ASTM G8-96(2019)
(Test Method)Standard Test Methods for Cathodic Disbonding of Pipeline Coatings
Standard Test Methods for Cathodic Disbonding of Pipeline Coatings
SIGNIFICANCE AND USE
4.1 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 more or less moisture-bearing and it constitutes an effective electrolyte. Damage to pipe coating is almost unavoidable during transportation and construction. Normal soil potentials as well as applied cathodic protection potentials may cause loosening of the coating, beginning at holiday edges, in some cases increasing the apparent size of the holiday. Holidays may also be caused by such potentials. While apparently loosened coating and cathodic holidays may not result in corrosion, this test provides accelerated conditions for loosening to occur and therefore gives a measure of resistance of coatings to this type of action.
4.2 The effects of the test may be evaluated by either physical examination or monitoring the current drawn by the test specimen and both of these two. 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 electrically stressed area propagates from the holiday to a boundary where the loosened coating leaves off for the more effective contact or bond attributed to an original condition throughout the specimen before electrical stressing was applied. Assumptions associated with test results include the following:
4.2.1 Attempting to loosen or disbond the coating at a new test hole made in the coating in an area that was not immersed represents maximum adhesion or bond as measured by the lifting technique used, and that the same lifting technique can be used at a test hole that was immersed thereby providing a means of comparing relative resistance to lifting.
4.2.2 Any relatively lesser bonded area at the immersed test holes in the coa...
SCOPE
1.1 These test methods cover accelerated procedures for simultaneously 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 in contact with inland soils and may or may not 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 for testing coatings submerged or immersed in the test solution at room 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 higher temperatures are required, see Test Method G42. If a specific test method is required with no options, see Test Method G80.
1.3 The values stated in SI units to 3 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.5 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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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.
Designation: G8 − 96 (Reapproved 2019)
Standard Test Methods for
Cathodic Disbonding of Pipeline Coatings
This standard is issued under the fixed designation G8; the number immediately following the designation indicates the year of original
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 These test methods cover accelerated procedures for
G12Test Method for Nondestructive Measurement of Film
simultaneously determining comparative characteristics of in-
Thickness of Pipeline Coatings on Steel (Withdrawn
sulating coating systems applied to steel pipe exterior for the
2013)
purposeofpreventingormitigatingcorrosionthatmayoccurin
G42Test Method for Cathodic Disbonding of Pipeline
underground service where the pipe will be in contact with
Coatings Subjected to Elevated Temperatures
inland soils and may or may not receive cathodic protection.
G80Test Method for Specific Cathodic Disbonding of Pipe-
They are intended for use with samples of coated pipe taken
line Coatings (Withdrawn 2013)
from commercial production and are applicable to such
G95TestMethodforCathodicDisbondmentTestofPipeline
samples when the coating is characterized by function as an
Coatings (Attached Cell Method)
electrical barrier.
3. Summary of Test Method
1.2 This test method is intended for testing coatings sub-
merged or immersed in the test solution at room temperature.
3.1 Both of the two test methods described subject the
When it is impractical to submerge or immerse the test
coating on the test specimen to electrical stress in a highly
specimen, Test Method G95 may be considered where the test conductive, alkaline electrolyte. Electrical stress is obtained
cell is cemented to the surface of the coated pipe specimen. If either by means of a sacrificial magnesium anode or from an
impressed current system. The coating is perforated before
higher temperatures are required, see Test Method G42.Ifa
starting the test.
specific test method is required with no options, see Test
3.1.1 In Method A, a magnesium anode is used with no
Method G80.
electrical monitoring during the test period. The results are
1.3 ThevaluesstatedinSIunitsto3significantdecimalsare
determined by physical examination after the test period is
toberegardedasthestandard.Thevaluesgiveninparentheses
concluded.
are for information only.
3.1.2 In Method B, either a magnesium anode or an im-
pressedcurrentsystemmaybeused.Electricalinstrumentation
1.4 This standard does not purport to address all of the
is provided for measuring the current in the cell circuit. The
safety concerns, if any, associated with its use. It is the
electrical potential is also measured, and upon conclusion of
responsibility of the user of this standard to establish appro-
the test period, the test specimen is physically examined.
priate safety, health, and environmental practices and deter-
3.1.3 In both test methods physical examination is con-
mine the applicability of regulatory limitations prior to use.
ducted by comparing the extent of loosened or disbonded
1.5 This international standard was developed in accor-
coating at the perforations in the immersed area with extent of
dance with internationally recognized principles on standard-
loosened or disbonded coating at a new test hole in the coating
ization established in the Decision on Principles for the
made in an area that was not immersed.
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
4. Significance and Use
Barriers to Trade (TBT) Committee.
