Cathodic Protection Network International Limited
Pipeline Corrosion Control

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CATHODIC PROTECTION NETWORK INTERNATIONAL LIMITED
74 DALCROSS
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Company No. 08505715

Cathodic Protection Network Laboratory 5

This is the fifth in the series of laboratory experiments that examine the measurement of corrosion and show that there is no way that the copper/copper-sulphate electrode can be used to determine the effect of cathodic protection or electronic corrosion control on a real corrosion cell.

It follows that the Cu/CuSO4 electrode cannot be used to measure any value that can be used as a criterion for the successful application of cathodic protection.

There are no demonstrations available that prove that the 'half-cell' , 'CSE' copper/copper-sulphate electrode can be consistently used to determine when corrosion has stopped.

Any publication, paper, book or training course that makes reference to the 'pipe-to-soil' potential or acronyms during the discourse, as evidence that 'protection' is achieved at a certain voltage between the pipeline or protected structure, is scientificly unsound.

There is no university that has a department of applied cathodic protection that has investigated this matter at PhD level and produced repeatedly demonstrable observations to substantiate the use of the copper/copper-sulphate electrode in field work or modelled field work.

Serious scientific investigation of this matter is deliberately blocked by a few people who have a vested interest is the status quo.

If you want to get a job in corrosion control you have to pay for a certificate from one of the global organisations that will not examine this subject because they cannot justify their advice upon which all their design calculations are based.
There seems to be many thousands of people who have paid money to corrosion control associations and organisations. These people need scientifically sound information that can be demonstrated simply as I do with the three nails experiment.




In the first experiments we used steel nails as probes to contact the electrolyte to show that the measuring circuit is influenced by every component in 'series'. This means that the nicol plated copper probes of the test leads supplied with the meter have a reaction with the electrolyte that must be added to the total value of all of the potentials and EMF's in the measuring circuit.

In this series 5 we used a traditional 'half-cell' which is copper in a saturated solution of copper-sulphate. The probe of this electrode is a wooden plug similar to that used in manufactured 'half-cells'.

For convenience of this test the half cell is stood in a roll of damp super-absorbant cloth to make it free standing.

The positions to which the half-cell is moved are shown on this picture.

Positions





The half-cell is connected to the positive connection of the top multimeter (in the picture) with the red lead.

The black lead of the top meter is connected to the pipe, thus giving the meter the same measurement as achieved in the traditional 'pipe-to-soil potential' measurement (this measurement is really a voltage).
The black lead is connected to the pipe through a coil of thin wire similar to that used in Close Interval Potential Surveys and other procedures in field work.
The reason we include this in this experiment is because the resistance of the thin wire itself must be considered as part of the measuring circuit.
In some circumstances in field work the wire itself can pick up energy from such sources a radio transmissions which can cause fluctuations on the meter readings.


1
The test beds are two identical steel trays filled with silicon sand that is dampenned with tap water.
These two trays are electrically connected with the green jumper leads seen with green croc clips at the bottom of the picture.
The multimeter at the bottom of the picture is set to measure micro-amps and is connected between the cathode on top of the Alexander Cell and the base electrode immediately under the cathode. There is no current flowing as the sample of electrolyte is not bridging the gap between the anode (working electrode) of the corrosion cell that is being measured.



In picture 2 it is seen that there is 0.579v potential difference between the pipe and the Cu/CuSO4 electrode. The Cu/CuSO4 electrode is in position 1.
The Alexander Cell is not connected to the pipe or activated. and the lower meter displays 0.0000


2





The multimeter at the bottom of the picture 3 is set to measure micro-amps and is connected between the cathode on top of the Alexander Cell and the base electrode immediately under the cathode through the connection tabs that are set in the insulating body of the corrosion cell, through which no current is flowing.
It is seen that there is 0.401v potential difference between the pipe and the Cu/CuSO4 electrode.


3





In picture 18 (below) you can see that the copper/copper-sulphate electrode has been moved and the 'pipe-to soil' potential difference is 0.754v
This means that the electrolyte at the contact point has a potential 0.754 different from the potential of the pipe that is connected to the other pole of the voltmeter.
The anode of the corrosion cell has been connected to the pipe through the coil. You can see the green jumper lead from the pipe connection on the Alexander cell to the crock clip on top of the coil.

