ASTM D5162-21

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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: D5162 − 15 D5162 − 21
Standard Practice for
Discontinuity (Holiday) Testing of Nonconductive Protective
Coating on Metallic Substrates
This standard is issued under the fixed designation D5162; 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 This practice covers procedures for determining discontinuities using two types of test equipment:
1.1.1 Test Method A—Low Voltage Wet Sponge, and
1.1.2 Test Method B—High Voltage Spark Testers.
1.2 This practice addresses metallic substrates. For concrete surfaces, refer to Practice D4787.
1.3 The values stated in SI units 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:
G62 Test Methods for Holiday Detection in Pipeline Coatings
D4787 Practice for Continuity Verification of Liquid or Sheet Linings Applied to Concrete Substrates
D7091 Practice for Nondestructive Measurement of Dry Film Thickness of Nonmagnetic Coatings Applied to Ferrous Metals
and Nonmagnetic, Nonconductive Coatings Applied to Non-Ferrous Metals
2.2 NACE Standard Practices:
SP0188–2006 Discontinuity (Holiday) Testing of Protective Coatings
SP0274–2011 High Voltage Electrical Inspection of Pipeline Coatings
SP0490–2007 Holiday Detection of Fusion Bonded Epoxy
2.3 ISO Standard:
ISO 29601 Paints and varnishes. Corrosion protection by protective paint systems. Assessment of porosity in a dry film
This practice is under the jurisdiction of ASTM Committee D01 on Paint and Related Coatings, Materials, and Applications and is the direct responsibility of
Subcommittee D01.46 on Industrial Protective Coatings.
Current edition approved Dec. 1, 2015Nov. 1, 2021. Published December 2015November 2021. Originally approved in 1991. Last previous edition approved in 20082015
as D5162 – 08.D5162 – 15. DOI: 10.1520/D5162-15.10.1520/D5162-21.
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
D5162 − 21
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 discontinuity, as used in this standard, n—a flaw, void, crack, thin spot, foreign inclusion, or contamination in the coating
film that significantly lowers the dielectric strength of the coating film. Afilm; a discontinuity may also be identified as a holiday
or pinhole.
3.1.2 holiday, as used in this standard, n—a term that identifies a discontinuity.
3.1.3 holiday detector, as used in this standard, n—a device that locates discontinuities in a nonconductive coating film applied
to an electrically conductive surface.
3.1.4 pinhole, as used in this standard, n—a film defect characterized by small pore like flaws in the coating which, when extended
entirely through the film, will appear as a discontinuity. Adiscontinuity; a pinhole in the finish coat may not appear as a
discontinuity.
4. Significance and Use
4.1 A coatingcoating/lining is applied to a metallic substrate to prevent corrosion, reduce abrasion corrosion or reduce product
contamination, or all three. both. The degree of coating continuity required is dictated by service conditions. Discontinuities in a
coatingcoating/lining are frequently very minute and may not be readily visible. This practice provides a procedure for electrical
detection of minute discontinuities in nonconductive coating systems.
4.2 Electrical testing to determine the presence and number of discontinuities in a coating film coating/lining is performed on a
nonconductive coatingcoating/lining applied to an electrically conductive surface. The allowable number of discontinuities should
be determined prior to conducting this test since the acceptable quantity of discontinuities will vary depending on coating film
thickness, design, and service conditions.
4.3 The low voltage wet sponge test equipment is generally used for determining the existence of detecting discontinuities in
coating films coatings/linings having a total thickness of 0.5 mm (20 mil) or less. High voltage spark test equipment is generally
used for determining the existences of detecting discontinuities in coating films coatings/linings having a total thickness of greater
than 0.5 mm (20 mil).
4.3.1 Coatings/linings less than 0.5 mm (20 mil) in thickness may be susceptible to damage if tested with high voltage spark
testing equipment. However, coatings/linings greater than 0.25 mm (10 mil) and less than 0.5 mm (20 mil) may be tested with high
voltage spark test equipment provided the voltage is calculated and set correctly, and the coating manufacturer approves its use.
4.4 Coatings that are applied at a thickness of less than 0.5 mm (20 mil) may be susceptible to damage if tested with high voltage
spark testing equipment. Consult the coating manufacturer for proper test equipment and inspection voltages.
4.4 To prevent damage to a coating film when using high voltage test instrumentation, total film thickness and dielectric strength
in a coating system shall be considered in selectingdetermining the appropriate voltage for detection of discontinuities.
Atmospheric conditions shall also be considered since the voltage required for the spark to gap a given distance in air varies with
the conductivity of the air at the time the test is conducted. SuggestedTable X1.1 startingin Appendix X1voltages are provided in
contains suggested voltages for high voltage Table 1.spark testing of low dielectric strength coatings/linings.