4.1 Breaksorholidaysinpipecoatingsmayexposethepipe
to possible corrosion, since after a pipe has been installed
These test methods are under the jurisdiction of ASTM Committee D01 on
Paint and Related Coatings, Materials, and Applications and are the direct For referenced ASTM standards, visit the ASTM website, www.astm.org, or
responsibility of Subcommittee D01.48 on Durability of Pipeline Coating and contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Linings. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved June 1, 2019. Published June 2019. Originally the ASTM website.
approved in 1969. Last previous edition approved in 2010 as G8–96(2010). DOI: The last approved version of this historical standard is referenced on
10.1520/G0008-96R19. www.astm.org.
Copyright ©ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA19428-2959. United States
G8 − 96 (2019)
underground, the surrounding earth will be more or less 5.1.1.2 Eachtestspecimenshallbeseparatedfromtheother
moisture-bearing and it constitutes an effective electrolyte. specimens, from the anodes and from the walls of the test
vessel by at least 38.1 mm (1.500 in.).
Damage to pipe coating is almost unavoidable during trans-
portation and construction. Normal soil potentials as well as 5.1.1.3 Depth of electrolyte shall permit the test length of
applied cathodic protection potentials may cause loosening of the specimen to be immersed as required in 7.4.
the coating, beginning at holiday edges, in some cases increas- 5.1.1.4 If electrical monitoring is to be performed as re-
ing the apparent size of the holiday. Holidays may also be quired in Method B, the reference electrode may be placed
anywhere in the vessel, provided it is separated from the
caused by such potentials. While apparently loosened coating
specimen and from the anode by not less than 38.1 mm (1.500
and cathodic holidays may not result in corrosion, this test
in.).
provides accelerated conditions for loosening to occur and
5.1.2 Magnesium Anode—The anode shall be made of a
therefore gives a measure of resistance of coatings to this type
magnesium alloy having a solution potential of −1.45 to −1.55
of action.
V with respect to a CuCuSO reference electrode in the
4.2 The effects of the test may be evaluated by either
electrolyte given in 6.1. It shall have a surface area not less
physical examination or monitoring the current drawn by the
than one third that of the total specimen area exposed to
test specimen and both of these two. Usually there is no
electrolyte (outside area exposed only). The anode shall be
correlation between the two methods of evaluation but both
provided with a factory-sealed, 4107-cmil (14-gage Awg),
methods are significant. Physical examination consists of
minimum,insulatedcopperwire.Anodeswithoutafactoryseal
assessing the effective contact of the coating with the metal
may be used if the magnesium extends above the cover.
surfaceintermsofobserveddifferencesintherelativeadhesive
5.1.3 Connectors—Wiring from anode to test specimen
bond. It is usually found that the electrically stressed area
shallbe4107-cmil(14-gageAwg),minimum,insulatedcopper.
propagates from the holiday to a boundary where the loosened
Attachmenttothetestspecimenshallbebysoldering,brazing,
coating leaves off for the more effective contact or bond
orboltingtothenonimmersedend,andtheplaceofattachment
attributed to an original condition throughout the specimen
shall be coated with an insulating material. A junction in the
beforeelectricalstressingwasapplied.Assumptionsassociated
connectingwireispermitted,providedthatitismadebymeans
with test results include the following:
of a bolted pair of terminal lugs soldered or mechanically
4.2.1 Attempting to loosen or disbond the coating at a new crimped to clean wire ends.
test hole made in the coating in an area that was not immersed 5.1.4 Holiday Tools—Holidays shall be made with conven-
represents maximum adhesion or bond as measured by the
tional drills of the required diameter. For use in preparing
lifting technique used, and that the same lifting technique can small-diameter pipe specimens such as 19.05 mm (0.750 in.)
be used at a test hole that was immersed thereby providing a nominal diameter pipe, the use of a drill modified by substan-
means of comparing relative resistance to lifting. tially grinding away the sharp cone point has been found
effectiveinpreventingperforationofthemetalwallofthepipe.
4.2.2 Any relatively lesser bonded area at the immersed test
Asharp-pointed knife with a safe handle is required for use in
holes in the coating was caused by electrical stressing and was
making physical examinations.
not attributable to an anomaly in the application process.
