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 6 of 18
DEZINCIFICATION
A corrosion phenomenon
resulting in the selective removal
of zinc from copper-zinc alloys.
(This phenomenon is one of the
more common forms of
dealloying.)
DIELECTRIC COATING
A coating that does not conduct
electricity.
DIELECTRIC SHIELD
An electrically nonconductive
material, such as a coating,
sheet or pipe, that is placed
between an anode and an
adjacent cathode, usually on the
cathode, to improve current
distribution in a cathodic
protection system.
DIFFERENTIAL
AERATION CELL
An electrochemical cell, the
electromotive force of which is
due to a difference in air
(oxygen) concentration at one
electrode as compared with that
at another electrode of the same
material.
DIFFUSION-LIMITED
CURRENT DENSITY
The current density that
corresponds to the maximum
transfer rate that a particular
species can sustain because of
the limitation of diffusion (often
referred to as
limiting current
density ).
DISBONDMENT
The loss of adhesion between a
coating and the substrate.
DISSIMILAR METALS
Different metals that could form
an anode-cathode relationship in
an electrolyte when connected by
a metallic path.
DOUBLE LAYER
The interface between an
electrode or a suspended particle
and an electrolyte created by
charge-charge interaction leading
to an alignment of oppositely
charged ions at the surface of the
electrode or particle. The
simplest model is represented by
a parallel plate condenser.
DOUBLER PLATE
An additional plate or thickness
of steel used to provide extra
strength at the point of anode
attachment to an offshore
platform.
DRAINAGE
Conduction of electric current
from an underground or
submerged metallic structure by
means of a metallic conductor.
DRIVING POTENTIAL
Difference in potential between
the anode and the steel
structure.
DRYING OIL
An oil capable of conversion from
a liquid to a solid by slow
reaction with oxygen in the air.
E
ELASTIC DEFORMATION
Changes of dimensions of a
material upon the application of a
stress within the elastic range.
Following the release of an
elastic stress, the material
returns to its original dimensions
without any permanent
deformation.
ELASTIC LIMIT
The maximum stress to which a
material may be subjected
without retention of any
permanent deformation after the
stress is removed.
ELASTICITY
The property of a material that
allows it to recover its original
dimensions following deformation
by a stress below its elastic limit.
ELECTRICAL
INTERFERENCE
Any electrical disturbance on a
metallic structure in contact with
an electrolyte caused by stray
current(s).
ELECTRICAL ISOLATION
The condition of being electrically
separated from other metallic
structures or the environment.
ELECTRO-OSMOSIS
The migration of water through a
semipermeable membrane as a
result of a potential difference
caused by the flow of electric
charge through the membrane.
ELECTROCHEMICAL
CELL
A system consisting of an anode
and a cathode immersed in an
electrolyte so as to create an
electrical circuit. The anode and
cathode may be different metals
or dissimilar areas on the same
metal surface.
ELECTROCHEMICAL
EQUIVALENT
The mass of an element or group
of elements oxidized or reduced
at 100% efficiency by the
passage of a unit quantity of
electricity.