TM 5-811-7
of steel reinforced concrete because galvanic corro-
when this is not clear, the criterion used most
sion will occur between the steel rebar and the
widely is based on current density required and soil
pipeline.
resistivity. If the soil resistivity is low (less than
5000 ohm-centimeters) and the current density
requirement is low (less than 1 milliampere per
2-2
Determining type and design of cathodic
square foot), a galvanic system can be used. How-
protection system.
ever, if the soil resistivity and/or current density
When all preliminary data have been gathered and
requirement exceed the above values, an impressed
the protective current has been estimated, the
current system should be used. Figure 2-1 will be
design sequence can begin. The first question to
used in the design sequence. Design sequences for
ask is: which type (galvanic or impressed current)
each type of cathodic protection system are given
cathodic protection system is needed? Conditions
in paragraphs a and b below.
at the site sometimes dictate the choice. However,
2-3
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