-
Embrittlement of stainless steels
upon extended exposure to temperatures between 400 and 510C
(730 and 930F). This type of embrittlement is caused by fine,
chromium-rich precipitates that segregate at grain boundaries:
time at temperature directly influences the amount of segregation.
Grain-boundary segregation of the chromium-rich precipitates
increases strength and hardness, decreases ductility and
toughness, and changes corrosion resistance. This type of
embrittlement can be reversed by heating above the precipitation
range.
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elastic deformation
-
A
change in dimensions directly proportional to and in phase with
an increase or decrease in applied force.
-
elasticity
-
The
property of a material by virtue of which deformation caused by
stress disappears upon removal of the stress. A perfectly elastic
body completely recovers its original shape and dimensions after
release of stress.
-
elastic limit
-
The maximum
stress that a material is capable of sustaining without any
permanent strain (deformation) remaining upon complete release of
the stress.
-
elastomer
-
A natural or
synthetic polymer, which at room temperature can be stretched
repeatedly to at least twice its original length, and which after
removal of the tensile loud will immediately and forcibly return
to approximately its original length.
-
electrical conductivity
-
See
conductivity.
-
electrical isolation
-
The
condition of being electrically separated from other metallic
structures or the environment.
-
electrical resistivity
-
The
electrical resistance offered by a material to the flow of
current, times the cross-sectional area of current flow and per
unit length of current path; the reciprocal of the conductivity.
Also called resistivity or specific resistance.
-
electrochemical admittance
-
The inverse of electrochemical impedance.
-
electrochemical cell
-
An
electrochemical system consisting of an anode and a
cathode in metallic contact and immersed in an electrolyte.
(The anode and cathode may be different
metals or dissimilar areas on the same metal surface.)
-
electrochemical corrosion
-
Corrosion
that is accompanied by a flow of electrons between cathodic and
anodic areas on metallic surfaces.
-
electrochemical equivalent
-
The weight of an element or group of elements oxidized or reduced
at 100%, efficiency by the passage of a unit quantity of
electricity. Usually expressed as grams per coulomb (1 amp/s).
-
electrochemical impedance
-
The frequency-dependent complex-valued proportionality factor (SE/6i) between the applied potential or current and the
response signal. This factor is the total opposition (11 or Ill
cm-) of an electrochemical system to the passage of charge. The
value is related to the corrosion rate under certain
circumstances.
-
electrochemical potential
-
The
partial derivative of the total electrochemical free energy at a
constituent with respect to the number of moles of this
constituent where all factors are kept constant. It is analogous
to the chemical potential of a constituent except
that it includes the electric as well as chemical contributions
to the free energy. The potential of an electrode in an
electrolyte relative to a reference electrode measured
under open circuit conditions.
-
electrochemical series
-
Same
as electromotive force series.
-
electrode
-
(I) An
electronic conductor used to establish
electrical contact with an electrolytic
part of a circuit. (2) An electronic conductor in
contact with an ionic conductor.
-
electrode polarization
-
Change
of electrode potential with respect to a reference
value. Often the free corrosion potential is used as the
reference value. The change may be caused, for
example, by the application of an external
electrical current or by the addition
of on oxidant or reductant.
-
electrodeposition
-
The
deposition of a substance on
an electrode by passing electric current
through 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 solution or external
circuit. It represents the reversible work to move a unit charge
from the electrode surface through
the solution to the reference
electrode.
-
electrode reaction
-
Interfacial
reaction equivalent to a
transfer of charge between electronic and
ionic conductors. See also anodic reaction and
cathodic reaction.
-
electrogalvanizing
-
The electroplating of
zinc upon iron or steel.
-
electrokinetic potential
-
This
potential, sometimes called
zeta potential, is a potential difference in
the 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; that is, it 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.
-
electroless plating
-
A
process in which metal ions in
a dilute aqueous solution are plated out on a
substrate by means of autocatalytic
chemical reduction.
-
electrolysis
-
Production of
chemical changes of the electrolyte
by the passage of current through
an electrochemical cell.
-
electrolyte
-
( 1) A
chemical substance or mixture, usually
liquid, containing ions that migrate in
an electric field. (2) A chemical compound or
mixture of compounds which when
molten or in solution will
conduct an electric current.
-
electrolytic cell
-
An
assembly, consisting of a vessel,
electrodes, and an electrolyte, in which
electrolysis can be carried out.
-
electrolytic cleaning
-
A
process of removing soil, scale.
or corrosion products from a metal surface by subjecting it as
an electrode to an electric
current in an electrolytic bath; process of cleaning, degreasing, of a metal by making
it an electrode in a suitable bath.
-
electrolytic protection
-
See
cathodic protection.
-
electromotive force
-
Electrical
potential; voltage.
