1、Designation: D7869 17Standard Practice forXenon Arc Exposure Test with Enhanced Light and WaterExposure for Transportation Coatings1This standard is issued under the fixed designation D7869; the number immediately following the designation indicates the year oforiginal adoption or, in the case of re
2、vision, 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 practice specifies the operating procedures for acontrolled irradiance xenon arc light and wa
3、ter apparatus. Theprocedure uses one or more lamp(s) and optical filter(s) toproduce irradiance similar to sunlight in the UV and visiblerange. It also simulates the water absorption and stress cyclesexperienced by automotive exterior coatings under naturalweathering conditions. This practice has al
4、so been foundapplicable to coatings on other transportation vehicles, such asaircraft, trucks and rail cars.1.2 This practice uses a xenon arc light source with speci-fied optical filter(s). The spectral power distribution (SPD) forthe lamp and special daylight filter(s) is as specified in AnnexA1.
5、The irradiance level used in this practice varies between0.40 and 0.80 W/(m2nm) at 340 nm. Water is sprayed on thespecimens during portions of several dark steps. The applica-tion of water is such that the coatings will absorb and desorbsubstantial amounts of water during testing. In addition, thecy
6、cling between wet/dry and warm/cool will induce mechani-cal stresses into the materials. These test conditions aredesigned to simulate the physical and chemical stresses fromenvironments in a subtropical climate, such as southernFlorida.1.3 The values stated in SI units are to be regarded asstandard
7、. No other units of measurement are included in thisstandard.1.4 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 safety and health practices and determine the applica-
8、bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D4517 Test Method for Low-Level Total Silica in High-Purity Water by Flameless Atomic Absorption Spectros-copyG113 Terminology Relating to Natural and Artificial Weath-ering Tests of Nonmetallic MaterialsG147 Pr
9、actice for Conditioning and Handling of Nonmetal-lic Materials for Natural and Artificial Weathering TestsG151 Practice for Exposing Nonmetallic Materials in Accel-erated Test Devices that Use Laboratory Light SourcesG155 Practice for Operating Xenon Arc Light Apparatus forExposure of Non-Metallic M
10、aterials3. Terminology3.1 Definitions applicable to this standard can be found inTerminology G113.3.2 transportation coatings, nexterior coatings used forvehicles subjected to natural weathering conditions such asautomobiles, aircraft, trucks, rail cars, etc.4. Summary of Practice4.1 Test specimens
11、are exposed to specific test conditionsdesigned to simulate the physical and chemical stresses fromenvironments in a subtropical climate, such as southernFlorida. The test conditions consist of a primary test cycle anda sub-cycle. The primary test cycle includes two long waterexposures and a single,
12、 long light exposure with precisespectral match to daylight as described in Annex A1.Itisdesigned to reproduce water penetration failures, such asadhesion, blistering and diffusion of small molecules (1).3Thesub-cycle consisting of shorter alternating water and light1This practice is under the juris
13、diction of ASTM Committee D01 on Paint andRelated Coatings, Materials, and Applications and is the direct responsibility ofSubcommittee D01.27 on Accelerated Testing.Current edition approved Feb. 1, 2017. Published March 2017. Originallyapproved in 2013. Last previous edition approved in 2013 as D78
14、69 13.DOI:10.1520/D7869-17.2For 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 website.3The boldface numbers in parenthes
15、es refer to the list of references at the end ofthis standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization establi
16、shed in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1exposures is designed to simulate cyclic stresses such ascracking and surface erosion. These two cycles are
