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Zincs vs. Magnesiums

Discussion in 'Technical Discussion' started by Celtic Knot, Apr 1, 2012.

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  1. Celtic Knot, Apr 1, 2012
    #1
    Celtic Knot

    Celtic Knot New Member

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    I was working on my boat yesterday getting it ready for Spring launch. A mechanic stopped by to chat and told me that i should have magnesum blocks in place of my zincs. He said that the zincs don't really do anything as I am in fresh water, that they should be replaced with magnesums?

    Does this make sense? or he just trying to sell me?
  2. NYCAP123, Apr 1, 2012
    #2
    NYCAP123

    NYCAP123 Senior Member

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    He's right.
  3. C4ENG, Apr 1, 2012
    #3
    C4ENG

    C4ENG Senior Member

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    On the galvanic chart series, magnesium is least nobble from Zinc which means the magnesium will then sacrifice itself to protect any zinc installed on the vessel making the zinc a more noble metal in that situation.
    Fresh water does carry less TDS to carry electric currents and atoms to flow through but I would be interested to know why or how magnesium could sacrifice itself better than zinc to preserve the more noble metals just because it is in fresh water oppose to salt water.
  4. NYCAP123, Apr 1, 2012
    #4
    NYCAP123

    NYCAP123 Senior Member

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  5. K1W1, Apr 1, 2012
    #5
    K1W1

    K1W1 Senior Member

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    Hi,

    If you can overcome the sales pitch there is some good info to be found here.

    Cathodic Protection - Marine Cathodic Protection - MGDUFF
  6. C4ENG, Apr 1, 2012
    #6
    C4ENG

    C4ENG Senior Member

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    K1
    I found the answer as to why mag would be better than zinc in fresh water in the link you sent. I cut and pasted for others to see......

    Not all anodes are suitable for every environment, for example the surface of a zinc or aluminium anode will if left in fresh water for some time become covered with an off white crust of oxide which effectively seals the anode and stops it working even when returned to salt water.
  7. C4ENG, Apr 1, 2012
    #7
    C4ENG

    C4ENG Senior Member

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