5.1.5 High-Resistance Voltmeter, for direct current, having
Ability to resist disbondment is a desired quality on a com-
an internal resistance of not less than 10 MΩ and having a
parative basis, but disbondment per se in this test is not
rangefrom0.01to5Vformeasuringpotentialtothereference
necessarily an adverse indication. The virtue of this test is that
electrode.
alldielectrictypecoatingsnowincommonusewilldisbondto
5.1.6 Reference Electrode, saturated CuCuSO of conven-
some degree thus providing a means of comparing one coating
tional glass or plastic tube with porous plug construction,
with another. Bond strength is more important for proper
preferably not over 19.05 mm (0.750 in.) in diameter, having a
functioning of some coatings than others and the same mea-
potential of −0.316 V with respect to the standard hydrogen
sured disbondment for two different coating systems may not
electrode.Acalomel electrode may be used, but measurements
represent equivalent loss of corrosion protection.
made with it shall be converted to the CuCuSO reference for
4.2.3 The amount of current in the test cell is a relative
reporting by adding−0.072 V to the observed reading.
indicator of the extent of areas requiring protection against
5.1.7 Thickness Gage, for measuring coating thickness in
corrosion;however,thecurrentdensityappearinginthistestis
accordance with Test Method G12.
much greater than that usually required for cathodic protection
5.1.8 Thermometer, for measuring electrolyte temperature,
in natural, inland soil environments.
general lab type, 1° subdivisions, 76.2 mm (3 in.) immersion.
5.2 Additional Apparatus for Method B:
5. Apparatus
5.2.1 High-Resistance Voltmeter, for direct current, having
5.1 Apparatus for Both Methods:
an internal resistance of not less than 10 MΩ and capable of
5.1.1 Test Vessel—A nonconducting material shall be used
measuring as low as 10 µVpotential drop across a shunt in the
for the vessel or as a lining in a metallic vessel. Dimensions of
test cell circuit.
the vessel shall permit the following requirements:
5.2.2 Precision Wire-Wound Resistor, 1-Ω 6 1%, 1-W
5.1.1.1 Test specimens shall be suspended vertically in the (minimum), to be used in the test cell circuit as a shunt for
vesselwithatleast25.4-mm(1-in.)clearancefromthebottom. current.
G8 − 96 (2019)
5.2.3 Volt-Ohm-Meter, for initial testing of apparent coating gradesalts,calculatedonananhydrousbasis:sodiumchloride,
resistance. sodium sulfate, and sodium carbonate. Use freshly prepared
5.2.4 Metallic Electrode, used temporarily with the volt- solution for each test.
ohm-meter to determine apparent initial holiday status of the
6.2 Materials for sealing the ends of coated pipe specimens
test specimen.
may consist of bituminous products, wax, epoxy, or other
5.2.5 Additional Connecting Wires, 4107-cmil (14-gage
materials, including molded elastomeric or plastic end caps.
Awg), minimum, insulated copper.
6.3 Plywood or plastic material has been found suitable for
5.2.6 Brass Studs, used at a terminal board, together with
the construction of test vessel covers and for the support
alligator clips or knife switches, for making and breaking
through apertures of test specimens and electrodes. Wood
circuits. Alligator clips shall not be used to connect to
dowels introduced through holes in the top ends of test
electrodes or specimens at the top location of test cells.
specimens have been found suitable for suspending test speci-
5.2.7 Zero-Resistance Ammeter,capableofmeasuringdirect
mens from the vessel cover.
current as low as 10 µAmay be used in the alternative method
given in 9.1.3 and substituted for the apparatus described in
7. Test Specimen
5.2.1 and 5.2.2.
5.2.8 Direct-Current Rectifier, capable of supplying con- 7.1 The test specimen shall be a representative piece of
production-coated pipe. One end shall be plugged or capped,
stant voltage at a voltage of 1.50 6 0.01 V, as measured
and sealed.
between the specimen and reference electrode.
5.2.9 Impressed Current Anode, shall be of the nonconsum-
7.2 One or three holidays shall be made in each specimen.
able type provided with a factory sealed, insulated copper
Three holidays are recommended. Recommended dimensions
wire.
are given in Fig. 2.Aspecimen with one holiday shall have it
5.2.10 Voltage Divider, 100-Ω, 25-W rheostat, to be used if
drilled in the middle of the immersed length. If three holidays
more than one specimen is to be tested as shown in Fig. 1.
are used, they shall be drilled 120° apart with one in the center
and the other two at locations one fourth the distance from top
6. Reagent and Materials
and bottom of the immersed test length. Each holiday shall be
6.1 The electrolyte shall consist of potable tap water with
drilledsothattheangularconepointofthedrillwillfullyenter
the addition of 1 mass% of each of the following technical-
the steel where the cylindrical portion of the drill meets the
steel surface. The drill diameter shall be not less than three
times the coating thickness, but it shall never be smaller than
Durion,amaterialfoundsuitableforthispurposeisavailablefromDurionCo.,
6.35mm(0.250in.)indiameter.Thesteelwallofthepipeshall
Inc., Dayton OH.
FIG. 1 Modification of Method B (Fig. 5) Using Impressed Current to Test More than One Specimen
G8 − 96 (2019)
Dimension mm (in.)
