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Corrosion Glossary - E
- Earth pigments: pigments used in paints
and obtained from the earth, including barytes, ocher, chalk and graphite
- Economic life: the total length of time
that an asset is expected to remain actively in service before it is expected
that it would be cheaper to replace the equipment rather than continuing to
maintain it. In practice, equipment is more often replaced for other reasons,
including because it no longer meets operational requirements for efficiency,
product quality, comfort etc., or because newer equipment can provide the same
quality and quantity of output more efficiently.
- Economizer: utilizes waste heat by transferring
heat from flue gases to warm incoming feedwater.
- Effluent: the stream emerging from a
unit, system or process, such as the softened water from an ion exchange softener.
- Elasticity: the property of certain
materials that enables them to return to their original dimensions after an
- Electrical steel: steel that includes
silicon. The silicon content allows the steel to minimize energy loss during
- Electric-arc furnace: an economical
method of steelmaking that is energized by an electric arc flowing between two
bottom electrodes. Furnace charges consist of purchased scrap.
- Electrochemical admittance: the reciprocal
of the electrochemical impedance, I/E.
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).
impedance spectroscopy (EIS): the frequency dependent, complex
valued proportionality factor, E/I, between the applied potential (or
current) and the response current (or potential) in an electrochemical cell.
This factor becomes the impedance when the perturbation and response are related
linearly (the factor value is independent of the perturbation magnitude) and
the response is caused only by the perturbation). The value may be related to
the corrosion rate when the measurement is made at the corrosion potential.
- Electrochemical potential (electrochemical tension):
the partial derivative of the total electrochemical free energy of the system
with respect to the number of moles of the constituent in a solution when all
other factors are constant. (Analogous to the chemical potential of the constituent
except that it includes the electrical as well as the chemical contributions
to the free energy).
- 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
- Electrodialysis: a process in which
a direct current is applied to a cell to draw charged ions through ion selective
semipermeable membranes, thus removing the ions from the solution.
nickel: the autocatalytic deposition of nickel/phosphorous and
nickel/boron have many useful corrosion and corrosion wear applications. Unlike
the electrolytic processes,
they produce a deposit with completely uniform coverage. In the case of Ni P,
deposits around 25 to 50 microns thick with a hardness of about 500Hv is obtained,
but thermal ageing at temperatures around 400°C can develop hardness values
in excess of 1000Hv.
- Electrolysis: production of chemical
changes of the electrolyte by the passage of current through an electrochemical
cell. (historical) 'Stray current corrosion'
- Electrolyte: a nonmetallic substance
that carries an electric current, or a substance which, when dissolved in water,
separates into ions which can carry an electric current.
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.
- Electromotive force series (emf series):
a list of elements arranged according to their standard electrode potentials,
with "noble" metals such as gold being positive and "active" metals such as
zinc being negative.
- Electron: a fundamental particle found
in the atom that carries a single negative charge.
- Electron volt: unit equal to the energy
of one electron moving through a potential difference of one volt.
- Electrophorus (historical): a
hand-held electrophorus can produce significant amounts of charge conveniently
and repeatedly. It is operated by first frictionally charging a flat insulating
plate called a "cake". In Volta's day, the cake was made of shellac/resin
mixtures or a carnauba wax film deposited on glass.
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 smooth the surface.
- Electrostatic precipitator: a device
for collecting dust, mist or fume from a gas stream, by placing an electrical
charge on the particle and removing that particle onto a collecting electrode.
- Electrostatic spraying: a deposition
method of spraying and charging a coating so that it is deposited on a substrate
usually grounded. A spray application process in which the coating and part
to be coated are oppositely charged; process provides excellent "wrap" of coating
around the part, even on sides opposite the spray gun. (See Corona Charge and
- Element, chemical: atom that has a unique
number of protons in its nucleus. Oxygen is an element with eight protons in
the nucleus. There are more than 100 elemental substances that cannot be chemically
separated into other elements. All matter is composed of one or more chemical
elements. As of 1988, 105 of 109 known elements have been assigned a name.
- Elution: the stripping of ions from
an ion exchange material by other ions, either because of greater affinity or
because of much higher concentration.
the severe loss of ductility or toughness or both, of a material, usually a
- Emulsion: a mixture of solids suspended
in a liquid.
- Emulsion paint:
coating in which resins are
suspended in water, then flow together with the aid of an emulsifier. Example:
- Enamel: broad classification of
paints that dry to a hard, usually
glossy finish. Most equipment-coating enamels require baking. Enamels for walls
- Endpoint: the point at which a process
is stopped because a predetermined value of a measurable variable is reached.
- 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.
- Energy conversion: process of changing
one form of energy into another.
- Environmental consequences: a failure
has environmental consequences if it could cause a breach of any known environmental
standard or regulation.
- 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,
liquid metal embrittlement, solid metal embrittlement,
stress-corrosion cracking, and sulfide stress
- Environmental Protection Agency (EPA):
established on December 2, 1970, the EPA is charged with protecting and enhancing
the environment for present and future generations to the fullest extent possible
under US Congressional law with responsibilities including the control of solid
waste, pesticides, radiation, and toxic substances, and the abatement of air
and water pollution.
extremely tough and durable synthetic resin used in some coatings. Epoxy
coatings are extremely tough,
durable and highly resistant to chemicals, abrasion, moisture and alcohol.
- Equilibrium: the state in which the
action of multiple forces produce a stead balance.
- 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).
- Equilibrium reaction: a chemical reaction
which proceeds primarily in one direction until the concentrations of reactants
and products reach an equilibrium.
- Equivalent weight: the weight in grams
of an element, compound or ion which would react with or replace 1 gram of hydrogen;
the molecular weight in grams divided by the valence.
- Erosion: the progressive loss of material
from a solid surface due to mechanical interaction between that surface and
a fluid, a multi-component fluid, or solid particles carried with the fluid.
a conjoint action involving corrosion and erosion in the presence of a moving
corrosive fluid. Leading to the accelerated loss of material.
- Estimated plant replacement value: the
estimated cost of capital works required to replace all the existing assets
with new assets capable of producing the same quantity and quality of output.
This is a key value often used in benchmarking activities.
- Etch: a roughened surface produced by
chemical, electrochemical or mechanical means. To dissolve unevenly a part of
the surface of a material to highlight microstructure in metallography.
- Etching: the use of a chemical solution
or primer to prepare a surface for priming or bonding by removing a layer of
the base metal (e.g. Alodine).
- Ettringite: A naturally occurring mineral
characterized as a high sulfate calcium sulfoaluminate ( 3 CaO . Al3O3
. 3 CaSO4 . 30-32 H2O ). It is formed as a cement hydration
product or by sulfate attack in mortar and concrete. It is also the product
of the principal expansion-producing reaction in expansive cements. Was designated
as "cement bacillus" in older literature.
- Evaporation: the change of state from
a liquid to a vapor.
- Evaporation rate: the quantity of
water of any other
liquid that is evaporated in a unit of time.
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).
- Exempt solvents: solvents whose use
is not subject to air pollution legislation.
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.
- Exothermic reaction or material: certain
materials undergo chemical reactions when
thermally sprayed and produce extra
heating. This can be useful in improving adhesion of the coating to the substrate.
- Expansion joint: The joint to permit
movement due to expansion without undue stress.
- Expert System: a knowledge based system
which makes or evaluates decisions based on rules established within the software.
ingredients added to
paint to increase coverage,
reduce cost, achieve durability, alter appearance, control rheology and influence
other desirable properties. Less expensive than prime hiding pigments such as
titanium dioxide. Examples: barium sulfate, calcium carbonate, clay, gypsum,
- 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.