Cathodic Protection Network International Limited
Pipeline Corrosion Control

Name & Registered Office:
CATHODIC PROTECTION NETWORK INTERNATIONAL
74 DALCROSS
BRACKNELL
BERKSHIRE
RG12 0UL

Cathodic Protection Network Laboratory 3

This is the fourth in the series examining the actual measuring of corrosion and the effects of cathodic protection.

In this series we use a copper/copper-sulphate electrode made of a plastic tube (the shell of a ball point pen) filled with copper-sulphate solution and a copper wire to connect to the probe of the meter.

The probe of this electrode is a wooden tooth pick that has a 'capillary action' because of the straight grain and strength of the wood.. This serves the same purpose as a 'luggin capillary' to contact the electrolyte in which the subject metal us immersed.



0000schematic1
1



xxxx


0000schematic







Dscf0103plus
xxxx





1
The arrangement has been changed to allow synchronous measurements of voltages to be displayed during this series.





3
The transformer/rectifier (TR) can be seen top left of the picture with the positive and negative connecting wires tucked out of sight behind the trays. The timer can be seen on the shelf below the TR.





4
The front four multimeters are connected to measure the pipe-to-soil voltages and their test leads are arranged so that all the probe positions and displayed voltages can be seen at each stage of the test.





28
In this picture you can see that the red light on the timer timer is on and the bottom red light on the TR is on.
The common of all the meters are connected to the subject nails that are connected to the negative of the TR.
  • The meter on the far left is connected between the half-cell on the right of the picture that is positioned in the front partition of the test tray and displays 2.17 volts.
  • The centre left of the four meters is connected to the half-cell that is in the second partition and the voltage is -2.0286 with reference to the subject nails and the negative of the TR.
  • The centre right meter is connected to the half-cell that is in the third partition and shows 2.929v
  • The right hand meter is connected to the half-cell in the fourth partition and shows 1.945v





    27
  • The meter on the far left is connected between the half-cell that is positioned in the front partition of the test tray and displays 1.65 volts.
  • The centre left of the four meters is connected to the half-cell that is in the second partition and the voltage is 1.693 volts .
  • The centre right meter is connected to the half-cell that is in the third partition and shows 0.778 volts
  • The right hand meter is connected to the half-cell in the fourth partition and shows 0.7855 volts.





    26
  • The meter on the far left is connected between the half-cell that is positioned in the front partition of the test tray and displays 1.65 volts.
  • The centre left of the four meters is connected to the half-cell that is in the second partition and the voltage is 1.693 volts .
  • The centre right meter is connected to the half-cell that is in the third partition and shows 0.779 volts
  • The right hand meter is connected to the half-cell in the fourth partition and shows 0.7883 volts.





    25
  • The meter on the far left is connected between the half-cell that is positioned in the front partition of the test tray and displays 1.65 volts.
  • The centre left of the four meters is connected to the half-cell that is in the second partition and the voltage is 1.693 volts .
  • The centre right meter is connected to the half-cell that is in the third partition and shows 0.780 volts
  • The right hand meter is connected to the half-cell in the fourth partition and shows 0.7901 volts.





    24
  • The meter on the far left is connected between the half-cell that is positioned in the front partition of the test tray and displays 1.10 volts.
  • The centre left of the four meters is connected to the half-cell that is in the second partition and the voltage is 1.882 volts .
  • The centre right meter is connected to the half-cell that is in the third partition and shows 0.732 volts
  • The right hand meter is connected to the half-cell in the fourth partition and shows 0.9265 volts.





    23
  • The meter on the far left is connected between the half-cell that is positioned in the front partition of the test tray and displays 1.11 volts.
  • The centre left of the four meters is connected to the half-cell that is in the second partition and the voltage is 1.881 volts .
  • The centre right meter is connected to the half-cell that is in the third partition and shows 0.732 volts
  • The right hand meter is connected to the half-cell in the fourth partition and shows 0.9279 volts.





    22
  • The meter on the far left is connected between the half-cell that is positioned in the front partition of the test tray and displays 1.11 volts.
  • The centre left of the four meters is connected to the half-cell that is in the second partition and the voltage is 1.880 volts .
  • The centre right meter is connected to the half-cell that is in the third partition and shows 0.733 volts
  • The right hand meter is connected to the half-cell in the fourth partition and shows 0.9291 volts.





