Nace CP 1, Course Manual

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NACE GLOSSARY OF CORROSION-RELATED TERMS
©
2002, NACE International. This publication may not be reprinted without the written consent of NACE International.
Page 5 of 18
CORROSION RATE
The rate at which corrosion
proceeds.
CORROSION
RESISTANCE
Ability of a material, usually a
metal, to withstand corrosion in a
given system.
CORROSIVENESS
The tendency of an environment
to cause corrosion.
COUNTER ELECTRODE
[See Auxiliary Electrode. ]
COUNTERPOISE
A conductor or system of
conductors arranged beneath a
power line, located on, above, or
most frequently, below the
surface of the earth and
connected to the footings of the
towers or poles supporting the
power line.
COUPLE
[See Galvanic Couple. ]
CRACKING (OF
COATING)
Breaks in a coating that extend
through to the substrate.
CRAZING
A network of checks or cracks
appearing on the surface of a
coating.
CREEP
Time-dependent strain occurring
under stress.
CREVICE CORROSION
Localized corrosion of a metal
surface at, or immediately
adjacent to, an area that is
shielded from full exposure to the
environment because of close
proximity of the metal to the
surface of another material.
CRITICAL HUMIDITY
The relative humidity above
which the atmospheric corrosion
rate of some metals increases
sharply.
CRITICAL PITTING
POTENTIAL (E
p
, E
pp
)
The lowest value of oxidizing
potential (voltage) at which pits
nucleate and grow. The value
depends on the test method
used.
CURING
Chemical process of developing
the intended properties of a
coating or other material (e.g.,
resin) over a period of time.
CURING AGENT
A chemical substance used for
curing a coating or other material
(e.g., resin). [Also referred to as
Hardener .]
CURRENT
(1) A flow of electric charge. (2)
The amount of electric charge
flowing past a specified circuit
point per unit time, measured in
the direction of net transport of
positive charges. (In a metallic
conductor, this is the opposite
direction of the electron flow.)
CURRENT DENSITY
The current to or from a unit area
of an electrode surface.
CURRENT EFFICIENCY
The ratio of the electrochemical
equivalent current density for a
specific reaction to the total
applied current density.
D
DC DECOUPLING DEVICE
A device used in electrical
circuits that allows the flow of
alternating current (AC) in both
directions and stops or
substantially reduces the flow of
direct current (DC).
DEALLOYING
The selective corrosion of one or
more components of a solid
solution alloy (also known as
parting or selective dissolution ).
DECOMPOSITION
POTENTIAL
The potential (voltage) on a
metal surface necessary to
decompose the electrolyte of an
electrochemical cell or a
component thereof.
DECOMPOSITION
VOLTAGE
[See Decomposition Potential. ]
DEEP GROUNDBED
One or more anodes installed
vertically at a nominal depth of
15 m (50 ft) or more below the
earth's surface in a drilled hole
for the purpose of supplying
cathodic protection.
DEPOLARIZATION
The removal of factors resisting
the current in an electrochemical
cell.
DEPOSIT ATTACK
Corrosion occurring under or
around a discontinuous deposit
on a metallic surface (also known
as
poultice corrosion ).