490.22 ± 12.7 (19.300 ± 0.500)
B 245.11 ± 12.7 (9.650± 0.500)
C 120.65 ± 6.35 (4.750± 0.250)
D 114.3 ± 6.35 (4.500 ± 0.250)
E 233.363, min (9.1875, min)
F 19.05, min (0.750, min)
G 762, min (30, min)
FIG. 2 Recommended Dimensions for Specimen
2 2 2 2
not be perforated. With small-diameter pipes, where there is mm (36 in. ).An area of 92 900 mm (1 ft ) has been found
dangerofperforatingthepipe,theholidayshallbestartedwith preferable when convenient.
a standard 60° cone point and finished with a drill that has had
8. Specimen Preparation
a substantial portion of the cone point ground away.
...
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: G8 − 96 (Reapproved 2019)
Standard Test Methods for
Cathodic Disbonding of Pipeline Coatings
This standard is issued under the fixed designation G8; 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 2. Referenced Documents
2.1 ASTM Standards:
1.1 These test methods cover accelerated procedures for
G12 Test Method for Nondestructive Measurement of Film
simultaneously determining comparative characteristics of in-
Thickness of Pipeline Coatings on Steel (Withdrawn
sulating coating systems applied to steel pipe exterior for the
2013)
purpose of preventing or mitigating corrosion that may occur in
G42 Test Method for Cathodic Disbonding of Pipeline
underground service where the pipe will be in contact with
Coatings Subjected to Elevated Temperatures
inland soils and may or may not receive cathodic protection.
G80 Test Method for Specific Cathodic Disbonding of Pipe-
They are intended for use with samples of coated pipe taken
line Coatings (Withdrawn 2013)
from commercial production and are applicable to such
G95 Test Method for Cathodic Disbondment Test of Pipeline
samples when the coating is characterized by function as an
Coatings (Attached Cell Method)
electrical barrier.
3. Summary of Test Method
1.2 This test method is intended for testing coatings sub-
merged or immersed in the test solution at room temperature.
3.1 Both of the two test methods described subject the
When it is impractical to submerge or immerse the test coating on the test specimen to electrical stress in a highly
specimen, Test Method G95 may be considered where the test conductive, alkaline electrolyte. Electrical stress is obtained
either by means of a sacrificial magnesium anode or from an
cell is cemented to the surface of the coated pipe specimen. If
impressed current system. The coating is perforated before
higher temperatures are required, see Test Method G42. If a
starting the test.
specific test method is required with no options, see Test
3.1.1 In Method A, a magnesium anode is used with no
Method G80.
electrical monitoring during the test period. The results are
1.3 The values stated in SI units to 3 significant decimals are
determined by physical examination after the test period is
to be regarded as the standard. The values given in parentheses
concluded.
are for information only.
3.1.2 In Method B, either a magnesium anode or an im-
pressed current system may be used. Electrical instrumentation
1.4 This standard does not purport to address all of the
is provided for measuring the current in the cell circuit. The
safety concerns, if any, associated with its use. It is the
electrical potential is also measured, and upon conclusion of
responsibility of the user of this standard to establish appro-
the test period, the test specimen is physically examined.
priate safety, health, and environmental practices and deter-
3.1.3 In both test methods physical examination is con-
mine the applicability of regulatory limitations prior to use.
ducted by comparing the extent of loosened or disbonded
1.5 This international standard was developed in accor-
coating at the perforations in the immersed area with extent of
dance with internationally recognized principles on standard-
loosened or disbonded coating at a new test hole in the coating
ization established in the Decision on Principles for the
made in an area that was not immersed.
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
4. Significance and Use
Barriers to Trade (TBT) Committee.
4.1 Breaks or holidays in pipe coatings may expose the pipe
to possible corrosion, since after a pipe has been installed
These test methods are under the jurisdiction of ASTM Committee D01 on
Paint and Related Coatings, Materials, and Applications and are the direct For referenced ASTM standards, visit the ASTM website, www.astm.org, or
responsibility of Subcommittee D01.48 on Durability of Pipeline Coating and contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Linings. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved June 1, 2019. Published June 2019. Originally the ASTM website.
approved in 1969. Last previous edition approved in 2010 as G8 – 96 (2010). DOI: The last approved version of this historical standard is referenced on
10.1520/G0008-96R19. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
G8 − 96 (2019)
underground, the surrounding earth will be more or less 5.1.1.2 Each test specimen shall be separated from the other
specimens, from the anodes and from the walls of the test
moisture-bearing and it constitutes an effective electrolyte.
