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 7 of 18
ELECTROCHEMICAL
POTENTIAL
The partial derivative of the total
electrochemical free energy of a
constituent with respect to the
number of moles of this
constituent where all other
factors are kept constant. It is
analogous to the chemical
potential of a constituent except
that it includes the electrical as
well as chemical contributions to
the free energy.
ELECTRODE
A conductor used to establish
contact with an electrolyte and
through which current is
transferred to or from an
electrolyte.
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.)
ELECTROKINETIC
POTENTIAL
A potential difference in a
solution caused by residual,
unbalanced charge distribution in
the adjoining solution, producing
a double layer. The
electrokinetic potential is different
from the electrode potential in
that it occurs exclusively in the
solution phase. This potential
represents the reversible work
necessary to bring a unit charge
from infinity in the solution up to
the interface in question but not
through the interface (also known
as zeta potential ).
ELECTROLYTE
A chemical substance containing
ions that migrate in an electric
field.
ELECTROLYTIC
CLEANING
A process for removing soil,
scale, or corrosion products from
a metal surface by subjecting the
metal as an electrode to an
electric current in an electrolytic
bath.
ELECTROMOTIVE FORCE
SERIES
A list of elements arranged
according to their standard
electrode potentials, the sign
being positive for elements
whose potentials are cathodic to
hydrogen and negative for those
anodic to hydrogen.
ELLIPSOMETRY
An optical analytical technique
employing plane-polarized light
to study films.
EMBRITTLEMENT
Loss of ductility of a material
resulting from a chemical or
physical change.
EMF SERIES
[See Electromotive Force
Series.]
ENAMEL
(1) A paint that dries to a hard,
glossy surface. (2) A coating that
is characterized by an ability to
form a smooth, durable film.
END EFFECT
The more rapid loss of anode
material at the end of an anode,
compared with other surfaces of
the anode, resulting from higher
current density.
ENDURANCE LIMIT
The maximum stress that a
material can withstand for an
infinitely large number of fatigue
cycles.
ENVIRONMENT
The surroundings or conditions
(physical, chemical, mechanical)
in which a material exists.
ENVIRONMENTAL
CRACKING
Brittle fracture of a normally
ductile material in which the
corrosive effect of the
environment is a causative
factor.
Environmental cracking is a
general term that includes all of
the terms listed below. The
definitions of these terms are
listed elsewhere in the
Glossary:
Corrosion Fatigue
Hydrogen Embrittlement
Hydrogen-Induced Cracking
⎯
(Stepwise Cracking)
Hydrogen Stress Cracking
Liquid Metal Cracking
Stress Corrosion Cracking
Sulfide Stress Cracking
The following terms have been
used in the past in connection
with environmental cracking but
are now obsolete and should not
be used:
Caustic Embrittlement
Delayed Cracking
Liquid Metal Embrittlement
Season Cracking
Static Fatigue
Sulfide Corrosion Cracking
Sulfide Stress Corrosion
Cracking