ASTM G8-96(2010)
(Test Method)Standard Test Methods for Cathodic Disbonding of Pipeline Coatings
Standard Test Methods for Cathodic Disbonding of Pipeline Coatings
SIGNIFICANCE AND USE
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.
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:
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.
Any relatively lesser bonded area at the immersed test holes in the coating was caused by elec...
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.
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: G8 − 96 (Reapproved 2010)
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 Thickness of Pipeline Coatings on Steel (Withdrawn
2013)
1.1 These test methods cover accelerated procedures for
G42Test Method for Cathodic Disbonding of Pipeline
simultaneously determining comparative characteristics of in-
Coatings Subjected to Elevated Temperatures
sulating coating systems applied to steel pipe exterior for the
G80Test Method for Specific Cathodic Disbonding of Pipe-
purposeofpreventingormitigatingcorrosionthatmayoccurin
line Coatings (Withdrawn 2013)
underground service where the pipe will be in contact with
G95TestMethodforCathodicDisbondmentTestofPipeline
inland soils and may or may not receive cathodic protection.
Coatings (Attached Cell Method)
They are intended for use with samples of coated pipe taken
from commercial production and are applicable to such
3. Summary of Test Method
samples when the coating is characterized by function as an
3.1 Both of the two test methods described subject the
electrical barrier.
coating on the test specimen to electrical stress in a highly
1.2 This test method is intended for testing coatings sub-
conductive, alkaline electrolyte. Electrical stress is obtained
merged or immersed in the test solution at room temperature.
either by means of a sacrificial magnesium anode or from an
When it is impractical to submerge or immerse the test
impressed current system. The coating is perforated before
specimen, Test Method G95 may be considered where the test
starting the test.
cell is cemented to the surface of the coated pipe specimen. If
3.1.1 In Method A, a magnesium anode is used with no
higher temperatures are required, see Test Method G42.Ifa
electrical monitoring during the test period. The results are
specific test method is required with no options, see Test
determined by physical examination after the test period is
Method G80.
concluded.
3.1.2 In Method B, either a magnesium anode or an im-
1.3 ThevaluesstatedinSIunitsto3significantdecimalsare
pressedcurrentsystemmaybeused.Electricalinstrumentation
toberegardedasthestandard.Thevaluesgiveninparentheses
is provided for measuring the current in the cell circuit. The
are for information only.
electrical potential is also measured, and upon conclusion of
1.4 This standard does not purport to address all of the
the test period, the test specimen is physically examined.
safety concerns, if any, associated with its use. It is the
3.1.3 In both test methods physical examination is con-
responsibility of the user of this standard to establish appro-
ducted by comparing the extent of loosened or disbonded
priate safety and health practices and determine the applica-
coating at the perforations in the immersed area with extent of
bility of regulatory limitations prior to use.
loosened or disbonded coating at a newtest hole in the coating
made in an area that was not immersed.
2. Referenced Documents
2 4. Significance and Use
2.1 ASTM Standards:
G12Test Method for Nondestructive Measurement of Film
4.1 Breaksorholidaysinpipecoatingsmayexposethepipe
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.
These test methods are under the jurisdiction of ASTM Committee D01 on
Damage to pipe coating is almost unavoidable during trans-
Paint and Related Coatings, Materials, and Applications and are the direct
responsibility of Subcommittee D01.48 on Durability of Pipeline Coating and
portation and construction. Normal soil potentials as well as
Linings.
applied cathodic protection potentials may cause loosening of
Current edition approved Dec. 1, 2010. Published December 2010. Originally
ε1 the coating, beginning at holiday edges, in some cases increas-
approvedin1969.Lastpreviouseditionapprovedin2003asG8–96(2003) .DOI:
ing the apparent size of the holiday. Holidays may also be
10.1520/G0008-96R10.
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 last approved version of this historical standard is referenced on
the ASTM website. www.astm.org.
Copyright ©ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA19428-2959. United States
G8 − 96 (2010)
caused by such potentials. While apparently loosened coating 5.1.1.4 If electrical monitoring is to be performed as re-
and cathodic holidays may not result in corrosion, this test quired in Method B, the reference electrode may be placed
anywhere in the vessel, provided it is separated from the
provides accelerated conditions for loosening to occur and
specimen and from the anode by not less than 38.1 mm (1.500
therefore gives a measure of resistance of coatings to this type
in.).
of action.