17、 designed toreplicate the common types of failures driven by the interactionof photo-oxidation during daylight and hydrolysis during waterexposure that are seen in a subtropical climate such as glossloss, color change, adhesion, blistering and cracking (2).5. Significance and Use5.1 This test proced
18、ure is used to simulate the physical andenvironmental stresses that a coating for exterior transportationapplications (for example, automotive) is exposed to in asubtropical climate, such as southern Florida. It has been foundthat such a subtropical climate causes particularly severedeterioration of
19、 such coatings. The long water exposures andwet/dry cycling found in southern Florida are particularlyimportant for this deterioration, in addition to the high dosageof solar radiation (3). This practice was developed to addressthe deficiencies of historical tests used for transportationcoatings, es
20、pecially automotive coatings (4).NOTE 1This test procedure was developed through eight years ofcooperative testing between automotive and aerospace OEMs, materialsuppliers, and test equipment manufacturers. See References for publishedpapers on this research.6. Apparatus6.1 The xenon arc light and w
21、ater apparatus shall complywith Practice G155.6.1.1 The xenon arc light and water apparatus shall have anuninsulated black panel thermometer as described in PracticeG151 unless otherwise agreed upon by contractual parties6.1.2 The xenon arc light and water apparatus must be ableto control irradiance
22、 at 340 nm, relative humidity, uninsulatedblack panel temperature and chamber temperature, and providewater spray on the front of the specimens.6.2 Mass balancewith a resolution of at least 0.1 g.7. Reagents and Materials7.1 Sponge. See Annex A2 for more detailed specifications.7.2 Purified Water, a
23、s specified in Practice G155 and 8.2.8. Apparatus Setup8.1 Maintain and calibrate the apparatus according to manu-facturers instructions.8.2 Water SprayThe water for spray and humidificationshall be of the same quality listed in Practice G155 and shallleave no objectionable deposits or stains on the
24、 exposedspecimens. The water shall have less than 1 mg per litre (1ppm) total dissolved solids and it shall have less than 0.1 mgper litre (0.1 ppm) silica.NOTE 2Silica levels should be determined using Test Method D4517or equivalent. A combination of deionization and reverse osmosis treat-ment can
25、effectively produce water with the desired purity. In certain casessome samples could exude materials into the chamber that can promotedeleterious effects on other samples.8.3 Qualify the sponges used for the water uptake per theprocedure in Annex A2. For each xenon arc light and waterapparatus, ver
26、ify the water uptake capability in accordancewith the procedure in Annex A3 before placing it into serviceand at least once per year thereafter. Follow the recommenda-tions of the manufacturer of the xenon arc light and waterapparatus for additional checks, if any.8.4 Fit the xenon arc light and wat
27、er apparatus with aspecial daylight filter(s) in accordance with the requirements ofAnnex A1.NOTE 3Contact the xenon arc light and water apparatus manufacturerfor the proper optical filter(s) required. Follow the manufacturersrecommendations for optical filter maintenance.8.5 Other optical filters m
28、ay be used by mutual agreementbetween the contractual parties.NOTE 4Minor differences in the resultant spectral power distribution(especially in the short wavelength UV region) can have an impact on thetest results. Follow the manufacturers recommendations for xenon arclamp and optical filter mainte
29、nance (5).9. Test Procedure9.1 Refer to Practice G147 for specimen preparation, con-ditioning and handling. All test specimens must be clean andfree from fingerprints or other surface contaminants beforetesting. Prepare a specimen for exposure to fit the specimenmounting fixture being used, if any.
