ASTM G179-04
(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 and health 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.
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: G179 – 04
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 E881 Practice for Exposure of Solar Collector Cover Ma-
terials to NaturalWeathering Under Conditions Simulating
1.1 This specification provides specific information for the
Stagnation Mode
manufacturing and use of metal black and white panel tem-
E903 Test Method for Solar Absorptance, Reflectance, and
perature devices to measure temperatures that estimate highest
Transmittance of Materials Using Integrating Spheres
maximum (black) and lowest maximum (white) temperatures
G7 Practice forAtmospheric Environmental Exposure Test-
of coated metal specimens during natural weathering tests.
ing of Nonmetallic Materials
1.1.1 The construction of a black or white panel has a
G113 TerminologyRelatingtoNaturalandArtificialWeath-
significant effect on the indicated temperature. This standard
ering Tests of Nonmetallic Materials
describes a robust construction from the panels investigated,
G147 Practice for Conditioning and Handling of Nonmetal-
which has been shown to provide the highest, most consistent
lic Materials for Natural and Artificial Weathering Tests
temperatures when compared side-by-side with other black
G151 Practice for Exposing Nonmetallic Materials in Ac-
panel constructions.
celerated Test Devices that Use Laboratory Light Sources
1.2 This specification includes details on design require-
2.2 ISO Standard:
ments and quantitative measurement techniques, which will
ISO 4892-1 Plastics: Exposure to Laboratory Light
lead to the proper selection of materials and use for black and
Sources—General Guidance
white panel temperature sensors.
1.3 This standard does not purport to address all of the
3. Terminology
safety concerns, if any, associated with its use. It is the
3.1 The definitions given in Terminologies G113 and E772
responsibility of the user of this standard to establish appro-
are applicable to this practice.
priate safety and health practices and determine the applica-
bility of regulatory requirements prior to use.
4. Significance and Use
NOTE 1—There is no equivalent ISO standard describing the selection
4.1 The measurement of the primary elements of weather;
and use of black panel sensors for natural weathering tests.
solar radiation, temperature, and moisture is necessary to
quantify the weather conditions during exposure in natural
2. Referenced Documents
weathering (outdoor) tests. This practice is applicable to
2.1 ASTM Standards:
weathering tests described in Practices G7, G24, or D4141
D523 Test Method for Specular Gloss
(Method A) and other standards in which these standards are
E220 Test Method for Calibration of Thermocouples By
referenced.
Comparison Techniques
4.2 The surface temperature of exposed materials depends
E430 Test Methods for Measurement of Gloss of High-
primarily on the amount of radiation absorbed, the emissivity
Gloss Surfaces by Abridged Goniophotometry
of the specimen, the thermal conduction within the specimen,
E772 Terminology Relating to Solar Energy Conversion
and the heat transfer between the specimen and the air in
contact with the specimen surface and specimen holder. Since
it is often not practical to measure the surface temperature of
This specification is under the jurisdiction of ASTM Committee G03 on
individual test specimens, a specified black or white panel
DurabilityofNonmetallicMaterialsandisthedirectresponsibilityofSubcommittee
temperature sensor is used to measure a reference temperature.
G03.02 on Joint Weathering Projects.
This reference temperature provides an indication of the
Current edition approved Jan. 1, 2004. Published January 2004. DOI: 10.1520/
G0179-04. temperature of a black or white specimen of similar construc-
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
tion to the panel sensor. It is important to locate the black 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.
3 4
Withdrawn. The last approved version of this historical standard is referenced Available from the American National Standards Institute (ANSI), 1430
on www.astm.org. Broadway, New York, NY 10018.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
G179 – 04
white panel sensor in proximity to the specimens, using the 6.2 Primer—The panel shall be treated with an automotive
samesupport,sothatitreceivesthesameradiationandcooling technology zinc phosphate and coated with an automotive
conditions as the test specimen. For sites where multiple after-market grade two-component epoxy primer to ensure
exposure racks are used, a single black or white panel adequate corrosion resistance. Apply the two-component ep-
temperature measurement made at the site and at the same oxy primer, according to the manufacturer’s recommendations.
exposure orientation as the exposure racks is acceptable. Allow to air-dry for 24 h or baked at 30 min at 60°C (140°F).
4.3 Black panels are used in weathering applications since Sand primer with 320-400 grit sandpaper. Remove sanding
they are an indicator of the maximum specimen temperature residue with a final wash solvent and a clean cloth.
achieved during exposure due to the high solar absorptance of
6.3 Sensor—The sensor shall consist of a Type T thermo-
the black coating. White panels are used as an indicator of the couple (copper/constantan) meeting accuracy requirements of
lowest maximum specimen temperature.
better than or equal to 6 1.0°C throughout the measuring
4.4 Consideration must be given to the panel construction range. The sensor shall be small enough to attach to the panel
(for example, type of metal, type of sensor, sensor mounting,
and have a known response throughout the expected tempera-
type of backing, coating system), as different configurations ture range. The thermocouple shall be attached to the panel by
may give different results. spot-welding it to the middle of the back side. The thermo-
couple junction must be in contact with the bare metal panel.
