Nace CP 1, Course Manual

Page: 324 / 535

RP0176-2003
2
NACE International
Current Density: The current to or from a unit area of an
electrode surface.
Depolarization: The removal of factors resisting the current
in an electrochemical cell.
Dielectric Shield: An electrically nonconductive material,
such as a coating, sheet, or pipe, that is placed between an
anode and an adjacent cathode, usually on the cathode, to
improve current distribution in a cathodic protection system.
Doubler Plate: An additional plate or thickness of steel
used to provide extra strength at the point of anode attach-
ment to a structure.
Electrical Isolation: The condition of being electrically
separated from other metallic structures or the environment.
Electrolyte: A chemical substance containing ions that
migrate in an electric field.
Epoxy: Type of resin formed by the reaction of aliphatic or
aromatic polyols (like bisphenol) with epichlorohydrin and
characterized by the presence of reactive oxirane end
groups.
Faying: Especially close fitting. The term originally
described the fit between hull timbers in wooden ships.
Foreign Structure: Any metallic structure that is not intend-
ed as a part of a system under cathodic protection.
Galvanic Anode: A metal that provides sacrificial protection
to another metal that is more noble when electrically coup-
led in an electrolyte. This type of anode is the electron
source in one type of cathodic protection.
Holiday: A discontinuity in a protective coating that exposes
unprotected surface to the environment.
Impressed Current: An electric current supplied by a de-
vice employing a power source that is external to the elec-
trode system. (An example is direct current for cathodic
protection.)
Interference Current (Stray Current): Current through
paths other than the intended circuit. For the purposes of
this standard, interference current is current discharged to
the electrolyte from a structure that may be either (1) not an
intended part of the circuit or (2) an intended part of the cir-
cuit that is not adequately connected to the current source.
Inorganic Zinc-Rich Coating (Paint): Coating containing a
metallic zinc pigment (typically 75 wt% zinc or more in the
dry film) in an inorganic vehicle.
“J” Tube: A curved tubular conduit designed and installed
on a structure to support and guide one or more pipeline
risers or cables.
Mill Scale: The oxide layer formed during hot fabrication or
heat treatment of metals.
Mudline: The ocean floor at the location of interest.
Padeye: A lifting or connection point that is shaped like an
eye and is used to accommodate hooks, tackle, or slings.
Pipeline: A conduit for carrying produced oil, water, and
gas between structures or between structures and onshore
processing facilities.
Platform: An offshore structure used to accommodate oil
and/or gas wells, related production equipment, pipelines,
and/or living quarters.
Polarization: The change from the open-circuit potential as
a result of current across the electrode/electrolyte interface.
Polymerization: The process of uniting a number of small
chemical units to form a larger one. The product of such a
union is called a polymer.
Primer: A coating material intended to be applied as the
first coat on an uncoated surface. The coating is specifi-
cally formulated to adhere to and protect the surface as well
as to produce a suitable surface for subsequent coats. (Also
referred to as Prime Coat.)
Reference Electrode: An electrode whose open-circuit
potential is constant under similar conditions of measure-
ment, which is used for measuring the relative potentials of
other electrodes.
Resin: Generally refers to a class within the broad family of
plastics or polymers and usually indicates stability for use
as a binder for coating materials. The term resin is usually
modified by other words to denote type, for example: alkyd
resin, vinyl resin, ester resin, or epoxy resin.
Riser: (1) That section of pipeline extending from the
ocean floor up to an offshore structure. (2) The vertical tube
in a steam generator convection bank that circulates water
and steam upward.
Silver/Silver Chloride Electrode: For the purposes of this
standard, a reference electrode that uses seawater as the
junction electrolyte, for example, the Ag/AgCl/seawater
electrode.
Splash Zone: The zone of the structure that is alternately in
and out of the water because of the influence of tides,
winds, and seas. Excluded from this zone are surfaces that
are wetted only during major storms.
Structure: Stationary structure (platform or subsea facility)
that is fixed to the sea floor by gravity, piling, and/or mooring
cables.