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galvanic stainless steel / copper silver braised joint

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  • GGB
    Hi. Does anyone has the answer to my questions please? I m proposing to easyflow braise a 38mm od s/s winery tube into 400mm (1-1/2 ) copper tube which will
    Message 1 of 3 , Aug 5, 2012
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      Hi.

      Does anyone has the answer to my questions please?

      I'm proposing to easyflow braise a 38mm od s/s winery tube into 400mm (1-1/2") copper tube which will form a reflux column.

      It's a tight fit. It will allow me to mount the column with winery s/s couplings onto a boiler. I was going to use a 50L keg but could also use an insulated water heater. The coupling will allow me to disassemble the column to remove packings.

      The copper tube was used in a boiler and I'm finding it a slow job to remove old copper chloride, carbonate and oxide deposits, using spirits of salts (HCl) and mechanical action.

      While reading around I discovered reference to galvanic action between s/s and copper.

      I searched here and found some information, but nothing about the wisdom or otherwise of braising s/s and copper together.

      Can anyone tell me please if this is likely to cause any problems? - I propose to clean out and dry the column and packing after each use.

      Also, now that I think of it, copper mesh/scrubbers don't seem to be readily available in NZ apart from the frugal packs sold at brewers supplies shops.

      Can I ask please if s/s scrubbers will be satisfactory in the copper column?

      Thank you!
      Paul
      NZ
    • RALPH JOHNSON
      Hi ,As far as I know there no problem between s/s and copper (only galv and copper) I bought my copper mesh from USA they use it in the ground to stop rodents
      Message 2 of 3 , Aug 5, 2012
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        Hi ,As far as I know there no problem between s/s and copper (only galv and copper) I bought my copper mesh from USA they use it in the ground to stop rodents ,maybe you should try similar companies in NZ,I had been using the same copper for 3years (cleaning regularly) the copper I bought from USA was enough to fill the column twice for 100USD.My collegue tried s/s scouring pads but not to sucessful and the "copper" scouring pads are only coated and didnt last.I cant recommend to much the use of an activated carbon filter my brew is comparable with most commertials because of it ,I dont use ANY plastics only s/s and glass containers.good luck R

        From: GGB <self.adhesive@...>
        To: new_distillers@yahoogroups.com
        Sent: Monday, 6 August 2012, 7:13
        Subject: [new_distillers] galvanic stainless steel / copper silver braised joint

         
        Hi.

        Does anyone has the answer to my questions please?

        I'm proposing to easyflow braise a 38mm od s/s winery tube into 400mm (1-1/2") copper tube which will form a reflux column.

        It's a tight fit. It will allow me to mount the column with winery s/s couplings onto a boiler. I was going to use a 50L keg but could also use an insulated water heater. The coupling will allow me to disassemble the column to remove packings.

        The copper tube was used in a boiler and I'm finding it a slow job to remove old copper chloride, carbonate and oxide deposits, using spirits of salts (HCl) and mechanical action.

        While reading around I discovered reference to galvanic action between s/s and copper.

        I searched here and found some information, but nothing about the wisdom or otherwise of braising s/s and copper together.

        Can anyone tell me please if this is likely to cause any problems? - I propose to clean out and dry the column and packing after each use.

        Also, now that I think of it, copper mesh/scrubbers don't seem to be readily available in NZ apart from the frugal packs sold at brewers supplies shops.

        Can I ask please if s/s scrubbers will be satisfactory in the copper column?

        Thank you!
        Paul
        NZ



      • daryl_bee
        Hi I m not sure I have the answer to your question but may have some insight. Pure copper and stainless steel have an electrochemical difference of 0.320V with
        Message 3 of 3 , Aug 6, 2012
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          Hi

          I'm not sure I have the answer to your question but may have some insight.

          Pure copper and stainless steel have an electrochemical difference of 0.320V with copper being the sacrificial metal. At less than 0.100V any galvanic corrosion will be insignificant whereas galvanic corrosion will be accelerated on unprotected joints if the potential difference is greater than .250-.300V. For high humidity (not salt laden) the potential difference should not exceed .450V. I'm not sure what the electrochemical conditions are in a still column but would guess that it would tend to be accelerating.

          This puts copper/stainless on the hairy edge of not good. Unfortunately there are not any reasonable metals to put between them as a buffer (titanium, silver, mercury, nickel). Perhaps a non metallic buffer - gaskets. Possibly a loose joint filled/buffered with silver solder.

          My $0.02
          Daryl


          --- In new_distillers@yahoogroups.com, "GGB" <self.adhesive@...> wrote:
          >
          > Hi.
          >
          > Does anyone has the answer to my questions please?
          >
          > I'm proposing to easyflow braise a 38mm od s/s winery tube into 400mm (1-1/2") copper tube which will form a reflux column.
          >
          > It's a tight fit. It will allow me to mount the column with winery s/s couplings onto a boiler. I was going to use a 50L keg but could also use an insulated water heater. The coupling will allow me to disassemble the column to remove packings.
          >
          > The copper tube was used in a boiler and I'm finding it a slow job to remove old copper chloride, carbonate and oxide deposits, using spirits of salts (HCl) and mechanical action.
          >
          > While reading around I discovered reference to galvanic action between s/s and copper.
          >
          > I searched here and found some information, but nothing about the wisdom or otherwise of braising s/s and copper together.
          >
          > Can anyone tell me please if this is likely to cause any problems? - I propose to clean out and dry the column and packing after each use.
          >
          > Also, now that I think of it, copper mesh/scrubbers don't seem to be readily available in NZ apart from the frugal packs sold at brewers supplies shops.
          >
          > Can I ask please if s/s scrubbers will be satisfactory in the copper column?
          >
          > Thank you!
          > Paul
          > NZ
          >
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