NOTE 2—At low irradiance, the temperature difference between backed
Care shall be taken to provide support to the spot weld joint to
andunbackedpanelswillbesmallcomparedtohigherlevelsofirradiance.
avoid loosening of the connection. This can be achieved by
Backed panels also have a slower response time due to the insulating
effects of the wood. adding a mounting point on the thermocouple lead, which can
NOTE 3—In an effort to provide temperature comparisons between act as a stress relief for the junction.
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
6.4.1 Black Coating—The top (exposed) surface of the
established. For instance, the temperature of specimens in a laboratory
panel shall be coated with a automotive technology high gloss
chamber with a black panel temperature of 60°C may be very different
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 panel at all wavelengths between 300 nm and 1000 nm shall be
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. clearcoat.
6.4.4 Clearcoat—Wipe prepared basecoat surface with a
NOTE 4—The selection of the proper type of panel backing is very
tack rag to remove dust and lint. Apply two coats of an
important since the measured temperatures will be different. Typically,
automotive after-market two-component urethane clearcoat,
backed black panels are 5 to 10°C higher than unbacked black panels
depending on the level of irradiance, wind speed, and other factors. If a
according to the manufacturers recommendations. Allow 5 to
more realistic exposure of the panel simulating test panel conditions is
10 min flash off between coats. Allow to air-dry for 24 h or
desired, the panel shall be mounted in the same manner (backed or
baked at 30 min at 60°C (140°F).
unbacked) as the test panels.
NOTE 6—ASTM subcommittee G03.02 has conducted natural weath-
6. Reference Panel Requirements ering exposures on commercially available black coatings for a period of
6 years. For more information about this study and the coatings used see
6.1 Substrate—Unless otherwise specified, the substrate
Appendix X1.
shall be a flat cold rolled steel panel with nominal dimensions
6.5 Backing (Backed Panels)—An exterior grade of 12 mm
of 300 mm long, 100 mm wide, and 1.0 mm thickness.
(nominal) thick plywood, with dimensions equal to the black
NOTE 5—Less corrosive materials may need to be used if the black or
panel, shall be used as the insulating backing for backed black
white panel is used in a corrosive environment. If a corrosion resistant
panels. The panel shall be attached to the backing using
material is used as a substrate, an alternate construction method may be
corrosion resistant screws to ensure uniform contact between
required.Alternate constructions may not compare to panel constructions
described in this specification. the panel and the wood substrate. The thermocouple lead shall
G179 – 04
be recessed in the wood the necessary distance to allow the greater than 2°C, the sensor with the farthest measurement
paneltositflatonthewoodbacking.Theedgesoftheplywood farthest from the mean of all measurements must be replaced
shall be sealed with a wood sealer or paint to prevent moisture and/or reattached to the panel and the verification procedure
penetration. Follow the guidelines in Practice G7 for replace- repeated.
ment of plywood backing. 7.3.3 At least one of the minimum five panels shall be
6.6 Sensor Monitoring—The temperature should be moni- retained as a primary reference temperature device. This
tored at frequent intervals to provide accurate and complete primary reference device shall be stored in a cool, dry location
data. A maximum allowable time interval for monitoring/ per Practice G147 (room temperature of 20 to 30°C and the
recording panel temperatures is 6 min. relative humidity ideally should be less than 60 %) and
shielded from any light source.
7.3.4 Verification of the remaining in-use panels will be
7. Calibration/Verification And Maintenance
made annually against the primary reference temperature
7.1 The panels must be calibrated and verified for accuracy
device. The temperature difference between the in-use and
prior to placing it in service and on an annual basis.
primary reference panels must be within a 6 2°C tolerance. If
7.2 Calibrate the panel, thermocouple, monitor system
the difference is greater than 2°C, the in-use panel’s sensor
against ice and boiling water baths per Test Method E220.
shall be replaced and/or reattached to the panel and the
Verify linearity against several mid range values.
verification procedure repeated.
7.3 Verificationmustbeperformedduringthesummerusing
7.4 Hemispherical spectral reflectance measurements
natural sunlight under unobstructed sunlight conditions when
should be performed in accordance with Test Method E903 to
wind speed is 8 km/h or less.
verify solar absorptance prior to placing panels in service. If a
NOTE 7—ASTM subcommittee G03.02.01 is developing a procedure
lot of panels is placed in service, then measurement is only
for conducting intercomparisons of black and white panels between sites.
requiredonarepresentativepanelfromtheentirelot.Forblack
7.3.1 The coated panels with their sensors attached shall be
panels, if the solar absorptance falls below the requirements of
situated on either static test fixture normal to the sun (6 2°) or 90 % at all wavelengths between 300 nm and 2500 nm, the
a tracking rack and allowed to stabilize for a minimum of 30
panels must be replaced or re-coated and the verification
min prior to initiating measurement. If a static test fixture is procedurerepeated.Forwhitepanels,ifthereflectancerequire-
used, measurements shall be performed within 1 hour of solar
ments fall below 90 % at all wavelengths between 300 nm and
noon under unobstructed sunlight conditions to maximize solar 1000 nm or 60 % for wavelengths between 1000 nm and 2500
radiant energy. If a tracking rack is used, measurements shall
nm, the panels must be replaced or re-coated and the verifica-
be performed within3hof solar noon under unobstructed tion procedure repeated.
sunlight conditions to maximize solar radiant energy. The
NOTE 9—Solar absorptance/reflection measurements can be made on a
sensor shall be connected to the appropriate readout device.
regular basis to monitor
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