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Thread: Soldering brass to copper

  1. #1
    Join Date
    Aug 2021
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    Default Soldering brass to copper

    I am being spectacularly unsuccessful trying to solder brass to copper. The issue seems to be that the copper oxidises very quickly (using borax flux) so the solder flows onto the brass but not the copper. Any advice about flux or solder would be much appreciated.

    Thanks.

  2. #2
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    Dec 2009
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    Your troubles will be over if you add a pinch of Tenacity Nr5 to your borax for any base metal soldering. Add too much and the glaze formed can be difficult to dissolve in pickle.
    It is available in small amounts here:https://www.ebay.co.uk/itm/333422785...id=EB15845783& Dennis.
    Last edited by Dennis; 20-08-2021 at 09:48 AM.

  3. #3
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    How clean is your copper to start with, and are both parts brought up to the same temperature?

  4. #4
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    I was about to ask if the temperature was not the problem as the borax going sticky is usually a good thing

  5. #5
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    What type of solder are you using, you can have issues with zinc coming to the surface from the Brass, also temperature and above all cleanliness, the longer you heat it more likely that you will have zinc contamination.

  6. #6
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    Aug 2021
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    I am soldering a small brass piece to a larger copper piece, so the brass gets hotter than the copper (since the rest of the copper acts as a heat sink, because copper is a good conductor). I understand that in this situation it is advisable to just heat the larger body and let the heat flow into the smaller body, but that did not seem to work, I don't think the joint got up to the required temperature without the flame directed at the actual joint.

    I cleaned the copper with steel wool prior to soldering.

  7. #7
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    Aug 2021
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    There seem to be two problems, getting the larger copper piece to the same temperature as the smaller brass piece, and a layer of oxide forming on the copper.

  8. #8
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    Will give that a go, thanks.

  9. #9
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    Quote Originally Posted by pcoz View Post
    There seem to be two problems, getting the larger copper piece to the same temperature as the smaller brass piece, and a layer of oxide forming on the copper.
    Bigger torch? Direct flame on the joint isn't good if the whole thing isn't up to temperature, you'll exhaust the flux in that area before the temperature is at the right point. If you can put up a pic of your setup for soldering this, it might be possible to make some specific recommendations rather than generalised ones.

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