Cathodic Protection Network Technotoy

The project is to combine corrosion data with computer

analysis.

Corrosion

Field data

Electronic measurements

Modelling cathodic protection

A battery is a corrosion cell

• We must start by measuring the corrosion reaction.

• We must use all available measuring techniques that can be applied in field work.

• We make measurements every day relating to batteries.

• But we make up different rules for measuring corrosion on pipelines.

We must use electronic instruments to measure corrosion.

• Technotoy is many instruments, electronic components, batteries, experimental models and real corrosion cells.

• A cathodic protection system is instruments, electronic components, real buried conductors and corrosion cells.

• A computer is an arrangement of switches that can be programmed to display the results of calculations based on the laws of nature.

• A spread sheet and a breadboard can be used to create a circuit/virtual circuit similar to that defined by the data that is gathered in field work.

Technotoy 8

Technotoy1 XLS functioning replica of the breadboard.

We can now use Technotoy to measure a corrosion reaction

• It can be seen that the corrosion reaction in this battery is now less than the manufactured level.

• The voltage shown in the previous picture is from a fully charged battery.

• The loss of EMF is due to the depletion of chemical reactants and the resistance of the corrosion products contained in the battery case.

IR drop in the battery

Cathodic protection ‘IR Drop in the soil’

The voltage drop

IR free measurement

DIN50918

DIN50918• In a closed circuit laboratory experiment it is possible to measure

the amount of charges resulting from the corrosion reaction.• The measuring circuit is composed of metal conductors and

contained chemicals that conduct electricity.• The displays are created electronically and there is no natural zero

as Gibbs Free Energy has proved.• Meters are designed to compare the electrical potential between the

input sockets. One of these sockets is regarded as common and the other is positive.

• This is important to replicate and make clear throughout this project as a computer requires a zero.

• DIN50918 is one way of establishing a zero potential for the purposes of studying corrosion but this zero is confined to each measuring circuit and cannot be transported. The universe does not have any zero potential.

DIN50918 anode

Anode = working electrode

• The working electrode is where the energy is released into the electrolyte creating an Electro Motive Force (EMF) that can be measured as an electrical potential in relation to another electrical potential.

• DIN50918 and the Daniell Cell are laboratory techniques to create measuring circuits that render repeated results on which scientific calculations can be made.

Daniell’s Cell

‘Open circuit measurements’• Neither of these two measuring methods would

work if their circuits were connected to outside influences by conduction.

• A ‘half-cell reaction’ is not a physical entity that can be separated from the whole cell.

• A piece of copper in a saturated solution of copper sulphate may be called a ‘half-cell’ as an item that can be sold but it can only be used as a reference potential in closed circuit condition.

• Our project will demonstrate measurements conforming to science.

CIPS measuring circuit.

CIPS measuring circuit

We can now try this on Technotoy.

• We can try to measure one corrosion cell that is in series with other corrosion cells.

• This is a pack of 8 batteries and we need to know the voltage available in one of them.

• It is clear that we cannot calculate this value from the measurement we are able to obtain.

CIPS voltage measurements.

CIPS analysis

Technotoy can model this.

CPN Dynamic Software can model this

Charges from power supply to remote earth.

One form of measurement

Resulting graph of ground potentials.

Charges pass from high potential to lower potential

The path of the charges is determined by resistance

The total groundbed resistance determines the current.

We can measure the output current but not the ground resistances

We must build in variable resistances.

The Technotoy in action

Technotoy 8 batteries

Define the actual measuring circuit.

• 8 corrosion cells in series, the batteries.• Conductors from both ends of the series.• Black conductor to black lower rail of

breadboard.• Red conductor to red lower rail of breadboard.• Conductors to green and blue metering posts.• Meter leads to common and active channels of

oscilloscope and 3 meters.

For this measuring structure common is zero.

• The meters are manufactured to see common as zero and in these pictures the oscilloscope has not been calibrated as there is no wave form.

