Galvanic reaction
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  1. #1
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    Jul 2002
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    I've seen dielectric unions between copper and steel lines but then again I've seen copper sweat to pipe thread adapters. Wasup wi dat?

  2. #2
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    going from copper to brass pipe

  3. #3
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    Mar 2003
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    Originally posted by incontrol
    I've seen copper sweat to pipe thread adapters. Wasup wi dat?
    What are you talking about?

  4. #4
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    Jul 2001
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    159
    i think he was talking about a female copper x female brass union

  5. #5
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    Jul 2001
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    i think he was talking about a female copper x female pipe thread union, copper x brass

  6. #6
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    Jul 2002
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    Just happened to run across a copper male NPT into female steel. We use the copper NPT going into brass but was wondering if the NPT copper into steel is going to be a problem.

  7. #7
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    Copper to steel is OK with Refrig., but not water.

  8. #8
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    Oct 2001
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    Well, it's never really "OK," since galvanic corrosion starts the instant you attach two dissimilar metals. But, in refrigeration we do it all the time, driers, accumulators, compressors, etc..

    The deal is, if ions are present (salt in solution for example) or any electric current (like water piping used for ground) the galvanic effects are accelerated drastically.

    So, for best practice, keep unions between dissimilar metals to a minimum, use dilectric unions when possible, use galvanizing compounds (cold galvanizing spray or zinc rich tape) when dilectric is not possible, and be aware that steel to copper connectinos are a designed in failure. . . .eventually.
    Hindsight is NOT a plan!

  9. #9
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    Jul 2001
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    159
    has anyone seen a dielectric union not leak within a year? i think it would be a miracle

  10. #10
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    Jan 2002
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    New Hampshire
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    Bama , that's clear

    It's the chemistry that's key. I'm finding that the metals worry the heck out of people, but the liquid is the key ingredient. Most of the time, the fluid is benign, and no electrolysis even occurs to any degree noticeable.

    If you master what the fluid is doing, the metals will last a long time.

    I do a bunch of steam work, but I have to eat, too. Hot and cold water systems make up the difference in my time.

    I agree, dielectric unions leak more than they protect, UNLESS the water or other fliud is a genuine problem.

    Let me add that a system with NO dissimilar metals would last longer......


    Longer than what?...That cast iron snowman boiler with brass valves and control wells and copper piping in YOUR basement, maybe? That's what, perhaps 90 years old? As old as the house? How old is your car? Your computer (I bet you have one)? your TV? Your microwave? Your nintendo?

    How long will those other things last?

    Sometimes, we worry about metal when we should focus on water chemistry.

    Noel

  11. #11
    Join Date
    Jan 2005
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    steeler nation
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    2,035
    the unions usually leak from over tightening and crushing the rubber gasket.just snug it. i prefer to use dielectric nipples when possible.

  12. #12
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    Jan 2003
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    San Jose, Ca
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    I seen more not leak that leak.
    You can have a problem with large temperature changes or when someone gets a bigger wrench to be sure it does not leak.
    Len
    Old snipes don't die they just loose their steam

  13. #13
    Join Date
    Jul 2004
    Location
    Victoria,Tx
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    6,680

    Smile Ok OK!

    Well, nothing lasts for a life time. Mr. Galvan of Spain came up with the idea of using dissimilar metals. Thus having an effect on metals. You can speed up or slow down the effects of corrision. Look at your boat tralier. Type K thermocouple. Two differant wires. Listen to Bama and Noel.

    [Edited by oroy54 on 03-03-2005 at 11:32 PM]

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