Damage to pipe coating is almost unavoidable during trans- vessel by at least 38.1 mm (1.500 in.).
portation and construction. Normal soil potentials as well as 5.1.1.3 Depth of electrolyte shall permit the test length of
the specimen to be immersed as required in 7.4.
applied cathodic protection potentials may cause loosening of
the coating, beginning at holiday edges, in some cases increas- 5.1.1.4 If electrical monitoring is to be performed as re-
quired in Method B, the reference electrode may be placed
ing the apparent size of the holiday. Holidays may also be
anywhere in the vessel, provided it is separated from the
caused by such potentials. While apparently loosened coating
specimen and from the anode by not less than 38.1 mm (1.500
and cathodic holidays may not result in corrosion, this test
in.).
provides accelerated conditions for loosening to occur and
5.1.2 Magnesium Anode—The anode shall be made of a
therefore gives a measure of resistance of coatings to this type
magnesium alloy having a solution potential of −1.45 to −1.55
of action.
V with respect to a CuCuSO reference electrode in the
4.2 The effects of the test may be evaluated by either
electrolyte given in 6.1. It shall have a surface area not less
physical examination or monitoring the current drawn by the
than one third that of the total specimen area exposed to
test specimen and both of these two. Usually there is no
electrolyte (outside area exposed only). The anode shall be
correlation between the two methods of evaluation but both
provided with a factory-sealed, 4107-cmil (14-gage Awg),
methods are significant. Physical examination consists of
minimum, insulated copper wire. Anodes without a factory seal
assessing the effective contact of the coating with the metal
may be used if the magnesium extends above the cover.
surface in terms of observed differences in the relative adhesive
5.1.3 Connectors—Wiring from anode to test specimen
bond. It is usually found that the electrically stressed area
shall be 4107-cmil (14-gage Awg), minimum, insulated copper.
propagates from the holiday to a boundary where the loosened
Attachment to the test specimen shall be by soldering, brazing,
coating leaves off for the more effective contact or bond
or bolting to the nonimmersed end, and the place of attachment
attributed to an original condition throughout the specimen
shall be coated with an insulating material. A junction in the
before electrical stressing was applied. Assumptions associated
connecting wire is permitted, provided that it is made by means
with test results include the following:
of a bolted pair of terminal lugs soldered or mechanically
4.2.1 Attempting to loosen or disbond the coating at a new crimped to clean wire ends.
test hole made in the coating in an area that was not immersed
5.1.4 Holiday Tools—Holidays shall be made with conven-
represents maximum adhesion or bond as measured by the tional drills of the required diameter. For use in preparing
lifting technique used, and that the same lifting technique can small-diameter pipe specimens such as 19.05 mm (0.750 in.)
be used at a test hole that was immersed thereby providing a nominal diameter pipe, the use of a drill modified by substan-
means of comparing relative resistance to lifting. tially grinding away the sharp cone point has been found
effective in preventing perforation of the metal wall of the pipe.
4.2.2 Any relatively lesser bonded area at the immersed test
A sharp-pointed knife with a safe handle is required for use in
holes in the coating was caused by electrical stressing and was
making physical examinations.
not attributable to an anomaly in the application process.
5.1.5 High-Resistance Voltmeter, for direct current, having
Ability to resist disbondment is a desired quality on a com-
an internal resistance of not less than 10 MΩ and having a
parative basis, but disbondment per se in this test is not
range from 0.01 to 5 V for measuring potential to the reference
necessarily an adverse indication. The virtue of this test is that
electrode.
all dielectric type coatings now in common use will disbond to
5.1.6 Reference Electrode, saturated CuCuSO of conven-
some degree thus providing a means of comparing one coating 4
tional glass or plastic tube with porous plug construction,
with another. Bond strength is more important for proper
preferably not over 19.05 mm (0.750 in.) in diameter, having a
functioning of some coatings than others and the same mea-
potential of −0.316 V with respect to the standard hydrogen
sured disbondment for two different coating systems may not
electrode. A calomel electrode may be used, but measurements
represent equivalent loss of corrosion protection.
made with it shall be converted to the CuCuSO reference for
4.2.3 The amount of current in the test cell is a relative
reporting by adding −0.072 V to the observed reading.
indicator of the extent of areas requiring protection against
5.1.7 Thickness Gage, for measuring coating thickness in
corrosion; however, the current density appearing in this test is
accordance with Test Method G12.
much greater than that usually required for cathodic protection
5.1.8 Thermometer, for measuring electrolyte temperature,
in natural, inland soil environments.
general lab type, 1° subdivisions, 76.2 mm (3 in.) immersion.
5.2 Additional Apparatus for Method B:
5. Apparatus
5.2.1 High-Resistance Voltmeter, for direct current, having
5.1 Apparatus for Both Methods:
an internal resistance of not less than 10 MΩ and capable of
5.1.1 Test Vessel—A nonconducting material shall be used
measuring as low as 10 µV potential drop across a shunt in the
for the vessel or as a lining in a metallic vessel. Dimensions of
test cell circuit.
the vessel shall permit the following requirements:
5.2.2 Precision Wire-Wound Resistor, 1-Ω 6 1 %, 1-W
5.1.1.1 Test specimens shall be suspended vertically in the (minimum), to be used in the test cell circuit as a shunt for
vessel with at least 25.4-mm (1-in.) clearance from the bottom. current.
