ASTM G179-04(2019)
(Specification)Standard Specification for Metal Black Panel and White Panel Temperature Devices for Natural Weathering Tests
Standard Specification for Metal Black Panel and White Panel Temperature Devices for Natural Weathering Tests
SCOPE
1.1 This specification provides specific information for the manufacturing and use of metal black and white panel temperature devices to measure temperatures that estimate highest maximum (black) and lowest maximum (white) temperatures of coated metal specimens during natural weathering tests.
1.1.1 The construction of a black or white panel has a significant effect on the indicated temperature. This standard describes a robust construction from the panels investigated, which has been shown to provide the highest, most consistent temperatures when compared side-by-side with other black panel constructions.
1.2 This specification includes details on design requirements and quantitative measurement techniques, which will lead to the proper selection of materials and use for black and white panel temperature sensors.
1.3 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 requirements prior to use.
Note 1: There is no equivalent ISO standard describing the selection and use of black panel sensors for natural weathering tests.
1.4 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:G179 −04(Reapproved 2019)
Standard Specification for
Metal Black Panel and White Panel Temperature Devices for
Natural Weathering Tests
This standard is issued under the fixed designation G179; 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 E220 Test Method for Calibration of Thermocouples By
Comparison Techniques
1.1 This specification provides specific information for the
E430 TestMethodsforMeasurementofGlossofHigh-Gloss
manufacturing and use of metal black and white panel tem-
Surfaces by Abridged Goniophotometry
perature devices to measure temperatures that estimate highest
E772 Terminology of Solar Energy Conversion
maximum (black) and lowest maximum (white) temperatures
E881 Practice for Exposure of Solar Collector Cover Mate-
of coated metal specimens during natural weathering tests.
rials to Natural Weathering Under Conditions Simulating
1.1.1 The construction of a black or white panel has a
Stagnation Mode
significant effect on the indicated temperature. This standard
E903 Test Method for Solar Absorptance, Reflectance, and
describes a robust construction from the panels investigated,
Transmittance of Materials Using Integrating Spheres
which has been shown to provide the highest, most consistent
G7 Practice for Atmospheric Environmental Exposure Test-
temperatures when compared side-by-side with other black
ing of Nonmetallic Materials
panel constructions.
G113 Terminology Relating to Natural andArtificial Weath-
1.2 This specification includes details on design require-
ering Tests of Nonmetallic Materials
ments and quantitative measurement techniques, which will
G147 Practice for Conditioning and Handling of Nonmetal-
lead to the proper selection of materials and use for black and
lic Materials for Natural and Artificial Weathering Tests
white panel temperature sensors.
G151 Practice for Exposing Nonmetallic Materials inAccel-
1.3 This standard does not purport to address all of the
erated Test Devices that Use Laboratory Light Sources
safety concerns, if any, associated with its use. It is the
2.2 ISO Standard:
responsibility of the user of this standard to establish appro-
ISO 4892-1 Plastics: Exposure to Laboratory Light
priate safety, health, and environmental practices and deter-
Sources—General Guidance
mine the applicability of regulatory requirements prior to use.
3. Terminology
NOTE 1—There is no equivalent ISO standard describing the selection
and use of black panel sensors for natural weathering tests.
3.1 The definitions given in Terminologies G113 and E772
1.4 This international standard was developed in accor-
are applicable to this practice.
dance with internationally recognized principles on standard-
4. Significance and Use
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
4.1 The measurement of the primary elements of weather;
mendations issued by the World Trade Organization Technical
solar radiation, temperature, and moisture is necessary to
Barriers to Trade (TBT) Committee.
quantify the weather conditions during exposure in natural
weathering (outdoor) tests. This practice is applicable to
2. Referenced Documents
weathering tests described in Practices G7, G24, or D4141
2.1 ASTM Standards:
(Method A) and other standards in which these standards are
D523 Test Method for Specular Gloss
referenced.
4.2 The surface temperature of exposed materials depends
This specification is under the jurisdiction of ASTM Committee G03 on
Weathering and Durability and is the direct responsibility of Subcommittee G03.02 primarily on the amount of radiation absorbed, the emissivity
on Natural and Environmental Exposure Tests.
of the specimen, the thermal conduction within the specimen,
Current edition approved July 1, 2019. Published August 2019. Originally
and the heat transfer between the specimen and the air in
approvedin2004.Lastpreviouseditionapprovedin2011asG179 – 04(2011).DOI:
contact with the specimen surface and specimen holder. Since
10.1520/G0179-04R19.
