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Hot dipped galvanized steel with copper based grease -- corroision question

  1. Oct 27, 2018 #1
    do you think copper based grease on the threads of a hot dipped galvanized pipe would likely noticeably(naked eye, no measuring equipment) speed up corrosion of the galvanized pipe in normal environments such as buried in typical soils, maybe slightly more corrosive locations than urban areas, or typical industrial environments?

    thanks
     
  2. jcsd
  3. Oct 27, 2018 #2

    anorlunda

    Staff: Mentor

    Your question suggests galvanic actions. Although Cu potential is more + than Zn, the quantity of Cu in the grease is very small compared to the mass of zinc on the pipes. I never heard Cu-Zn reactions being a problem on copper clad boat hulls with zinc sacraficial anodes.

    I would look first att some electrical wiring problem that could cause galvanic currents. Those can be devastating.
     
  4. Oct 27, 2018 #3

    Tom.G

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    Science Advisor

    Is the Copper electrically connected to the Zinc?
    Have you ever had to replace the sacrificial Zn, if so there was galvanic action somewhere. If not, why bother with it?
     
  5. Oct 28, 2018 #4

    anorlunda

    Staff: Mentor

    There are always galvanic currents present with boats in salt water. The sacrificial anode needs replacement at intervals a function of local conditions.

    Contacts between dissimilar metals in salt water also create galvanic currents at the interface. However, after a short time the one with the lesser anodic index become plated with the other, and the reaction mostly stops. That would be a problem only if such a big area becomes plated that it sacrifices the entire sacrificial anode.

    The idea of a sacrificial anode is that if there is a current to someplace else, that it comes from the sacrificial anode in preference to the other metals (whether or not the dissimilar metals are in contact with each other.)

    In this thread, we have a tiny mass of copper in grease, and a much larger mass of zinc on the hot dipped pipe. That's why I said that if there is serious damage, the galvanic current must be going someplace other than the grease.
     
  6. Oct 28, 2018 #5

    jim hardy

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    Gold Member

    I can tell you that we used copper bearing Fel-Pro anti-seize compound all over my power plant.
    I used it on my boat trailer wheels which saw salt water.
    on spark plugs in aluminum lawnmower and outboard motor cylinder heads
    on automobile exhaust manifold bolts and wheel lug nuts
    and have yet to notice anything detrimental

    in short, I'm a "True Believer" in copper bearing grease.

    That said, i have changed my ways around aluminum and buy "Anti Seize for Aluminum" at my auto parts store. Though i never had any trouble with copper based.

    There's a nickel bearing version too that might be better around seawater. We preferred it around the reactor area because copper activates noticeably
     
    Last edited: Oct 28, 2018
  7. Oct 31, 2018 #6
    i use zinc grease for aluminum, galvanized steal as well sometimes. copper grease just seams like it's a lot better for conductivity, i'll get the DLO out one of these days and check for any real difference.

    thanks everyone
     
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