lets talk about modern way to avoid electrolysis and galvanic corrosion

Discussion in 'Boat Design' started by goldhunter_2, Sep 5, 2015.

  1. goldhunter_2
    Joined: Apr 2010
    Posts: 44
    Likes: 3, Points: 0, Legacy Rep: 36
    Location: USA

    goldhunter_2 Junior Member

    I am a bit old fashion shall we say:eek: an wounder what new trains of thoughts or modern remedies may be out there now. I'd like to hear some discussion on best way to avoid electrolysis and galvanic corrosion with the ever increasing electrical systems of a comfortable cursing live aboard. Even with everything grounded by ground wire directly back to batteries you still get "bleed off current" and all 3 hull material options I am looking at as well as most every hull out there is subject to these issues.

    General reference information so everyone is basically discussing the same situations:(everyone always ask for more background info so here it is in advance)

    1) Basically all electric (no gen, no diesel engines) sailing catamaran --- two 10hp PMA electric drives, solar panels, 3-5 high voltage lithium battery packs divided use on separate systems

    2) Hull materials and lay up considerations are:

    a) Aluminum ,5086 or 5083 0.190" (3/16") skin, lightened framing,
    Pros; easiest and most economical for me, easy to repair, safest for
    on-board fires , excellent future resale value.
    Cons; galvanic corrosion is issue with any dissimilar metal fitting or
    bolts etc used, severally subject to electrolysis particular on a heavily
    electric boat :( absorbs heat or cold temps.

    b) Carbon fiber, layup form inside out of hull is as follows- epoxy resin,
    fiberglass mat for finish/90 degree CF/coremat/+45 degree
    CF/coremat/-45 degree CF/ coremat/0 degree CF/fiberglass mat for
    finish/ two layers of Kevlar along the keel to protect on dryouts
    Pros; 2nd most economical to build but will require more skilled
    labor Cons; due to the graphite galvanic corrosion will be a issue
    anywhere a metal bolt or fitting is attached , hull is still subject to
    electrolysis. Epoxy is subject to heat issues.

    c) Fiberglass with dyivcell H-80 cored hull and decks . epoxy resin,
    same basic layup with light weight glass on interior and exterior
    skins mat/90/+45/-45/0/Core above water line/90/-45/+45/0/mat
    two layers Kevlar along keel. Pros; easiest to find skilled labor and
    materials , commonly recognized method , foam core provide some
    insulation an flotation. Cons; surprisingly the most expensive all
    around choice :confused: it burns, will have to be careful no holes
    are ever drilled through core areas, epoxy subject to heat issues ,
    slapping some zinc tabs on the bottom would be a common option in
    most similar hulls out there today.

    Given the known reference information of a all electric, high voltage systems, choices of hull options what are some modern solutions to avoid or eliminate Electrolysis and Galvanic corrosion to the hulls?

  2. gonzo
    Joined: Aug 2002
    Posts: 16,354
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    Location: Milwaukee, WI

    gonzo Senior Member

    Passive systems are very reliable and effective. Otherwise, you can have something like Mercathode, where a voltage is applied to the material lower in the electrolytic scale. They have more possibilities of failure though.
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