anodes for aluminium hulls

Discussion in 'Boat Design' started by rick gray, Dec 11, 2015.

  1. rick gray
    Joined: Dec 2012
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    rick gray Junior Member

    what do you use for catholic protection (anodes) for small aluminium hulls in salt water? I think hull and components have to be grounded to battery ? what about lightning? rod? to ground out hull? My computer corrects spelling, but not intent? Cathodic? is the POPE well Grounded?
     
  2. Mr Efficiency
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    Mr Efficiency Senior Member

  3. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    Oh, and you need to speak to the Pope about that ! :D
     
  4. gonzo
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    gonzo Senior Member

    You need magnesium anodes.
     
  5. Ad Hoc
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    Ad Hoc Naval Architect


  6. Barry
    Joined: Mar 2002
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    Barry Senior Member

    ABYC July 2008-2009 has a pertinent discussion.
    2.10.2 Notes:3 Page 8 E-2
    3. If magnesium anodes are used in salt water, the negative potential may exceed the 1200mv maximum recommended potential and create the condition for cathodic corrosion.

    There is a table further on that lists metals and alloys in order of their Galvanic corrosion potential range in millivolts tested under a specific set of parameters and
    zinc anodes show a corrosion potential of -980 to -1030mv and magnesium alloys show a corrosion potential of -1600 to -1630 mv

    Therefore magnesium anodes are not the way to go as they are above the max recommended by ABYC

    Immediately below zinc are aluminum alloys but since the boat is aluminum you need to be above the aluminum corrosion potential value. So zinc is what is required.
     
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