Cathodic Protection Study 1
A laboratory technique which cannot be applied in field work has resulted in a long term misunderstanding between cathodic protection theory and practice. This technique concerns the measurment of electrical voltage and this particular value is used as the basis of all cathodic protection calculations. This causes errors in orders of magnitude.
Many of today's pipeline leaks are caused by problems between cathodic protection theory
and practice. Improved technology can dramatically reduce pipeline repair and replacement, spillage clear-up,
environmental claims etc.
A small, but very significant, mistake was made in the early years of cathodic protection
and this has influenced all work since. A laboratory measurement was applied in field
work but the critical configuration, that is necessary to ensure accuracy, was overlooked.
A detailed description of the laboratory technique is to be found on this website and field
experiments are detailed in the on-line cathodic protection course.
The picture below illustrates the traditional method of recording and analysing cathodic protection readings
which have been taken using Procedure 1, as defined on this website.
The Spreadsheet from which this picture was taken will be sent to members as an attachment to email
The industry has now recognised that an error exists (refered to as 'the error caused by the IR Drop in the soil.')
but the issue is still not widely understood, with the result that up to 90% of cathodic protection activities are unproductive,
and many expensive contracts are a total waste of money as the information they provide is subject
to errors as high as 200 or 300% of the true value.
The traditional voltage measurement includes an unknown number of undefined variables and consequently the
problem is like trying to evaluate B from the information
A=1 and A+B+C+D = 5.
It simply cannot be done, yet many cathodic protection activities are based entirely on such readings.
These pages show that 'Instant Off' readings and CIPS techniques do not remove the IR drop in the soil
and experiments included in the on-line cathodic protection course make this irrefutable.
These pages demonstrate how the errors occur, and gives a clear explanation of the readings
on which the whole industry is based. They show that all cathodic protection can be
described in simple terms, supported by the basic laws of electricity.
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