    21
  • The meter on the far left is connected between the half-cell that is positioned in the front partition of the test tray and displays 1.12 volts.
  • The centre left of the four meters is connected to the half-cell that is in the second partition and the voltage is 1.870 volts .
  • The centre right meter is connected to the half-cell that is in the third partition and shows 0.739 volts
  • The right hand meter is connected to the half-cell in the fourth partition and shows 0.9363 volts.





    20
  • The meter on the far left is connected between the half-cell that is positioned in the front partition of the test tray and displays 3.84 volts.
  • The centre left of the four meters is connected to the half-cell that is in the second partition and the voltage is 2.831 volts .
  • The centre right meter is connected to the half-cell that is in the third partition and shows 1.997 volts
  • The right hand meter is connected to the half-cell in the fourth partition and shows 2.4504 volts.





    19
  • The meter on the far left is connected between the half-cell that is positioned in the front partition of the test tray and displays 3.84 volts.
  • The centre left of the four meters is connected to the half-cell that is in the second partition and the voltage is 2.827 volts .
  • The centre right meter is connected to the half-cell that is in the third partition and shows 1.999 volts
  • The right hand meter is connected to the half-cell in the fourth partition and shows 2.4520 volts.





    18
  • The meter on the far left is connected between the half-cell that is positioned in the front partition of the test tray and displays 3.84 volts.
  • The centre left of the four meters is connected to the half-cell that is in the second partition and the voltage is 2.826 volts .
  • The centre right meter is connected to the half-cell that is in the third partition and shows 2.002 volts
  • The right hand meter is connected to the half-cell in the fourth partition and shows 2.4541 volts.





    17
  • The meter on the far left is connected between the half-cell that is positioned in the front partition of the test tray and displays 3.88 volts.
  • The centre left of the four meters is connected to the half-cell that is in the second partition and the voltage is 2.739 volts .
  • The centre right meter is connected to the half-cell that is in the third partition and shows 2.086 volts
  • The right hand meter is connected to the half-cell in the fourth partition and shows 2.4990 volts.





    16
  • The meter on the far left is connected between the half-cell that is positioned in the front partition of the test tray and displays 3.89 volts.
  • The centre left of the four meters is connected to the half-cell that is in the second partition and the voltage is 2.738 volts .
  • The centre right meter is connected to the half-cell that is in the third partition and shows 2.087 volts
  • The right hand meter is connected to the half-cell in the fourth partition and shows 2.5005 volts.





    15
  • The meter on the far left is connected between the half-cell that is positioned in the front partition of the test tray and displays 1.28 volts.
  • The centre left of the four meters is connected to the half-cell that is in the second partition and the voltage is 1.852 volts .
  • The centre right meter is connected to the half-cell that is in the third partition and shows 0.814 volts
  • The right hand meter is connected to the half-cell in the fourth partition and shows 1.0496 volts.





    14
  • The meter on the far left is connected between the half-cell that is positioned in the front partition of the test tray and displays 1.28 volts.
  • The centre left of the four meters is connected to the half-cell that is in the second partition and the voltage is 1.852 volts .
  • The centre right meter is connected to the half-cell that is in the third partition and shows 0.815 volts
  • The right hand meter is connected to the half-cell in the fourth partition and shows 1.0499 volts.





    13
  • The meter on the far left is connected between the half-cell that is positioned in the front partition of the test tray and displays 1.78 volts.
  • The centre left of the four meters is connected to the half-cell that is in the second partition and the voltage is 1.500 volts .
  • The centre right meter is connected to the half-cell that is in the third partition and shows 0.946 volts
  • The right hand meter is connected to the half-cell in the fourth partition and shows 0.9439 volts.




    >

    12
  • The meter on the far left is connected between the half-cell that is positioned in the front partition of the test tray and displays 1.78 volts.
  • The centre left of the four meters is connected to the half-cell that is in the second partition and the voltage is 1.900 volts .
  • The centre right meter is connected to the half-cell that is in the third partition and shows 0.946 volts
  • The right hand meter is connected to the half-cell in the fourth partition and shows 0.9441 volts.




