ASTM G8-24
(Test Method)Standard Test Methods for Cathodic Disbonding of Coated Steel
Standard Test Methods for Cathodic Disbonding of Coated Steel
SIGNIFICANCE AND USE
4.1 Breaks or holidays in a coating applied over steel exposes the substrate to a potential corrosion cell. When the steel is subjected to cathodic protection by the polarization of the steel via sacrificial anodes or impressed current, the exposed steel at the holiday becomes the cathode in the corrosion cell. When the electrolyte is neutral or slightly alkaline, hydroxyl ions form from the reduction of oxygen and, when paired with a suitable cation from the electrolyte, form an alkaline solution. Depending on the strength of this alkaline solution and the concentration of the alkaline compound, this alkalinity may disrupt the adhesion between the coating and the steel, disbonding the coating from the steel.
4.2 Current density of the cathodic cell also can affect the degree of cathodic disbondment. The greater the current density generated by the concentration of electrons at the anode, the greater the number of hydroxyl ions formed, thus increasing the alkalinity available for disrupting the adhesion between the coating and the steel substrate. Likewise, the concentration of oxygen in the electrolyte will affect the concentration of hydroxyl ions formed at the cathode.
4.3 For these reasons it is often useful to measure pH, oxygen, and current density when conducting a cathodic disbondment test.
SCOPE
1.1 These test methods apply to procedures for determining the degree of disbondment of a coating from a steel substrate when placed in contact with an electrolyte and a potential is applied to the steel. Specimens may include coated steel pipe or coated flat or curved steel plate. The coating applied to the steel substrate shall be non-metallic and shall not show flow characteristics at the test temperature.
1.2 These test methods apply to specimens that are immersed in an electrolyte bath or specimens with an attached electrolyte cell at ambient room temperature, 21 °C to 25 °C (70 °F to 77 °F), conditions. If higher temperatures are required, use Test Method G42.
1.3 These test methods apply to methods of polarization including sacrificial anodes or impressed current applied to the steel by a rectifier.
1.4 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.6 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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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.
Designation: G8 − 24
Standard Test Methods for
1
Cathodic Disbonding of Coated Steel
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
2.1 ASTM Standards:
1.1 These test methods apply to procedures for determining
A36 Specification for Carbon Structural Steel
the degree of disbondment of a coating from a steel substrate
D1141 Practice for Preparation of Substitute Ocean Water
when placed in contact with an electrolyte and a potential is
D5162 Practice for Discontinuity (Holiday) Testing of Non-
applied to the steel. Specimens may include coated steel pipe
conductive Protective Coating on Metallic Substrates
or coated flat or curved steel plate. The coating applied to the
D7091 Practice for Nondestructive Measurement of Dry
steel substrate shall be non-metallic and shall not show flow
Film Thickness of Nonmagnetic Coatings Applied to
characteristics at the test temperature.
Ferrous Metals and Nonmagnetic, Nonconductive Coat-
1.2 These test methods apply to specimens that are im-
ings Applied to Non-Ferrous Metals
mersed in an electrolyte bath or specimens with an attached
G42 Test Method for Cathodic Disbonding of Pipeline
electrolyte cell at ambient room temperature, 21 °C to 25 °C
Coatings Subjected to Elevated Temperatures
(70 °F to 77 °F), conditions. If higher temperatures are
G95 Test Method for Cathodic Disbondment Test of Pipeline
required, use Test Method G42.
Coatings (Attached Cell Method)
1.3 These test methods apply to methods of polarization
3. Summary of Test Method
including sacrificial anodes or impressed current applied to the
3.1 Three test methods are described in this standard. In
steel by a rectifier.
each method, an artificial holiday or defect is applied to the
1.4 The values stated in SI units are to be regarded as the specimen’s coating film through to the steel substrate. The
standard. The values given in parentheses are for information specimen is immersed in a defined electrolyte with the steel
only. polarized to a defined voltage.
