Galvanic isolating compound

Discussion in 'Materials' started by fallguy, Nov 11, 2021.

  1. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    Does anyone have any recommendations for isolating a 316 grade stainless bolt from an aluminum female thread? My boat is largely silicon free, but wondering about Dow Corning 4 which I have on hand.

    Bolts are mostly all 3/8-16 threading, but a bit nervous about degrading the female hole overtime. Boat is headed for saltwater eventually.

    I have 5 bolts going into the aluminum and want to add four more. The 5 should be able to be removed someday without shredding the threading (hehe).
     
  2. Barry
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    Barry Senior Member

    It is unlikely that you could put on a thread sealer which would become a load bearing interface between threads on a bolt. The sealant, etc would just move out of the way and permit contact.
    Aluminum and 316 are recognized as being relatively compatible as they allow ss fittings on fuel tanks and they are not that far apart on the galvanic scale.
    The biggest issue will be running a SS bolt into the aluminum thread and not have it gall. On our fuel tanks, though NPT, we would weld on an aluminum fitting and then, at the start, turn in a SS fitting. A couple of times we
    had to remove the SS fitting and the aluminum thread would be damaged. The cure for us was to run in a SS bushing, run in the SS fitting, and if we had to remove something, we would hold the bushing with a wrench and turn the fitting out

    Unless the aluminum female thread is very long, this will be the weakest part of the joint, so perhaps if space permits, you could do something similar as above
     
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  3. Rumars
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    Rumars Senior Member

    There are 2 things for that on the market, Tef-Gel and Duralac. Both will do what you ask, but have different best use cases, Duralac for (semi)permanent things, Tef-Gel for often tinkered with ones. Why that is so? Duralac is a paste that sets more or less solid, Tef-Gel stays a slippery grease forever.
     
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  4. fallguy
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    fallguy Senior Member

    I am going to pray I haven't already galled my female ally threads and order some duralac. I really want anti-seize compound, but that is copper based and seems wrong. Now, for 5 bolts; wonder how much it'll cost.
     
  5. fallguy
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    fallguy Senior Member

    729E27E0-AF57-4EAF-B1F6-B85356FD2F99.png No finding the duralac in the US.

    I am gonna use Starbrite..thanks for all the posts..comments welcome
     
  6. fallguy
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    fallguy Senior Member

    I have also used candle wax, but guessing some Texas sun could melt it.
     
  7. Rumars
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    Rumars Senior Member

    It's fine, just remember this stuff is the absolute opposite of thredlocker, if it vibrates and is not otherwise secured, check the screws regularly.
     
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  8. Mr Efficiency
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    Mr Efficiency Senior Member

    Use a spring washer ?
     
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  9. fallguy
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    fallguy Senior Member

    I'm gonna use lock washers and the thing is screwed to the deck on a cleat and the bolts are all in a vertical orientation and extra long..the tube is like 10" deep and so the bolts extend through 0.300" of aluminum and beyond about 1.5".
     
  10. fallguy
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    fallguy Senior Member

    I used candle wax on my stainless
    To stainless connections, but probably need to use something different on them. Those cannot turn out. Possibly could use a wire.
     
  11. SolGato
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    SolGato Senior Member

    +1 for Tef-Gel.

    I use it on all dissimilar metals along with polycarbonate as a physical isolator, making my own isolation washers, plates, etc..

    The Tef-Gel as already mentioned stays sticky making removal easy, and I’ve noticed it’s tacky enough to serve as a minor vibration thread locker if enough is used.

    I have removed a number of fasteners after many months/years of service in the tropics, even some below the waterline, and been impressed with how well it has protected the threads.
     
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  12. hoytedow
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    hoytedow Carbon Based Life Form

  13. fallguy
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    fallguy Senior Member

    No access to reverse and nyloc and ss are never gonna happen on my boat.
     
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  14. missinginaction
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    missinginaction Senior Member

    I'm just curious. Why are you so adamant regarding stainless and Nyloc's?
     

  15. fallguy
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    fallguy Senior Member

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