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Corrosion Glossary - B
- Backfill: material placed in a drilled
hole to fill space around anodes, vent pipe, and buried components of a cathodic
- Back-flow: flow of water in a pipe or
line in a direction opposite to normal flow. often associated with back siphonage
or the flow of possibly contaminated water into a potable water system.
- Back-flow preventer: a device or system
installed in a water line to stop back-flow. (See vacuum breaker, air gap.)
- Backwash: the process in which beds
of filter or ion exchange media are subjected to flow opposite to the service
flow direction to loosen the bed and to flush suspended matter collected during
the service run.
- Bacteria: single-celled organisms (singular
form=bacterium) which lack well-defined nuclear membranes and other specialized
functional cell parts and reproduce by cell division or spores. Bacteria may
be free-living organisms or parasites. Bacteria (along with fungi) are decomposers
that break down the wastes and bodies of dead organisms, making their components
available for reuse. Bacterial cells range from about 1 to 10 mm in length and
from 0.2 to 1 mm in width. They exist almost everywhere on earth. Despite their
small size, the total weight of all bacteria in the world likely exceeds that
of all other organisms combined.
- Bactericide: any substance or agent
which kills bacteria, both disease causing and non disease causing. Spores and
nonbacterial microorganisms (e.g., algae, fungi, and viruses) are not necessarily
killed by a bactericide.
- Baffle: a plate or wall for deflecting
gases or liquids.
- Bainite: a metastable aggregate of ferrite
and cementite resulting from the transformation of austenite at temperatures
below the pearlite range but above the martensite start temperature.
- Bar: (what did you think?) a
shape of steel that is available in different forms such as rounds, squares,
hexagons and rectangles.
- Barometric pressure: atmospheric pressure
as determined by a barometer usually expressed in mm of mercury or Mega Pascal
- Base: a substance that releases hydroxyl
ions when dissolved in water. Bases react with acids to form a neutral salt
and water. (See alkali.)
- Base exchange: synonymous with cation
- Base material: see preferred term substrate.
- Base metal: see preferred term substrate.
- Batch: a quantity of material treated
or produced as a unit.
- Batch operation: a process method in
which a quantity of material is processed or treated usually with a single charge
of reactant in a single vessel, and often involving stirring. Example: the neutralization
of a specific volume of an acid with a base in a vessel, with stirring or mixing,
is a batch operation.
- Beach marks: macroscopic progression
marks on a fatigue fracture or stress-corrosion
cracking surface that indicate successive positions of the advancing crack
front. The classic appearance is of irregular elliptical or semielliptical rings,
radiating outward from one or more origins. See also striation.
- Bed: the ion exchanger or filter media
in a column or other tank or operational vessel.
- Bed depth: the height of the ion exchanger
or filter media in the vessel after preparation for service.
- Bed expansion: the increase in the volume
of a bed of ion exchange or filter media during upflow operations, such as backwashing,
caused by lifting and separation of the media. Usually expressed as the percent
of increase of bed depth.
- Beerstone scale:
beerstone scale or calcium oxalate (CaC2O4) is a type
of scale common in the brewing industry. This precipitate is largely due to
a reaction between alkaline cleaners (caustic), hard water minerals (calcium
and magnesium) and protein (amino acids).
- Bicarbonate alkalinity: the alkalinity
of a water due to the presence of bicarbonate ions (hco3).
- Billet: a square form of semi-finished
steel that later is rolled into a finished
product such as a bar.
- Binder: a cementing medium used in producing
composite or agglomerate powders.
- Bioassay: test which determines the
effect of a chemical on a living organism.
- Biochemical oxygen demand (BOD): the
amount of oxygen (measured in mg/L) required in the oxidation of organic matter
by biological action under specific standard test conditions. Widely used to
measure the amount of organic pollution in waste water and streams.
- Biocide: a chemical which can kill or
inhibit the growth of living organisms such as bacteria, fungi, molds, and slimes.
