ASTM G95-07(2013)
(Test Method)Standard Test Method for Cathodic Disbondment Test of Pipeline Coatings (Attached Cell Method)
Standard Test Method for Cathodic Disbondment Test of Pipeline Coatings (Attached Cell Method)
SIGNIFICANCE AND USE
4.1 Damage to 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. This test method provides accelerated conditions for cathodic disbondment to occur 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 specimen. 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 test method is that all dielectric-type coatings now in common use will disbond to some degree, thus providing a means of comparing one coating to another.
4.5 The current density appearing in this test method is much greater than that usually required for cathodic protection in nat...
SCOPE
1.1 This test method covers accelerated procedures for simultaneously determining comparative characteristics of coating systems applied to steep pipe exterior for the purpose of preventing or mitigating corrosion that may occur in underground service where the pipe will be in contact with natural soils and will receive cathodic protection. They are intended for use with samples of coated pipe taken from commercial production and are applicable to such samples when the coating is characterized by function as an electrical barrier.
1.2 This test method is intended to facilitate testing of coatings where the test cell is cemented to the surface of the coated pipe specimen. This is appropriate when it is impractical to submerge or immerse the test specimen as required by Test Methods G8, G42, or G80. Coating sample configuration such as flat plate and small diameter pipe may be used, provided that the test procedure remains unchanged.2
1.3 This test method allows options that must be identified in the report.
1.4 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.5 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
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: G95 − 07 (Reapproved 2013)
Standard Test Method for
Cathodic Disbondment Test of Pipeline Coatings (Attached
Cell Method)
ThisstandardisissuedunderthefixeddesignationG95;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginal
adoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
2.1 ASTM Standards:
1.1 This test method covers accelerated procedures for
G8Test Methods for Cathodic Disbonding of Pipeline Coat-
simultaneously determining comparative characteristics of
ings
coating systems applied to steep pipe exterior for the purpose
G12Test Method for Nondestructive Measurement of Film
of preventing or mitigating corrosion that may occur in
Thickness of Pipeline Coatings on Steel (Withdrawn
underground service where the pipe will be in contact with
2013)
natural soils and will receive cathodic protection. They are
G42Test Method for Cathodic Disbonding of Pipeline
intended for use with samples of coated pipe taken from
Coatings Subjected to Elevated Temperatures
commercial production and are applicable to such samples
G62Test Methods for Holiday Detection in Pipeline Coat-
when the coating is characterized by function as an electrical
ings
barrier.
G80Test Method for Specific Cathodic Disbonding of Pipe-
1.2 This test method is intended to facilitate testing of
line Coatings (Withdrawn 2013)
coatings where the test cell is cemented to the surface of the
coated pipe specimen. This is appropriate when it is impracti- 3. Summary of Test Method
cal to submerge or immerse the test specimen as required by
3.1 The test method described subjects the coating on the
Test Methods G8, G42,or G80. Coating sample configuration
testspecimentoelectricalstressinahighlyconductivealkaline
such as flat plate and small diameter pipe may be used,
electrolyte. Electrical stress is obtained from an impressed
provided that the test procedure remains unchanged.
direct-current system. An intentional holiday is to be made in
the coating prior to starting of test.
1.3 This test method allows options that must be identified
3.1.1 Electrical instrumentation is provided for measuring
in the report.
the current and the potential throughout the test cycle. At the
1.4 The values stated in SI units are to be regarded as the
conclusion of the test period, the test specimen is physically
standard. The values given in parentheses are for information
examined.
only.
3.1.2 Physical examination is conducted by comparing the
1.5 This standard does not purport to address all of the
extent of loosened or disbonded coating at the intentional
safety concerns, if any, associated with its use. It is the
holiday in the immersed area with extent of loosened or
responsibility of the user of this standard to establish appro-
disbondedcoatingatareferenceholidaymadeinthecoatingin
priate safety and health practices and determine the applica-
an area that was not immersed.
bility of regulatory limitations prior to use.
