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.
Faraday 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) metals.
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 crevice corrosion)
Filler: 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 paint application.
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 filter.
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 painted surface.
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 of ships.
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 mechanics.
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 or bicarbonates.
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 steel.
Fretting: surface damage resulting from relative motion between surfaces in contact under pressure.
Fretting corrosion: the deterioration at the interface between contacting surfaces as the result of corrosion and slight oscillatory slip between the two surfaces.
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.

Link to glossary of corrosion and materials maintenance terms