ASTM D6676-01

Standard Test Method for Cathodic Disbonding of Exterior Pipeline Coatings at Elevated Temperatures Using Interior Heating

SCOPE
1.1 This test method describes an accelerated procedure for determining comparative characteristics of coating systems applied to the exterior of steel pipe for the purpose of preventing or mitigating corrosion that may occur in underground or immersion where the pipe is carrying heated media and is under cathodic protection. This test method is intended for use with samples of coated pipe, or with a specimen cut from the section of coated pipe or flat plates, and is applicable to such samples when the coating is characterized by function as an electrical barrier.
1.2 This test method is intended to simulate conditions when external coatings are exposed to high temperature inside the pipe and to an ambient temperature outside, and thus are subjected to temperature gradient. If elevated temperatures are not required, see Test Method G8. If a specific test method is required with no options, see Test Method G80. If elevated temperatures are required but without temperature gradient, see Test Method G42.
1.3 The values stated in SI units to three significant decimals are to be regarded as the standard. The values given in parentheses are for information only.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 09-May-2001
• Technical Committee: D01 - Paint and Related Coatings, Materials, and Applications
• Drafting Committee: D01.48 - Durability of Pipeline Coating and Linings

Relations

• Replaced By: ASTM D6676-01e1 - Standard Test Method for Cathodic Disbonding of Exterior Pipeline Coatings at Elevated Temperatures Using Interior Heating (Withdrawn 2010)
• Effective Date: 10-May-2001