G8 − 96 (2019)
5.2.3 Volt-Ohm-Meter, for initial testing of apparent coating grade salts, calculated on an anhydrous basis: sodium chloride,
resistance. sodium sulfate, and sodium carbonate. Use freshly prepared
5.2.4 Metallic Electrode, used temporarily with the volt- solution for each test.
ohm-meter to determine apparent initial holiday status of the
6.2 Materials for sealing the ends of coated pipe specimens
test specimen.
may consist of bituminous products, wax, epoxy, or other
5.2.5 Additional Connecting Wires, 4107-cmil (14-gage
materials, including molded elastomeric or plastic end caps.
Awg), minimum, insulated copper.
6.3 Plywood or plastic material has been found suitable for
5.2.6 Brass Studs, used at a terminal board, together with
the construction of test vessel covers and for the support
alligator clips or knife switches, for making and breaking
through apertures of test specimens and electrodes. Wood
circuits. Alligator clips shall not be used to connect to
dowels introduced through holes in the top ends of test
electrodes or specimens at the top location of test cells.
specimens have been found suitable for suspending test speci-
5.2.7 Zero-Resistance Ammeter, capable of measuring direct
mens from the vessel cover.
current as low as 10 µA may be used in the alternative method
given in 9.1.3 and substituted for the apparatus described in
7. Test Specimen
5.2.1 and 5.2.2.
7.1 The test specimen shall be a representative piece of
5.2.8 Direct-Current Rectifier, capable of supplying con-
stant voltage at a voltage of 1.50 6 0.01 V, as measured production-coated pipe. One end shall be plugged or capped,
and sealed.
between the specimen and reference electrode.
5.2.9 Impressed Current Anode, shall be of the nonconsum-
7.2 One or three holidays shall be made in each specimen.
able type provided with a factory sealed, insulated copper
Three holidays are recommended. Recommended dimensions
wire.
are given in Fig. 2. A specimen with one holiday shall have it
5.2.10 Voltage Divider, 100-Ω, 25-W rheostat, to be used if
drilled in the middle of the immersed length. If three holidays
more than one specimen is to be tested as shown in Fig. 1.
are used, they shall be drilled 120° apart with one in the center
and the other two at locations one fourth the distance from top
6. Reagent and Materials
and bottom of the immersed test length. Each holiday shall be
6.1 The electrolyte shall consist of potable tap water with
drilled so that the angular cone point of the drill will fully enter
the addition of 1 mass % of each of the following technical-
the steel where the cylindrical portion of the drill meets the
steel surface. The drill diameter shall be not less than three
times the coating thickness, but it shall never be smaller than
Durion, a material found suitable for this purpose is available from Durion Co.,
6.35 mm (0.250 in.) in diameter. The steel wall of the pipe shall
Inc., Dayton OH.
FIG. 1 Modification of Method B (Fig. 5) Using Impressed Current to Test More than One Specimen
G8 − 96 (2019)
Dimension mm (in.)
490.22 ± 12.7 (19.300 ± 0.500)
B 245.11 ± 12.7 (9.650± 0.500)
C 120.65 ± 6.35 (4.750± 0.250)
D 114.3 ± 6.35 (4.500 ± 0.250)
E 233.363, min (9.1875, min)
F 19.05, min (0.750, min)
G 762, min (30, min)
FIG. 2 Recommended Dimensions for Specimen
2 2 2 2
not be perforated. With small-diameter pipes, where there is mm (36 in. ). An area of 92 900 mm (1 ft ) has been found
danger of perforating the pipe, the holiday shall be started with preferable when convenient.
a standard 60° con
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: G8 − 96 (Reapproved 2010) G8 − 96 (Reapproved 2019)
Standard Test Methods for
Cathodic Disbonding of Pipeline Coatings
This standard is issued under the fixed designation G8; 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
1.1 These test methods cover accelerated procedures for simultaneously 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 in contact with inland soils and may or may not 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 for testing coatings submerged or immersed in the test solution at room 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 higher temperatures are required, see Test Method G42. If a specific test method is
required with no options, see Test Method G80.
1.3 The values stated in SI units to 3 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.5 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.
2. Referenced Documents
2.1 ASTM Standards:
G12 Test Method for Nondestructive Measurement of Film Thickness of Pipeline Coatings on Steel (Withdrawn 2013)
G42 Test Method for Cathodic Disbonding of Pipeline Coatings Subjected to Elevated Temperatures
G80 Test Method for Specific Cathodic Disbonding of Pipeline Coatings (Withdrawn 2013)
G95 Test Method for Cathodic Disbondment Test of Pipeline Coatings (Attached Cell Method)
3. Summary of Test Method
3.1 Both of the two test methods described subject the coating on the test specimen to electrical stress in a highly conductive,
alkaline electrolyte. Electrical stress is obtained either by means of a sacrificial magnesium anode or from an impressed current
system. The coating is perforated before starting the test.