4.5 The coating manufacturer shall be consulted to obtain the following information, which wouldinformation that can affect the
accuracy of this test to determine discontinuities:
4.5.1 Establish the length of time required to adequately dry or cure the applied coating film coating/lining prior to testing.
Solvents retained in an uncured coating film coating/lining may form an electrically conductive path through the film to the
substrate.substrate and may be a fire hazard.
4.5.2 Determine whether the coatingcoating/lining contains electrically conductive fillers or pigments that may affect the normal
dielectric properties.
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4.6 This practice is intended for use with new coatingscoatings/linings applied to metal substrates. Its use on a coatinglining
previously exposed to an immersion condition has often resulted in damage to the coatinglining and has produced erroneous
detection of discontinuities due to permeation or moisture absorption of the coating.lining. Deposits may also be present on the
surface causing telegraphing (current traveling through a moisture path to a discontinuity, giving an erroneous indication) or
current leakage across the surface of the coatingcoating/lining due to contamination. The use of a high voltage tester on previously
exposed coatings has to coatings/linings must be carefully considered because of possible spark-through, whichspark-through that
will damage an otherwise sound coating.coating/lining. Although a low voltage tester can be used without damaging the
coating,coating/lining, it may also produce erroneous results.
5. Test Methods
TEST METHOD A—LOW VOLTAGE WET SPONGE TESTING
5.1 Apparatus:Apparatus:
5.1.1 Low Voltage Holiday Detector—an electronic device powered by a self-contained battery with voltages ranging from 5 to
90 V dc, depending on the equipment manufacturer’s circuit design. It is used to locate discontinuities in a nonconductive coating
applied to a conductive substrate. Operation includes the use of an open-cell sponge electrode wetted with a solution for exploring
the coating surface, a signal return connection, and an audible or visual indicator, or both, for signaling a point of coating
discontinuity.
5.1.2 Low Voltage Wet Sponge Tester—a sensitivity device with the operating voltage being of little importance other than being
part of the particular electronic circuit design.
5.1.1 WetLow Sponge Type Instruments—Voltage Holiday Detector—a An electronic device powered by a self-contained battery
with voltages ranging from 5 to 90 V dc, depending on the equipment manufacturer’s circuit design. It is used to locate
discontinuities in a nonconductive coating/lining applied to a conductive substrate. Operation includes the use of an open-cell
sponge electrode wetted with a solution for exploring the coating surface, a signal return connection, and an audible or visual
indicator, or both, for signaling a point of coating discontinuity. A number of commercially available, industry-accepted,
instruments are available. The following electronic principle describes two types of devices generally used; others may be available
but are not described in this practice.
5.1.1.1 Lightweight, Self-Contained, Portable Devices—basedBased on the electrical principle of an electromagnetic sensitive
relay or a solid-state electronic relay circuit that energizes an audible or visual indicator when a coating discontinuity is detected.
Generally, this equipment is capable of being recalibrated in the field adjusted by the user.
5.1.1.2 Lightweight, Self-Contained, Portable Devices—alsoAlso based on the principle of an electronic relaxation oscillator
circuit that reacts significantly to the abrupt drop in electrical resistance between the high dielectric value of the coating film
coating/lining and the conductive substrate at the point of coating film a discontinuity. This results in a rise in oscillator frequency
as well as in the audible signal from the device. Generally, this equipment is incapable of being recalibrated in the field adjusted
by the user.
5.1.2 Low Sudsing, Non-ionic Wetting Agent.
5.2 Verifying Operation of Detector (instrument):
5.2.1 The instrument shall be tested for sensitivity prior to initial use and periodically thereafter, in accordance with the equipment
manufacturer’s instructions.
5.2.2 Test the battery for proper voltage output. Refer to the manufacturer’s instructions.
5.2.3 Switch the instrument to the “on position,” if applicable.
5.2.4 Wet the sponge with a wetting solution consisting of tap water and a wetting agent (see 5.4.6).
5.2.5 Connect the signal return wire to the instrument ground output terminal.
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5.2.6 Touch the signal return wire clip to the wetted sponge. The instrument should signal in accordance with the instrument
manufacturer’s instructions.
5.2.7 If the instrument should fail to signal, it shall be considered defective.
5.3 Instrument Calibration:
5.3.1 The instrument shall be calibrated by the manufacturer or accredited calibration laboratory at the frequency required by the
manufacturer. A certificate of calibration may be required.
5.4 Procedure:Procedure:
5.4.1 Sufficient drying or curing of the coatingcoating/lining shall be allowed prior to conducting a test. The length of time
required shall be obtained from the coating manufacturer. Solvents retained in the coating film could produce erroneous indicators.