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: D 6676 – 01
Standard Test Method for
Cathodic Disbonding of Exterior Pipeline Coatings at
Elevated Temperatures Using Interior Heating
This standard is issued under the fixed designation D 6676; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope G 80 Test Method for Specific Cathodic Disbonding of
Pipeline Coatings
1.1 This test method describes an accelerated procedure for
G 95 Test Method for Cathodic Disbondment Test of Pipe-
determining comparative characteristics of coating systems
line Coatings (Attached Cell Method)
applied to the exterior of steel pipe for the purpose of
preventing or mitigating corrosion that may occur in under-
3. Summary of Test Method
ground or immersion where the pipe is carrying heated media
3.1 The test method described, subjects the coating on the
and is under cathodic protection. This test method is intended
test specimen to electrical stress in a highly conductive alkaline
for use with samples of coated pipe, or with a specimen cut
electrolyte. Electrical stress is obtained from an impressed
from the section of coated pipe or flat plates, and is applicable
direct- current system. An intentional holiday is to be made in
to such samples when the coating is characterized by function
the coating prior to starting of test.
as an electrical barrier.
3.1.1 Electrical instrumentation is provided for measuring
1.2 This test method is intended to simulate conditions
the current and the potential throughout the test cycle. At the
when external coatings are exposed to high temperature inside
conclusion of the test period, the test specimen is physically
the pipe and to an ambient temperature outside, and thus are
examined.
subjected to temperature gradient. If elevated temperatures are
3.1.2 Physical examination is conducted by comparing the
not required, see Test Method G 8. If a specific test method is
extent of loosened or disbonded coating at the intentional
required with no options, see Test Method G 80. If elevated
holiday in the immersed area with extent of loosened or
temperatures are required but without temperature gradient, see
disbonded coating at a reference holiday made in the coating in
Test Method G 42.
an area that was not immersed.
1.3 The values stated in SI units to three significant deci-
3.1.3 The cathodic stress is applied under conditions of a
mals are to be regarded as the standard. The values given in
constant temperature gradient, simulating a heated pipeline
parentheses are for information only.
with an exterior coating.
1.4 This standard does not purport to address all of the
3.1.4 Specimens that can be used are: (a) piece of pipe (Fig.
safety concerns, if any, associated with its use. It is the
1) or (b) samples cut from pipe or flat plate (Figs. 2-4).
responsibility of the user of this standard to establish appro-
3.1.4.1 Some coatings rely on application tension (such as
priate safety and health practices and determine the applica-
tape) for maximum cathodic disbondment resistance. Cut
bility of regulatory limitations prior to use.
coupons or flat plates must not be used.
2. Referenced Documents
4. Significance and Use
2.1 ASTM Standards:
4.1 Damage to a pipe coating is almost unavoidable during
G 8 Test Methods for Cathodic Disbonding of Pipeline
2 transportation and construction. Breaks or holidays in pipe
Coatings
coatings may expose the pipe to possible corrosion since, after
G 12 Test Method for Nondestructive Measurement of Film
2 a pipe has been installed underground, the surrounding earth
Thickness of Pipeline Coatings on Steel
will be moisture-bearing and will constitute an effective
G 42 Test Method for Cathodic Disbonding of Pipeline
2 electrolyte. Applied cathodic protection potentials may cause
Coatings Subjected to Elevated Temperatures
loosening of the coating, beginning at holiday edges. Sponta-
G 62 Test Method for Holiday Detection in Pipeline Coat-
2 neous holidays may also be caused by such potentials. Usually
ings
exterior pipeline coatings applied over pipes carrying hot
media (oil, gas) are exposed to high temperature inside the pipe
This test method is under the jurisdiction of ASTM Committee D01 on Paint
and low temperature outside and subjected to temperature
and Related Coatings, Materials, and Applications and is the direct responsibility of
gradient. Heat flux is directed from metal (substrate) to the
Subcommittee D01.48 on Durability of Pipeline Coatings and Linings.
Current edition approved May 10, 2001. Published July 2001. coating. This test method provides accelerated conditions for
Annual Book of ASTM Standards, Vol 06.02.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
D 6676
this test is much greater than that usually required for cathodic
protection in natural, inland soil environments.
4.6 Test voltages higher than those recommended may
result in the formation of chlorine gas. The subsequent chemi-
cal effects on the coating could cast doubt on the interpretation
of the test results. Filter tube with fritted disk (see Test Method
G 95) or layer of sand (40 mesh) put on the coated surface may
reduce this effect.
5. Apparatus
5.1 Test Vessel for Pipe Specimen (Fig. 4)—A suitable
nonreactive vessel shall be used, capable of withstanding
internal heating at test temperature and suitable to accommo-
date a test specimen, an anode. Heating the test sample can be
provided by internally heating. The pipe sample may be filled
with a suitable heat transfer material (oil, steel, shot, sand,
FIG. 1 Pipe Specimen Heated Inside
copper chips, etc.) A thermocouple or thermometer and heater
can be immersed in the heat transfer medium to effectively
control the temperature of the sample. Dimensions of the
vessel shall permit the following requirements:
5.1.1 Test specimen shall be suspended vertically in the
vessel with at least 25 mm (1 in.) clearance from the bottom.
5.1.2 Test specimen shall be separated by not less than 38
mm (1 ⁄2 in.), and a vertically suspended anode can be placed
at an equal distance from each specimen not less than the
separation distance.
5.1.3 Test specimen shall be separated from any wall of the
vessel by not less than 13 mm ( ⁄2in.).
5.1.4 Depth of electrolyte shall permit the test length of the
specimen to be immersed as required in 7.4.
FIG. 2 Flat Specimen Heated Over Hot Plate
5.1.5 The reference electrode may be placed anywhere in
cathodic disbondment to occur under simulated heating and the vessel, provided it is separated from the specimen and from
provides a measure of resistance of coatings to this type of the anode by not less than 38 mm (1 ⁄2 in.).
action. 5.2 Test Vessel for Flat or Cut From Pipe Specimens (Fig.
4.2 The effects of the test are to be evaluated by physical 4)—A transparent plastic of glass tube that is centered over the
examinations and monitoring the current drawn by the test intentional holiday and sealed to the test sample surface with a
specimens. Usually there is no correlation between the two waterproof sealing material. The cylinder is to be 101.6 mm
methods of evaluation, but both methods are significant. (4.0 in. nominal diameter) and of sufficient height to contain
