ASTM G8-96
(Test Method)Standard Test Methods for Cathodic Disbonding of Pipeline Coatings
Standard Test Methods for Cathodic Disbonding of Pipeline Coatings
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 and health practices and determine the applicability of regulatory limitations prior to use.
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn. Contact ASTM
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Designation:G8–96
Standard Test Methods for
Cathodic Disbonding of Pipeline Coatings
ThisstandardisissuedunderthefixeddesignationG8;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginal
adoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscript
epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope of Pipeline Coatings (Attached Cell Method)
1.1 These test methods cover accelerated procedures for
3. Summary of Test Methods
simultaneously determining comparative characteristics of in-
3.1 Both of the two test methods described subject the
sulating coating systems applied to steel pipe exterior for the
coating on the test specimen to electrical stress in a highly
purposeofpreventingormitigatingcorrosionthatmayoccurin
conductive, alkaline electrolyte. Electrical stress is obtained
underground service where the pipe will be in contact with
either by means of a sacrificial magnesium anode or from an
inland soils and may or may not receive cathodic protection.
impressed current system. The coating is perforated before
They are intended for use with samples of coated pipe taken
starting the test.
from commercial production and are applicable to such
3.1.1 In Method A, a magnesium anode is used with no
samples when the coating is characterized by function as an
electrical monitoring during the test period. The results are
electrical barrier.
determined by physical examination after the test period is
1.2 This test method is intended for testing coatings sub-
concluded.
merged or immersed in the test solution at room temperature.
3.1.2 In Method B, either a magnesium anode or an im-
When it is impractical to submerge or immerse the test
pressedcurrentsystemmaybeused.Electricalinstrumentation
specimen,Test Method G95 may be considered where the test
is provided for measuring the current in the cell circuit. The
cell is cemented to the surface of the coated pipe specimen. If
electrical potential is also measured, and upon conclusion of
higher temperatures are required, see Test Method G42. If a
the test period, the test specimen is physically examined.
specific test method is required with no options, see Test
3.1.3 In both test methods physical examination is con-
Method G80.
ducted by comparing the extent of loosened or disbonded
1.3 ThevaluesstatedinSIunitsto3significantdecimalsare
coating at the perforations in the immersed area with extent of
toberegardedasthestandard.Thevaluesgiveninparentheses
loosened or disbonded coating at a new test hole in the coating
are for information only.
made in an area that was not immersed.
1.4 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
4. Significance and Use
responsibility of the user of this standard to establish appro-
4.1 Breaksorholidaysinpipecoatingsmayexposethepipe
priate safety and health practices and determine the applica-
to possible corrosion, since after a pipe has been installed
bility of regulatory limitations prior to use.
underground, the surrounding earth will be more or less
moisture-bearing and it constitutes an effective electrolyte.
2. Referenced Documents
Damage to pipe coating is almost unavoidable during trans-
2.1 ASTM Standards:
portation and construction. Normal soil potentials as well as
G12 TestMethodforNondestructiveMeasurementofFilm
2 applied cathodic protection potentials may cause loosening of
Thickness of Pipeline Coatings on Steel
the coating, beginning at holiday edges, in some cases increas-
G42 Test Method for Cathodic Disbonding of Pipeline
ing the apparent size of the holiday. Holidays may also be
Coatings Subjected to Elevated Temperatures
caused by such potentials. While apparently loosened coating
G80 Test Method for Specific Cathodic Disbonding of
and cathodic holidays may not result in corrosion, this test
Pipeline Coatings
provides accelerated conditions for loosening to occur and
G95 Test Method for Specific Cathodic Disbondment Test
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
ThesetestmethodsareunderthejurisdictionofASTMCommitteeD-1onPaint
and Related Coatings, Materials, and Applications and are the direct responsibility
physical examination or monitoring the current drawn by the
of Subcommittee D01.48 on Durability of Pipeline Coatings and Linings.
test specimen and both of these two. Usually there is no
Current edition approved May 10, 1996. Published July 1996. Originally
correlation between the two methods of evaluation but both
published asG8–69T. Last previous editionG8–90.
