1、Designation: G 179 04Standard Specification forMetal Black Panel and White Panel Temperature Devices forNatural Weathering Tests1This standard is issued under the fixed designation G 179; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revis
2、ion, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This specification provides specific information for themanufacturing and use of metal black and whi
3、te 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 temperature. This stan
4、darddescribes 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 measurement techni
5、ques, 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 appro-priate safe
6、ty 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:2D 523 Test Method for Specular Glo
7、ssE 220 Test Method for Calibration of Thermocouples ByComparison TechniquesE 430 Test Methods for Measurement of High-Gloss Sur-faces by GoniophotometryE 772 Terminology Relating to Solar Energy ConversionE 881 Practice for Exposure of Solar Collector Cover Ma-terials to Natural Weathering Under Co
8、nditions SimulatingStagnation ModeE 903 Test Method for Solar Absorptance, Reflectance, andTransmittance of Materials Using Integrating SpheresG 7 Practice for Atmospheric Environmental Exposure ofNonmetallic MaterialsG 113 Terminology Relating to Natural and ArtificialWeathering Tests of Nonmetalli
9、c MaterialsG 147 Practice for Conditioning and Handling of Nonme-tallic Materials for Natural and Artificial Weathering TestsG 151 Practice for Exposing Nonmetallic Materials in Ac-celerated Test Devices that use Laboratory Light Sources2.2 ISO Standard:ISO 4892-1 Plastics: Exposure to Laboratory Li
10、ghtSourcesGeneral Guidance33. Terminology3.1 The definitions given in Terminologies G 113 and E 772are applicable to this practice.4. Significance and Use4.1 The measurement of the primary elements of weather;solar radiation, temperature, and moisture is necessary toquantify the weather conditions d
11、uring exposure in naturalweathering (outdoor) tests. This practice is applicable toweathering tests described in Practices G 7, G 24, or D 4141(Method A) and other standards in which these standards arereferenced.4.2 The surface temperature of exposed materials dependsprimarily on the amount of radi
12、ation 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 ofindividual test specimens, a s
13、pecified 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 orwhite panel sensor in proxim
14、ity to the specimens, using thesame support, so that it receives the same radiation and coolingconditions as the test specimen. For sites where multiple1This specification is under the jurisdiction of ASTM Committee G03 onDurability of Nonmetallic Materials and is the direct responsibility of Subcom
15、mitteeG03.02 on Joint Weathering Projects.Current edition approved Jan. 1, 2004. Published January 2004.2For 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 standard
16、s Document Summary page onthe ASTM website.3Available from the American National Standards Institute (ANSI), 1430Broadway, New York, NY 10018.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.exposure racks are used, a single black or
17、white paneltemperature measurement 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 of
18、the black coating. White panels are 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 res
19、ults.NOTE 2At low irradiance, the 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 betweenlabora
20、tory and natural weathering, some users have used the black panelsdescribed in Practice G 151 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
21、 temperature of specimens in a laboratorychamber 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: (
22、a) Unbacked metal panels, or(b) Backed 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 pane
23、l.5.1.2 Backed PanelsThese panels are 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.
24、NOTE 4The selection of the proper type 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
25、the panel simulating test panel conditions 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 lon
26、g, 100 mm wide, and 1.0 mm thickness.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
27、panel constructionsdescribed in this 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 t
28、he manufacturers recommendations.Allow 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 req
29、uirements ofbetter than or equal to 6 1.0C throughout the measuringrange. The sensor shall be small enough to attach to the paneland have a known response throughout the expected tempera-ture range. The thermocouple shall be attached to the panel byspot-welding it to the middle of the back side. The
30、 thermo-couple junction must be in contact 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 co
31、ating colors are commonly used on temperaturereference 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 sen
32、sorhas been spot-welded to the panel. The coated panel shallabsorb 90 % or greater at all wavelengths from 300 to 2500 nmper Test Method E 903.6.4.2 White CoatingThe top (exposed) surface of thepanel shall be coated with a automotive technology high glosswhite basecoat clearcoat system after the the
33、rmocouple sensorhas been spot-welded to 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 E 903.6.4.3 BasecoatWipe the prepared primer surface with atack rag to remove dust
34、 and lint. Apply two to three coats ofeither 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
35、 lint. Apply two coats of anautomotive after-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 ex
36、posures on commercially available black 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 b
37、acking for backed blackpanels. The panel shall be attached to the backing usingcorrosion resistant screws to ensure uniform contact betweenthe panel and the wood substrate. The thermocouple lead shallbe recessed in the wood the necessary distance to allow thepanel to sit flat on the wood backing. Th
38、e edges of the plywoodshall be sealed with a wood sealer or paint to prevent moistureG179042penetration. Follow the guidelines in Practice G 7 for replace-ment of plywood backing.6.6 Sensor MonitoringThe temperature should be moni-tored at frequent intervals to provide accurate and completedata. A m
39、aximum allowable time interval for 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
40、 ice and boiling water baths per Test Method E 220.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 pr
41、ocedurefor conducting intercomparisons 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 (6 2) ora tracking rack and allowed to stabilize for a minimum of 30min prior to initiating measurement.
42、 If a static test fixture isused, measurements 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
43、 radiant energy. Thesensor shall be 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 E 881, Table 2 and Annex X2, provides guidance onmounting fixtures perpendic
44、ular to the incoming solar radiation 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
45、 within a 6 2C tolerance. Thisprocedure 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 b
46、e placed between 10 mm and25 mm of each 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 ver
47、ification procedurerepeated.7.3.3 At 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 G 147 (room temperature of 20 to 30C and therelative humidity ideally should be less
48、than 60 %) andshielded from any light 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 6 2C tolerance. Ifthe difference is greater
49、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 E 903 toverify solar absorptance prior to placing panels in service. If alot of panels is placed in service, then measurement is onlyrequired on a representative panel from the entire lot. For blackpanels, if the solar absorptance falls below the requirements of90 % at all wavelengths between 300 nm and 2500 nm, thepanels must be
