ASTM D4787-93(1999)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: D 4787 – 93 (Reapproved 1999)
Standard Practice for
Continuity Verification of Liquid or Sheet Linings Applied to
Concrete Substrates
This standard is issued under the fixed designation D 4787; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope 2.2 NACE Standards:
RP0188-88 Discontinuity (Holiday) Testing of Protective
1.1 This practice covers procedures that may be used to
Coatings
allow the detection of discontinuities in nonconductive linings
applied to concrete substrates.
3. Terminology
1.2 Discontinuities may include pinholes, internal voids,
3.1 Definitions of Terms Specific to This Standard:
holidays, cracks, and conductive inclusions.
3.1.1 discontinuity—a localized lining site that has a dielec-
1.3 This practice describes detection of discontinuities uti-
tric strength less than a determined test voltage.
lizing a low voltage wet sponge holiday detector and a high
3.1.2 conductive underlayment—a continuous layer applied
voltage pulsating or continuous dc spark tester. Linings with
to the prepared concrete surface prior to the application of a
thickness in excess of 20 mils must be tested utilizing high
nonconductivelininglayer(s)thatwillallowhighvoltagespark
voltage spark testing equipment.
testing for discontinuities in the lining.
NOTE 1—For further information on discontinuity testing refer to
3.1.3 spark-over—the distance a spark, from a high voltage
NACE Standard RP0188-88 or Practice D 5162.
tester, will jump across a space from a grounded surface at a
1.4 This practice describes procedures both with and with-
specific electrical voltage.
out the use of a conductive underlayment.
3.1.4 high voltage spark tester—an electrical device (in
1.5 The values stated in the inch-pound units are to be
excess of 800 V) used to locate discontinuities in a noncon-
regarded as the standard. The values given in parentheses are
ductive protective coating applied to a conductive substrate.
for information only.
3.1.5 low voltage tester—a low voltage wet sponge electri-
1.6 This standard does not purport to address all of the
cal detector used to locate discontinuities in nonconductive
safety concerns, if any, associated with its use. It is the
linings applied to conductive substrates.
responsibility of the user of this standard to establish appro-
3.1.5.1 Discussion—This test instrument is not suitable for
priate safety and health practices and determine the applica-
testing linings in excess of 20 mils.
bility of regulatory limitations prior to use. For a specific
3.1.6 test voltage—that electrical voltage established which
hazard statement, see Section 7.
will allow a discontinuity at the thickest lining location site to
be tested, but which will not damage the lining.
2. Referenced Documents
3.1.6.1 Discussion—The test voltage must always be set
2.1 ASTM Standards:
wellbelowthedielectricbreakdownstrengthofthelining.This
D 149 Test Method for Dielectric Breakdown Voltage and
voltage should be recommended by the lining manufacturer.
Dielectric Strength of Solid Electrical Insulating Materials
The dielectric breakdown voltage strength of a solid can be
at Commercial Power Frequencies
determined by Test Method D 149.
D 5162 Practice for Discontinuity (Holiday) Testing of
4. Summary of Practice
Nonconductive Protective Coating on Metallic Substrates
4.1 This practice allows for high and low voltage electrical
detection of discontinuities in new linings applied to concrete
This practice is under the jurisdiction of ASTM Committee D01 on Paint and
substrates through the utilization of a continuous conductive
Related Coatings, Materials, and Applications and is the direct responsibility of
underlayment applied to the prepared concrete surface prior to
Subcommittee D01.46 on Industrial Protective Coatings.
Current edition approved Jan. 10, 1999. Published September 1999. Originally
the application of the nonconductive lining layer(s) or by
published as D 4787 – 88. Last previous edition D 4787 – 88.
determining the conductivity of the concrete substrate to be
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
Available from NationalAssociation of Corrosion Engineers, P.O. Box 218340,
the ASTM website.
Houston, TX 77218.