    11
  • The meter on the far left is connected between the half-cell that is positioned in the front partition of the test tray and displays 1.83 volts.
  • The centre left of the four meters is connected to the half-cell that is in the second partition and the voltage is 1.901 volts .
  • The centre right meter is connected to the half-cell that is in the third partition and shows 0.814 volts
  • The right hand meter is connected to the half-cell in the fourth partition and shows 0.9461 volts.




    10
  • The meter on the far left is connected between the half-cell that is positioned in the front partition of the test tray and displays 1.83 volts.
  • The centre left of the four meters is connected to the half-cell that is in the second partition and the voltage is 1.901 volts .
  • The centre right meter is connected to the half-cell that is in the third partition and shows 0.947 volts
  • The right hand meter is connected to the half-cell in the fourth partition and shows 0.9466 volts.




    9
  • The meter on the far left is connected between the half-cell that is positioned in the front partition of the test tray and displays 1.47 volts.
  • The centre left of the four meters is connected to the half-cell that is in the second partition and the voltage is 1.536 volts .
  • The centre right meter is connected to the half-cell that is in the third partition and shows 0.874 volts
  • The right hand meter is connected to the half-cell in the fourth partition and shows 1.1671 volts.




    8
  • The meter on the far left is connected between the half-cell that is positioned in the front partition of the test tray and displays 1.47 volts.
  • The centre left of the four meters is connected to the half-cell that is in the second partition and the voltage is 1.537 volts .
  • The centre right meter is connected to the half-cell that is in the third partition and shows 0.874 volts
  • The right hand meter is connected to the half-cell in the fourth partition and shows 1.1669 volts.




    7
  • The meter on the far left is connected between the half-cell that is positioned in the front partition of the test tray and displays 1.34 volts.
  • The centre left of the four meters is connected to the half-cell that is in the second partition and the voltage is 1.501 volts .
  • The centre right meter is connected to the half-cell that is in the third partition and shows 0.851 volts
  • The right hand meter is connected to the half-cell in the fourth partition and shows 1.2554 volts.




    6
  • The meter on the far left is connected between the half-cell that is positioned in the front partition of the test tray and displays 1.34 volts.
  • The centre left of the four meters is connected to the half-cell that is in the second partition and the voltage is 1.501 volts .
  • The centre right meter is connected to the half-cell that is in the third partition and shows 0.851 volts
  • The right hand meter is connected to the half-cell in the fourth partition and shows 1.2547 volts.








    5
  • The meter on the far left is connected between the half-cell that is positioned in the front partition of the test tray and displays 3.80 volts.
  • The centre left of the four meters is connected to the half-cell that is in the second partition and the voltage is 2.079 volts .
  • The centre right meter is connected to the half-cell that is in the third partition and shows 2.283 volts
  • The right hand meter is connected to the half-cell in the fourth partition and shows 2.9654 volts.




    4
  • The meter on the far left is connected between the half-cell that is positioned in the front partition of the test tray and displays 3.80 volts.
  • The centre left of the four meters is connected to the half-cell that is in the second partition and the voltage is 2.079 volts .
  • The centre right meter is connected to the half-cell that is in the third partition and shows 2.283 volts
  • The right hand meter is connected to the half-cell in the fourth partition and shows 2.9652 volts.




    31
  • The meter on the far left is connected between the half-cell that is positioned in the front partition of the test tray and displays 3.80 volts.
  • The centre left of the four meters is connected to the half-cell that is in the second partition and the voltage is -2.8784 volts .
  • The centre right meter is connected to the half-cell that is in the third partition and shows 2.285 volts
  • The right hand meter is connected to the half-cell in the fourth partition and shows 1.8nn volts.




    32
  • The meter on the far left is connected between the half-cell that is positioned in the front partition of the test tray and displays 3.80 volts.
  • The centre left of the four meters is connected to the half-cell that is in the second partition and the voltage is -2.8866 volts .
  • The centre right meter is connected to the half-cell that is in the third partition and shows 2.275 volts
  • The right hand meter is connected to the half-cell in the fourth partition and shows 1.8nn volts.




    33
  • The meter on the far left is connected between the half-cell that is positioned in the front partition of the test tray and displays 1.43 volts.
  • The centre left of the four meters is connected to the half-cell that is in the second partition and the voltage is -0.9310 volts .
  • The centre right meter is connected to the half-cell that is in the third partition and shows 1.08n volts
  • The right hand meter is connected to the half-cell in the fourth partition and shows 1.477 volts.