3.1.1 Method A—The specimens are immersed in an elec-
1.5 This standard does not purport to address all of the
trolyte immersion bath. A specified metallic anode is used to
safety concerns, if any, associated with its use. It is the
polarize the specimen with no electrical monitoring during the
responsibility of the user of this standard to establish appro-
test period.
priate safety, health, and environmental practices and deter-
3.1.2 Method B—The specimens are immersed in an elec-
mine the applicability of regulatory limitations prior to use.
trolyte immersion bath. Polarization of the specimen is con-
1.6 This international standard was developed in accor-
ducted using an impressed current potentiostat at a specified
dance with internationally recognized principles on standard-
DC voltage with electrical monitoring during the test period.
ization established in the Decision on Principles for the
3.1.3 Method C—The specimens shall have a cell contain-
Development of International Standards, Guides and Recom-
ing the electrolyte attached to the surface of the specimen.
mendations issued by the World Trade Organization Technical
Polarization of the specimen is conducted using an impressed
Barriers to Trade (TBT) Committee.
current potentiostat at a specified DC voltage with electrical
monitoring during the test period.
3.2 Upon completion of immersion exposure, a physical
1
These test methods are under the jurisdiction of ASTM Committee D01 on
examination is conducted by comparing the extent of loosened
Paint and Related Coatings, Materials, and Applications and are the direct
responsibility of Subcommittee D01.48 on Durability of Pipeline Coating and
2
Linings. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Feb. 1, 2024. Published February 2024. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1969. Last previous edition approved in 2019 as G8 – 96 (2019). DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/G0008-24. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1
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G8 − 24
or disbonded coating at the holiday in the immersed area with
...
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 2019) G8 − 24
Standard Test Methods for
1
Cathodic Disbonding of Pipeline CoatingsCoated Steel
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 acceleratedapply to 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 determining the degree of disbondment of a coating from a steel substrate when placed
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.an electrolyte and a potential is applied to the steel. Specimens may include coated steel pipe or coated flat or curved steel
plate. The coating applied to the steel substrate shall be non-metallic and shall not show flow characteristics at the test temperature.
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 These test methods apply to specimens that are immersed in
an electrolyte bath or specimens with an attached electrolyte G95 may be considered where the test cell is cemented to the surface
of the coated pipe specimen. cell at ambient room temperature, 21 °C to 25 °C (70 °F to 77 °F), conditions. If higher temperatures
are required, seeuse Test Method G42. If a specific test method is required with no options, see Test Method G80.
1.3 These test methods apply to methods of polarization including sacrificial anodes or impressed current applied to the steel by
a rectifier.
1.4 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.
1.5 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 environmental practices and determine the applicability of
regulatory limitations prior to use.
1.6 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
2.1 ASTM Standards:
A36 Specification for Carbon Structural Steel
1
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 June 1, 2019Feb. 1, 2024. Published June 2019February 2024. Originally approved in 1969. Last previous edition approved in 20102019 as
G8 – 96 (2010).(2019). DOI: 10.1520/G0008-96R19.10.1520/G0008-24.
2
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.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1
---------------------- Page: 1 ----------------------
G8 − 24
D1141 Practice for Preparation of Substitute Ocean Water
D5162 Practice for Discontinuity (Holiday) Testing of Nonconductive Protective Coating on Metallic Substrates
G12D7091 Test Method Practice for Nondestructive Measurement of Dry Film Thickness of Pipeline Coatings on SteelNon-
magnetic Coatings Applied to Ferrous Metals and Nonmagnetic, Nonconductive Coatings Applied to Non-Ferrous Metals
(Withdrawn 2013)
G42 Test Method for Cathodic Disbonding of Pipeline Coatings Subjected to Elevated Temperatures
3
G80 Test Method for Specific Cathodic Disbonding of Pipeline Coatings (Withdrawn 2013)
G95 Test Method for Cat
...
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