Biocides can be harmful to humans, too. Biocides kill spores of living organisms
also, and since spores are the most resistant of all life forms, a biocide may
be properly defined as a sterilizing agent.
- Biocorrosion: see
Microbiologically Influenced Corrosion.
- Biodegradable: subject to degradation
to simpler substances by biological action, such as the bacterial breakdown
of detergents, sewage wastes and other organic matter.
- Biologically induced corrosion: see
Microbiologically Influenced Corrosion.
- Biostat: a chemical which can inhibit
without killing them the growth of living organisms such as bacteria, fungi,
molds, and slimes.
- Binder: solid ingredients in a
coating that hold the pigment
particles in suspension and attach them to the substrate. Consists of resins
(e.g., oils, alkyd, latex). The nature and amount of binder determine many of
a paint performance properties.
- Black oxide: a black finish on a metal
produced by immersing it in hot oxidizing salts or salt solutions.
- Blast furnace: the mother of the
steel industry furnaces, it creates
combustion by forcing a current of air under pressure and obtains iron by the
reduction of iron ore with suitable fuel and fluxes at high temperatures.
- Blasting: a method of cleaning or surface
roughening by a forcibly projected stream of sharp angular abrasive. A pressurized
stream of particulates (ceramic, plastic, metal, , etc.) applied on a surface
to clean, peen or abrade.
- Bleach: a strong oxidizing agent and
disinfectant formulated to break down organic matter and destroy biological
organisms. Commonly refers to a 5.25 percent nominal solution of sodium hypochlorite
(household bleach) which is equivalent to 3 percent to 5 percent available free
chlorine (strength varies with shelf life). Sodium hypochlorite is also available
commercially in concentrations of between 5 percent and 15 percent available
chlorine. Dry bleach is a dry calcium hypochlorite with 70 percent available
- Bleeding: a defect in which pigment
from a lower coat of paint diffuses
into an upper coat and discolors the latter.
a raised area, often dome shaped, resulting from either loss of adhesion between
a coating or deposit and the base metal or delamination under the pressure of
expanding gas trapped in a metal in a near-subsurface zone.
formation of dome-shaped projections in paints or varnish films resulting from
local loss of adhesion and lifting of the film from the underlying surface.
- Blowdown: the withdrawal of water containing
a high concentration of solids from an evaporating water system (such as a boiler
system) in order to maintain the solids-to-water concentration ratio within
specified limits. Blowdown is normally performed in boiler and cooling water
operations. The term may also refer to removal of other solutions of undesirable
quality from a system or vessel.
- Blowdown valve: a valve generally used
to continuously regulate concentration of solids in the boiler, not a drain
- Bloom: 1) (metallurgy) larger than billets,
blooms are square or rectangular semi-finished shapes that are rolled into finished
products such as beams. 2) (paint
coating) the appearance of a hazy deposit of oil or waxlike material on
a coated surface that mars the surface appearance by lowering the gloss or giving
a mottled or nonuniform appearance. This is caused by the migration to the surface
of an oil, plasticizer, or noncrosslinked coating constituent when the coated
part is exposed to a cycle of heat, humidity, and cooling.
- Blushing: a whitening of the surface
of a coating which occurs when
the coating is applied under conditions of high relative humidity. Usually caused
by a combination of high relative humidity and fast evaporating solvents.
- BOD: abbreviation for "biochemical oxygen
- Body: thickness or viscosity of a fluid
- Boiler: a closed vessel in which water
is heated, steam is generated, steam is superheated, or any combination thereof,
under pressure or vacuum by the application of heat from combustible fuels,
electricity or nuclear energy.
- Boiler efficiency: the term “boiler
efficiency” is often substituted for combustion or thermal efficiency. True
boiler efficiency is the measure of fuel-to-steam efficiency.
- Boiler water: a term construed to mean
a representative sample of the circulating boiler water, after the generated
steam has been separated and before the incoming feed water or added chemical
becomes mixed with it so that its composition is affected.