5.1.2 Magnesium Anode—The anode shall be made of a
4.2 The effects of the test may be evaluated by either
magnesium alloy having a solution potential of −1.45 to −1.55
physical examination or monitoring the current drawn by the
V with respect to a CuCuSO reference electrode in the
test specimen and both of these two. Usually there is no
electrolyte given in 6.1. It shall have a surface area not less
correlation between the two methods of evaluation but both
than one third that of the total specimen area exposed to
methods are significant. Physical examination consists of electrolyte (outside area exposed only). The anode shall be
assessing the effective contact of the coating with the metal provided with a factory-sealed, 4107-cmil (14-gage Awg),
minimum,insulatedcopperwire.Anodeswithoutafactoryseal
surfaceintermsofobserveddifferencesintherelativeadhesive
may be used if the magnesium extends above the cover.
bond. It is usually found that the electrically stressed area
5.1.3 Connectors—Wiring from anode to test specimen
propagates from the holiday to a boundary where the loosened
shallbe4107-cmil(14-gageAwg),minimum,insulatedcopper.
coating leaves off for the more effective contact or bond
Attachmenttothetestspecimenshallbebysoldering,brazing,
attributed to an original condition throughout the specimen
orboltingtothenonimmersedend,andtheplaceofattachment
beforeelectricalstressingwasapplied.Assumptionsassociated
shall be coated with an insulating material. A junction in the
with test results include the following:
connectingwireispermitted,providedthatitismadebymeans
4.2.1 Attempting to loosen or disbond the coating at a new
of a bolted pair of terminal lugs soldered or mechanically
test hole made in the coating in an area that was not immersed
crimped to clean wire ends.
represents maximum adhesion or bond as measured by the
5.1.4 Holiday Tools—Holidays shall be made with conven-
lifting technique used, and that the same lifting technique can
tional drills of the required diameter. For use in preparing
be used at a test hole that was immersed thereby providing a
small-diameter pipe specimens such as 19.05 mm (0.750 in.)
means of comparing relative resistance to lifting.
nominal diameter pipe, the use of a drill modified by substan-
4.2.2 Any relatively lesser bonded area at the immersed test tially grinding away the sharp cone point has been found
effectiveinpreventingperforationofthemetalwallofthepipe.
holes in the coating was caused by electrical stressing and was
Asharp-pointed knife with a safe handle is required for use in
not attributable to an anomaly in the application process.
making physical examinations.
Ability to resist disbondment is a desired quality on a com-
5.1.5 High-Resistance Voltmeter, for direct current, having
parative basis, but disbondment per se in this test is not
an internal resistance of not less than 10 MΩ and having a
necessarily an adverse indication. The virtue of this test is that
rangefrom0.01to5Vformeasuringpotentialtothereference
alldielectrictypecoatingsnowincommonusewilldisbondto
electrode.
some degree thus providing a means of comparing one coating
5.1.6 Reference Electrode, saturated CuCuSO of conven-
with another. Bond strength is more important for proper
tional glass or plastic tube with porous plug construction,
functioning of some coatings than others and the same mea-
preferably not over 19.05 mm (0.750 in.) in diameter, having a
sured disbondment for two different coating systems may not
potential of −0.316 V with respect to the standard hydrogen
represent equivalent loss of corrosion protection.
electrode.Acalomel electrode may be used, but measurements
4.2.3 The amount of current in the test cell is a relative
made with it shall be converted to the CuCuSO reference for
indicator of the extent of areas requiring protection against
reporting by adding−0.072 V to the observed reading.
corrosion;however,thecurrentdensityappearinginthistestis
5.1.7 Thickness Gage, for measuring coating thickness in
much greater than that usually required for cathodic protection
accordance with Test Method G12.
in natural, inland soil environments.
5.1.8 Thermometer, for measuring electrolyte temperature,
general lab type, 1° subdivisions, 76.2 mm (3 in.) immersion.