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 fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
the ASTM website. 4th Floor, New York, NY 10036, http://www.ansi.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
G179−04(2019)
NOTE 5—Less corrosive materials may need to be used if the black or
it is often not practical to measure the surface temperature of
white panel is used in a corrosive environment. If a corrosion resistant
individual test specimens, a specified black or white panel
material is used as a substrate, an alternate construction method may be
temperature sensor is used to measure a reference temperature.
required.Alternate constructions may not compare to panel constructions
This reference temperature provides an indication of the
described in this specification.
temperature of a black or white specimen of similar construc-
6.2 Primer—The panel shall be treated with an automotive
tion to the panel sensor. It is important to locate the black or
technology zinc phosphate and coated with an automotive
white panel sensor in proximity to the specimens, using the
after-market grade two-component epoxy primer to ensure
samesupport,sothatitreceivesthesameradiationandcooling
adequate corrosion resistance. Apply the two-component ep-
conditions as the test specimen. For sites where multiple
oxy primer, according to the manufacturer’s recommendations.
exposure racks are used, a single black or white panel
Allow to air-dry for 24 h or baked at 30 min at 60 °C (140 °F).
temperature measurement made at the site and at the same
Sand primer with 320-400 grit sandpaper. Remove sanding
exposure orientation as the exposure racks is acceptable.
residue with a final wash solvent and a clean cloth.
4.3 Black panels are used in weathering applications since
6.3 Sensor—The sensor shall consist of a Type T thermo-
they are an indicator of the maximum specimen temperature
achieved during exposure due to the high solar absorptance of couple (copper/constantan) meeting accuracy requirements of
the black coating. White panels are used as an indicator of the
better than or equal to 61.0 °C throughout the measuring
lowest maximum specimen temperature. range. The sensor shall be small enough to attach to the panel
and have a known response throughout the expected tempera-
4.4 Consideration must be given to the panel construction
ture range. The thermocouple shall be attached to the panel by
(for example, type of metal, type of sensor, sensor mounting,
spot-welding it to the middle of the back side. The thermo-
type of backing, coating system), as different configurations
couple junction must be in contact with the bare metal panel.
may give different results.
Care shall be taken to provide support to the spot weld joint to
NOTE 2—At low irradiance, the temperature difference between backed
andunbackedpanelswillbesmallcomparedtohigherlevelsofirradiance. avoid loosening of the connection. This can be achieved by
Backed panels also have a slower response time due to the insulating
adding a mounting point on the thermocouple lead, which can
effects of the wood.
act as a stress relief for the junction.
NOTE 3—In an effort to provide temperature comparisons between
laboratory and natural weathering, some users have used the black panels
6.4 Two coating colors are commonly used on temperature
described in Practice G151 or ISO 4892-1 in natural weathering tests.
reference panels in natural weathering tests: (a) Black coating,
Direct comparisons between black panel temperatures in laboratory and
or (b) White coating.
natural weathering should not be made unless correlation has been
established. For instance, the temperature of specimens in a laboratory
6.4.1 Black Coating—The top (exposed) surface of the
chamber with a black panel temperature of 60 °C may be very different
panel shall be coated with a automotive technology high gloss
from the temperature of outdoor specimens when the outdoor black panel
black basecoat clearcoat system after the thermocouple sensor
reads 60 °C.
has been spot-welded to the panel. The coated panel shall
absorb90 %orgreateratallwavelengthsfrom300to2500nm
5. Reference Panel Types
per Test Method E903.
5.1 Two types of reference panel sensors are commonly
6.4.2 White Coating—The top (exposed) surface of the
used in natural weathering tests: (a) Unbacked metal panels, or
panel shall be coated with a automotive technology high gloss
(b) Backed metal panels.
white basecoat clearcoat system after the thermocouple sensor
5.1.1 Unbacked Panels—These panels are mounted directly
has been spot-welded to the panel.The reflectance of the white
to the fixture by securing the top and bottom edges of the panel
panelatallwavelengthsbetween300nmand1000nmshallbe
to the fixture. Ambient air can circulate on the front and back
90 % or greater and 60 % or greater between 1000 nm and
side of the panel to provide maximum cooling conditions for
2500 nm per Test Method E903.
the panel.