- Boiling water reactor (BWR): nuclear
reactor in which water, used as both coolant and moderator, boils in the reactor
core. The steam from the boiling water is used to turn the turbine-generator.
- Bond: the state of adhesion between
the coating and the substrate which strength depends on the details of the spraying
process and the materials used. Bonding mechanisms may be mechanical, physical,
chemical or metallurgical or a combination of these.
- Bond coat: a preliminary (or prime coat)
of material that improves adherence of the subsequent spray deposit.
- Bonding: a) firmly connecting together
various elements, shields or housings of a device to prevent potential differences
and possible interference. b) a method used to produce good electrical contact
between metallic parts of any device. c) the means employed to obtain an electromagnetically
homogenous mass having an equipotential surface.
- Bonding force: the force that holds
two atoms together; it results from a decrease in energy as two atoms are brought
closer to one another.
- Bond strength: the strength of the adhesion
between the coating and the substrate. A number of test methods are in use to
measure the bond strength of coatings.
- Boronizing: the diffusion of boron into
the surface of a component (usually steel) by a high temperature (~
900°C) gas or pack process. Produces
hard phases within the surface (Typically 100 µm deep).
- Brackish water:
water having salinity values
ranging from approximately 500 to 5,000 parts per million (milligrams per liter).
- Brazing: a joining process wherein coalescence
is produced by heating to suitable temperatures above 425oC and by
using a non-ferrous filler metal having a melting point below that of the base
metals. The filler metal is distributed between the closely filled surfaces
of the joint by capillary attraction. See also soldering.
- Breakdown potential: the least noble
potential where pitting or crevice corrosion, or both, will initiate and propagate.
- Breakpoint chlorination: a chlorination
procedure in which chlorine is added until the chlorine demand is satisfied
and a dip (breakpoint) in the chlorine residual occurs. Further additions of
chlorine produce a chlorine residual proportional to the amount added.
- Breakthrough: the appearance in the
effluent from a water conditioner of the material being removed by the conditioner,
such as hardness in the effluent of a softener, or turbidity in the effluent
of a mechanical filter; an indication that regeneration, backwashing, or other
treatment is necessary for further service.
- Breeder reactor: nuclear fission reactor
that makes more usable new fuel (plutonium-239) than it consumes.
- Bridging bar: see
- Brine: a strong solution of salt(s)
(usually sodium chloride and other salts too) with total dissolved solids concentrations
in the range of 40,000 to 300,000 or more milligrams per liter. Potassium or
sodium chloride brine is used in the regeneration stage of cation and/or anion
exchange water treatment equipment.
- British thermal unit (Btu): quantity
of heat required to raise the temperature of one pound of water by one degree
- Brittle fracture: separation of a solid
accompanied by little or no macroscopic plastic deformation. Typically, brittle
fracture occurs by rapid crack propagation with less expenditure of energy than
for ductile fracture.
- Buckle: alternate bulges and hollows
recurring along the length of a flat product with the edges remaining relatively
- Buffer: a chemical substance which stabilizes
pH values in solutions.
- Buffer capacity: a measure of the capacity
of a solution or liquid to neutralize acids or bases. This is a measure of the
capacity of water for offering a resistance to changes in pH.
- Bumps: high and low spots in a
coating surface caused by unwanted
flowing that occurs during curing. Caused by surface tension gradients that
arise during curing.
- Bunker oil: residual fuel oil of high
viscosity commonly used in marine and stationary steam power plants. (No. 6
- Bur: the thin ridge or roughness left
by a cutting operation such as slitting, shearing, blanking or sawing
- Busheling: a widely traded form of steel
scrap consisting of sheet clips and stampings from metal production. Bushel
baskets were used to collect the material through World War II, giving rise
to the term.
- Bypass: a connection or a valve system
that allows untreated water to flow through a
water system while a water treatment
unit is being regenerated, backwashed or serviced.