1、Designation: G179 04 (Reapproved 2011)Standard Specification forMetal Black Panel and White Panel Temperature Devices forNatural Weathering Tests1This standard is issued under the fixed designation G179; the number immediately following the designation indicates the year oforiginal adoption or, in t
2、he case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This specification provides specific information for themanufacturing and use of meta
3、l black and white panel tem-perature devices to measure temperatures that estimate highestmaximum (black) and lowest maximum (white) temperaturesof coated metal specimens during natural weathering tests.1.1.1 The construction of a black or white panel has asignificant effect on the indicated tempera
4、ture. This standarddescribes a robust construction from the panels investigated,which has been shown to provide the highest, most consistenttemperatures when compared side-by-side with other blackpanel constructions.1.2 This specification includes details on design require-ments and quantitative mea
5、surement techniques, which willlead to the proper selection of materials and use for black andwhite panel temperature sensors.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish ap
6、pro-priate safety and health practices and determine the applica-bility of regulatory requirements prior to use.NOTE 1There is no equivalent ISO standard describing the selectionand use of black panel sensors for natural weathering tests.2. Referenced Documents2.1 ASTM Standards:2D523 Test Method fo
7、r Specular GlossE220 Test Method for Calibration of Thermocouples ByComparison TechniquesE430 Test Methods for Measurement of Gloss of High-Gloss Surfaces by Abridged GoniophotometryE772 Terminology Relating to Solar Energy ConversionE881 Practice for Exposure of Solar Collector Cover Ma-terials to
8、Natural Weathering Under Conditions SimulatingStagnation ModeE903 Test Method for Solar Absorptance, Reflectance, andTransmittance of Materials Using Integrating Spheres3G7 Practice for Atmospheric Environmental Exposure Test-ing of Nonmetallic MaterialsG113 Terminology Relating to Natural andArtifi
9、cial Weath-ering Tests of Nonmetallic MaterialsG147 Practice for Conditioning and Handling of Nonmetal-lic Materials for Natural and Artificial Weathering TestsG151 Practice for Exposing Nonmetallic Materials in Ac-celerated Test Devices that Use Laboratory Light Sources2.2 ISO Standard:ISO 4892-1 P
10、lastics: Exposure to Laboratory LightSourcesGeneral Guidance43. Terminology3.1 The definitions given in Terminologies G113 and E772are applicable to this practice.4. Significance and Use4.1 The measurement of the primary elements of weather;solar radiation, temperature, and moisture is necessary toq
11、uantify the weather conditions during exposure in naturalweathering (outdoor) tests. This practice is applicable toweathering tests described in Practices G7, G24, or D4141(Method A) and other standards in which these standards arereferenced.4.2 The surface temperature of exposed materials dependspr
12、imarily on the amount of radiation absorbed, the emissivityof the specimen, the thermal conduction within the specimen,and the heat transfer between the specimen and the air incontact with the specimen surface and specimen holder. Sinceit is often not practical to measure the surface temperature ofi
13、ndividual test specimens, a specified black or white paneltemperature sensor is used to measure a reference temperature.This reference temperature provides an indication of thetemperature of a black or white specimen of similar construc-tion to the panel sensor. It is important to locate the black o
14、r1This specification is under the jurisdiction of ASTM Committee G03 onWeathering and Durability and is the direct responsibility of Subcommittee G03.02on Natural and Environmental Exposure Tests.Current edition approved July 1, 2011. Published August 2011. Originallyapproved in 2004. Last previous
15、edition approved in 2010 as G179 04(2010).DOI: 10.1520/G0179-04R11.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM we
16、bsite.3Withdrawn. The last approved version of this historical standard is referencedon www.astm.org.4Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West
17、Conshohocken, PA 19428-2959, United States.white panel sensor in proximity to the specimens, using thesame support, so that it receives the same radiation and coolingconditions as the test specimen. For sites where multipleexposure racks are used, a single black or white paneltemperature measurement