-
electromotive force series (emf
series)
-
A list of elements
arranged according to their standard
electrode potentials (Hydrogen electrode is a
reference point nd given the value zero), with "noble" metals such as
gold being positive and "active" metals
such as zinc being negative.
-
electron flow
-
A movement
of electrons in an external
circuit connecting an anode and cathode in a
corrosion cell; the current flow is
arbitrarily considered to be in an opposite
direction to the electron flow.
-
electroplating
-
Electrodepositing
a metal or alloy in an
adherent form on an object serving as a
cathode.
-
electropolishing
-
A
technique commonly used to prepare
metallographic specimens, in which a
high polish is produced by making the specimen the anode
in an electrolytic cell, where
preferential dissolution at high points smooths
the surface.
-
electrotinning
-
Electroplating tin on an object.
-
embrittlement
-
Loss of load carrying capacity of a metal or alloy;
The severe loss of ductility or
toughness or both, of a material, usually a
metal or alloy. Many forms of
embrittlement can lead to brittle
fracture. Many forms can occur
during thermal treatment or elevated-temperature service
(thermally induced embrittlement). Some of these forms of
embrittlement, which affect steels, include blue
brittleness, 885F (475C)
embrittlement, quench-age embrittlement, sigma-phase embrittlement, strain-age
embrittlement, temper embrittlement,
tempered martensite embrittlement, and thermal
embrittlement. In addition,
steels and other metals and alloys can be
embrittled by environmental conditions
(environmentally assisted embrittlement). The
forms of environmental embrittlement
include acid embrittlement,
caustic embrittlement, corrosion embrittlement, creep-rupture embrittlement,
hydrogen embrittlement, liquid metal
embrittlement, neutron embrittlement, solder
embrittlement, solid metal embrittlement, and
stress-corrosion cracking.
-
endurance limit
-
The
maximum stress that a material can withstand for an infinitely
large number of fatigue cycles; maximum cyclic stress level a metal can withstand
without fatigue failure. See also fatigue strength.
-
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 corrosion fatigue,
high-temperature hydrogen
attack, hydrogen blistering, hydrogen embrittlement, liquid
metal embrittlement, solid
metal embrittlement, stress-corrosion cracking, and sulfide stress cracking. The following terms have been used in the past in
connection with environmental
cracking, but are becoming
obsolete: caustic embrittlement,
delayed fracture, season cracking, static fatigue,
stepwise cracking, sulfide corrosion
cracking, and sulfide stress-corrosion cracking. See
also embrittlement.
-
environmentally assisted
embrittlement
-
See embrittlement.
-
epoxy
-
Resin formed by the
reaction of bisphenol and
epichlorohydrin.
-
equilibrium (reversible)
potential
-
The potential of
an electrode in an electrolytic solution when
the forward rate of a given reaction
is exactly equal to the
reverse rate. The equilibrium potential
can only be defined with respect to a
specific electrochemical reaction.
-
erosion
-
Destruction of
metals or other materials by
the abrasive action of moving fluids, usually
accelerated by the presence of solid
particles or matter in
suspension. When corrosion occurs simultaneously, the term erosion-corrosion
is often used.
-
erosion-corrosion
-
A
conjoint action involving corrosion
and erosion in the presence of a
moving corrosive fluid, leading to the accelerated
loss of material.
-
eutectic
-
(1) An
isothermal reversible reaction in
which a liquid solution is converted into two or
more intimately mixed solids on
cooling, the number of solids
formed being the same as the number
of components in the system. (2) An alloy having the composition indicated by the
eutectic point on an equilibrium
diagram. (3) An alloy
structure of intermixed solid constituents formed by a eutectic
reaction.
-
eutectoid
-
(1)
An isothermal reversible reaction in
which a solid solution is converted into two or
more intimately mixed solids on
cooling, the number of solids
formed being the same as the number
of components in the system. (2) An alloy having the composition indicated by the
eutectoid point on an equilibrium
diagram. (3) An alloy
structure of intermixed solid constituents formed by a eutectoid
reaction.
-
exchange current
-
When an
electrode reaches dynamic
equilibrium in a solution, the rate of
anodic dissolution balances the rate of cathodic
plating. The rate at which either positive or
negative charges are entering or leaving
the surface at this point is
known as the exchange current.
-
exchange current density
-
The
rate of charge transfer per
unit area when an electrode reaches dynamic equilibrium (at its
reversible potential) in a solution; that is, the rate of anodic
charge transfer (oxidation) balances
the rate of cathodic charge
transfer (reduction).
-
exfoliation
-
Corrosion that
proceeds laterally from the
sites of initiation along planes parallel to
the surface, generally at grain boundaries,
forming corrosion products that force
metal away from the body of
the material. giving rise to a
layered appearance.
-
external circuit
-
The
wires, connectors, measuring devices, current sources, etc. that
are used to bring about or
measure the desired electrical
conditions within the test cell. It is
this portion of the cell through which electrons
travel.