• The breadboard is manufactured in the same configuration as the spreadsheet that I have designed.

• Formula will be entered into each cell to define the connections to which each cell has a ‘jump lead’.

• The display on each meter will then be the ‘goal seek’ for the values in each part of the circuit to which they are connected.

Set zero on Excel

Cells relate to other cells

• We can describe the jumper connections to the computer using formula.

• We can describe the electronic resistances in the circuit by the formula of Ohms Law between cells on the spreadsheet.

• The spreadsheet can then display the balance of electrical potentials over the whole of Technotoy.

We can then display this balance on a computer screen.

And zoom in to see the values and calculations.

The two displays.• The first is a spread sheet with schematic

overlay of many oilfields.• The next is zoomed in to part of that

spreadsheet to a single oilfield and includes flowlines, delivery lines, manifolds and facilities.

• I created this spreadsheet in the early 1990’s using real data but it is limited in the information that could be gathered at that time.

• The software that I am developing now will be able to calculate where electrical charges are leaving the metal conductors and entering the ground.

We need a corrosion cell.

• For the breadboard we can us batteries as they are each a corrosion cell.

• When we couple the breadboard with Orac we can embed the Alexander Cell as this allows us to make potential measurements at the interface specified in DIN50918.

• The Oscilloscope has a pH probe that can be included for the purposes of the Pourbaix diagrams.

Rechargeable battery

• We can use a rechargeable battery in our experiments but it must be remembered that tat this has a reversible reaction whereas corrosion cells on pipelines do not.

Corrosion cell.

Faraday, charges = metal loss

Equilibrium without current flowing

CP balances equilibrium

• No current flowing in a corrosion cell means no corrosion.

• We cannot measure this on a pipeline as we cannot separate the anode from the cathode metallic path.

• I we use a battery we are introducing other metals and electrolytes into the measuring circuit.

Technotoy ready• This will all be made into

a single portable instrument to fit into a survey vest pocket.

• A solar panel on the hat will top up the batteries.

• The probes will be on the ‘walking sticks’ and the display mounted with the trailing conductor.

The measuring circuits.

The breadboard

The corrosion cells

The data logger

• The data logger is the centre meter connected via TS232c to the lower panel of the computer display

The oscilloscope• The oscilloscope is the

blue item on the white backboard that is connected by USB to the computer and displayed on the top panel.

• The scope probe connection is available to connect anywhere in the measuring circuitry

The computer is connected to the internet to transfer data.

The voltages that are presently measured.

• In order to relate this project to historical data we must model the actual measuring circuit of the ‘pipe-to-soil potential measurement.

• We need to examine the item known as a ‘half-cell’ that is sometimes called a reference electrode.

What is a ‘half-cell’

• It is copper in a saturated solution of copper-sulphate.

• Copper sulphate crystals result from copper being dissolved in sulphuric acid until the acid can dissolve no more.

• At this stage the reaction has stabilised with no electrical current flowing, no energy transfer.

Copper, copper-sulphate.

Pipe-to-soil enabled.

The half-cell in a circuit

• When a copper/copper-sulphate electrode is included in a circuit the energy flow can be measured.

• The energy created by the other half of the cell is compared to the energy created by the copper in the solution of copper-sulphate.

• During this energy flow the Cu/CuSO4 electrode is subject to the charge transfer.

Science• This is one page of many

written by my partner during an investigation and report into corrosion noise.

• This section of the report examines the function of the reference electrode in corrosion reaction measurements.

• These pages are part of my own intellectual property.

What happens on contact?

• This takes 25 pages of scientific notation that can be summed up as the whole measuring circuit instantly reaches equilibrium with no current flowing.

• This is in a closed circuit condition in a laboratory where each influence can be controlled.

• This examines the reaction within a single corrosion cell.

Our project is to examine field data

• Our physical model makes it possible to measure individual corrosion cells in closed circuit conditions and embed each into a combined circuit measuring many corrosion cells in parallel and in series.

• This must be done in definable and measurable steps.