  • When making observations in these experiments we must not make assumptions about the sources of electrical energy that disturb the displayed measurement.


    18





    In picture 19 you can see that the copper/copper-sulphate electrode has been moved and the resulting 'pipe-to soil' voltage is 0.734
    This means that the electrolyte at the contact point has a potential 0.020 different from the potential of the electrolyte in the previous location.


    19





    In picture 20 you can see that the copper/copper-sulphate electrode has been moved and the resulting 'pipe-to soil' voltage is 0.736
    This means that the electrolyte at the contact point has a potential 0.002 different from the potential of location 1 with this measuring circuit.


    20





    In picture 4 you can see that the Alexander Cell is not connected to the pipe and the Cu/CuSO4 electrode is in position 4. The 'pipe-to-soil voltage 0.578 is seen on the meter.


    4






    The Cu/CuSO4 electrodeis in position 3 and 0.401 is seen on the voltmeter.
    We can see that the measuring circuit is Meter common > pipe > thin wire > coil / Meter volts input >CuCuSO4 electrode > damp cloth position 3 > stainless steel tray > pipe.
    We know that the circuit must be complete on this meter or we would have no reading displayed.
    We cannot make any further deductions about the voltage that we see on the meter as it is very easy to dream up theories that turn out to be wrong.


    5







    The Cu/CuSO4 electrode is now in position 1 and 0.577 is seen on the voltmeter.
    This location has a potential 0.176v different from location 3 with this measuring circuit.


    6





    The Cu/CuSO4 electrode has been moved again and 0.600 is seen on the voltmeter.
    Position 2 has a potential 0.023v different to location 1 with this measuring circuit.


    7






    8

    The Cu/CuSO4 electrode has been moved again and 0.577 is seen on the voltmeter.






    In this picture 9 the micro-ameter shows a reading of -0.1592 that is due to the sample of the electrolyte being placed across the gap between the anode and the cathode of the corrosion cell.
    The Cu/CuSO4 electrode is in the same position as the previous picture and the reading is still 0.577 volts.
    The corrosion reaction has not been detected by the Cu/CuSO4 method of measurement.


    9





    In the picture below (11) the micro-ameter shows a reading of -0.1568 that is the corrosion current.
    The Cu/CuSO4 electrode is in a different position to the previous picture and the reading is still 0.401 volts.
    The only change in the 'pipe-to-soil measurement is due to the position of the Cu/CuSO4 electrode.


    11







    In the picture below (12) the micro-ameter shows a reading of -0.1568 that is the corrosion current.
    The Cu/CuSO4 electrode is in the same position to the previous picture and the reading is now 0.402 volts.
    The only change in the 'pipe-to-soil measurement is due to fluctuations of the Cu/CuSO4 electrode.


    12





    In the picture below (13) the micro-ameter shows a reading of -0.1572 that is the corrosion current.
    The Cu/CuSO4 electrode is in a different position to the previous picture and the reading is now 0.578 volts.
    The only change in the 'pipe-to-soil measurement is due to fluctuations of the Cu/CuSO4 electrode and the change of it's contact position.


    13





    In the picture below (14) the micro-ameter shows a reading of --0.1318 that is the effect of the impressed current cathodic protection system reversing the current in the corrosion cell. The corrosion current has been stopped and charges are now flowing from the cathodic protection anode through the electrolyte and returning to the TR negative terminal through the pipe.
    The Cu/CuSO4 electrode is in the same position as the previous picture and the reading is now 0.836 volts.
    The change in the 'pipe-to-soil measurement is due to charges in the electrolyte at the position in which the Cu/CuSO4 electrode is placed.
    In this model, the steel trays are used as the anode of the impressed current system so that the whole content of the trays are at the same potential until a path of lower resistance is introduced.
    In the application of cathodic protection in the field, the anodes are placed remote from subject structure so that charges are available from 'remote earth'.
    This is important to understand in cathodic protection design.


