Cathodic Protection Training Course

PRACTICAL

Two experiments that demonstrate detectable corrosion activity.

First Experiment.

You require the use of a digital voltmeter with an impedance of at least 10 mega-ohms per volt.



You require two 'dead' dry cell batteries and a new dry cell battery.


You can either make or buy suitable arrangements to hold the dry cells in series or in parallel for these experiments.







1. Label each dry cell.

2. Measure the voltage of each dry cell and record.





3. Combine each pair of dry cells in series and in parallel and record the voltages of each pair.

4. Combine all three dry cells in series and record the combined voltage.

5. Combine all three dry cells in parallel and record the voltage.



Write a report about the above experiment explaining the readings that you obtained in terms of the corrosion reactions that are causing the voltages.




Second Experiment

You will require a plastic tray of damp sand or mud and a mild steel rod about 100 to 150 mms in length. (A large nail will suffice.)



1. Clean ONE END of the rod with abrasive material such as emmery cloth or sandpaper.


2. Lay the rod (nail) on the surface of the damp sand in the tray.


3. Clean both probes on the end of the conductor leads attached to each pole of the voltmeter.


4. Switch the volmeter range to Direct Current Voltage, at the lowest value of complete volts.




5. Place one probe in the sand 5mm from the cleaned end of the steel rod.


6. Place the other probe in the sand 5mm from the other end of the steel rod.


7. Note the reading on the meter.


8. Move one probe in steps of 5mm away from the steel rod, noting the voltages shown on the meter.






9. Make a diagram of the tray showing the steps and position of the rod.


10. Plot the voltages and distances and produce a graph of the values.


11. Report on the experiment and your conclusions.




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