Annual Book of ASTM Standards, Vol 06.02. methods are significant. Physical examination consists of
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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.
G8
assessing the effective contact of the coating with the metal with another. Bond strength is more important for proper
surfaceintermsofobserveddifferencesintherelativeadhesive functioning of some coatings than others and the same mea-
bond. It is usually found that the electrically stressed area sured disbondment for two different coating systems may not
propagates from the holiday to a boundary where the loosened represent equivalent loss of corrosion protection.
coating leaves off for the more effective contact or bond 4.2.3 The amount of current in the test cell is a relative
attributed to an original condition throughout the specimen indicator of the extent of areas requiring protection against
beforeelectricalstressingwasapplied.Assumptionsassociated corrosion; however, the current density appearing in this test is
with test results include the following: much greater than that usually required for cathodic protection
NOTE 1—Test hole made in non-immersed area after testing not shown (see Fig. 5).
FIG. 1 Test Assembly for Method A Using a Magnesium Anode
4.2.1 Attempting to loosen or disbond the coating at a new in natural, inland soil environments.
test hole made in the coating in an area that was not immersed
5. Apparatus
represents maximum adhesion or bond as measured by the
lifting technique used, and that the same lifting technique can 5.1 Apparatus for Both Methods:
be used at a test hole that was immersed thereby providing a 5.1.1 Test Vessel—A nonconducting material shall be used
means of comparing relative resistance to lifting. for the vessel or as a lining in a metallic vessel. Dimensions of
4.2.2 Any relatively lesser bonded area at the immersed test the vessel shall permit the following requirements:
holes in the coating was caused by electrical stressing and was 5.1.1.1 Test specimens shall be suspended vertically in the
not attributable to an anomaly in the application process. vesselwithatleast25.4-mm(1-in.)clearancefromthebottom.
Ability to resist disbondment is a desired quality on a com- 5.1.1.2 Eachtestspecimenshallbeseparatedfromtheother
parative basis, but disbondment per se in this test is not specimens, from the anodes and from the walls of the test
necessarily an adverse indication. The virtue of this test is that vessel by at least 38.1 mm (1.500 in.).
all dielectric type coatings now in common use will disbond to 5.1.1.3 Depth of electrolyte shall permit the test length of
some degree thus providing a means of comparing one coating the specimen to be immersed as required in 7.4.
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.
G8
5.1.1.4 If electrical monitoring is to be performed as re- Asharp-pointed knife with a safe handle is required for use in
quired in Method B, the reference electrode may be placed making physical examinations.
anywhere in the vessel, provided it is separated from the 5.1.5 High-Resistance Voltmeter, for direct current, having
specimen and from the anode by not less than 38.1 mm (1.500 an internal resistance of not less than 10 MV and having a
in.). rangefrom0.01to5Vformeasuringpotentialtothereference
5.1.2 Magnesium Anode—The anode shall be made of a electrode.
magnesium alloy having a solution potential of − 1.45 5.1.6 Reference Electrode, saturated CuCuSO of conven-
to−1.55 V with respect to a CuCuSO reference electrode in tional glass or plastic tube with porous plug construction,
theelectrolytegivenin6.1.Itshallhaveasurfaceareanotless preferably not over 19.05 mm (0.750 in.) in diameter, having a
than one third that of the total specimen area exposed to potential of−0.316 V with respect to the standard hydrogen
electrolyte (outside area exposed only). The anode shall be electrode.Acalomel electrode may be used, but measurements
provided with a factory-sealed, 4107-cmil (14-gage Awg), made with it shall be converted to the CuCuSO reference for
minimum,insulatedcopperwire.Anodeswithoutafactoryseal reporting by adding−0.072 V to the observed reading.
may be used if the magnesium extends above the cover. 5.1.7 Thickness Gage, for measuring coating thickness in
5.1.3 Connectors—Wiring from anode to test specimen accordance with Test Method G12.
shallbe4107-cmil(14-gageAwg),minimum,insulatedcopper. 5.1.8 Thermometer, for measuring electrolyte temperature,
Attachmenttothetestspecimenshallbebysoldering,brazing, general lab type, 1° subdivisions, 76.2 mm (3 in.) immersion.
