ASTM G42-11(2019)e1
(Test Method)Standard Test Method for Cathodic Disbonding of Pipeline Coatings Subjected to Elevated Temperatures
Standard Test Method for Cathodic Disbonding of Pipeline Coatings Subjected to Elevated Temperatures
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 describes an accelerated procedure for determining comparative characteristics of insulating coating systems applied to steel pipe exterior for the purpose of preventing or mitigating corrosion that may occur in underground service where the pipe will be exposed to high temperatures and is under cathodic protection. This test method is intended for use with samples of coated pipe taken from commercial production and is applicable to such samples when the coating is characterized by function as an electrical barrier.
1.2 This test method is intended for testing coatings submerged or immersed in the test solution at elevated temperature. When it is impractical to submerge or immerse the test specimen, Test Method G95 may be considered where the test cell is cemented to the surface of the coated pipe specimen. If room temperatures are required, see Test Methods G8. If a specific test method is required with no options, see Test Method G80.
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 Warning—Mercury has been designated by EPA and many state agencies as a hazardous material that can cause central nervous system, kidney, and liver damage. Mercury, or its vapor, may be hazardous to health and corrosive to materials. Caution should be taken when handling mercury and mercury-containing products. See the applicable product Material Safety Data Sheet (MSDS) for details and EPA’s website (http://www.epa.gov/mercury/faq.htm) for additional information. Users should be aware that selling mercury or mercury-containing products, or both, in your state may be prohibited by state law.
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, health, and env...
General Information
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Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
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Designation: G42 − 11 (Reapproved 2019)
Standard Test Method for
Cathodic Disbonding of Pipeline Coatings Subjected to
Elevated Temperatures
ThisstandardisissuedunderthefixeddesignationG42;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginal
adoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
ε NOTE—Editorial changes were made throughout in July 2019.
1. Scope 1.5 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
1.1 This test method describes an accelerated procedure for
responsibility of the user of this standard to establish appro-
determining comparative characteristics of insulating coating
priate safety, health, and environmental practices and deter-
systems applied to steel pipe exterior for the purpose of
mine the applicability of regulatory limitations prior to use.
preventing or mitigating corrosion that may occur in under-
1.6 This international standard was developed in accor-
ground service where the pipe will be exposed to high
dance with internationally recognized principles on standard-
temperaturesandisundercathodicprotection.Thistestmethod
ization established in the Decision on Principles for the
is intended for use with samples of coated pipe taken from
Development of International Standards, Guides and Recom-
commercialproductionandisapplicabletosuchsampleswhen
mendations issued by the World Trade Organization Technical
the coating is characterized by function as an electrical barrier.
Barriers to Trade (TBT) Committee.
1.2 This test method is intended for testing coatings sub-
2. Referenced Documents
merged or immersed in the test solution at elevated tempera-
ture. When it is impractical to submerge or immerse the test
2.1 ASTM Standards:
specimen, Test Method G95 may be considered where the test
G8Test Methods for Cathodic Disbonding of Pipeline Coat-
cell is cemented to the surface of the coated pipe specimen. If
ings
room temperatures are required, see Test Methods G8.Ifa
G12Test Method for Nondestructive Measurement of Film
specific test method is required with no options, see Test
Thickness of Pipeline Coatings on Steel (Withdrawn
Method G80.
2013)
G80Test Method for Specific Cathodic Disbonding of Pipe-
1.3 The values stated in SI units to three significant deci-
line Coatings (Withdrawn 2013)
mals are to be regarded as the standard. The values given in
G95TestMethodforCathodicDisbondmentTestofPipeline
parentheses are for information only.
Coatings (Attached Cell Method)
1.4 Warning—Mercury has been designated by EPA and
E1Specification for ASTM Liquid-in-Glass Thermometers
many state agencies as a hazardous material that can cause
E2251Specification for Liquid-in-Glass ASTM Thermom-
central nervous system, kidney, and liver damage. Mercury, or
eters with Low-Hazard Precision Liquids
its vapor, may be hazardous to health and corrosive to
3. Summary of Test Method
materials.Cautionshouldbetakenwhenhandlingmercuryand
mercury-containing products. See the applicable product Ma-
3.1 This test method subjects the coating on the test speci-
terial Safety Data Sheet (MSDS) for details and EPA’s website
men to electrical stress in a highly conductive electrolyte. The
(http://www.epa.gov/mercury/faq.htm) for additional informa-
coating is artificially perforated before starting the test. The
tion. Users should be aware that selling mercury or mercury-
electrical stress is produced by connecting the test specimen to
containingproducts,orboth,inyourstatemaybeprohibitedby
the negative terminal of a source of direct current and by
state law.
