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Copper and Aluminium

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  • Copper and Aluminium

    Do they mix?

    Hey there... we all know that if we are to CONNECT a galvanized pipe to a copper pipe it'll eventualy corrode...

    What about aluminium? Water based radiant floor heating is composed of pex tubing and aluminium to radiate he heat. Copper has (I think!) a greater heat radiation than PEX. So other than cost, would running copper be better for heat radiation than PEX? If so, does copper and aluminium have a tendancy to corrode one another even if aluminium does not corrode but can oxide.

    Thanks!

  • #2
    Re: Copper and Aluminium

    When connecting different materials the compatability between them is determined by the Anodic Index. The larger the difference between the 2 metals the worse the corrosion will be. Take a fook at the following link and the chart to see what the difference in Anodic Index Voltage...

    http://www.engineersedge.com/galvanic_capatability.htm

    You will see copper is 0.35 and aluminum is 0.75 yielding a difference of 0.40 which says that it is not a good combination so the connection should be insulated by using a dielectric connector.

    However, given the right environmental controls a difference of 0.50 can be tolerated. One area where this combination may be found is in a boiler and it can stand up to corrosion pretty well there because the water in a boiler should be oxygen deficient allowing the proper environment for these metals to coexist in harmony. If a boiler system was leaking or, plumbed in PEX wothout an oxygen barrier then there would be too much oxygen in the system and corrosion would occur.

    Aluminum as a material for heat exchanger construction in a boiler does have other problems and would not be my top choice.
    411 Plumb Appliance Stimulus Package

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    • #3
      Re: Copper and Aluminium

      I read you Redwood... but this is this valid only if water runs through from one pipe to another?

      Say i would take a sheet of copper and and sheet of auminium and would let the rest for a year at normal indoor conditions... would there be corrosion?

      What I was refering to in my original message is instead of using PEX, I would (other than cost prohibition) use copper like in this installation:

      http://www.infloor.com/radianttrak.html

      I assume that PEX heat radiation is less than copper. I would run copper pipes and then have then encased into a (rather) thick plate of aluminium in order to heat the floor...

      thanks!

      Comment


      • #4
        Re: Copper and Aluminium

        In the computer cooling industry, I've seen coolers built with copper bases leading to aluminum heatsinks. These were meant for air cooled computers so there's only ambient humidity to worry about in terms of moisture. Lately it seems that manufacturers are going to all aluminum for cost considerations.

        A friend of mine who built a liquid cooled computer said it ran great for about 2 years, he said that every 6 months he'd need to change fluid which would turn a green-black color. His cooling blocks were copper encased in aluminum, so perhaps it was corrosion he was having problems with.

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        • #5
          Re: Copper and Aluminium

          Did he have biocides and anti corrosive stuff in his coolant or was it straight water?

          Comment


          • #6
            Re: Copper and Aluminium

            Originally posted by HornyPotter View Post
            I read you Redwood... but this is this valid only if water runs through from one pipe to another?

            Say i would take a sheet of copper and and sheet of auminium and would let the rest for a year at normal indoor conditions... would there be corrosion?

            ...
            Is all you have to do is add water and you would have a battery! And I do know that aluminum to copper wire connections need to be made with a special sealant

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            • #7
              Re: Copper and Aluminium

              condensation of the surrounding air would act as the electrolyte.

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              • #8
                Re: Copper and Aluminium

                i duno. FHW baseboard heater? Copper pipe aluminium heatsinks/fins seems to work ok

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                • #9
                  Re: Copper and Aluminium

                  Originally posted by snake View Post
                  condensation of the surrounding air would act as the electrolyte.

                  indeed! bummer...

                  Comment


                  • #10
                    Re: Copper and Aluminium

                    Originally posted by cpw View Post
                    Did he have biocides and anti corrosive stuff in his coolant or was it straight water?
                    He used a branded computer coolant, something similar to ethylene glycol. can't remember which, but probably Thermaltake. I never knew you were supposed to add biocides to liquid cooled computers, the system is pretty much closed so how would anything living get in?

                    Comment


                    • #11
                      Re: Copper and Aluminium

                      Originally posted by Arthur96 View Post
                      i duno. FHW baseboard heater? Copper pipe aluminium heatsinks/fins seems to work ok
                      Absence of moisture???

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                      • #12
                        Re: Copper and Aluminium

                        Sorry, I don't understand why u would even consider copper when pex will do the job. I have done at least 100 jobs like in the sample and they are cost effective and emitt heat just fine. Add insulation under the product and u are done. We use oxy barrier tubing and spray silicone in transfer plates to eliminate sqeaking.

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                        • #13
                          Re: Copper and Aluminium

                          Hey Njoy...

                          Metal against metal has a greater heat dissipation then metal against plastic. If it wouldn't be true, heat sinks would be made out of plastic! Same for engine manifolds.

                          At any rate, I agree that PEX is more cost effective... I was just curious about corrosive effect of Aluminium and Copper.

                          Thanks!

                          Comment


                          • #14
                            Re: Copper and Aluminium

                            Originally posted by wathman View Post
                            He used a branded computer coolant, something similar to ethylene glycol. can't remember which, but probably Thermaltake. I never knew you were supposed to add biocides to liquid cooled computers, the system is pretty much closed so how would anything living get in?
                            I was looking at some requirements for a liquid cooled super computer, and part of the specs are biocide and anti-corrosives.

                            Comment


                            • #15
                              Re: Copper and Aluminium

                              http://www.xoxide.com/water-cooling-coolant-dye.html

                              I looked up some of the prepared coolants available these days, Seems like the most expensive ones do have biocides in them. Supposedly they are anti-corrosive too. Expensive stuff, think I'll just stick to air cooled systems.

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