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Posted by Paul K. Dickman on April 29, 2008, 6:35 pm
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>
>> Ed's right , you have etched the zinc out of the surface.
>>
>> If you are lucky and it is not too deep, you can use a hydrogen peroxide
>> pickle technique to strip back the copper rich surface.
>>
>> http://www.artmetal.com/files/imported/project/TOC/finishes/nonfe/H2O2.html
>>
>> It will leave the surface dull, but well within the range of hand
>> polishing. 4 gal is a lot of peroxide though.
>>
>> It is also a great technique for cleaning up when you burn out the zinc
>> with a torch after silver brazing or etching it out with acid flux.
>>
>> HCl is a little strong for general cleaning. I prefer citric acid or
>> sodium bisulfate (AKA Sparex, or sold in the pool supply section under
>> various brand names as a granular ph reducer for pool water).
>>
>> Paul K. Dickman
>>
> Good link! Sadly hydrogen peroxide is not so easy to come by this side of
> the pond thanks to the activities of a few of our eastward facing citizens
The mix uses only 3% solution. Over here, that strength is sold at drug
stores as a topical antiseptic.
Paul K. Dickman
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Posted by Don Foreman on April 29, 2008, 4:44 pm
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>
>> Ok, so I am an idiot. I pushed things too far and may have cost myself
>> a bit of money in the process. I work with beer equipment and had some
>> old brass draft beer towers that needed some love. One of the cleaning
>> chemicals I work with is hydrochloric acid and I've noticed that when
>> I use this on brass parts they shine. I think this may work on the
>> tower I have so I soak it in a solution of 7 oz. hydrochloric acid and
>> 4 gallons of water overnight. First day it looks good, second day it
>> looks better, third even better, fourth day it is pink! What happened?
>> Is there anything I can do to restore the shine? Any help would be
>> appreciated because I would like to save this thing if I can. Thanks
>> in advance.
A similar thing happens when silver-brazing brass: the surface zinc
boils off leaving just copper on the surface.
A buffing wheel will restore the brass look. An automotive buffer
with rubbing compound might even work though it might take a while.
I've not found a chemical that will preferentially remove copper while
leaving zinc.
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Posted by Ed Huntress on April 29, 2008, 5:13 pm
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>
>
>>
>>> Ok, so I am an idiot. I pushed things too far and may have cost myself
>>> a bit of money in the process. I work with beer equipment and had some
>>> old brass draft beer towers that needed some love. One of the cleaning
>>> chemicals I work with is hydrochloric acid and I've noticed that when
>>> I use this on brass parts they shine. I think this may work on the
>>> tower I have so I soak it in a solution of 7 oz. hydrochloric acid and
>>> 4 gallons of water overnight. First day it looks good, second day it
>>> looks better, third even better, fourth day it is pink! What happened?
>>> Is there anything I can do to restore the shine? Any help would be
>>> appreciated because I would like to save this thing if I can. Thanks
>>> in advance.
>
> A similar thing happens when silver-brazing brass: the surface zinc
> boils off leaving just copper on the surface.
>
> A buffing wheel will restore the brass look. An automotive buffer
> with rubbing compound might even work though it might take a while.
> I've not found a chemical that will preferentially remove copper while
> leaving zinc.
Be careful using a power buffer on dezincified brass. My only experience
with it is with brass parts that have lost their zinc from prolonged
exposure to salt water, but I've found that the surface varies in hardness
and it really looks like hell when you use power to cut down to clean brass.
That's why I suggested using fine wet-dry. I've used that with success, even
though it takes some work to do it by hand.
I'm very interested in the peroxide treatment that was suggested, however.
Unfortunately, I no longer have my uncle's boat to try it on. <g>
--
Ed Huntress
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Posted by Bruce in Bangkok on April 29, 2008, 9:10 pm
Please log in for more thread options On Tue, 29 Apr 2008 08:58:33 -0700 (PDT), "edramshaw@gmail.com"
>Ok, so I am an idiot. I pushed things too far and may have cost myself
>a bit of money in the process. I work with beer equipment and had some
>old brass draft beer towers that needed some love. One of the cleaning
>chemicals I work with is hydrochloric acid and I've noticed that when
>I use this on brass parts they shine. I think this may work on the
>tower I have so I soak it in a solution of 7 oz. hydrochloric acid and
>4 gallons of water overnight. First day it looks good, second day it
>looks better, third even better, fourth day it is pink! What happened?
>Is there anything I can do to restore the shine? Any help would be
>appreciated because I would like to save this thing if I can. Thanks
>in advance.
I've had the same problem using much higher proportions of acid (works
faster). You have de-zinced the surface. Try a scotch-bright and scrub
it just a bit. It will probably clean right up.
Bruce-in-Bangkok
(correct Address is bpaige125atgmaildotcom)
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