connecting an anode to the positive terminal. Electrical instru-
mentation is provided for measuring the current flowing in the
1 2
This test method is under the jurisdiction of ASTM Committee D01 on Paint For referenced ASTM standards, visit the ASTM website, www.astm.org, or
and Related Coatings, Materials, andApplications and is the direct responsibility of contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Subcommittee D01.48 on Durability of Pipeline Coating and Linings. Standards volume information, refer to the standard’s Document Summary page on
CurrenteditionapprovedJuly1,2019.PublishedJuly2019.Originallyapproved the ASTM website.
in1975.Lastpreviouseditionapprovedin2011asG42–11.DOI:10.1520/G0042- The last approved version of this historical standard is referenced on
11R19E01. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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G42 − 11 (2019)
cell.Theelectricalpotentialisalsomeasured,andthespecimen this test is much greater than that usually required for cathodic
is physically examined at intervals during the test period and protection in natural, inland soil environments.
upon conclusion of the test. 4.6.2 Test voltages higher than those recommended may
result in the formation of chlorine gas. The subsequent chemi-
3.1.1 The cathodic stress is applied under conditions of a
cal effects on the coating could cast doubt on the interpretation
constant-elevated temperature.
of the test results.
4. Significance and Use
5. Apparatus
4.1 Damage to pipe coating is almost unavoidable during
5.1 Test Vessel—Asuitablenonreactivevesselshallbeused,
transportation and construction. Breaks or holidays in pipe
capable of withstanding internal heating at not less than 60°C
coatings may expose the pipe to possible corrosion since, after
and suitable for continuous circulation of the electrolyte.
a pipe has been installed underground, the surrounding earth
A19-L(5-gal)cylindricalglassvesselhasbeenfoundsuitable,
will be moisture-bearing and will constitute an effective
having an approximate diameter of 300 mm (12 in.) and a
electrolyte. Applied cathodic protection potentials may cause
depth of 300 mm. A flat bottom is required for operation of a
loosening of the coating, beginning at holiday edges. Sponta-
magnetic stirring rod. An alternate means of heating the test
neousholidaysmayalsobecausedbysuchpotentials.Thistest
sample can be provided by internally heating.The pipe sample
method provides accelerated conditions for cathodic disbond-
may be filled with a suitable heat transfer material (oil, steel
ment to occur and provides a measure of resistance of coatings
shot, etc.). A thermocouple or thermometer and heater can be
to this type of action.
immersedintheheattransfermediumtoeffectivelycontrolthe
4.2 The effects of the test are to be evaluated by physical
temperature of the sample. Dimensions of the vessel shall
examinations and monitoring the current drawn by the test
permit the following requirements:
specimen. Usually there is no correlation between the two
5.1.1 Test specimens shall be suspended vertically in the
methods of evaluation, but both methods are significant.
vessel with at least 25 mm (1 in.) clearance from the bottom.
Physicalexaminationconsistsofassessingtheeffectivecontact
5.1.2 Test specimens shall be separated by not less than
of the coating with the metal surface in terms of observed
38mm (1 ⁄2 in.), and a vertically suspended anode can be
differences in the relative adhesive bond. It is usually found
placed at an equal distance from each specimen not less than
that the cathodically disbonded area propagates from an area
the separation distance.
where adhesion is zero to an area where adhesion reaches the
5.1.3 Testspecimensshallbeseparatedfromanywallofthe
originallevel.Anintermediatezoneofdecreasedadhesionmay
vessel by not less than 13 mm ( ⁄2 in.).
also be present.
5.1.4 Depth of electrolyte shall permit the test length of the
4.3 Assumptions associated with test results include: specimen to be immersed as required in 7.4.
5.1.5 The reference electrode may be placed anywhere in
4.3.1 Maximum adhesion, or bond, is found in the coating
that was not immersed in the test liquid, and thevessel,provideditisseparatedfromthespecimenandfrom
the anode by not less than 38 mm (1 ⁄2 in.).
4.3.2 Decreased adhesion in the immersed test area is the
result of cathodic disbondment.
5.2 Anode—The anode shall be provided with a factory-
sealed, insulated copper wire lead.
4.4 Ability to resist disbondment is a desired quality on a
comparative basis, but disbondment in this test method is not
5.3 Connectors—Wiring from anode to test specimen shall
necessarily an adverse indication of coating performance. The
be 4107 cmil (14-gage Awg), minimum, insulated copper.
virtueofthistestmethodisthatalldielectric-typecoatingsnow
Attachment to the test specimen shall be by soldering or
in common use will disbond to some degree, thus providing a
brazing to the non-immersed end, and the place of attachment
means of comparing one coating to another.
shall be coated with an insulating material. A junction in the
connectingwireispermitted,providedthatitismadebymeans
4.5 The current density appearing in this test method is
of a bolted pair of terminal lugs soldered or mechanically
much greater than that usually required for cathodic protection
crimped to clean wire ends.
in natural environments.
