Nace CP 1, Course Manual

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Underground Corrosion Control 3:10
CP 1 – Cathodic Protection Tester Course Manual
©
NACE International, 2000
02/01/05
Applications of Galvanic Anode Systems
The following are among the conditions where galvanic anodes are used:
•
When a relatively small amount of current is required.
•
Usually restricted to lower resistivity electrolytes.
•
For local cathodic protection to provide current to a specific area on a
structure. Some operators install galvanic anodes at each location where
a leak is repaired rather than installing a complete cathodic protection
system. Such practices may be encountered on bare metal or very poorly
coated systems where complete cathodic protection may not be feasible
because of cost.
•
When additional current is needed at problem areas. Some structures
with overall impressed current cathodic protection systems may have
isolated points where additional current in relatively small amounts is
needed. These requirements can be met with galvanic anodes. Typical
applications include:
•
Poorly or incompletely coated buried valve installations
•
Shorted casings that cannot be cleared
•
Isolated sections where the coating has been badly damaged
•
Areas where electrical shielding impairs effective current distribution
from remotely located impressed current systems
•
In cases of cathodic interference, if the conditions are suitable, galvanic
anodes can be used at the discharge point on the foreign line to return
interfering current.
•
To provide protection to structures located near many other
underground metallic structures where conditions make it difficult to
install impressed current systems without creating stray current
interference problems. Galvanic anodes can be an economical choice for
a cathodic protection current source under such conditions.