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D 4787 – 93 (1999)
tested. The conductivity of concrete varies, depending on air inclusions or voids; and the compatibility of conductive
moisture content, type, density, and location of rebars. Test the underlayments with the specified lining.
conductivity of the concrete by attaching the ground wire to
5.8 Acontinuous dc high voltage tester stresses a lining to a
rebar or other metallic ground permanently installed in the
greater degree than the pulsating dc high voltage tester.
concrete. If a metallic ground is not available, the ground wire
shall be placed directly against the bare concrete surface and
6. Apparatus
weighted with a damp cloth or paper sand-filled bag. If the test
6.1 High Voltage Spark Tester—An electrical detector with
indicates the concrete provides an insufficient ground, a con-
a voltage rating in excess of 800 V. The detector is to consist
ductive underlayment will be required if a continuity test is to
of an electrical energy source, an exploring electrode, a ground
be conducted.
connection, and ground wire. The detector shall be equipped
5. Significance and Use
with a visual or audible indicator, or both.
5.1 The electrical conductivity of concrete is primarily
6.1.1 Electrical Energy Source—Either a-c, d-c, or pulsat-
influenced by the presence of moisture. Other factors which
ing d-c type with the appropriate test voltage.
affect the continuity of concrete include the following:
6.1.2 Exploring Electrode—The full length shall be capable
5.1.1 Presence of metal rebars,
of maintaining continuous contact with the surface being
5.1.2 Cement content and type,
inspected.
5.1.3 Aggregate types,
6.1.3 Ground Wire, stranded 14 to 16 gage copper wire.
5.1.4 Admixtures,
6.1.4 Visual or Audible Indicators, or both, to signal a
5.1.5 Porosity,
closed electrical circuit. Such signals shall be essential for
5.1.6 Above or below grade elevation,
testing the underlayment for electrical conductivity and for
5.1.7 Indoor or outdoor location,
exposing discontinuities in the lining after it has been applied.
5.1.8 Temperature and humidity, and
6.1.5 High Voltage Pulsating DC Spark Tester—A device
5.1.9 Age of concrete.
used to locate discontinuities where electrical pulses are
5.2 The electrical conductivity of concrete itself may be
generatingbetween20and60cps.Eachpulseisonforaperiod
successfully used for high-voltage continuity testing of linings
of time between 20 and 200 µs.
applied directly with no specific conductive underlayment
installed. However, the voltage required to find a discontinuity
6.1.6 High Voltage Continuous DC Spark Tester—Adevice
may vary greatly from point to point on the structure. This used to locate discontinuities where the voltage is continuously
variance may reduce the test reliability. present on the surface of the protective coating.
5.3 Although the most common conductive underlayments
6.2 Low Voltage Tester—An electrical device powered by a
are liquid primers applied by trowel, roller, or spray, and which
5 to 90 volt battery. The detector consists of an electrical
contain carbon or graphite fillers, others may take the form of
energy source, an open-cell sponge electrode, a ground wire,
the following:
and an audible indicator. The device may contain a variable
5.3.1 Sheet-applied graphite veils,
range selector that has no effect on the sensitivity of the
5.3.2 Conductive polymers,
detector which must range between 80 000 and 100 000 V.
5.3.3 Conductive graphite fibers,
5.3.4 Conductive metallic fibers, and
7. Hazards
5.3.5 Conductive metallic screening.
7.1 Solvents retained in the applied underlayment or lining
5.4 Liquid-applied conductive underlayments may be desir-
may create an explosive environment with the high voltage
able as they can serve to address imperfections in the concrete
testers as well as produce an erroneous result.
surface and provide a better base for which to apply the lining.
5.5 This practice is intended for use only with new linings
8. Conductive Underlayments
applied to concrete substrates. Inspecting a lining previously
exposed to an immersion condition could result in damaging
8.1 The conductive underlayment shall not rely on the
the lining or produce an erroneous detection of discontinuities
concrete substrate’s electrical properties.
due to permeation or moisture absorption of the lining.
8.2 The specified lining shall be compatible with the speci-
Deposits may also be present on the surface causing telegra
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