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Dielelectric corrosion-problem?

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  • Dielelectric corrosion-problem?

    I was watching this old house yesterday and Richard was installing some new work on a boiler. He threaded a copper male adapter into a galvanived female tee. I was always under the assumption that was a problem-2 dissimilar metals touching. I've taken out 10 year old water heaters with the copper male adapter threaded right into the tank with no evidence of corrosion. Is this a problem or is it overblown?
    Buy cheap, buy twice.

  • #2
    Re: Dielelectric corrosion-problem?

    I Always use brass for adapting between copper and gal here.Brass adaptor is threaded x capillary.Male No.3 or Female No. 2 or in Yorkshire Brand.

    Besides no threaded copper fittings available.

    Comment


    • #3
      Re: Dielelectric corrosion-problem?

      Yes it is a problem and as Josh posted he should have used brass in between.

      Mark
      "Somewhere a Village is Missing Twelve Idiots!" - Casey Anthony

      I never lost a cent on the jobs I didn't get!

      Comment


      • #4
        Re: Dielelectric corrosion-problem?

        Originally posted by gear junkie View Post
        I was watching this old house yesterday and Richard was installing some new work on a boiler. He threaded a copper male adapter into a galvanived female tee. I was always under the assumption that was a problem-2 dissimilar metals touching. I've taken out 10 year old water heaters with the copper male adapter threaded right into the tank with no evidence of corrosion. Is this a problem or is it overblown?

        Ive seem Richard Trethewey make a few mistakes on This Old House but I don't think he made one here. I didn't see the episode but if he was installing a copper fitting into a galv. tee on a closed heating system not a problem. The boiler water won't have enough oxygen to cause corrosion. Besides the adapter will reduce the effects of electrolysis.

        If the adapter was on the potable water a brass nipple or dielectric union would have been the right choice like the Aussi mentioned.

        Comment


        • #5
          Re: Dielelectric corrosion-problem?

          I guess you are right it would depend what he is piping on the boiler. I would still be careful as it only takes something like 10ppb of oxygen for galvanic corrsion to be present which is not much.

          Mark
          "Somewhere a Village is Missing Twelve Idiots!" - Casey Anthony

          I never lost a cent on the jobs I didn't get!

          Comment


          • #6
            Re: Dielelectric corrosion-problem?

            every dissimilar metal will react with each other.
            copper flex connectors for water heaters have gotten much better and the nipples that are factory installed in the heaters now are plastic lined and this has basically eliminated the issue.

            on larger installations i have found that brass nipples are a better go between than a dielectric union.

            even a common brass angle stop screwed into a gal. nipple will eventually corrode much faster than gal. into gal.

            copper and gal. steel are just much farther away on the table of compatibility. can't think of the proper name of that table, but the closer the metals are listed to each other, the better the mix is.

            i think it's called the galvanic table

            rick.
            phoebe it is

            Comment


            • #7
              Re: Dielelectric corrosion-problem?

              Galvanic Table?...did you just make that up?

              I can't remember the less reactive metal is cathode?? more reactive anode??

              I was told that a brass male/female adapter would be an approved fitting to reduce galvanic corrosion. Was I lied to?

              Comment


              • #8
                Re: Dielelectric corrosion-problem?

                I believe Ben's question was regarding a CxMIP copper adapter

                Mark
                "Somewhere a Village is Missing Twelve Idiots!" - Casey Anthony

                I never lost a cent on the jobs I didn't get!

                Comment


                • #9
                  Re: Dielelectric corrosion-problem?

                  Try this thread from a while back

                  http://www.ridgidforum.com/forum/sho...09&postcount=3

                  http://www.ridgidforum.com/forum/sho...5309#post45309

                  For thos that did not follow my link;

                  PREVENTING ELECTROLYSIS

                  Electrolytic Corrosion (Electrolysis) occurs when dissimilar metals are in contact in the presence of an electrolyte, such as water (moisture) containing very small amounts of acid. The dissimilar metals set up a galvanic action that results in the deterioration of one of them. The following is a list of the more common commercial metals, sequenced according to what is known as the "Galvanic Series":
                  THE GALVANIC SERIES

