stage 5 of Computerization of cathodic protection

1. Computerizing of DCVG
At present DCVG is merely
presented as graphs of voltages

2. Computers are adding machines
• We can use them to make extremely big calculations.
• Computers can make trillions of floating point
calculations per second.
• We need to put in real scientific data to allow computers
to calculate the results of any adjustment that we make
to our cathodic protection systems.
• If we can do this we can use the computer to trigger
actions in response to any event.
• In this way we can program computers to control
corrosion to networks of pipelines.
• The present ‘remote monitoring’ systems are producing
data that cannot be computed.

3. DCVG simulation.
• Two Cu/Cuso4 electrodes
are connected through
the centre multi-meter
• This is connected to the
computer display that
records the voltages.
• This measuring circuit is
NOT connected to the
pipeline or the cathodic
protection system.
• The meter on the right
shows the corrosion
current in the Alexander
Cell.

4. DCVG at Guararema training
centre

5. Note the exact positions of the two
electrodes

6. In the frame above.
• One Cu/CuSO4 electrode is on remote
earth near the Alexander Cell.
• The other is positioned in the ‘shells of
resistance’ that create potential zones as
the charges approach a coating fault on
the pipeline.
• This allows real measurements to be seen
and recorded.

7. Positions of electrodes

8. The previous slide shows the
reaction current.
• It also shows the voltage between the
Cu/CuSO4 electrode immediately close to the
anode of a corrosion cell as specified in
DIN50918.
• This electrode is in a circuit that is embedded in
the circuit containing other electrical influences.
• The other electrode is in contact with the main
circuit in the same way as is found in corrosion
control field work.

9. Anode reaction potential.

10. DCVG 128.7 mv positive

11. 11.7 micro-amps corrosion current

12. All readings visible

13. Measurements at this point of time.
• Dry cell battery corrosion cell 1.3205
potential difference between the positive
and negative breadboard rails.
• DCVG potential difference between the
points of contact of the two Cu/CuSO4
electrodes.
• 11.6 micro amps passing between the
anode and the cathode of the Alexander
Cell (corrosion cell)

14. Complete circuits can be examined
• We can compare the circuits
on the Technotoy to the
equivalent circuits that we
experience in cathodic
protection field work.
• The DCVG measuring circuit is
separate from the cathodic
protection circuit and the
corrosion circuits of any
corrosion cells.
• DCVG is NOT measuring
corrosion or the pipeline
circuit.
• DCVG is measuring ground
potential variations.

15. Oscilloscope and logged voltages
• You can see in this
picture that the voltages
through the breadboard
at the black and the
yellow terminals are
being recorded on the
oscilloscope.
• You can also see the
voltages on the data
logged and presented in
graphic format at the
same time.

16. Note the electrode positions and
DCVG voltage

17. Cu/CuSO4 electrode on anode

18. DIN50918

19. Replication of DIN50918
• Note that contact with the
electrolyte/metal interface is
through a tooth pick that is
damp and conductive.
• This is the Luggin capillary and
does not disturb the corrosion
reaction.
• However, we cannot replicate
the closed circuit conditions
required with the return
electrode in contact with the
other circuits.
• This illustrates why we cannot
use Cu/CuSO4 electrodes as
reference potentials for the
purpose of our calculations.

20. DCVG is a voltage between two
electrodes.
• It can be seen in this
picture that the
slightest change of
position of either of
the electrodes causes
a change in the
recorded values.

21. Cu/CuSO4 electrode on cathode
• Moving one electrode from the
anode of the Alexander cell to
the cathode has changed the
DCVG voltage to 10.95 mv
• This is only possible to
measure if the electrode is
positioned at the interface and
cannot be measured in the
field.
• Some people try to say that we
can measure ‘anodic anodic’
‘cathodic cathodic’ but this is
nonsense with no scientific
foundation.

22. 3.6 micro-amps reaction current

23. DCVG 123.0 mv positive.

24. This series was without cathodic
protection.
• The next series will include measurements
with impressed current and switching.
• I would like to see any presentations or
written information from others who claim
that they invented DCVG.
• It is not sufficient to say that Mr X or Ms Y
invented it and has now died.

25. This is where I first used DCVG in
1974

26. Oscilloscope

27. Sample of data logger capability.

28. Circuit sketch.

29. Data acquisition.
• The DCVG measuring circuit is between two Cu/CuSO4
electrodes as in field work.
• The base of the Alexander Cell is in contact with remote
earth, but corrosion has not been activated by cleaning
the anode on top.
• The Alexander cell is connected to the pipeline and so
the current measurement is influenced by the whole
circuit, as in real life. The meter is set to micro-amps and
these are not logged.
• The Oscilloscope is connected to the whole circuit
through the breadboard.
• The left hand multimeter is not in logging mode and is
just displaying the breadboard voltages.

30. ‘Natural’ pipe-to-soil potentials.
• The measurements that we have recorded have not
been subject to impressed current or sacrificial anode
cathodic protection.
• The term ‘natural’ is sometimes used to describe this
status but the correct term is ‘as found’ because the
equilibrium between the structure and the electrolyte is
not natural as soon as the structure is constructed.
• Technotoy includes some of the influences that are in
play everywhere that cathodic protection systems are
designed, constructed and commissioned.
• We can now examine the effects of both impressed
current and sacrificial anode systems on the recorded
measurements.