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Monel Hardware

Discussion in 'Technical Discussion' started by dainisk, Mar 19, 2014.

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  1. dainisk, Mar 19, 2014
    #1
    dainisk

    dainisk Member

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    My marlin board (swim platform) has it's support strutts attached by through hull bolts in three places, all under the water line. However, the bolts suffer from what I understand to be crevice corrosion and I need to replace them almost every year.
    A suggestion was made that I should use bolts made from Monel, silicon bronze or even nylon. However, I have not been able to source these locally or on-line. I live in Australia, but would be happy to buy them from anywhere. Does anyone know a good source?
  2. SeaEric, Mar 19, 2014
    #2
    SeaEric

    SeaEric YF Historian

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    Google: Jamestown Distributors. They're in Rhode Island, USA. I have had good experiences with them in available selection of fasteners, price and customer service.
  3. about time, Mar 20, 2014
    #3
    about time

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    Have you bonded the bolts to your bonding system? If bonded and sealed properly you should not have an issue with a fiberglass hull.
  4. Marmot, Mar 20, 2014
    #4
    Marmot

    Marmot Senior Member

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    Crevice corrosion has nothing to do with bonding or hull type.
  5. about time, Mar 20, 2014
    #5
    about time

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    So crevice corrosion is not more common in a wooden hull? And crevice corrosion is not due to moisture around the fastener? I am hoping for an education here.
  6. Capt J, Mar 20, 2014
    #6
    Capt J

    Capt J Senior Member

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    I'm not expert on this, but I believe it has to do with the swim platform supports vibrating on the bolts and wearing into them and corrossion getting between the two parts.
  7. Fishtigua, Mar 20, 2014
    #7
    Fishtigua

    Fishtigua Senior Member

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  8. about time, Mar 20, 2014
    #8
    about time

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    so according to wiki, there is an electrolyte (moisture) involved, that allows for the transfer of electrons from one material to the other (pretty much the definition of MOST corrosion) for the transfer of electrons to occur there must be a potential, the purpose of a bonding system is to redirect that potential to a sacrificial anode. I must be missing something.
  9. dainisk, Mar 20, 2014
    #9
    dainisk

    dainisk Member

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    Yes, this is nothing to do with galvanic action - bonding. Steve D'Antonio had an excellent article on this matter in the September 2013 issue of Passagemaker. Hopefully with no infringement of copyright, I've scanned one page in the image below.

    Attached Files:

  10. Caltexflanc, Mar 20, 2014
    #10
    Caltexflanc

    Caltexflanc Senior Member

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    What it has to do with is proper bedding of the bolts.
  11. about time, Mar 20, 2014
    #11
    about time

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    always use and maintain cathodic protection
  12. about time, Mar 20, 2014
    #12
    about time

    about time Member

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    or you can use a monel or bronze swim platform support, in addition to the fasteners