Physical examination consists of assessing the effective contact 127.0 mm (5.0 in.) of electrolyte.
of the coating with the metal surface in terms of observed 5.3 Impressed-Current Anode—Anode shall be of the plati-
differences in the relative adhesive bond. It is usually found num wire type, 0.51 mm (0.020 in.)–24 gage diameter. It shall
that the cathodically disbonded area propagates from an area be of sufficient length to extend outside the confines of the test
where adhesion is zero to an area where adhesion reaches the cell and shall be connected to the wire from the power source
original level. An intermediate zone of decreased adhesion may with a bolted or compressed fitting.
also be present. 5.4 Anode Assembly—Anode shall be suspended inside the
4.3 Assumptions associated with test results include: test vessel so that the tip of the anode assembly closest to the
4.3.1 Maximum adhesion, or bond, is found in the coating holiday is 25.4 mm (1 in.) above, and the edge of the anode
that was not immersed in the test liquid, and assembly is 12.7 mm ( ⁄2 in.) above, and the edge of the anode
4.3.2 Decreased adhesion in the immersed test area is the assembly is 12.7 mm ( ⁄2in.) offset from the holiday.
result of cathodic disbondment.
5.5 Reference Electrode—Saturated Cu-CuSO of conven-
4.4 Ability to resist disbondment is a desired quality on a tional glass or plastic tube with porous plug construction,
comparative basis, but disbondment in this test method is not preferably not over 19.05 mm (0.750) in.) in diameter, having
necessarily an adverse indication of coating performance. The a potential of -0.316 V with respect to the standard hydrogen
virtue of this test method is that all dielectric-type coatings now electrode. A saturated calomel electrode may be used, but
in common use will disbond to some degree, thus providing a measurements made with it shall be converted to the Cu-
means of comparing one coating to another. CuSO reference for reporting by adding -0.072 V to the
4.5 The amount of current flowing in the test cell is a observed reading.
relative indicator of the extent of areas requiring protection 5.6 Reference Electrode Placement—Submerge the tip of
against corrosion; however, the current density appearing in the reference electrode 25.4 mm (1 in.) into the electrolyte.
D 6676
FIG. 3 Test Set-Up for Cathode Disbonding Test with Coated Pipe Coupon (or Flat Coupon) Heated Over Hot Plate
5.7 High-Impedance Multimeter—For making direct cur- 5.15.2 Pipe Specimens—Solid Heat Exchange Medium—
rent and voltage measurements. Multimeter must have an Heaters suitable for controlling temperature at 80° 6 1°C or as
internal resistance of not less than 10 MV and be capable of otherwise specified shall be employed inside the coated pipe.
measuring as low as 10 μ V potential drop across a shunt in the 5.15.3 Flat Plates—Heater plate, or equivalent, shall be
test cell circuit, and voltage up to 10 V. used for heating coated samples. The heater shall be adjustable
5.8 Direct-Current Power Supply—Capable of supplying to produce and control a temperature of 80° 6 1°C or other
low-ripple voltage at 1.5, 6 0.01, V, as measured between the specified temperature on the uncoated surface of testing panel.
test specimen and reference electrode. 5.16 Thermometers or Thermocouples, to measure tempera-
5.9 Precision Wire-Wound Resistor—1 V6 1 %, 1-W ture of heat transfer medium or on the uncoated surface of
(minimum) to be used in the test cell circuit as a shunt for panel over hot plate and in electrolyte.
measuring current. 5.17 Sharp-Pointed Knife, with a safe handle is required for
5.10 Thickness Gage—for measuring coating thickness in use in making physical examination.
accordance with Test Method G 12.
6. Reagents and Materials
5.11 Holiday Detector—for locating holidays in the coating
of the test specimen in accordance with Test Methods G 62.
6.1 Potable Tap Water or Higher Purity Water (distilled or
5.12 Connections—Wiring from current source to the speci-
demineralized water is satisfactory) with 1 weight percent of
men shall be by either soldering, brazing, or bolting to the
each of the following technical-grade salts, calculated on an
non-immersed area of the specimen. A junction in the connec-
anhydrous basis: sodium chloride, sodium sulfate, and sodium
tion wire is not desirable but, if necessary, may be made by
carbonate.
means of a bolted pair of terminal lugs, soldering or mechani-
NOTE 1—The resulting solution has a pH of 10 or higher and a
cally crimping to clean wire ends.
resistivity of 25 to 50 V·CM at room temperature.
5.13 Additional Connecting Wires—If additional wiring is
necessary, it shall be stranded, insulated copper and not less 6.2 Materials, bituminous products, wax, epoxy, or other
than 1.75 mm (0.069 in.–15 gage) diameter. materials, including molded elastomeric or plastic end caps,
5.14 Holiday Tools—A drill and a suitable drill bit that will capable of withstanding the test temperature, for sealing the
accomplish drilling of test hole, as described in 9.2. ends of coated pipe specimens.
5.15 Heaters: 6.3 Plywood, has been found suitable for the construction of
5.15.1 Pipe Specimens—Liquid Heat Exchange Medium— nonconductive test vessel covers and for the support through
Circulating bath with built-in heater shall be used for heating apertures of test specimens and electrodes. Wood dowels
the heat transfer medium (silicone oil or other) to produce and introduced through holes in the top ends of test specimens have
control temperature of 80° 6 1°C (or other temperature as been found suitable for suspending test specimens from the
specified) inside of the coated pipe samples connected with the vessel cover.
bath by the hoses. 6.4 Hoses, capable of withstanding the test temperature of
D 6676
FIG. 4 Test Set-Up for Cathodic Disbonding Test at Elevated Temperature
80° 6 1°C for connection of the plastic end caps in pipe 7.3 The end of the pipe, which will protrude above the
specimens with circulating bath. immersion line, shall be provided with suitable supporting
6.5 Sand, (40 mesh), to be used over hot plate for more means and a separate wire connection for electrical purposes,
consistent better uniform heating of flat panels. soldered, or brazed to the pipe. The protruding end, including
hanger and wire connections, shall be protected and sealed
7. Test Specimen (Coated Pipes)
with an insulating coating material.
7.1 The test specimen shall be a representative piece of
7.4 The specimen test area shall consist of the area between
coated pipe. Each end shall be plugged, sealed, or capped with
the edge of the bottom end seal and the immersion line. The
inlet and outlet nozzles connected with circulating bath.
bottom end seal area shall not be considered part of the area
7.2 One holiday shall be made in the middle of the im-
tested. Coated specimens of any suitable diameter and length
mersed length by drilling a radial hole through the coating so
of pipe may be used, but the immersed area shall not be less
2 2 2 2
that the angular cone point of the drill will fully enter the steel
than 23 200 mm (36 in. ). An area of 92 900 mm (1 ft ) has
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