Nace CP 1, Course Manual

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CHAPTER 9
Troubleshooting
CP 1 – Cathodic Protection Tester Course Manual
©
NACE International, 2000
07/01/04
Introduction
In this course we have been teaching you various techniques used to
monitor cathodic protection. As previously discussed, monitoring is
essential to ensure the continued proper performance of cathodic protection.
From time to time you will encounter problems with the cathodic protection
you are monitoring. Many of these problems can be solved by some basic
troubleshooting techniques when structure-to-electrolyte potential
measurements indicate inadequate protection or when some other
malfunction occurs.
Electrical Isolation
General
A single metallic contact (called a “short circuit” or “short”) can destroy the
effectiveness of an entire cathodic protection system. The entire structure
that is accidentally shorted to the protected facility becomes part of the
system to be protected. The severity of the problem depends on the position
and surface area of the shorting structure. Cathodic protection is achieved
only if current passes from the electrolyte to the metal. If all the current
passes from the shorting structure to the protected structure by the short, no
cathodic protection is achieved on the protected structure. This is illustrated
in Figure 9.1.