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  1. #1

    Default Corrosion removal

    This posting is to find remedies for future corrosion removal.
    The problem I ran into was a Korean 5 1/2" brass pendulum bob with a 2 1/2" spot of hard green/brown corrosion. I tried a couple fluids from my shop bench and no luck. So then is attacked the corrosion spot with red cake jewelers rouge and a motor buff wheel. It took a bit of work, and heavy pressure to finally remove the spot. But, upon close examination I found the rouge and buff erroded away some of the brass. This disturbed me, so I will not do this again. It doesn't look so bad at a glance, tho close examination reveals the uneven pock-marked surface.
    What should I have used to remove this spot? Does anyone have any suggestions? Fluids, acids, or neutralizers.

  2. #2
    Registered User Scottie-TX's Avatar
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    Default Re: Corrosion removal (RE: Bob Reichel)

    BOB, I doubt your procedure caused the pocking erosion. I believe it was pre-existent and caused by the severe oxidation. I've experienced that also with plates. It's so deep, there's really no way to remove it.

  3. #3
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    Default Re: Corrosion removal (RE: Scottie-TX)

    I was going to post a similar question this evening. A couple of months ago, I cleaned a movement and it got left on my bench still disassembled when life took one of its zigs while I was zagging. I looked at it yesterday with the intention of giving it another quick cleaning to remove accumulated dust before assembling. Three wheels had blue/white corrosion on the brass around the hubs.Was this a reaction caused by the first cleaning, and if so, why? I used the same cleaning solution I always have (ammonia/Murphy's/acetone mix that has been posted so often) and have never had this happen before. I cleaned most off with a wire bush, but some remains in crevices and I would like to neutralize it. Any ideas as to cause and remedy?
    Regards,
    Arthur

  4. #4
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    Default Re: Corrosion removal (RE: Arthur Cagle)

    The blue corrosion you experienced is what happens when the copper ih the brass reacts with the ammonia in the presence of air (which contains a high percentage of nitrogen). Blue or blue green is a typical color of copper nitrates.(or is it nitrite - I aced inorganic chemistry far too long ago to remember) Anyway - if it looks like turquoise, that is what you have. It occurs when you don't get all the ammonia completely rinsed off. It will occur much worse if you inadvertently leave part of a piece sticking out of the cleaning solution, when you are soaking them. You will get a line that is darned near impossible to remove.

  5. #5
    Registered User Scottie-TX's Avatar
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    Default Re: Corrosion removal (RE: Arthur Cagle)

    My guess would be the parts affected were not totally dry and the solution remained on them to cause the condition. I believe mosture may be necessary to cause corrosion. How do you dry your parts?

  6. #6
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    Default Re: Corrosion removal (RE: Scottie-TX)

    Quote Originally Posted by Scottie-TX View Post
    My guess would be the parts affected were not totally dry and the solution remained on them to cause the condition. I believe mosture may be necessary to cause corrosion. How do you dry your parts?
    Pre-existent pitting from corrosion cannot be removed. After the corrosion is removed the area can be cleaned, sanded, polished - but pitting will remain unless you grind down the entire surface to a level plain. (That's usually not practical and easier said than done.)

    Corrosion is caused by moisture, humidity, a wet environment. Corrosion is also caused or accelerated by subjection to acids and other chemicals.

    Acidic solutions can be neutralized with sodium bicarbonate (baking soda). Residual moisture after cleaning can be removed by blow drying, oven drying, etc..

  7. #7
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    Default Re: Corrosion removal (RE: Scottie-TX)

    Quote Originally Posted by Scottie-TX View Post
    My guess would be the parts affected were not totally dry and the solution remained on them to cause the condition. I believe mosture may be necessary to cause corrosion. How do you dry your parts?
    Rinse in hot water then use a hair dryer. I recently picked up an old hot air corn popper to make a dryer...guess I'd better get crackin' on it.

    Thanks Scottie and Dave for your responses. Anyone know what will neutralize the corrosion? I suppose the old Coke soak would work...

  8. #8

    Default Re: Corrosion removal (RE: Arthur Cagle)

    Is there a way to chemically "un-do" the green corrosion, similar to the way electrolysis un-does rusting?
    1. Check out the REPAIR HINTS & HOW-TO's forum! Click Here.

  9. #9
    Registered User Scottie-TX's Avatar
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    Default Re: Corrosion removal (RE: bangster)

    Well, yes, I believe so. I would think the salt formation created by a base would be reduced - consumed - by an acid such as those available for cleaning battery terminals and the associated buildup.

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    Default Re: Corrosion removal (RE: bangster)

    Quote Originally Posted by bangster View Post
    Is there a way to chemically "un-do" the green corrosion, similar to the way electrolysis un-does rusting?
    Not that I know of. What does work is a micro etching sandblaster. It's sort of like an airbrush that can sandblast the corrosion off.

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