Nace CP 1, Course Manual

Page: 323 / 535

RP0176-2003
NACE International
1
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Section 1: General
1.1 This standard provides guidelines for establishing mini-
mum requirements for the control of corrosion on steel fixed
offshore structures associated with petroleum production,
and on the external portions of associated oil and gas hand-
ling equipment. Fixed structures include platforms, tension
leg platforms (TLPs), and subsea templates. This standard
does not include guidelines for corrosion control of tempor-
arily moored mobile vessels used in petroleum production.
1.2 For this standard, corrosion on structures is divided into
three zones: the submerged, splash, and atmospheric
zones. Each zone is examined separately.
1.3 This standard does not designate guidelines for every
specific situation because of the complexity of environ-
mental conditions. In many instances, there may be several
solutions to the problem and, when appropriate, meritorious
alternative solutions have been included.
1.4 This standard does not include guidelines for corrosion
control of the internal portions of wells, piping, and assoc-
iated equipment that may be installed on or attached to
structures.
1.5 This standard includes corrosion control of the external
surfaces of attached pipelines above the splash zone.
When ownership of the pipeline is different from that of the
structure, the structure owner’s responsibility for the pipeline
usually ends at a designated point or valve on the structure.
1.6 Underwater pipelines and pipeline risers are specifi-
cally excluded from this standard.
1.7 Alternative methods are acceptable to accomplish the
objectives of this standard; however, deviation should be
made only if, in the opinion of a competent corrosion
specialist, the objectives expressed in the standard have
been achieved.
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Section 2: Definitions
NOTE: Additional definitions for cathodic protection and
coatings technology may be found in NACE Standard
RP0169,
1
the NACE Corrosion Engineer’s Handbook,
2
and
the NACE International 2002 Glossary of Corrosion-Related
Terms.
3
Anchor Pattern: The irregular peak and valley pattern cre-
ated on the surface of steel by the effect of blasting media
hitting the steel at high velocity.
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 en-
ter the solution at the anode.
Atmospheric Zone: The zone of the structure that extends
upward from the splash zone and is exposed to sun, wind,
spray, and rain.
Calcareous Coating or Deposit: A layer consisting of cal-
cium carbonate and other salts deposited on the surface.
When the surface is cathodically polarized as in cathodic
protection, this layer is the result of the increased pH ad-
jacent to the protected surface.
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 be-
tween a coating and the coated surface caused by products
of a cathodic reaction.
Cathodic Protection: A technique to reduce the corrosion
of a metal surface by making that surface the cathode of an
electrochemical cell.
Chalking: The development of loose, removable powder
(pigment) at the surface of an organic coating, usually
caused by weathering. Controlled chalking provides for
self-cleaning of the surface and leaves the surface in good
condition for recoating.
Chlorinated Rubber: A particular film former used as a
binder, made by chlorinating rubber.
Corrosion: The deterioration of a material, usually a metal,
that results from a reaction with its environment.
Corrosion Specialist: A person who, by reason of his/her
education and/or experience, is qualified to evaluate and
solve problems related to the corrosion of materials. In this
standard, corrosion specialist refers to one who is qualified
in the control of corrosion in marine environments.
Crosslink: The result of a chemical reaction linking two
chains in the molecular structure of a coating and changing
the final state of the coating.
Current: (1) A flow of electric charge. (2) The amount of
electric charge flowing past a specified circuit point per unit
time, measured in the direction of net transport of positive
charges. (In a metallic conductor, this is the opposite direc-
tion of the electron flow.)