3.1.1 In Method A, a magnesium anode is used with no electrical monitoring during the test period. The results are determined
by physical examination after the test period is concluded.
3.1.2 In Method B, either a magnesium anode or an impressed current system may be used. Electrical instrumentation is
provided for measuring the current in the cell circuit. The electrical potential is also measured, and upon conclusion of the test
period, the test specimen is physically examined.
These test methods are under the jurisdiction of ASTM Committee D01 on Paint and Related Coatings, Materials, and Applications and are the direct responsibility of
Subcommittee D01.48 on Durability of Pipeline Coating and Linings.
Current edition approved Dec. 1, 2010June 1, 2019. Published December 2010June 2019. Originally approved in 1969. Last previous edition approved in 20032010 as
ε1
G8 – 96 (2003)(2010). . DOI: 10.1520/G0008-96R10.10.1520/G0008-96R19.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
The last approved version of this historical standard is referenced on www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
G8 − 96 (2019)
3.1.3 In both test methods physical examination is conducted by comparing the extent of loosened or disbonded coating at the
perforations in the immersed area with extent of loosened or disbonded coating at a new test hole in the coating made in an area
that was not immersed.
4. Significance and Use
4.1 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 more or less moisture-bearing and it constitutes an effective electrolyte. Damage to pipe
coating is almost unavoidable during transportation and construction. Normal soil potentials as well as applied cathodic protection
potentials may cause loosening of the coating, beginning at holiday edges, in some cases increasing the apparent size of the holiday.
Holidays may also be caused by such potentials. While apparently loosened coating and cathodic holidays may not result in
corrosion, this test provides accelerated conditions for loosening to occur and therefore gives a measure of resistance of coatings
to this type of action.
4.2 The effects of the test may be evaluated by either physical examination or monitoring the current drawn by the test specimen
and both of these two. 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 electrically stressed area propagates from the holiday to a
boundary where the loosened coating leaves off for the more effective contact or bond attributed to an original condition throughout
the specimen before electrical stressing was applied. Assumptions associated with test results include the following:
4.2.1 Attempting to loosen or disbond the coating at a new test hole made in the coating in an area that was not immersed
represents maximum adhesion or bond as measured by the lifting technique used, and that the same lifting technique can be used
at a test hole that was immersed thereby providing a means of comparing relative resistance to lifting.
4.2.2 Any relatively lesser bonded area at the immersed test holes in the coating was caused by electrical stressing and was not
attributable to an anomaly in the application process. Ability to resist disbondment is a desired quality on a comparative basis, but
disbondment per se in this test is not necessarily an adverse indication. The virtue of this test is that all dielectric type coatings
now in common use will disbond to some degree thus providing a means of comparing one coating with another. Bond strength
is more important for proper functioning of some coatings than others and the same measured disbondment for two different
coating systems may not represent equivalent loss of corrosion protection.
4.2.3 The amount of current in the test cell is a relative indicator of the extent of areas requiring protection against corrosion;
however, the current density appearing in this test is much greater than that usually required for cathodic protection in natural,
inland soil environments.
5. Apparatus
5.1 Apparatus for Both Methods:
5.1.1 Test Vessel—A nonconducting material shall be used for the vessel or as a lining in a metallic vessel. Dimensions of the
vessel shall permit the following requirements:
5.1.1.1 Test specimens shall be suspended vertically in the vessel with at least 25.4-mm (1-in.) clearance from the bottom.
5.1.1.2 Each test specimen shall be separated from the other specimens, from the anodes and from the walls of the test vessel
by at least 38.1 mm (1.500 in.).
5.1.1.3 Depth of electrolyte shall permit the test length of the specimen to be immersed as required in 7.4.
5.1.1.4 If electrical monitoring is to be performed as required in Method B, the reference electrode may be placed anywhere
in the vessel, provided it is separated from the specimen and from the anode by not less than 38.1 mm (1.500 in.).
5.1.2 Magnesium Anode—The anode shall be made of a magnesium alloy having a solution potential of −1.45 to −1.55 V with
respect to a CuCuSO reference electrode in the electrolyte given in 6.1. It shall have a surface area not less than one third that
of the total specimen area exposed to electrolyte (outside area exposed only). The anode shall be provided with a factory-sealed,
4107-cmil (14-gage Awg), minimum, insulated copper wire. Anodes without a factory seal may be used if the magnesium extends
above the cover.
5.1.3 Connectors—Wiring from anode to test specimen shall be 4107-cmil (14-gage Awg), minimum, insulated copper.
Attachment to the test specimen shall be by soldering, brazing, or bolting to the nonimmersed end, and the place of attachment
shall be coated with an insulating material. A junction in the connecting wire is permitted, provided that it is made by means of
a bolted pair of terminal lugs soldered or mechanically crimped to clean wire ends.