5.4.2 The surface shall be clean, dry, and free of oil, dirt oil and other contaminates.contaminants. Measure the film thickness of
the coating with a nondestructive dry film thickness gage. gage in accordance with Practice D7091. If the coating film average
thickness of the coating film for the area being inspected exceeds 0.5 mm (20 mil),mil) use the procedures for high voltage spark
testing described in Test Method B, High Voltage Spark Testing.
5.4.3 Test the instrument for sensitivity in accordance with 5.3.
5.4.4 Attach the signal return (ground) wire from the instrument terminal to the metallic substrate and ensure a good electrical
contact.
5.4.5 Attach the exploring sponge lead to the other terminal.
5.4.6 Wet the sponge with a solution consisting of tap water and a low sudsing wetting agent, combined at a ratio of not more
than ⁄2 fluid oz of wetting agent to 1 gal water. Wetting agents are typically supplied by the equipment manufacturer. An example
of a low sudsing wetting agent is one used in photographic development. Ionic wetting agents (for example, salt water) should not
be used. The sponge shall be wetted sufficiently to barely avoid dripping of the solution while the sponge is moved over the coating.
The wetting agent residue must be removed prior to executing repairs to the coating.
5.4.6.1 Sodium chloride (salt) shall not be added to the wetting solution because of the potential erroneous indications of
discontinuities. The salt, after drying on the coated surface, may form a continuous path of conductivity across the surface. It may
also interfere with adhesion of subsequent coats.
5.2.7 Sodium chloride (salt) shall not be added to the wetting solution because of the potential erroneous indications of
discontinuities. The salt, after drying on the coated surface, may form a continuous path of conductivity across the surface. It will
also interfere with intercoat adhesion of additional coats.
5.4.7 Contact a bare spot on the conductive substrate with the wetted sponge to verify that the instrument is properly connected.
This procedure shall be repeated periodically during the test.testing.
5.4.8 For open areas move the sponge over the surface of the coating at a moderate rate, with a maximum rate of 0.3 m/s (1 ft/s),
using a double pass over each area. For internal pipe coatingslinings a single pass is appropriate as a double pass could lead to
telegraphing and false positives. Apply sufficient pressure to maintain a wet surface. If a discontinuity is detected, turn the sponge
on end to determine the exact location of the discontinuity. Improved accuracy of location can be achieved using a corner of the
sponge if practical. It should be noted that the detection of pinholes depends on the migration of the moisture in to the holes and
therefore the sponge may have to be moved over the surface at a slower rate to maximize detection, particularly for small holes
in thicker coatings.
5.4.9 Discontinuities that require repair shall be identified with a marker that is compatible with the repair coating or one that is
easily removed. Marking the defects with makingmasking tape is acceptable providing the tape adhesive does not affect the
subsequent repair.
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5.4.10 To prevent telegraphing take care to ensure that the solution is wiped dry wipe dry any solution from a previously detected
discontinuity where possible before continuing the test.
5.4.11 The wetting agent must be completely removed by rinsing the holiday area prior to repair.
5.4.12 Wet sponge holiday detection is not recommended between coats of a multicoat system. However, when a test is conducted
between coats of a multicoat system, a wetting agent shall not be used and allany residue left by the test water must be completely
removed prior to applying additional coats.
5.3 Verifying Operation of Equipment:
5.3.1 The instrument shall be tested for sensitivity prior to initial use and periodically thereafter, in accordance with the equipment
manufacturer’s instructions.
5.3.2 Test the battery for proper voltage output. Refer to the manufacturer’s instructions.
5.3.3 Switch the instrument to the “on position,” if applicable.
5.3.4 Wet the sponge with a wetting solution consisting of tap water and a wetting agent (see 5.2.6).
5.3.5 Connect the signal return wire to the instrument ground output terminal.
5.3.6 Touch the signal return wire alligator clip to the wetted sponge. The instrument signal should signal in accordance with the
instrument manufacturer’s instructions.
5.3.7 If the instrument should fail to signal, it shall be considered defective.
5.4 Verifying Instrument Calibration:
5.4.1 Verify instrument calibration in accordance with the manufacturer’s latest published instructions. If out of calibration, the
instrument shall be calibrated in accordance with the instrument manufacturer’s latest published instructions, or returned for
calibration. A certificate of calibration, renewed annually, may be required if the quality management system that controls the
testing dictates.
TEST METHOD B—HIGH VOLTAGE SPARK TESTING
5.5 Apparatus:Apparatus:
5.5.1 High Voltage Detector (in excess of 500 V)—Detector—anAn electronic device used to locate discontinuities in a
nonconductive protective coating coating/lining applied to a conductive substrate. It consists of an electrical voltage source, an
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