    14
    The schematic explanation below is part of the Cathodic Protection Network Intellectual Property.


    charges





    In this picture (15) you can see that the 'pipe-to-soil' voltage is 0.724 on the top meter with the Cu/CuSO4 electrode placed in a different position, closer to the low resistance path to the pipe.
    You can see that the corrosion current is -0.1358 and that corrosion has been stopped with a 'pipe-to-soil potential measurement of -0.724 v proving that the position of the 'half-cell' causes error that make the 'criterion' impossible to compute.


    15







    In picture 16 you can see that the copper/copper-sulphate electrode has been moved and the resulting 'pipe-to soil' voltage is 0.726.
    This means that the electrolyte at the contact point has a potential 0.726 different from the potential of the pipe that is connected to the other pole of the voltmeter.
    This proves that the electrolyte has potential zones that result from the passage of cathodic protection current as well as from the corrosion reactions and other features.
    The corrosion cell current has been reversed by the cathodic protection and is still seen to be -0.1378


    16





    In picture 17 you can see that the copper/copper-sulphate electrode has been moved and the resulting 'pipe-to soil' voltage is 0.771
    This means that the electrolyte at the contact point has a potential 0.771 different from the potential of the pipe that is connected to the other pole of the voltmeter.
    This is further proof that the electrolyte has potential zones that result from the passage of cathodic protection current as well as from the corrosion reactions and other features.
    The corrosion cell current has been reversed by the cathodic protection and is seen to be -0.1398


    17





    In picture 21 you can see that the copper/copper-sulphate electrode has been moved and the resulting 'pipe-to soil' voltage is 0.708
    This means that the electrolyte at the contact point has a potential 0708 v different from the potential of the pipe that is connected to the other pole of the voltmeter.

    The corrosion cell current is seen to be -0.1588


    21





    In picture 22 you can see that the 'pipe-to soil' voltage is 0.581

    The corrosion cell current is seen to be -0.1798


    22





    In picture 23 you can see that the 'pipe-to soil' voltage is 0.582

    The corrosion cell current is seen to be -0.1758


    23





    In picture 24 you can see that the 'pipe-to soil' voltage is 0.610

    The corrosion cell current is seen to be -0.2062


    24





    In picture 25 you can see that the 'pipe-to soil' voltage is 0.610

    The corrosion cell current is seen to be -0.2069


    25





    In picture 26 you can see that the 'pipe-to soil' voltage is 0.728

    The corrosion cell current is seen to be -0.1800


    26





    In picture 27 you can see that the 'pipe-to soil' voltage is 0.689

    The corrosion cell current is seen to be -0.1798


    27





    In picture 28 you can see that the 'pipe-to soil' voltage is 0.564

    The corrosion cell current is seen to be -0.1043


    28





    In picture 29 you can see that the 'pipe-to soil' voltage is 0.566

    The corrosion cell current is seen to be -0.1134


    29





    In picture 30 you can see that the 'pipe-to soil' voltage is 0.553

    The corrosion cell current is seen to be -0.1188


    30






    31
  • The top meter shows a potential difference of 0.412v
  • The bottom meter shows the current through the corrosion cell is -0.2930 micro-amps.
  • This could be because the presence of the Cu/CuSO4 electrode is altering the corrosion reaction when placed too close to the metal-to-electrolyte interface.
  • This can be corrected by the use of a Luggin capillary at this point of contact and thus recreating the conditions specified in DIN50918




    32
  • The top meter shows a potential difference of 0.433v
  • The Cu/CuSO4 electrode is now placed on the cathode of the corrosion cell, and subject to the IR Drop due to diffusion of the charges through the sample of electrolyte.
  • The bottom meter shows a current of -0.3269 micro-amps
  • This is due to the lower reststance caused by the greater surface area of the sample electrolyte plus the absorbant padding that is supporting the Cu/CuSO4 electrode.




    33
  • The top meter shows 164.1mv
  • The lower meter shows -02720 micro amps
  • The pipe has been turned over exposing bare metal to the electrolyte
  • The Cu/CuSO4 electrode has been placed close to the point where the bare metal touches the electrolyte and this is similar to the conditions witnessed when following an excavation down to a coating fault with 'pipe-to-soil potential measurements'
  • I have documentary and photographic evidence to prove this fact.




