Nace CP 1, Course Manual

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Monitoring Cathodic Protection Effectiveness and Recordkeeping 7:3
CP 1 – Cathodic Protection Tester Course Manual
©
NACE International, 2000
07/01/04
potential survey has been conducted, however, other indirect measurements
can be used to monitor a system before the next potential survey. For
example, measuring current output of a rectifier does not provide any
information about the protection level of a system. If an annual corrosion
survey indicated that a well coated structure was adequately protected with
10 amps and after the survey the structure became electrically shorted to
some large bare structure, would measuring 10 amps at the rectifier still
represent adequate protection on the structure of interest? The answer is
probably no. The only way current output can be used, as a measure of
cathodic protection is if the system has remained unchanged since the
potential survey was conducted. Therefore, all other measurements and
tests that are done between potential surveys are based on the assumption
that everything is the same as during the potential survey.
Other procedures for monitoring the effectiveness of cathodic protection,
which may be conducted at specified intervals or as appropriate, include:
•
Coupon test stations
•
Electric resistance probe test stations
•
Structure examination by excavation or divers
•
Close interval potential surveys