Corrosion Glossary - B

Backfill: material placed in a drilled hole to fill space around anodes, vent pipe, and buried components of a cathodic protection system.
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 (MPa).
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 exchange.
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 chlorine.
Bleeding: a defect in which pigment from a lower coat of paint diffuses into an upper coat and discolors the latter.
Blister: 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.
Blistering: 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 valve.
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 demand".
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 425^oC 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 pit gauge
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 Fahrenheit.
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 flat.
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 fuel oil)
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.