Nace CP 1, Course Manual

Page: 453 / 535

RP0290-2000
NACE International 11
Electrical Isolation: The condition of being electrically
separated from other metallic structures or the environment.
Electrode Potential: The potential of an electrode in an
electrolyte as measured against a reference electrode. (The
electrode potential does not include any resistance losses in
potential in either the electrolyte or the external circuit. It
represents the reversible work to move a unit of charge
from the electrode surface through the electrolyte to the
reference electrode.)
Energizing: The process of initially applying power to turn
on an impressed current cathodic protection system.
Immediate Voltage Shift: The difference between the
potential value when the power source is on and the instant-
off value. (This is also referred to as IR Drop.)
Instant Off Potential: The polarized potential of an
electrode with respect to a reference electrode taken
immediately after the impressed current flow is stopped
(closely approximates the IR-free value when there was
current flow).
Overlay: A layer of concrete or mortar placed over and
usually bonded onto the worn or cracked surface of a
concrete slab to restore or improve the function of the
previous surface.
Polarization: The change from the open-circuit potential as
a result of current across the electrode/electrolyte interface.
Polarization Decay: The decrease in electrode potential
with time resulting from the interruption of applied current.
Potential Survey: Obtaining potentials with respect to a
reference electrode at multiple locations on the surface of
the concrete structure.
Prestressed Concrete: Concrete in which internal
stresses of such magnitude and distribution are introduced
that the tensile stresses resulting from the service loads are
counteracted to a desired degree; in reinforced concrete the
prestress is commonly introduced by tensioning the
tendons.
Rectifier: An electrical device for converting alternating
current to direct current.
Reference Electrode: An electrode whose open-circuit
potential is constant under similar conditions of
measurement, which is used for measuring the relative
potentials of other electrodes.
Step-and-Touch Potentials: The electrical potential
gradients that may exist between two points on the
electrolyte surface equal to one pace (one meter) or
between a grounded metallic object and a point on the
electrolyte surface separated by the distance equal to a
human’s normal reach (one meter).
Stray Current: Current through paths other than the
intended circuit.
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Appendix B—Additional Information Useful for Design
1. Site-related:
a. Location
b. Climate
c. Exposure
d. Use
e. Access
f. Environmental factors
g. Chloride source
h. Possible stray current sources
2. Structure-related:
a. Use restrictions
b. Design load
c. Construction dates
d. Repair details and history
e. Concrete design properties
f. Reinforcing details
g. Other embedments
h. Overlays, sealers, membranes
i. Chloride test and chemical analysis
j. Chloride source
k. Potential survey
l. Delamination survey
m. Cover survey
n. Continuity of embedded metal
o. Existing cathodic protection
p. Electrical isolation from foreign structures
q. Location and details of joints
r. Location and details of drains and scuppers and
drainage conditions
s.
Location and details of railings
t. Location of lighting, conduits, and pipes
u. Prestressed elements
v. Sulfates
w. Carbon dioxide
x. pH
y. Resistivity
3. System-related:
a. Circuit resistances
b. Power supply rating and location
c. Current distribution
d. Anode current densities
e. Instrumentation for monitoring
f. Physical, electrical, and environmental protection
of components
g.
Maintenance interval
h. Materials
i. Equipment