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Galvanic Corrosion Contrl

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Bruce Stevens
Bruce Stevens Member Posts: 133
say it is not needed, it is a great way to make the transition.

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  • J im Young
    J im Young Member Posts: 3
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    Galvanic Corrosion Control

    Can the transition from steel to copper tube in a hot water heating system be made with a brass valve at the branches? Steel to brass to copper?
  • J im Young
    J im Young Member Posts: 3
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    Is this method of protection as good as a dialetric nipple or union.
  • J im Young
    J im Young Member Posts: 3
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    Thanks Can you tell me where in piping literature that using a brass valve between steel pipe and copper tube i a heating system is an effective form of galvanic control.
  • hr
    hr Member Posts: 6,106
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    if you go to www.copper.org

    you can find all sorts of reading material on this subject. Everything from a basic galvanic chart to PHD authored case studies.

    Basically in a closed loop, sealed system once the O2 is out corrosion cannot occur, regardless of the "blend" of materials used.

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  • radioconnection_2
    radioconnection_2 Member Posts: 70
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    oxygen

    Oxygen has nothing to do with electrolysis. Oxygen is responsible for oxidation (rust.) Corrosion due to dissimilar metals is electrolysis and is more related to the water PH. A lack of oxygen will not stop galvanic related damage to one of the dissimilar metals in a closed loop!

    Pete
  • Aidan (UK)
    Aidan (UK) Member Posts: 290
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    Galvanic Corrosion Control

    >Corrosion due to dissimilar metals is electrolysis and is more related to the water PH.

    True, but galvanic corrosion produces oxygen.

    SFAIK, galvanic corrosion occurs between dissimilar metals which are immersed in a suitable electrolyte. You will get a small current flowing through the water and through the metals. The galvanic current splits the water into oxygen and hydrogen. The oxygen dissolves in the water and corrodes the steel components.

    The hydrogen is usually discharged from an air vent, or it appears at a radiator air vent, from where it can be collected in a jar and ignited to prove that galvanic corrosion is happening.

    In a heating system, the best solution is to make sure the water isn't a suitable electrolyte by adding an inhibitor. Most inhibitors make the water alkaline ( pH 8 or 9). You don't need brass couplers or dielectric unions in a heating system.

    If the water is acidic (pH<7) it will encourage galvanic corrosion. The usual cause of acidic water is active soldering flux residues which hasn't been flushed out, anti-freeze that has degraded and/or neglect of the corrosion inhibitors.
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