    34
  • The pipe-to soil reading is 163.7
  • The corrosion current is -0.2718





    35
  • The pipe-to soil reading is 179.1
  • The corrosion current is -0.2712





    36
  • The pipe-to soil reading is 232.0
  • The corrosion current is -0.2704





    37
  • The pipe-to soil reading is 247.8
  • The corrosion current is -0.2702





    38
  • The pipe-to soil reading is 283.3
  • The corrosion current is -0.2692





    39
  • The pipe-to soil reading is 217.3
  • The corrosion current is -0.2688





    41
  • The pipe-to soil reading is 313.7
  • The corrosion current is -0.2710




    Let us see if there can be any correlation between the voltages that we recorded and the corrosion status of the measurable corrosion cell.







    1
    0

    The top multimeter (in the picture) shows 0.401v
    The bottom multimeter set on micro-amps shows -0.1568




    Row number 1Picture numberCu/CuSO4 positionPotentialCorrosion Current
    Row number 22Cu/CuSO4 position 10.579-0.0000
    Row number 33Cu/CuSO4 position 20.401-0.0000
    Row number 418Cu/CuSO4 position 40.759-0.0000
    Row number 519Cu/CuSO4 position 10.734-0.0000
    Row number20Cu/CuSO4 position 20.736-0.0000
    Row number4Cu/CuSO4 position 40.578-0.0000
    Row number5Cu/CuSO4 position 30.401-0.0000
    Row number6Cu/CuSO4 position 10.577-0.0000
    Row number7Cu/CuSO4 position 20.600-0.0000
    Row number8Cu/CuSO4 position 10.577-0.0000
    Row number9Cu/CuSO4 position 10.577-0.1592
    Row number11Cu/CuSO4 position 20.401-0.1568
    Row number12Cu/CuSO4 position 30.402-0.1568
    Row number13Cu/CuSO4 position 40.578-0.1572
    Row number14Cu/CuSO4 position 40.836-0.1316
    Row number15Cu/CuSO4 position 20.724-0.1356
    Row number16Cu/CuSO4 position 30.726-0.1378
    Row number17Cu/CuSO4 position 40.771-0.1398
    Row number21Cu/CuSO4 position 10.708-0.1588
    Row number22Cu/CuSO4 position 50.581-0.1798
    Row number23Cu/CuSO4 position 50.582-0.1758
    Row number24Cu/CuSO4 position 60.610-0.2062
    Row number25Cu/CuSO4 position 60.610-0.2069
    Row number26Cu/CuSO4 position 70.728-0.1800
    Row number27Cu/CuSO4 position 10.689-0.1798
    Row number28Cu/CuSO4 position 10.564-0.1043
    Row number29Cu/CuSO4 position 20.566-0.1134
    Row number30Cu/CuSO4 position 70.553-0.1188
    Row number31Cu/CuSO4 position 50.412-0.2930
    Row number32Cu/CuSO4 position 60.433-0.3269
    Row number33Cu/CuSO4 position 1164.1-0.2720
    Row number34Cu/CuSO4 position 1163.7-0.2718
    Row number35Cu/CuSO4 position 1179.1-0.2712
    Row number36Cu/CuSO4 position 1232.0-0.2704
    Row number37Cu/CuSO4 position 1247.8-0.2702
    Row number38Cu/CuSO4 position 8283.3-0.2692
    Row number39Cu/CuSO4 position 2217.3-0.2686
    Row number41Cu/CuSO4 position 1313.7-0.2710
    Row number0Cu/CuSO4 position 10.401-0.1568
    Row number1Cu/CuSO4 position 10.401-0.1568

    This data was put onto a spread sheet.


    excel 1


    Attempts were made to relate the voltages to the currents.


    excel 2



    excel 2


    A variety of relationships were tried including Cu/CuSO4 positions and picture numbers as this data might be available from CIPS surveys.

    This experiment need to be carried out by a university at PhD level as it has impact on the credibility of all present cathodic protection work.

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