ASTM D6676/D6676M-13

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

SIGNIFICANCE AND USE
4.1 Damage to a pipe coating is almost unavoidable during transportation and construction. Breaks or holidays in pipe coatings may expose the pipe to possible corrosion since, after a pipe has been installed underground, the surrounding earth will be moisture-bearing and will constitute an effective electrolyte. Applied cathodic protection potentials may cause loosening of the coating, beginning at holiday edges. Spontaneous holidays may also be caused by such potentials. Usually exterior pipeline coatings applied over pipes carrying hot media (oil, gas) are exposed to high temperature inside the pipe and low temperature outside and subjected to temperature gradient. Heat flux is directed from metal (substrate) to the coating. This test method provides accelerated conditions for cathodic disbondment to occur under simulated heating and provides a measure of resistance of coatings to this type of action.  
4.2 The effects of the test are to be evaluated by physical examinations and monitoring the current drawn by the test specimens. Usually there is no correlation between the two methods of evaluation, but both methods are significant. Physical examination consists of assessing the effective contact of the coating with the metal surface in terms of observed differences in the relative adhesive bond. It is usually found that the cathodically disbonded area propagates from an area where adhesion is zero to an area where adhesion reaches the original level. An intermediate zone of decreased adhesion may also be present.  
4.3 Assumptions associated with test results include:  
4.3.1 Maximum adhesion, or bond, is found in the coating that was not immersed in the test liquid, and  
4.3.2 Decreased adhesion in the immersed test area is the result of cathodic disbondment.  
4.4 Ability to resist disbondment is a desired quality on a comparative basis, but disbondment in this test method is not necessarily an adverse indication of coating performance. The virtue of this...
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 required but without temperature gradient, see Test Method G42.  
1.3 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.  
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: 31-Oct-2013
• ICS: 19.040 - Environmental testing
• ICS: 25.220.01 - Surface treatment and coating in general
• Technical Committee: D01 - Paint and Related Coatings, Materials, and Applications
• Drafting Committee: D01.48 - Durability of Pipeline Coating and Linings

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D6676/D6676M − 13
Standard Test Method for
Cathodic Disbonding of Exterior Pipeline Coatings at
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Elevated Temperatures Using Interior Heating
This standard is issued under the fixed designation D6676/D6676M; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope G8Test Methods for Cathodic Disbonding of Pipeline Coat-
ings
1.1 This test method describes an accelerated procedure for
G12Test Method for Nondestructive Measurement of Film
determining comparative characteristics of coating systems
Thickness of Pipeline Coatings on Steel (Withdrawn
applied to the exterior of steel pipe for the purpose of
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2013)
preventing or mitigating corrosion that may occur in under-
G42Test Method for Cathodic Disbonding of Pipeline
ground or immersion where the pipe is carrying heated media
Coatings Subjected to Elevated Temperatures
and is under cathodic protection. This test method is intended
G62Test Methods for Holiday Detection in Pipeline Coat-
for use with samples of coated pipe, or with a specimen cut
ings
from the section of coated pipe or flat plates, and is applicable
G95TestMethodforCathodicDisbondmentTestofPipeline
to such samples when the coating is characterized by function
Coatings (Attached Cell Method)
as an electrical barrier.
1.2 This test method is intended to simulate conditions
3. Summary of Test Method
when external coatings are exposed to high temperature inside
3.1 The test method described, subjects the coating on the
the pipe and to an ambient temperature outside, and thus are
testspecimentoelectricalstressinahighlyconductivealkaline
subjected to temperature gradient. If elevated temperatures are
electrolyte. Electrical stress is obtained from an impressed
required but without temperature gradient, see Test Method
direct- current system.An intentional holiday is to be made in
G42.
the coating prior to starting of test.
1.3 The values stated in either SI units or inch-pound units
3.1.1 Electrical instrumentation is provided for measuring
are to be regarded separately as standard. The values stated in
the current and the potential throughout the test cycle. At the
each system may not be exact equivalents; therefore, each
conclusion of the test period, the test specimen is physically
system shall be used independently of the other. Combining
examined.
values from the two systems may result in non-conformance
3.1.2 Physical examination is conducted by comparing the
with the standard.
extent of loosened or disbonded coating at the intentional
holiday in the immersed area with extent of loosened or
1.4 This standard does not purport to address all of the
disbondedcoatingatareferenceholidaymadeinthecoatingin
safety concerns, if any, associated with its use. It is the
an area that was not immersed.
responsibility of the user of this standard to establish appro-
3.1.3 The cathodic stress is applied under conditions of a
priate safety and health practices and determine the applica-
constant temperature gradient, simulating a heated pipeline
bility of regulatory limitations prior to use.
with an exterior coating.
2. Referenced Documents
3.1.4 Specimensthatcanbeusedare:(a)pieceofpipe(Fig.
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1)or(b) samples cut from pipe or flat plate (Fig. 2 and Fig. 3).
2.1 ASTM Standards:
3.1.4.1 Some coatings rely on application tension (such as
tape) for maximum cathodic disbondment resistance. Cut
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This test method is under the jurisdiction of ASTM Committee D01 on Paint
coupons or flat plates must not be used.
and Related Coatings, Materials, andApplications and is the direct responsibility of
Subcommittee D01.48 on Durability of Pipeline Coating and Linings.
4. Significance and Use
Current edition approved Nov. 1, 2013. Published November 2013. Originally
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approved in 2001. Last previous edition approved in 2001 as D6676–01 which
4.1 Damage to a pipe coating is almost unavoidable during
was withdrawn January 2010 and reinstated in November 2013. DOI: 10.1520/
transportation and construction. Breaks or holidays in pipe
D6676_D6676M-13.
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For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
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Standards volume information, refer to the standard’s Document Summary page on The last approved version of this historical standard is referenced on
the ASTM website. www.astm.org.
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D6676/D6676M − 13
4.3.1 Maximum adhesion, or bond, is found i
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