6.4.3 Basecoat—Wipe the prepared primer surface with a
5.1.2 Backed Panels—These panels are mounted onto a
tack rag to remove dust and lint. Apply two to three coats of
plywood substrate, which insulates the back of the panel. The
either an acrylic or a polyester basecoat, according to the
panel and backing are then mounted on the exposure frame.
manufactures recommendations. Allow 5 to 10 min flash off
Ambient air is only cooling the front side of the panel since the
between coats and allow to dry for 30 min before applying
back side is insulated, resulting in higher surface temperatures.
NOTE 4—The selection of the proper type of panel backing is very clearcoat.
important since the measured temperatures will be different. Typically,
6.4.4 Clearcoat—Wipe prepared basecoat surface with a
backed black panels are 5 to 10 °C higher than unbacked black panels
tack rag to remove dust and lint. Apply two coats of an
depending on the level of irradiance, wind speed, and other factors. If a
automotive after-market two-component urethane clearcoat,
more realistic exposure of the panel simulating test panel conditions is
desired, the panel shall be mounted in the same manner (backed or
according to the manufacturers recommendations. Allow 5 to
unbacked) as the test panels.
10 min flash off between coats. Allow to air-dry for 24 h or
baked at 30 min at 60 °C (140 °F).
6. Reference Panel Requirements
NOTE 6—ASTM subcommittee G03.02 has conducted natural weath-
6.1 Substrate—Unless otherwise specified, the substrate
ering exposures on commercially available black coatings for a period of
shall be a flat cold rolled steel panel with nominal dimensions
6 years. For more information about this study and the coatings used see
of 300 mm long, 100 mm wide, and 1.0 mm thickness. Appendix X1.
G179−04(2019)
6.5 Backing (Backed Panels)—An exterior grade of 12 mm Aminimum of five panels shall be placed between 10 mm and
(nominal) thick plywood, with dimensions equal to the black 25 mm of each other. The maximum allowable temperature
panel, shall be used as the insulating backing for backed black difference between any two sensors is 2 °C. If the difference is
panels. The panel shall be attached to the backing using greater than 2 °C, the sensor with the farthest measurement
corrosion resistant screws to ensure uniform contact between farthest from the mean of all measurements must be replaced
the panel and the wood substrate. The thermocouple lead shall and/or reattached to the panel and the verification procedure
be recessed in the wood the necessary distance to allow the repeated.
paneltositflatonthewoodbacking.Theedgesoftheplywood 7.3.3 At least one of the minimum five panels shall be
shall be sealed with a wood sealer or paint to prevent moisture retained as a primary reference temperature device. This
penetration. Follow the guidelines in Practice G7 for replace- primary reference device shall be stored in a cool, dry location
ment of plywood backing. per Practice G147 (room temperature of 20 to 30 °C and the
relative humidity ideally should be less than 60 %) and
6.6 Sensor Monitoring—The temperature should be moni-
shielded from any light source.
tored at frequent intervals to provide accurate and complete
7.3.4 Verification of the remaining in-use panels will be
data. A maximum allowable time interval for monitoring/
made annually against the primary reference temperature
recording panel temperatures is 6 min.
device. The temperature difference between the in-use and
primary reference panels must be within a 62 °C tolerance. If
7. Calibration/Verification And Maintenance
the difference is greater than 2 °C, the in-use panel’s sensor
7.1 The panels must be calibrated and verified for accuracy
shall be replaced and/or reattached to the panel and the
prior to placing it in service and on an annual basis.
verification procedure repeated.
7.2 Calibrate the panel, thermocouple, monitor system
7.4 Hemispherical spectral reflectance measurements
against ice and boiling water baths per Test Method E220.
should be performed in accordance with Test Method E903 to
Verify linearity against several mid range values.
verify solar absorptance prior to placing panels in service. If a
7.3 Verificationmustbeperformedduringthesummerusing
lot of panels is placed in service, then measurement is only
natural sunlight under unobstructed sunlight conditions when
requiredonarepresentativepanelfromtheentirelot.Forblack
wind speed is 8 km/h or less.
panels, if the solar absorptance falls below the requirements of
90 % at all wavelengths between 300 nm and 2500 nm, the
NOTE 7—ASTM subcommittee G03.02.01 is developing a procedure
panels must be replaced or re-coated and the verification
for conducting intercomparisons of black and white panels between sites.
procedurerepeated.Forwhitepanels,ifthereflectancerequire-
7.3.1 The coated panels with their sensors attached shall be
ments fall below 90 % at all wavelengths between 300 nm and
situated on either static test fixture normal to the sun (62°) or
1000 nm or
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