5. Apparatus
5.2 Additional Apparatus for Method B:
5.1 Apparatus for Both Methods: 5.2.1 High-Resistance Voltmeter, for direct current, having
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.
5.1.1.2 Eachtestspecimenshallbeseparatedfromtheother
5.2.3 Volt-Ohm-Meter, for initial testing of apparent coating
specimens, from the anodes and from the walls of the test
resistance.
vessel by at least 38.1 mm (1.500 in.).
5.2.4 Metallic Electrode, used temporarily with the volt-
5.1.1.3 Depth of electrolyte shall permit the test length of
ohm-meter to determine apparent initial holiday status of the
the specimen to be immersed as required in 7.4. test specimen.
G8 − 96 (2010)
FIG. 1 Modification of Method B (Fig. 5) Using Impressed Current to Test More than One Specimen
5.2.5 Additional Connecting Wires, 4107-cmil (14-gage 6.2 Materials for sealing the ends of coated pipe specimens
Awg), minimum, insulated copper. may consist of bituminous products, wax, epoxy, or other
5.2.6 Brass Studs, used at a terminal board, together with materials, including molded elastomeric or plastic end caps.
alligator clips or knife switches, for making and breaking
6.3 Plywood or plastic material has been found suitable for
circuits. Alligator clips shall not be used to connect to
the construction of test vessel covers and for the support
electrodes or specimens at the top location of test cells.
through apertures of test specimens and electrodes. Wood
5.2.7 Zero-Resistance Ammeter,capableofmeasuringdirect
dowels introduced through holes in the top ends of test
current as low as 10 µAmay be used in the alternative method
specimens have been found suitable for suspending test speci-
given in 9.1.3 and substituted for the apparatus described in
mens from the vessel cover.
5.2.1 and 5.2.2.
5.2.8 Direct-Current Rectifier, capable of supplying con-
7. Test Specimen
stant voltage at a voltage of 1.50 6 0.01 V, as measured
7.1 The test specimen shall be a representative piece of
between the specimen and reference electrode.
production-coated pipe. One end shall be plugged or capped,
5.2.9 Impressed Current Anode, shall be of the nonconsum-
and sealed.
able type provided with a factory sealed, insulated copper
wire.
7.2 One or three holidays shall be made in each specimen.
5.2.10 Voltage Divider, 100-Ω, 25-W rheostat, to be used if Three holidays are recommended. Recommended dimensions
more than one specimen is to be tested as shown in Fig. 1.
are given in Fig. 2.Aspecimen with one holiday shall have it
drilled in the middle of the immersed length. If three holidays
6. Reagent and Materials
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
6.1 The electrolyte shall consist of potable tap water with
and bottom of the immersed test length. Each holiday shall be
the addition of 1 mass% of each of the following technical-
drilledsothattheangularconepointofthedrillwillfullyenter
gradesalts,calculatedonananhydrousbasis:sodiumchloride,
the steel where the cylindrical portion of the drill meets the
sodium sulfate, and sodium carbonate. Use freshly prepared
steel surface. The drill diameter shall be not less than three
solution for each test.
times the coating thickness, but it shall never be smaller than
6.35mm(0.250in.)indiameter.Thesteelwallofthepipeshall
not be perforated. With small-diameter pipes, where there is
Durion,amaterialfoundsuitableforthispurposeisavailablefromDurionCo.,
Inc., Dayton OH. dangerofperforatingthepipe,theholidayshallbestartedwith
G8 − 96 (2010)
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
a standard 60° cone point and finished with a drill that has had mm (36 in. ).An area of 92 900 mm (1 ft ) has been found
a substantial portion of the cone point ground away.
preferable when convenient.
NOTE 1—Before making the holiday, see 8.1.
8. Specimen Preparation
7.3 The end of the pipe which will protrude above the
8.1 Before making artificial holidays, verify the continuity
immersion line shall be provided with suitable supporting
means and a separate wire connection for electrical purposes, of the coating and the effectiveness of the end-cap seal as
soldered, brazed, or bolted to the pipe. The protruding end, follows:
including hanger and wire connections, shall be protected and
8.1.1 Immerse the test specimen and a
...
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