    34
  • The meter on the far left is connected between the half-cell that is positioned in the front partition of the test tray and displays 1.43 volts.
  • The centre left of the four meters is connected to the half-cell that is in the second partition and the voltage is -0.9345 volts .
  • The centre right meter is connected to the half-cell that is in the third partition and shows 1.08n volts
  • The right hand meter is connected to the half-cell in the fourth partition and shows 1.478 volts.




    35
  • The meter on the far left is connected between the half-cell that is positioned in the front partition of the test tray and displays 1.96 volts.
  • The centre left of the four meters is connected to the half-cell that is in the second partition and the voltage is -1.2979 volts .
  • The centre right meter is connected to the half-cell that is in the third partition and shows 1.036 volts
  • The right hand meter is connected to the half-cell in the fourth partition and shows 1.940 volts.




    36
  • The meter on the far left is connected between the half-cell that is positioned in the front partition of the test tray and displays 1.96 volts.
  • The centre left of the four meters is connected to the half-cell that is in the second partition and the voltage is -1.2881 volts .
  • The centre right meter is connected to the half-cell that is in the third partition and shows 1.036 volts
  • The right hand meter is connected to the half-cell in the fourth partition and shows 1.940 volts.




    37
  • The centre left of the four meters is connected to the half-cell that is in the first partition and the voltage is 1.96 volts .
  • The centre left meter is connected to the half-cell that is in the fourth partition and shows -1.2894 volts




    38
  • The centre left of the four meters is connected to the half-cell that is in the first partition and the voltage is 1.96 volts .
  • The centre left meter is connected to the half-cell that is in the fourth partition and shows -1.2895 volts




    39
  • The centre left of the four meters is connected to the half-cell that is in the first partition and the voltage is 2.00 volts .
  • The centre left meter is connected to the half-cell that is in the fourth partition and shows -0.8906 volts




    40
  • The centre left of the four meters is connected to the half-cell that is in the first partition and the voltage is 1.99 volts .
  • The centre left meter is connected to the half-cell that is in the fourth partition and shows -0.8884 volts




    41
  • The centre left of the four meters is connected to the half-cell that is in the first partition and the voltage is 2.00 volts .
  • The centre left meter is connected to the half-cell that is in the fourth partition and shows -0.9547 volts




    42
  • The centre left of the four meters is connected to the half-cell that is in the first partition and the voltage is 2.00 volts .
  • The centre left meter is connected to the half-cell that is in the fourth partition and shows -0.9538 volts



    Let us now try to see what conclusions we can draw from the data gathered in the pictures in this series as they are voltages gathered in the same way as we gather voltages with the same meters in our field work.

    cips


    As you can see in this diagram we are measuring voltages when we carry out a Close Interval Potential Survey.
    But the measuring circuit for each voltage is as the picture below.

    circuit


    The variations in this test series can be compared to the variations in ground potentials shown in this diagram.

    diferelectrolyte.jpg


    In these tests we have made many voltage measurements but on a single CIPS survey we record millions of voltages.

    graph


    Each voltage recorded in a CIPS survey should be considered in the same way as we consider each voltage in this test series if it is to indicate the corrosion status of the pipeline. But when you examine how the data loggers and software record and display the information it make nonsense of all the claims that are made for the survey technique.

    graph dots


    The instrument makes voltage measurements at the rate of 40,000 per second and the software takes samples of a set number of voltages in the 'on' mode and in the 'off' mode. The software then averages each sample and allocates them to an 'on point' on the graph and an 'off point' on the graph, as shown in the drawing above.

    These on and off potentials are plotted as seen in the next drawing and show the trends of the voltages over a distance axis that is co-ordinated with time and the GPS position.

    graph dots joined


    The interpretation of the off potential into the 'polarised potential' is absurd as for that we require to know the exact voltage at which the 'kick' occurs, as seen in the picture below.

    timekick


    However, the CIPS survey results need not be wasted if we can relate them to the actual corrosion status of the pipeline at each location.

    We can do that using a corrosion cell in which the corrosion current itself can be measured when charged with a sample of the electrolyte to take into consideration the pH of the backfill and the temperature at the time of the test.

    This is why I had to design the Alexander Cell.

    Link to next page

    Email Cathodic Protection Network International Limited