4. Significance and Use
4.1 Damage to pipe coating is almost unavoidable during
transportation and construction. Breaks or holidays in pipe
This test method is under the jurisdiction of ASTM Committee D01 on Paint
and Related Coatings, Materials, andApplications and is the direct responsibility of
Subcommittee D01.48 on Durability of Pipeline Coating and Linings. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved June 1, 2013. Published June 2013. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1987. Last previous edition approved in 2007 as G95– 07. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/G0095-07R13. the ASTM website.
2 4
For other cathodic disbondment testing procedures, consult Test Methods G8, The last approved version of this historical standard is referenced on
G42, and G80. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
G95 − 07 (2013)
coatings may expose the pipe to possible corrosion since, after 4.3.2 Decreased adhesion in the immersed test area is the
a pipe has been installed underground, the surrounding earth result of cathodic disbondment.
will be moisture-bearing and will constitute an effective
4.4 Ability to resist disbondment is a desired quality on a
electrolyte. Applied cathodic protection potentials may cause
comparative basis, but disbondment in this test method is not
loosening of the coating, beginning at holiday edges. Sponta-
necessarily an adverse indication of coating performance. The
neousholidaysmayalsobecausedbysuchpotentials.Thistest
virtueofthistestmethodisthatalldielectric-typecoatingsnow
method provides accelerated conditions for cathodic disbond-
in common use will disbond to some degree, thus providing a
ment to occur and provides a measure of resistance of coatings
means of comparing one coating to another.
to this type of action.
4.5 The current density appearing in this test method is
4.2 The effects of the test are to be evaluated by physical
much greater than that usually required for cathodic protection
examinations and monitoring the current drawn by the test
in natural environments.
specimen. Usually there is no correlation between the two
methods of evaluation, but both methods are significant.
5. Apparatus
Physicalexaminationconsistsofassessingtheeffectivecontact
of the coating with the metal surface in terms of observed
5.1 Test Vessel—A transparent plastic or glass tube that is
differences in the relative adhesive bond. It is usually found
centered over the intentional holiday and sealed to the test
that the cathodically disbonded area propagates from an area
sample surface with a waterproof sealing material. The cylin-
where adhesion is zero to an area where adhesion reaches the
der is to be 101.6 mm (4.0 in. nominal diameter) and of
originallevel.Anintermediatezoneofdecreasedadhesionmay
sufficient height to contain 127.0 mm (5.0 in.) of electrolyte.
also be present.
Fig. 1 and Fig. 2 apply to this entire section.
4.3 Assumptions associated with test results include:
NOTE 1—Size of vessel shall remain unchanged. Sealing procedure
4.3.1 Maximum adhesion, or bond, is found in the coating
must be altered to accommodate specimen having a diameter less than
that was not immersed in the test liquid, and 101.60 mm (4 in.).
FIG. 1 Typical Test Set Up
G95 − 07 (2013)
5.8 Direct-Current Power Supply—Capable of supplying
low-ripple voltage at 3.0, 60.01, V, as measured between the
test specimen and reference electrode.
5.9 PrecisionWire-WoundResistor—1Ω,61%,1-W(mini-
mum)tobeusedinthetestcellcircuitasashuntformeasuring
current.
5.10 Thickness Gage—For measuring coating thickness in
accordance with Test Method G12.
5.11 HolidayDetector—Forlocatingholidaysinthecoating
of the test specimen in accordance with Test Methods G62.
5.12 Connections—Wiringfromcurrentsourcetothespeci-
men shall be by either soldering, brazing, or bolting to the
non-immersed area of the specimen.Ajunction in the connec-
tion wire is not desirable but, if necessary, may be made by
means of a bolted pair of terminal lugs, soldering or mechani-
cally crimping to clean wire ends.
5.13 Additional Connecting Wires—If additional wiring is
necessary, it shall be stranded, insulated copper and not less
than 1.75 mm (0.069 in. -14 gage) diameter.
5.14 Holiday Tools—Adrill and a suitable drill bit that will
accomplish drilling of test hole, as described under 8.2.A
sharp-pointed knife, with a safe handle is required for use in
making physical examination.
FIG. 2 Anode Assembly
6. Reagent and Materials
6.1 The electrolyte shall consist of distilled or deionized
water with the addition of 3 mass % of technical grade sodium
5.2 Filter Tube—Anode assembly shall be constructed uti-
chloride. Use freshly prepared solution for each test.
lizing an immer
...
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