18、 made at the site and at the sameexposure orientation as the exposure racks is acceptable.4.3 Black panels are used in weathering applications sincethey are an indicator of the maximum specimen temperatureachieved during exposure due to the high solar absorptance ofthe black coating. White panels ar
19、e used as an indicator of thelowest maximum specimen temperature.4.4 Consideration must be given to the panel construction(for example, type of metal, type of sensor, sensor mounting,type of backing, coating system), as different configurationsmay give different results.NOTE 2At low irradiance, the
20、temperature difference between backedand unbacked panels will be small compared to higher levels of irradiance.Backed panels also have a slower response time due to the insulatingeffects of the wood.NOTE 3In an effort to provide temperature comparisons betweenlaboratory and natural weathering, some
21、users have used the black panelsdescribed in Practice G151 or ISO 4892-1 in natural weathering tests.Direct comparisons between black panel temperatures in laboratory andnatural weathering should not be made unless correlation has beenestablished. For instance, the temperature of specimens in a labo
22、ratorychamber with a black panel temperature of 60C may be very differentfrom the temperature of outdoor specimens when the outdoor black panelreads 60C.5. Reference Panel Types5.1 Two types of reference panel sensors are commonlyused in natural weathering tests: (a) Unbacked metal panels, or(b) Bac
23、ked metal panels.5.1.1 Unbacked PanelsThese panels are mounted directlyto the fixture by securing the top and bottom edges of the panelto the fixture. Ambient air can circulate on the front and backside of the panel to provide maximum cooling conditions forthe panel.5.1.2 Backed PanelsThese panels a
24、re mounted onto aplywood substrate, which insulates the back of the panel. Thepanel and backing are then mounted on the exposure frame.Ambient air is only cooling the front side of the panel since theback side is insulated, resulting in higher surface temperatures.NOTE 4The selection of the proper t
25、ype of panel backing is veryimportant since the measured temperatures will be different. Typically,backed black panels are 5 to 10C higher than unbacked black panelsdepending on the level of irradiance, wind speed, and other factors. If amore realistic exposure of the panel simulating test panel con
26、ditions isdesired, the panel shall be mounted in the same manner (backed orunbacked) as the test panels.6. Reference Panel Requirements6.1 SubstrateUnless otherwise specified, the substrateshall be a flat cold rolled steel panel with nominal dimensionsof 300 mm long, 100 mm wide, and 1.0 mm thicknes
27、s.NOTE 5Less corrosive materials may need to be used if the black orwhite panel is used in a corrosive environment. If a corrosion resistantmaterial is used as a substrate, an alternate construction method may berequired. Alternate constructions may not compare to panel constructionsdescribed in thi
28、s specification.6.2 PrimerThe panel shall be treated with an automotivetechnology zinc phosphate and coated with an automotiveafter-market grade two-component epoxy primer to ensureadequate corrosion resistance. Apply the two-component ep-oxy primer, according to the manufacturers recommendations.Al
29、low to air-dry for 24 h or baked at 30 min at 60C (140F).Sand primer with 320-400 grit sandpaper. Remove sandingresidue with a final wash solvent and a clean cloth.6.3 SensorThe sensor shall consist of a Type T thermo-couple (copper/constantan) meeting accuracy requirements ofbetter than or equal to
30、 61.0C throughout the measuring range.The sensor shall be small enough to attach to the panel andhave a known response throughout the expected temperaturerange. The thermocouple shall be attached to the panel byspot-welding it to the middle of the back side. The thermo-couple junction must be in con
31、tact with the bare metal panel.Care shall be taken to provide support to the spot weld joint toavoid loosening of the connection. This can be achieved byadding a mounting point on the thermocouple lead, which canact as a stress relief for the junction.6.4 Two coating colors are commonly used on temp
32、eraturereference panels in natural weathering tests: (a) Black coating,or (b) White coating.6.4.1 Black CoatingThe top (exposed) surface of thepanel shall be coated with a automotive technology high glossblack basecoat clearcoat system after the thermocouple sensorhas been spot-welded to the panel.