                  1. Aluminum
                  2. Zinc
                  3. Steel
                  4. Iron
                  5. Nickel
                  6. Stainless Steel 400 Series
                  7. Tin
                  8. Lead
                  9. Brass
                  10. Copper
                  11. Bronze
                  12. Stainless Steel 300Series

                  When any two metals in this list are in contact, with an electrolyte present, the one with the lower number is corroded. The galvanic action increases as the metals are farther apart in the Galvanic Series. It is not always true that there is greater corrosion the further down the scale one goes. In certain cases one metal immediately following another may be very corrosive.One of the most important facts that an architect should know about a metal or an alloy is its reaction with other metals or alloys with which it may be in contact.This data is given in the Galvanic Series. Here the metals are listed in a sequence in which each metal is corroded by all that follow it. In other words, when two different metals are in contact with each other in the presence of moisture, there will be a flow of current from one metal (the "anode") to the other metal (the "cathode"), and one will be eaten away, or disintegrated, while the other (the"cathode") will remain intact.
                  Last edited by Bob D.; 07-15-2007, 11:44 AM.
                  ---------------
                  Light is faster than sound. That's why some people seem really bright until you hear them speak.
                  ---------------
                  “If I had my life to live over again, I'd be a plumber.” - Albert Einstein
                  ---------
                  "Its a table saw.... Do you know where your fingers are?"
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                  Comment


                  • #10
                    Re: Dielelectric corrosion-problem?

                    Rick,

                    I think you are looking for the Galvanic Corrosion Table.

                    Mark
                    "Somewhere a Village is Missing Twelve Idiots!" - Casey Anthony

                    I never lost a cent on the jobs I didn't get!

                    Comment


                    • #11
                      Re: Dielelectric corrosion-problem?

                      It is called the galvanic table or series the terms are active (Anodic) "less noble" or less active (Chathodic) "noble"

                      http://www.eaa1000.av.org/technicl/c...n/galvanic.htm
                      You will never expand your mind, if you do not challenge your beliefs.

                      By the reading of this post, you acknowledge and agree that the poster shall not be responsible or liable, directly or indirectly, for any damage or loss caused or alleged to be caused by or in connection with use of or reliance on any content contained herein.

                      Comment


                      • #12
                        Re: Dielelectric corrosion-problem?

                        Good link Honda.

                        I'm still not clear why copper #33 and steel #30 are fairly close to each other on the scale but have a strong reaction to each other.
                        Last edited by plumberscrack; 07-15-2007, 11:42 AM.

                        Comment


                        • #13
                          Re: Dielelectric corrosion-problem?

                          Just did a boiler last week, used brass fittings with male copper adaptors to run the zones of the 1-1/4" manifolds.
                          I see it all the time...boilers that have copper right into BM or CI, I prefer not to.
                          If Tretheway is doing it...well, he's considered the cream de la cream round these parts.
                          Still not gonna do it though.

                          Comment


                          • #14
                            Re: Dielelectric corrosion-problem?

                            I believe iron is at -.44 while copper is at +.34.

                            Mark
                            "Somewhere a Village is Missing Twelve Idiots!" - Casey Anthony

                            I never lost a cent on the jobs I didn't get!

                            Comment


                            • #15
                              Re: Dielelectric corrosion-problem?

                              Originally posted by PLUMBER RICK View Post
                              every dissimilar metal will react with each other.
                              copper flex connectors for water heaters have gotten much better and the nipples that are factory installed in the heaters now are plastic lined and this has basically eliminated the issue.

                              on larger installations i have found that brass nipples are a better go between than a dielectric union.

                              even a common brass angle stop screwed into a gal. nipple will eventually corrode much faster than gal. into gal.

                              copper and gal. steel are just much farther away on the table of compatibility. can't think of the proper name of that table, but the closer the metals are listed to each other, the better the mix is.

                              i think it's called the galvanic table

                              rick.
                              How does the inner plastic lining prevent corrosion? The metals are still touching each other. From the comments of the general public, the majority of you are saying a brass fitting can be substituted for a dielectric union? Is this right?
                              Buy cheap, buy twice.

                              Comment

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