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A Conductivity change of a tank (glass coating on steel)

  1. Jan 1, 2017 #1

    rollingstein

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    Suppose I have a tank which is made of steel coated with a thin layer of glass on the inside to protect the steel from corrosion (the material stored inside the tank is corrossive; say for arguments sake Water with 10% Hydochloric Acid).

    In theory, till the glass is intact there is an electrically insulating barrier between the steel of the tank and the water inside. My question is, how much would be the conductivity change if the glass broke down at some spot. Say, for calculation's sake a 5 mm dia spot in the glass coating got corroded.

    Would the resultant contact between the conductive water and steel be enough to give a significant change in conductivity that could be monitored to trigger an alarm?

    Or is the idea technically unfeasable because the change would be too small?

    To enable quantitative estimates I looked up some numbers:

    Tank Volume: 10,000 Litres
    Tank Shape: Cylindrical
    Steel Thickness of tank wall: 8 mm
    Glass Coating Thickness inside Tank: 2 mm

    Electrical conductivity:
    Steel 7x106 Siemens/m
    Glass lining: 10-11 Siemens/m
     
  2. jcsd
  3. Jan 1, 2017 #2
    Certainly ...you wouldn't need a hole that big either , the smallest crack or hole would show a change in resistance and could trigger an alarm , this would work with ordinary domestic tap water too , which is slightly conductive....

    Coating steel and copper with a thin coating of glass is called enamelling , enamelled bowls for domestic purposes were very common a 100 years ago , a thin coating of glass dust applied to the surface , and heat to red heat , the glass melts , bonds to the surface in one continuous protective coating , perhaps half a mm thick
     
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