Also, not all the cases were discolored. Out of 200 cases, maybe a dozen were and they were anywhere from a few speckles to maybe one side of the case discolored. These cases were heavily tarnished prior to cleaning. As an experiment I took a couple of cases and decided to really overdo it to see what the result would be. I took a 10 ounce glass and filled it with water and added a heaping teaspoon of citric acid and let it sit for 24 hours. The new piece of brass came out looking the same and the two fired cases came out shiny, one had a slight pink tinge on the side. Since I last posed, I read an interesting post elsewhere. The person stated that brass is subjected to two types of corrosion which manifest itself as either a brownish black stain or a pinkish red stain. It was his contention that it is possible that the darker oxidation obscures the pinkish oxidation. The pink oxidation comes to light after cleaning when the acid removes the darker oxidation. It was his belief that this occurs on the surface and does not harm the brass. His comment about it being on the surface seems to jibe with my experience, I was able to remove the discoloration when I tumbled the brass, a couple pieces cleaned up with fine steel wool. Is he right? It seems to make sense, I do not know, I am not a scientist or engineer. As far as not answering my question, there is always something to learn reading your posts.

  8. #8
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    Out of curiosity, what was your source of citric acid?
    When you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind. [Lord Kelvin]

  9. #9
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    I purchased it at the local food store. It is Ball's Citric Acid. It states that it is used for canning tomatoes and replaces lemon juice. Hopefully there is nothing I should have been aware of haha!

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