A to Z listing
Search this site
Corrosion Glossary - F
- Fail-safe: pertaining to a system or
component that automatically places itself in a safe operating mode in the event
of a failure.
- Failure: an item of equipment has suffered
a failure when it is no longer capable of fulfilling one or more of its intended
functions. Note that an item does not need to be completely unable to function
to have suffered a failure.
- Failure analysis: the systematic investigation
of a component failure with the objectives of determining why the component
failed and the corrective actions needed to prevent future failures.
- Failure mode: the basic material behavior
that resulted in the failure. Examples of failure mode include: ductile fracture,
brittle fracture, fatigue fracture, corrosion, erosion, wear, and distortion.
- Failure Modes and Effects Analysis (FMEA):
a structured method of determining equipment functions, functional failures,
assessing the causes of failures and their failure effects. The first part of
a Reliability Centered Maintenance analysis is a Failure Modes and Effects Analysis.
- Failure Modes, Effects and Criticality Analysis
(FMECA): a structured method of assessing the causes of failures
and their effect on production, safety, cost, quality etc.
shield (cage): a network of parallel wires connected to a common
conductor at one end to provide electrostatic shielding without affecting electromagnetic
waves. The common conductor is usually grounded.
- Fast reactor: nuclear reactor that employs
fast (high speed) neutrons to sustain the fission process. Such reactors require
the coolant to be a heavy liquid metal (such as sodium) or a gas (such as helium)
to prevent the energetic neutrons generated during the fission process from
being slowed down.
- Fatigue: a cumulative effect causing
a material to fail after repeated applications of stress none of which exceeds
the ultimate tensile strength. The fatigue strength (or fatigue limits) is the
stress that will cause failure after specified number cycles.
- Fatigue strength: the maximum stress
that can be sustained for a specified number of cycles without failure, the
stress being completely reversed within each cycle unless otherwise staled.
- Fatigue wear: wear of a solid surface
caused by fracture arising from material fatigue.
- Feed pump: a pump that supplies water
to a boiler.
- Feedwater: water introduced into a boiler
during operation. it includes make-up and return condensate.
- Feedwater treatment: the treatment of
boiler feed water by the addition of chemicals to prevent the formation of scale
or to eliminate other objectionable characteristics.
- Ferrite: a solid solution of one or
more elements in body-centered cubic iron. unless otherwise designated (for
instance, as chromium ferrite), the solute is generally assumed to be carbon.
On some equilibrium diagrams, there are two ferrite regions separated by an
austenite area. The lower area is alpha ferrite; the upper, delta ferrite. If
there is no designation, alpha ferrite is assumed.
- Ferritic: pertaining to the body-centered
cubic crystal structure (bcc) of many ferrous (iron-base)
- Ferrography: an analytical method of
assessing machine health by quantifying and examining ferrous wear particles
suspended in the lubricant or hydraulic fluid.
- Filiform corrosion: corrosion that occurs
under some coatings in the form
of randomly distributed threadlike filaments. (a special form of
a solid inert material added to a synthetic resin or rubber, either to change
its physical properties or simply to dilute it for economy.
- Film: a thin, not necessarily visible,
layer of material.
- Film build: thickness produced in a
- Filter: porous material through which
fluids or fluid and solid mixtures are passed to separate matter held in suspension.
- Filtrate: the effluent liquid from a
- Fin: a fin is an extended surface, a
solid, experiencing energy transfer by conduction within its boundaries, as
well as energy transfer with its surroundings by convection and/or radiation,
used to enhance heat transfer by increasing surface area.
- Fines: the portion of a powder composed
of particles which are smaller than the specified size.
- Fin tube: a tube with one or more fins.
- Fired pressure vessel: a vessel containing
a fluid under pressure exposed to heat from the combustion of fuel.
- Firetube: a type of boiler design in
which combustion gases flow inside the tubes and water flows outside the tubes.
- Fish eyes: areas on a steel fracture
surface having a characteristic white crystalline appearance with craters distinguished
by a center which consists of a uniform flat painted region, surrounded by a
depression, followed by a ridge of paint. Fish-eyes are caused by non-dispersed
fluid globules in the paint or by air-borne droplets that are deposited on the
- Flakes: short, discontinuous internal
fissures in wrought metals attributed to stresses produced by localized transformation
and decreased solubility of hydrogen during cooling after hot working. In a
fracture surface, flakes appear as bright silvery areas; on an etched surface,
they appear as short, discontinuous cracks.
- Flame hardening: the localized surface
heating of a medium carbon steel by an impinging gas flame so that the temperature
is raised above 900°C. The part is quenched (or self-quenches by virtue of the
remaining cool bulk of the component) and tempered to produce a hard martensitic
structure at the surface.
- Flame spraying: A thermal spraying process
in which an oxyfuel gas flame is the source of heat for melting the surfacing
material. Compressed gas may or may not be used for atomizing and propelling
the surfacing material to the substrate.
- Flammability: susceptibility to combustion.
- Flash point: the lowest temperature
at which, under specified conditions, fuel oil gives off enough vapor to flash
into a momentary flame when ignited.
- Flashing: the process of producing steam
by discharging water into a region of pressure lower than the saturation pressure
that corresponds to the water temperature
- Flat: a surface with minimal reflection,
commonly fewer than seven units of gloss when measured at a 60º angle. “Gunship
Quality” is when the coating has no more than three units of gloss when measured
at an 85º angle. Flat is the opposite of gloss.
