Nace CP 1, Руководство по эксплуатации

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RP0196-2004
6
NACE International
that the installation is made in accordance with the
drawings and specifications.
5.3.2 Deviations from construction documents and
specifications shall be noted on as-built drawings and
specifications.
5.4 Inspection and Handling
5.4.1 Galvanic anodes shall be inspected for
conformance to specifications for correct galvanic
anode material and size, length of lead wire, and
method of wire connection. All wire and connections
shall be carefully inspected for integrity. Damage to
galvanic anode assemblies during handling and
installation shall be avoided. If defects are not
repaired, the anode must be rejected.
5.4.2 Stationary reference electrodes installed as part
of the galvanic anode CP system shall be inspected
and tested for conformance to the specifications. The
stationary reference electrode shall be tested with
reference to an accurate calibrated reference electrode
in the electrolyte in which the stationary reference
electrode is placed. If a difference in potential exists
between the stationary and test reference electrode,
the stationary electrode shall be replaced with one that
matches the calibrated portable electrode to within ±10
mV.
5.5 Installation
5.5.1 Construction practices shall conform to all
applicable local and national codes.
5.5.2 Test boxes shall be installed at a location for
safe and convenient ground access.
5.5.3 All cables shall be protected from abrasion and
sharp objects.
5.5.4 Short circuits shall not exist between the cables
and the tank structure or conduit.
5.5.5 The preferred method of galvanic anode
installation is to ensure that the anodes are electrically
isolated from the tank, except through an accessible
electrical connection that can be disconnected for
testing of the system.
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Section 6: Criteria for CP
6.1 Introduction
6.1.1 The purpose of this section is to list the criteria
for CP, which, when complied with, either separately or
collectively, indicate that adequate CP of submerged
portions of steel water tank interiors has been
achieved.
6.2 General
6.2.1 The objective of using galvanic anode CP is to
control the corrosion of submerged portions of steel
water tank interiors.
6.2.2 The selection of a particular criterion for
achieving the objective in Paragraph 6.2.1 depends, in
part, on prior experience with similar structures and
environments wherein the criterion has been used
successfully.
6.2.3 The criteria in Paragraph 6.3 were developed
through laboratory experiment or were determined
empirically by evaluating data obtained from
successfully operated CP systems. It is not intended
that persons responsible for corrosion control be
limited to these criteria if it can be demonstrated by
other means that the control of corrosion has been
achieved.
6.2.4 Extended periods of time can be required to
achieve polarization of uncoated or poorly coated
tanks.
6.3 Criteria for Steel Water Tanks
6.3.1 A negative polarized tank-to-water potential of at
least 850 mV relative to a CSE.
OR
6.3.2 A minimum of 100 mV of cathodic polarization
between the structure surface and a stable reference
electrode contacting the electrolyte. The formation or
decay of polarization can be measured to satisfy this
criterion.
CAUTIONARY NOTE: This criterion is only applicable
to steel water tanks not having corrosion cells caused
by connection to more noble metals such as copper,
brass, or passive stainless steel (e.g., heated water
tanks wherein the submerged heater tube is of copper
or brass materials and is electrically continuous with
the submerged metal of the tank).
6.4 Measurement Procedures
6.4.1 Potential measurements on water tank interiors
should be made with the reference electrode located in
the water (electrolyte) as close as possible to the tank
steel surface. Consideration shall be given to voltage