5.4 Holiday Tools—Holidays shall be made with conven-
4.6 That any relatively lesser bonded area was caused by
tional drills of the required diameter. For use in preparing
electrical stressing in combination with the elevated and or
small-diameterpipespecimenssuchas19-mm( ⁄4-in.)nominal
depressed temperature and was not attributable to an anomaly
diameter pipe, the use of a drill modified by substantially
in the application process. Ability to resist disbondment is a
grinding away the sharp cone point has been found effective in
desired quality on a comparative basis, but most insulating
preventing perforation of the metal wall of the pipe. A
materials will disbond to some extent under the accelerated
sharp-pointed knife with a safe handle is required for use in
conditions of this test. Bond strength is more important for
making physical examinations.
proper functioning of some coatings than others and the same
measured disbondment for two different coating systems may 5.5 Multimeters:
not represent equivalent loss of corrosion protection.
4.6.1 The amount of current flowing in the test cell may be
a relative indicator of the extent of areas requiring protection
Duriron, a material found suitable for this purpose is available from Duriron
against corrosion; however, the current density appearing in Co., Inc., Dayton, OH.
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G42 − 11 (2019)
5.5.1 Multimeter, for direct current, having an internal 5.14 Brass Studs, used at a terminal board, together with
resistanceofnotlessthan10MΩandhavingarangefrom0.01 alligator clips or knife switches, for making and breaking
to 5 V for measuring potential to the reference electrode. circuits. Alligator clips shall not be used to connect the
electrodes or specimens at the top location of test cells.
5.5.2 Multimeter, for direct current, having an internal
resistance of not less than 11 MΩ and capable of measuring as
6. Reagents and Materials
low as 10 µV potential drop across a shunt in the test cell
circuit.
6.1 The electrolyte shall consist of potable tap water or
5.5.3 Multimeter, for initial testing of apparent coating
higher purity water (distilled or demineralized water is satis-
resistance.
factory) with the addition of 1 weight% of each of the
following technical-grade salts, calculated on an anhydrous
5.6 Reference Electrode—Saturated Cu CuSO electrode
basis: sodium chloride, sodium sulfate, and sodium carbonate.
having a potential of −0.316 V with respect to the standard
hydrogen electrode shall be the standard of reference in these
NOTE 2—The resulting solution has a pH of 10 or higher and a
test methods. Other electrodes may be used but measurements resistivity of 25 to 50 Ω·cm at room temperature.
thusobtainedshallbeconvertedtotheCuCuSO referencefor
6.2 Materials for sealing the ends of coated pipe specimens
reporting by making the proper correction.
may consist of bituminous products, wax, epoxy, or other
materials, including molded elastomeric or plastic end caps,
NOTE1—AsaturatedCuCuSO electrodereading−1.50Vat25°Cwill
read −1.53 V at 60°C, a scale increase of 0.03 V capable of withstanding the test temperature.
5.6.1 Asaturated calomel electrode at 25°C is converted to 6.3 Plywood has been found suitable for the construction of
Cu CuSO by adding −0.07 V to the observed reading. If the nonconductive test vessel covers and for the support through
saturated calomel electrode reads −1.43 V at 25°C, it will read apertures of test specimens and electrodes. Wood dowels
−1.46 V at 60°C, a scale increase of 0.03 V. It follows that a introducedthroughholesinthetopendsoftestspecimenshave
saturatedcalomelelectrodereadingof−1.46Vat60°Cisequal been found suitable for suspending test specimens from the
to a saturated Cu CuSO reading of −1.50 V at 25°C. vessel cover.
5.6.2 A0.1normalcalomelelectrodeat25°Cisconvertedto
7. Test Specimen
Cu CuSO by subtracting −0.02 V from the observed reading.
Since the potential change due to an increase from 25°C to
7.1 The test specimen shall be a representative piece of
60°C is negligible, it follows that a 0.1 normal calomel
production-coated pipe. One end shall be plugged, sealed, or
electrode reading −1.52 V at 60°C is equal to a saturated Cu
capped.
CuSO reading of −1.50 V at 25°C.
7.2 One holiday shall be made in the middle of the im-
5.7 Thermometers, two, mercury-filled type or liquid-in-
mersed length by drilling a radial hole through the coating so
glass, accurate to 61°C. One shall be of the full-immersion
that the angular cone point of the drill will fully enter the steel
type for measuring temperature near the bottom of the vessel,
where the cylindrical portion of the drill meets the steel
and a second thermometer shall be of the partial-total-
surface.Thedrilldiametershallbenotlessthanthreetimesthe
immersion type for measuring temperature near the top of the 1
coating thickness, but it shall never be less than 6 mm ( ⁄4 in.)
vessel. Liquid-in-glass thermometers shall conform to Speci-
in diameter. The steel wall of the pipe shall not be perforated.
fications E1 or E2251. Electronic temperature reading devices
Withsmall-diameterpipes,wherethereisdangerofperforating
such as RTDs, thermistors or thermocouple of equal or better
the pipe, the holiday shall be started with a standard 60° cone
accuracy may be used.
pointandfinished
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