-
- backfill
- Material placed in a drilled hole to fill space around
anodes, vent pipe, and buried components of a cathodic
protection system.
-
- bainite
- A metastable aggregate of ferrite and cementite
resulting from the transformation of austenite at
temperatures below the pearlite range but above M„
the martensite start temperature. Bainite formed in
the upper part of the bainite transformation range has a
feathery appearance; bainite formed in the lower part of
the range has an acicular appearance resembling that of
tempered martensite.
-
- banded structure
- A segregated structure consisting of alternating nearly
parallel bands of different composition, typically
aligned in the direction of primary hot working.
-
- base
- A chemical substance that yields hydroxyl ions (OH ) when
dissolved in water. Compare with acid.
-
- base metal
- (1) The metal present in the largest proportion in an
alloy; brass, for example, is a copper-base alloy. (2) An
active metal that readily oxidizes, or that
dissolves to form ions. (3) The metal to be brazed, cut,
soldered, or welded. (4) After welding, that part of the
metal which was not melted.
-
- 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. Beach marks (also known as clamshell marks or
arrest marks) are typically found on service fractures
where the part is loaded randomly, intermittently, or
with periodic variations in mean stress or alternating
stress. See also striation.
-
- biaxial stress
- See principal stress (normal).
-
- bimetallic corrosion
- (Galvanic Corrosion) Corrosion resulting from dissimilar
metal contact.
-
- biological corrosion
- Deterioration of metals as a result of the metabolic
activity of microorganisms.
-
- bipolar electrode
- An electrode in an electrolytic cell that
is not mechanically connected to the power supply, but is
so placed in the electrolyte, between the anode and
cathode, that the part nearer the anode becomes
cathodic and the part nearer the cathode becomes anodic.
Also called intermediate electrode.
-
- bituminous coating
- Coal tar or asphalt-based coating.
-
- black liquor
- The liquid material remaining from pulpwood cooking in
the soda or sulfate paper-making process.
-
- black oxide
- A black finish on a metal produced by immersing it in hot
oxidizing salts or salt solutions.
-
- blister
- A raised area, often dome shaped, resulting from (1) loss
of adhesion between a coating or deposit and the base
metal or (2) delamination under the pressure of expanding
gas trapped in a metal in a near-subsurface zone. Very
small blisters may be called pinhead blisters or pepper
blisters.
-
- blow down
- (1) Injection of air or water under high pressure through
a tube to the anode area for the purpose of purging the
annular space and possibly correcting high resistance
caused by gas blocking. (2) In connection with boilers or
cooling towers, the process of discharging a significant
portion of the aqueous solution in order to remove
accumulated salts, deposits, and other impurities.
-
- blue brittleness
- Brittleness exhibited by some steels after being heated
to a temperature within the range of about 200 to 370 ºC
(400 to 700 ºF), particularly if the steel is worked at
the elevated temperature.
-
- blushing
- Whitening and loss of gloss of a usually organic coating
caused by moisture. Also called blooming.
-
- brackish water
- (1) Water having salinity values ranging from
approximately 0.5 to l7 parts per thousand. (2) Water
having less salt than seawater, but undrinkable.
-
- breakdown potential
- The least noble potential where pitting or crevice
corrosion, or both, will initiate and propagate.
-
- brightener
- An agent or combination of agents added to an
electroplating bath to produce a smooth, lustrous
deposit.
-
- brine
- Seawater containing a higher concentration of dissolved
salt than that of the ordinary ocean.
-
- 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.
-
- burning
- (1) Permanently damaging a metal or alloy by heating to
cause either incipient melting or intergranular
oxidation. See also over-heating. (2) In grinding,
getting the work hot enough to cause discoloration or to
change the microstructure by tempering or hardening.
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