- Flat-rolled steel: steel processed on
rolls with flat faces as opposed to grooved or cut faces. Flat-rolled products
include sheet, strip and tin plate, among others.
- Floating: a term used to describe a
mottled, blotchy, or streaked appearance in a paint film. This is due to the
separation and uneven distribution of the different pigments in the paint.
- Floc: an agglomeration of finely divided
suspended particles in a larger, usually gelatinous particle the result of physical
attraction or adhesion to a coagulant compound.
- Flocculation: the process of causing
a "floc" to form after treatment with a coagulant by gentle stirring or mixing.
- Flooding: a uniform color change occurring
in a wet paint film after application. A separation occurring as a result of
different rates of pigment settling caused by a difference in pigment density
and size or flocculation of one of the pigments.
- Flowcoating: a system of applying paint
where the paint is allowed to flow over and drain off the workpiece.
- Flow control: a device designed to limit
or restrict the flow of water or regenerant; may include a throttling valve,
an orifice of fixed diameter, or a pressure compensating orifice.
- Flow velocity: the distance traveled
by a packet of fluid in a unit of time.The average flow velocity can be calculated
by dividing the flow rate by the cross sectional area.
- Flue: a passage for products of combustion.
- Flue gas: the gaseous product of combustion
in the flue to the stack.
- Fluid shear stress: shear stress in
a flowing liquid is the force exerted as one layer moves past another. In a
flowing fluid all the molecules of the fluid "rub" against one another as they
travel down the tube. Fluid molecules also exert a "rubbing" force on the walls
of the tube. This rib or shear force can be calculated for flow in a tube if
you know the fluid velocity, roughness of the tube, fluid properties, and diameter
of the tube.
- Flush tank: a tank or chamber in which
water is stored for rapid release.
- Flush valve: a self-closing valve designed
to release a large volume of water when tripped.
- Foaming: the continuous formation of
bubbles which have sufficiently high surface tension to remain as bubbles beyond
the disengaging surface.
- Fogged metal: a metal whose luster has
been reduced because of a surface film, usually a corrosion product layer.
- Forced circulation: the circulation
of water in a boiler by mechanical means external to the boiler.
- Forced-draft fan: a fan supplying air
under pressure to the fuel burning equipment.
- Foreign structure: any metallic structure
that is not intended as part of a cathodic protection system of interest.
- Fossil fuel: natural, burnable, carbon
based substance resulting from millions of years of biological decay of ancient
plant and animal matter. Coal, oil, and natural gas are common examples.
- Fouling: the accumulation of refuse
in gas passages or on heat absorbing surfaces which results in undesirable restriction
to the flow of gas or heat.
- Fouling organism: any aquatic organism
with a sessile adult stage that attaches to and fouls underwater structures
- Fractography: descriptive treatment
of fracture, especially in metals, with specific reference to photographs of
the fracture surface. Macrofractography involves photographs at low magnification
(< 25x); microfractography, photographs at high magnification (>25x).
Fracture mechanics: a quantitative analysis
for evaluating structural behavior in terms of applied stress, crack length,
and specimen or machine component geometry. see also linear elastic fracture
- Fracture toughness: a generic term for
measures of resistance to extension of a crack. the term is sometimes restricted
to results of fracture mechanics tests, which are directly applicable in fracture
control. however, the term commonly includes results from simple tests of notched
or precracked specimens not based on fracture mechanics analysis. results from
test of the latter type are often useful for fracture control, based on either
service experience or empirical correlations with fracture mechanics tests.
see also stress-intensity factor.
- Free ash: ash which is not included
in the fixed ash.
- Free available chlorine: the concentration
of residual chlorine present as dissolved gas, hypochlorous acid or hypochlorite,
not combined with ammonia or in other less readily available form. (see chlorination)
- Free carbon: the part of the total carbon
in steel or cast iron that is present in elemental form as graphite or temper
carbon. contrast with combined carbon.
- Free carbon dioxide: carbon dioxide
present in water as the gas, or as carbonic acid, but not that combined in carbonates
- Free corrosion
potential: corrosion potential in the absence of net electrical
current flowing to or from the metal surface.
- Free ferrite: ferrite that is formed
directly from the decomposition of hypoeutectoid austenite during cooling, without
the simultaneous formation of cementite, also called proeutectoid ferrite.
- Free machining: pertains to the machining
characteristics of an alloy to which one or more ingredients have been introduced
to give small broken chips, lower power consumption, better surface finish,
and longer tool life; among such additions are sulfur or lead to steel, lead
to brass, lead and bismuth to aluminum, and sulfur or selenium to stainless
- Fretting: surface damage resulting from
relative motion between surfaces in contact under pressure.
corrosion: the deterioration at the interface between contacting
surfaces as the result of corrosion and slight oscillatory slip between the
- Friction: the reaction force resulting
from surface interaction and adhesion during sliding. The friction Coefficient
is defined as the friction force divided by the load.
- Friction stir welding (FSW): a welding
process that utilizes local friction heating to produce continuous solid state
seams. It allows butt and lap joints to be made in low melting point materials
(such as aluminum alloys) without the use of filler metals.
- FTA: Fault Tree Analysis .
- Fuel: a substance containing combustible
used for generating heat.
- Functional failure: The inability of
an item of equipment to fulfill one or more of its functions.
- Fused coatings: a process in which the
coating material is deposited by thermal spraying and then fused by post heat
treatment. This can be done by flame, induction heating, furnace or by laser.
- Fused and crushed powder: powder formed
from a fused solid mass which is then crushed to the appropriate size for spraying.