Nace CP 1, Руководство по эксплуатации

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TM0101-2001
NACE International 1
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Section 1: General
1.1 This standard provides procedures to test compliance
with the cathodic protection (CP) criteria presented in NACE
Standard RP0285
1
on buried or submerged steel tank
systems, including galvanized steel components. Included
are instrumentation and general measurement guidelines,
procedures for three commonly used testing methods,
recommendations
on taking voltage drops into
consideration and preventing incorrect data from being
collected and used, and procedures for testing for electrical
continuity between tanks and other metallic equipment. A
method of testing cathodic protection using coupons is
described in Appendix A.
1.2 The provisions of this test method shall be applied by
personnel who have acquired, by education and related
practical experience, knowledge of the principles of cathodic
protection of buried and submerged metallic tank systems.
1.3 Sometimes a given test technique is ineffective or only
partially effective. Conditions that may cause this to occur
include elevated temperatures, disbonded dielectric or
thermally insulating coatings, shielding, bacterial attack, and
unusual contaminants in the electrolyte.
1.4 Deviation from this test method may be warranted in
specific
situations if corrosion-control personnel can
demonstrate that adequate cathodic protection has been
achieved.
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Section 2: Definitions
(1)
Anode: The electrode of an electrochemical cell at which
oxidation occurs. Electrons flow away from the anode in the
external circuit. Corrosion usually occurs and metal ions
enter the solution at the anode.
Cable: A bound or sheathed group of insulated conductors.
Cathode: The electrode of an electrochemical cell at which
reduction is the principal reaction. Electrons flow toward the
cathode in the external circuit.
Cathodic Disbondment: The destruction of adhesion
between a coating and the coated surface caused by
products of a cathodic reaction.
Cathodic Polarization: The change of electrode potential
in the active (negative) direction caused by current across
the electrode/electrolyte interface. See also
Polarization.
Cathodic Protection: A technique to reduce the corrosion
of a metal surface by making that surface the cathode of an
electrochemical cell.
Cathodic Protection Coupon: A metal sample
representing the tank at the test site, used for cathodic
protection testing, and having a chemical composition
approximating that of the tank. The coupon size should be
small to avoid excessive current drain on the cathodic
protection system.
Coating: A liquid, liquefiable, or mastic composition that,
after application to a surface, is converted into a solid
protective, decorative, or functional adherent film.
Conductor: A bare or insulated material suitable for
carrying electric current.
Contact Resistance: The resistance in the measurement
circuit present in the interface between a reference
electrode and an electrolyte.
Corrosion: The deterioration of a material, usually a metal,
that results from a reaction with its environment.
Corrosion Potential (E
corr
): The potential of a corroding
surface in an electrolyte relative to a reference electrode
under open-circuit conditions (also known as rest potential,
open-circuit potential, or freely corroding potential).
Criterion: A standard for assessment of the effectiveness
of a cathodic protection system.
Current Density: The current to or from a unit area of an
electrode surface.
Electrical Isolation: The condition of being electrically
separated from other metallic structures or the environment.
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(1)
Definitions in this section reflect common usage among practicing corrosion-control personnel and apply specifically to how terms are used
in this standard. As much as possible, these definitions are in accord with those in the “NACE International Glossary of Corrosion-Related
Terms.”