Nace CP 1, Course Manual

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NACE GLOSSARY OF CORROSION-RELATED TERMS
©
2002, NACE International. This publication may not be reprinted without the written consent of NACE International.
Page 10 of 18
HIGH-PRESSURE WATER
JETTING
Water jetting performed at
pressures from 70 to 170 MPa
(10,000 to 25,000 psig).
HIGH-TEMPERATURE
HYDROGEN ATTACK
A loss of strength and ductility of
steel by high-temperature
reaction of absorbed hydrogen
with carbides in the steel,
resulting in decarburization and
internal fissuring.
HOLIDAY
A discontinuity in a protective
coating that exposes unprotected
surface to the environment.
HYDROGEN BLISTERING
The formation of subsurface
planar cavities, called hydrogen
blisters, in a metal resulting from
excessive internal hydrogen
pressure. Growth of near-
surface blisters in low-strength
metals usually results in surface
bulges.
HYDROGEN
EMBRITTLEMENT
A loss of ductility of a metal
resulting from absorption of
hydrogen.
HYDROGEN-INDUCED
CRACKING
Stepwise internal cracks that
connect adjacent hydrogen
blisters on different planes in the
metal, or to the metal surface
(also known as
stepwise
cracking ).
HYDROGEN
OVERVOLTAGE
Overvoltage associated with the
liberation of hydrogen gas.
HYDROGEN STRESS
CRACKING
Cracking that results from the
presence of hydrogen in a metal
in combination with tensile
stress. It occurs most frequently
with high-strength alloys.
I
IMPINGEMENT
CORROSION
A form of erosion-corrosion
generally associated with the
local impingement of a high-
velocity, flowing fluid against a
solid surface.
IMPRESSED CURRENT
An electric current supplied by a
device employing a power source
that is external to the electrode
system. (An example is direct
current for cathodic protection.)
IMPRESSED CURRENT
ANODE
An electrode, suitable for use as
an anode when connected to a
source of impressed current,
which is generally composed of a
substantially inert material that
conducts by oxidation of the
electrolyte and, for this reason, is
not corroded appreciably.
IMPULSE DIELECTRIC
TEST
A method of applying voltage to
an insulated wire through the use
of electric pulses (usually 170 to
250 pulses per second) to
determine the integrity of the
wire’s insulation.
INCLUSION
A nonmetallic phase such as an
oxide, sulfide, or silicate particle
in a metal.
INORGANIC ZINC-RICH
COATING
Coating containing a metallic zinc
pigment (typically 75 wt% zinc or
more in the dry film) in an
inorganic vehicle.
INSTANT-OFF
POTENTIAL
The polarized half-cell potential
of an electrode taken
immediately after the cathodic
protection current is stopped,
which closely approximates the
potential without IR drop (i.e., the
polarized potential) when the
current was on.
INTERCRYSTALLINE
CORROSION
[See Intergranular Corrosion. ]
INTERDENDRITIC
CORROSION
Corrosive attack of cast metals
that progresses preferentially
along paths between dendrites.
INTERFERENCE BOND
An intentional metallic
connection, between metallic
systems in contact with a
common electrolyte, designed to
control electrical current
interchange between the
systems.
INTERFERENCE
CURRENT
[See Stray Current. ]
INTERGRANULAR
CORROSION
Preferential corrosion at or along
the grain boundaries of a metal
(also known as
intercrystalline