orboltingtothenonimmersedend,andtheplaceofattachment 5.2 Additional Apparatus for Method B:
shall be coated with an insulating material. A junction in the 5.2.1 High-Resistance Voltmeter, for direct current, having
connectingwireispermitted,providedthatitismadebymeans an internal resistance of not less than 10 MV and capable of
of a bolted pair of terminal lugs soldered or mechanically measuring as low as 10 µVpotential drop across a shunt in the
crimped to clean wire ends.0 test cell circuit.
5.2.2 Precision Wire-Wound Resistor,1-V6 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-ResistanceAmmeter,capableofmeasuringdirect
current as low as 10 µAmay 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 con-
stant 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 nonconsum-
able type provided with a factory sealed, insulated copper
wire.
5.2.10 Voltage Divider, 100-V, 25-W rheostat, to be used if
more than one specimen is to be tested as shown in Fig. 4.
6. Reagent and Materials
6.1 The electrolyte shall consist of potable tap water with
FIG. 2 Test Assembly for Method B Using a Magnesium Anode
the addition of 1 mass% of each of the following technical-
gradesalts,calculatedonananhydrousbasis:sodiumchloride,
5.1.4 Holiday Tools—Holidays shall be made with conven-
sodium sulfate, and sodium carbonate. Use freshly prepared
tional drills of the required diameter. For use in preparing
solution for each test.
small-diameter pipe specimens such as 19.05 mm (0.750 in.)
nominal diameter pipe, the use of a drill modified by substan-
tially grinding away the sharp cone point has been found
Durion,amaterialfoundsuitableforthispurposeisavailablefromDurionCo.,
effectiveinpreventingperforationofthemetalwallofthepipe. Inc., Dayton OH.
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.
G8
FIG. 3 Test Assembly for Method B Using an Impressed Current with One Specimen
FIG. 4 Modification of Method B (Fig. 3) Using Impressed Current to Test More than One Specimen
6.2 Materials for sealing the ends of coated pipe specimens specimens have been found suitable for suspending test speci-
may consist of bituminous products, wax, epoxy, or other mens from the vessel cover.
materials, including molded elastomeric or plastic end caps.
7. Test Specimen
6.3 Plywood or plastic material has been found suitable for
the construction of test vessel covers and for the support 7.1 The test specimen shall be a representative piece of
through apertures of test specimens and electrodes. Wood production-coated pipe. One end shall be plugged or capped,
dowels introduced through holes in the top ends of test and sealed.
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.
G8
Dimension mm (in.)
490.22 6 12.7 (19.300 6 0.500)
B 245.11 6 12.7 ( 9.6506 0.500)
C 120.65 6 6.35 ( 4.7506 0.250)
D 114.3 6 6.35 ( 4.500 6 0.250)
E 233.363, min ( 9.1875, min)
F 19.05, min ( 0.750, min)
G 762, min (30, min)
FIG. 5 Recommended Dimensions for Specimen
7.2 One or three holidays shall be made in each specimen. a standard 60° cone point and finished with a drill that has had
Three holidays are recommended. Recommended dimensions a substantial portion of the cone point ground away.
are given in Fig. 5.Aspecimen with one holiday shall have it
NOTE 1—Before making the holiday, see 8.1.
drilled in the middle of the immersed length. If three holidays
are used, they shall be drilled 120° apart with one in the center 7.3 The end of the pipe which will protrude above the
immersion line shall be provided with suitable supporting
and the other two at locations one fourth the distance from top
and bottom of the immersed test length. Each holiday shall be means and a separate wire connection for electrical purposes,
soldered, brazed, or bolted to the pipe. The protruding end,
drilledsothattheangularconepointofthedrillwillfullyenter
including hanger and wire connections, shall be protected and
the steel where the cylindrical portion of the drill meets the
steel surface. Th
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