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 4 of 18
COATING SYSTEM
The complete number and types
of coats applied to a substrate in
a predetermined order. (When
used in a broader sense, surface
preparation, pretreatments, dry
film thickness, and manner of
application are included.)
COLD LAP
(1) Discontinuity caused by
solidification of the meniscus of a
partially cast anode as a result of
interrupted flow of the casting
stream. The solidified meniscus
is covered with metal when the
flow resumes. Cold laps can
occur along the length of an
anode. (2) A protective film
consisting of one or more coats,
applied in a predetermined
order
by prescribed methods to an as-
specified dry film thickness,
including any reinforcing material
that may be specified.
COLD SHUT
Horizontal surface discontinuity
caused by solidification of a
portion of a meniscus during the
progressive filling of a mold,
which is later covered with more
solidifying metal as the molten
metal level rises. Cold shuts
generally occur at corners
remote from the point of pour.
COMMERCIAL BLAST
CLEANED SURFACE
A commercial blast cleaned
surface, when viewed without
magnification, shall be free of all
visible oil, grease, dust, dirt, mill
scale, rust, coating, oxides,
corrosion products, and other
foreign matter. Random staining
shall be limited to no more than
33 percent of each unit area
(approximately 58 cm
2
[9.0 in.
2
])
of surface and may consist of
light shadows, slight streaks, or
minor discolorations caused by
stains of rust, stains of mill scale,
or stains of previously applied
coating. [See NACE No.
3/SSPC-SP 6.]
CONCENTRATION CELL
An electrochemical cell, the
electromotive force of which is
caused by a difference in
concentration of some
component in the electrolyte.
(This difference leads to the
formation of discrete cathodic
and anodic regions.)
CONCENTRATION
POLARIZATION
That portion of polarization of a
cell produced by concentration
changes resulting from passage
of current though the electrolyte.
CONDUCTIVE COATING
(1) A coating that conducts
electricity. (2) An electrically
conductive, mastic-like material
used as an impressed current
anode on reinforced concrete
surfaces.
CONDUCTIVE
CONCRETE
A highly conductive cement-
based mixture containing coarse
and fine coke and other material
used as an impressed current
anode on reinforced concrete
surfaces.
CONDUCTIVITY
(1) A measure of the ability of a
material to conduct an electric
charge. It is the reciprocal of
resistivity. (2) The current
transferred across a material
(e.g., coating) per unit potential
gradient.
CONTACT CORROSION
[See Galvanic Corrosion. ]
CONTINUITY BOND
A connection, usually metallic,
that provides electrical continuity
between structures that can
conduct electricity.
CONTINUOUS ANODE
A single anode with no electrical
discontinuities.
CONVERSION COATING
[See Chemical Conversion
Coating .]
CORROSION
The deterioration of a material,
usually a metal, that results from
a reaction with its environment.
CORROSION FATIGUE
Fatigue-type cracking of metal
caused by repeated or fluctuating
stresses in a corrosive
environment characterized by
shorter life than would be
encountered as a result of either
the repeated or fluctuating stress
alone or the corrosive
environment alone.
CORROSION INHIBITOR
A chemical substance or
combination of substances that,
when present in the environment,
prevents or reduces corrosion.
CORROSION POTENTIAL
(E
corr
)
The potential of a corroding
surface in an electrolyte relative
to a reference electrode under
open-circuit conditions (also
known as
rest potential, open-
circuit potential , or freely
corroding potential ).