33、The coated panel shallabsorb 90 % or greater at all wavelengths from 300 to 2500 nmper Test Method E903.6.4.2 White CoatingThe top (exposed) surface of thepanel shall be coated with a automotive technology high glosswhite basecoat clearcoat system after the thermocouple sensorhas been spot-welded to
34、 the panel. The reflectance of the whitepanel at all wavelengths between 300 nm and 1000 nm shall be90 % or greater and 60 % or greater between 1000 nm and2500 nm per Test Method E903.6.4.3 BasecoatWipe the prepared primer surface with atack rag to remove dust and lint. Apply two to three coats ofei
35、ther an acrylic or a polyester basecoat, according to themanufactures recommendations. Allow 5 to 10 min flash offbetween coats and allow to dry for 30 min before applyingclearcoat.6.4.4 ClearcoatWipe prepared basecoat surface with atack rag to remove dust and lint. Apply two coats of anautomotive a
36、fter-market two-component urethane clearcoat,according to the manufacturers recommendations. Allow 5 to10 min flash off between coats. Allow to air-dry for 24 h orbaked at 30 min at 60C (140F).NOTE 6ASTM subcommittee G03.02 has conducted natural weath-ering exposures on commercially available black
37、coatings for a period of6 years. For more information about this study and the coatings used seeAppendix X1.6.5 Backing (Backed Panels)An exterior grade of 12 mm(nominal) thick plywood, with dimensions equal to the blackpanel, shall be used as the insulating backing for backed blackpanels. The panel
38、 shall be attached to the backing usingcorrosion resistant screws to ensure uniform contact betweenthe panel and the wood substrate. The thermocouple lead shallG179 04 (2011)2be recessed in the wood the necessary distance to allow thepanel to sit flat on the wood backing. The edges of the plywoodsha
39、ll be sealed with a wood sealer or paint to prevent moisturepenetration. Follow the guidelines in Practice G7 for replace-ment of plywood backing.6.6 Sensor MonitoringThe temperature should be moni-tored at frequent intervals to provide accurate and completedata. A maximum allowable time interval fo
40、r monitoring/recording panel temperatures is 6 min.7. Calibration/Verification And Maintenance7.1 The panels must be calibrated and verified for accuracyprior to placing it in service and on an annual basis.7.2 Calibrate the panel, thermocouple, monitor systemagainst ice and boiling water baths per
41、Test Method E220.Verify linearity against several mid range values.7.3 Verification must be performed during the summer usingnatural sunlight under unobstructed sunlight conditions whenwind speed is 8 km/h or less.NOTE 7ASTM subcommittee G03.02.01 is developing a procedurefor conducting intercompari
42、sons of black and white panels between sites.7.3.1 The coated panels with their sensors attached shall besituated on either static test fixture normal to the sun (62) ora tracking rack and allowed to stabilize for a minimum of 30min prior to initiating measurement. If a static test fixture isused, m
43、easurements shall be performed within 1 hour of solarnoon under unobstructed sunlight conditions to maximize solarradiant energy. If a tracking rack is used, measurements shallbe performed within3hofsolar noon under unobstructedsunlight conditions to maximize solar radiant energy. Thesensor shall be
44、 connected to the appropriate readout device.Prior to performing the measurements, the data collection /readout device shall be calibrated per manufacturers recom-mendations.NOTE 8Practice E881, Table 2 and Annex X2, provides guidance onmounting fixtures perpendicular to the incoming solar radiation
45、 atdifferent geographical locations at different times of the year.7.3.2 Due to the absence of a standard reference materialand temperature probes for this application, an inter-comparison of a series of five panels shall be performed toconfirm that all panels are within a 62C tolerance. Thisprocedu
46、re is essential in identifying any panel-to-panel dis-crepancies. Measurements shall be performed and data shall becollected for 1 h within1hofsolar noon for under unob-structed sunlight conditions to maximize solar radiant energy.A minimum of five panels shall be placed between 10 mm and25 mm of ea
47、ch other. The maximum allowable temperaturedifference between any two sensors is 2C. If the difference isgreater than 2C, the sensor with the farthest measurementfarthest from the mean of all measurements must be replacedand/or reattached to the panel and the verification procedurerepeated.7.3.3 At
48、least one of the minimum five panels shall beretained as a primary reference temperature device. Thisprimary reference device shall be stored in a cool, dry locationper Practice G147 (room temperature of 20 to 30C and therelative humidity ideally should be less than 60 %) andshielded from any light
49、source.7.3.4 Verification of the remaining in-use panels will bemade annually against the primary reference temperaturedevice. The temperature difference between the in-use andprimary reference panels must be within a 62C tolerance. Ifthe difference is greater than 2C, the in-use panels sensorshall be replaced and/or reattached to the panel and theverification procedure repeated.7.4 Hemispherical spectral reflectance measurementsshould be performed in accordance with Test Method E903 toverify solar absorptance prior to placing panels in service
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