5.1.4 Holiday Tools—Holidays shall be made with conventional drills of the required diameter. For use in preparing
small-diameter pipe specimens such as 19.05 mm (0.750 in.) nominal diameter pipe, the use of a drill modified by substantially
grinding away the sharp cone point has been found effective in preventing perforation of the metal wall of the pipe. A sharp-pointed
knife with a safe handle is required for use in making physical examinations.
5.1.5 High-Resistance Voltmeter, for direct current, having an internal resistance of not less than 10 MΩ and having a range from
0.01 to 5 V for measuring potential to the reference electrode.
G8 − 96 (2019)
5.1.6 Reference Electrode, saturated CuCuSO of conventional glass or plastic tube with porous plug construction, preferably
not over 19.05 mm (0.750 in.) in diameter, having a potential of −0.316 V with respect to the standard hydrogen electrode. A
calomel electrode may be used, but measurements made with it shall be converted to the CuCuSO reference for reporting by
adding −0.072 V to the observed reading.
5.1.7 Thickness Gage, for measuring coating thickness in accordance with Test Method G12.
5.1.8 Thermometer, for measuring electrolyte temperature, general lab type, 1° subdivisions, 76.2 mm (3 in.) immersion.
5.2 Additional Apparatus for Method B:
5.2.1 High-Resistance Voltmeter, for direct current, having an internal resistance of not less than 10 MΩ and capable of
measuring as low as 10 μV potential drop across a shunt in the test cell circuit.
5.2.2 Precision Wire-Wound Resistor, 1-Ω 6 1 %, 1-W (minimum), to be used in the test cell circuit as a shunt for current.
5.2.3 Volt-Ohm-Meter, for initial testing of apparent coating resistance.
5.2.4 Metallic Electrode, used temporarily with the volt-ohm-meter to determine apparent initial holiday status of the test
specimen.
5.2.5 Additional Connecting Wires, 4107-cmil (14-gage Awg), minimum, insulated copper.
5.2.6 Brass Studs, used at a terminal board, together with alligator clips or knife switches, for making and breaking circuits.
Alligator clips shall not be used to connect to electrodes or specimens at the top location of test cells.
5.2.7 Zero-Resistance Ammeter, capable of measuring direct current as low as 10 μA may be used in the alternative method
given in 9.1.3 and substituted for the apparatus described in 5.2.1 and 5.2.2.
5.2.8 Direct-Current Rectifier, capable of supplying constant voltage at a voltage of 1.50 6 0.01 V, as measured between the
specimen and reference electrode.
5.2.9 Impressed Current Anode, shall be of the nonconsumable type provided with a factory sealed, insulated copper wire.
5.2.10 Voltage Divider, 100-Ω, 25-W rheostat, to be used if more than one specimen is to be tested as shown in Fig. 1.
6. Reagent and Materials
6.1 The electrolyte shall consist of potable tap water with the addition of 1 mass % of each of the following technical-grade
salts, calculated on an anhydrous basis: sodium chloride, sodium sulfate, and sodium carbonate. Use freshly prepared solution for
each test.
FIG. 1 Modification of Method B (Fig. 5) Using Impressed Current to Test More than One Specimen
Durion, a material found suitable for this purpose is available from Durion Co., Inc., Dayton OH.
G8 − 96 (2019)
6.2 Materials for sealing the ends of coated pipe specimens may consist of bituminous products, wax, epoxy, or other materials,
including molded elastomeric or plastic end caps.
6.3 Plywood or plastic material has been found suitable for the construction of test vessel covers and for the support through
apertures of test specimens and electrodes. Wood dowels introduced through holes in the top ends of test specimens have been
found suitable for suspending test specimens from the vessel cover.
7. Test Specimen
7.1 The test specimen shall be a representative piece of production-coated pipe. One end shall be plugged or capped, and sealed.
7.2 One or three holidays shall be made in each specimen. Three holidays are recommended. Recommended dimensions are
given in Fig. 2. A specimen with one holiday shall have it drilled in the middle of the immersed length. If three holidays are used,
they shall be drilled 120° apart with one in the center and the other two at locations one fourth the distance from top and bottom
of the immersed test length. Each holiday shall be drilled so that the angular cone point of the drill will fully enter the steel where
the cylindrical portion of the drill meets the steel surface. The drill diameter shall be not less than three times the coating thickness,
but it shall never be smaller than 6.35 mm (0.250 in.) in diameter. The steel wall of the pipe shall not be perforated. With
small-diameter pipes, where there is danger of perforating the pipe, the holiday shall be started with a standard 60° cone point and
finished with a drill
...
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