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electronic rust protection does it work...

Discussion in 'General Electronics' started by Craig, Sep 9, 2003.

  1. Craig

    Craig Guest

  2. Robert Baer

    Robert Baer Guest

    Firstly, there is a lot of verbage on the site and little explaination
    as to their methodology or how it might work, other than the method is
    not a DC durrent thru a conductive fluid (usually water).
    So, on to the patent, 4,767,512 by Cowatch et al. dated August 30,
    1988:
    Abstract
    An effective process of preventing the oxidation of metal objects by
    capacitive coupling is disclosed. An electric current is impressed into
    the metal object by treating the metal object as the negative plate of a
    capacitor. This is achieved by a capacitive coupling between the metal
    object, a dielectric material and a positive plate. Pulses of direct
    current are provided to the positive plate. The metal object has a
    common ground with the means for providing the pulses.
    ************
    If taken literally or exactly as described, there is *ZERO* net DC
    current as that is the nature of an insulator. Therefore, during the
    pulse, there would be protection, and during the absense of the pulse
    the bias is opposite and may even be sufficent to *enhance* corrosion
    beyond that driven by oxidation differentials in the metal as it rusts.
    ***
    In the claims, it is mentioned that the pulse amplitude ranges from
    10E-6 to 10E+6 volts, at a current in the microampere range (more on
    this later), and at a frequency from 10E0 to 10E6 hertz.
    It is also mentioned in the claims that the dielectric material has a
    puncture voltage of at least about 10 kilovolts.

    Problems withclaim statements:
    1) Charging a capacitor requires a displacement current, and to achieve
    a displacement current of only a few microamperes, especially with large
    amplitude pulses, requiers the voltage to be rampped over a long period
    of time - mainly due to the huge capacitance made with large surfaces.
    Remember C*V=I*T.
    2) Note that 10E6V is 100 times larger than that 10KV insulating
    capability. Major problems in that region.
    ***
    The method might work given the proper drive, but the coatings needed
    (on the surface to be protected) for implimentation may give the
    observed protection without regard to the electrical drive.
     
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