30、Follow the manufacturersguidelines for specimen size and mounting.9.1.1 Seal any cut edges on the test specimens if required, asagreed between contractual parties. For example, (a) rust andcorrosion products from the cut edges of metal panels maystain the test specimens, (b) by-products from the cut
31、 edges ofplastic substrates may leach out and contaminate testspecimens, and (c) other panels may not require any edgesealing at all.NOTE 5Air-dry primers, plastic barrier tapes and silicone sealantshave often been found suitable for edge sealing.9.2 Fill all unused specimen positions in the xenon a
32、rc lightand water apparatus exposure area with inert specimens (forexample, anodized aluminum panels) to maintain desiredairflow.NOTE 6Refer to the manufacturers instructions for proper operationof the apparatus.9.3 Program the xenon arc light and water apparatus to runthe exposure cycle shown in Ta
33、ble 1 and in accordance withmanufacturers instructions. The duration of the test in terms ofnumber of cycles, hours, or radiant dosage shall be agreed uponby contractual parties.9.4 Specimens shall be repositioned at a minimum of everytwo weeks of operation to improve uniformity of exposure. SeePrac
34、tice G151, Appendix X2 for more specific guidance andfigures on repositioning of specimens in both rotating rack andflat array xenon arc light and water apparatus.9.4.1 Specimens in a rotating rack apparatus shall be repo-sitioned to the position immediately above it; specimens in thetop position sh
35、all be repositioned to the bottom position.9.4.2 Specimens in a flat array apparatus shall be reposi-tioned to the position immediately to the left; specimens in theleft-most position shall be repositioned to the right-mostposition, with front-back and back-front repositioning if appli-cable.D7869 1
36、72NOTE 7Specimen repositioning in 9.4.1 and 9.4.2 is required tocompensate for variations in light, water, relative humidity and tempera-ture within the test chamber.9.5 The test shall be interrupted for repositioning andspecimen evaluations only during a step without water spray.10. Report10.1 The
37、test report shall conform to Practice G151. Thereport shall also include the average of three water collectionmeasurements for each position in the xenon arc light andwater apparatus, in accordance with Annex A3.11. Keywords11.1 accelerated; automotive; coatings; durability; exposuretest; irradiance
38、; lightfastness; weathering; xenon arcANNEXES(Mandatory Information for Equipment Manufacturers)A1. DAYLIGHT FILTER IRRADIANCE LIMITS BY WAVELENGTHA1.1 Conformance to the spectral power distribution inTable A1.1 is a design parameter for a xenon-arc source withthe different optical filters provided.
39、 Manufacturers of equip-ment claiming conformance to this standard shall be respon-sible for determining conformance to the spectral powerdistribution table for all lamp/filter combinations provided, andprovide information on maintenance procedures to minimizeany spectral changes that may occur duri
40、ng normal use.TABLE 1 Exposure CycleStep Number Step Minutes FunctionIrradiance SetPointAat 340 nmW/(m2nm)Black PanelTemperatureSet PointAChamber AirTemperatureSet PointARelative HumiditySet PointA1 240 dark + spray 40C 95 %2 30 light 0.40 50C 42C 50 %3 270 light 0.80 70C 50C 50 %4 30 light 0.40 50C
41、 42C 50 %5 150 dark + spray 40C 95 %6 30 dark + spray 40C 95 %7 20 light 0.40 50C 42C 50 %8 120 light 0.80 70C 50C 50 %9 10 dark 40C 50 %10 Repeat subcycle steps 6 to 9 (shown in bold) an additional 3 times (for a total or 24h=1cycle).AThe set point is the target condition for the sensor used at the
42、 operational control point and is programmed by the user. When the exposure cycle calls for a particularset point, the user programs the apparatus to use that exact number. Operational fluctuations are deviations from the indicated set point during equilibrium operation. Themaximum allowable operati
43、onal fluctuation during equilibrium conditions for the exposure cycle above is 0.02 W/(m2nm) for irradiance, 2.5C for black paneltemperature, 2C for chamber air temperature, and 10 % for relative humidity.Wavelength BandTotal Irradiance Over IndicatedWavelength Band(W/m2)(nm) Minimum Maximum 290 0.0
44、0 0.005290 # 295 0.00 0.01295 # 300 0.01 0.04300 # 305 0.10 0.20305 # 310 0.38 0.56310 # 320 2.29 3.10320 # 330 4.76 5.82330 # 340 6.84 7.56340 # 350 7.69 9.40350 # 360 8.13 11.00360 # 370 8.32 12.47370 # 380 8.30 13.83380# 390 8.64 14.40390# 400 9.23 17.15Note: Irradiance in W/m2normalized to 0.80
45、W/(m2nm) at 340 nm.D7869 173(Mandatory Information)A2. SPONGE QUALIFICATION PROCEDUREA2.1 Cut a section of the homogeneous sponge material toa maximum size of 57 mm wide, 127 mm long and 19 mmthick. Both sides of the sponge shall have the same waterabsorbance capability. Do not use multi-layer spong
46、es.A2.2 Weigh a damp sponge.A2.2.1 Thoroughly saturate the cut sponge with water bysoaking it in at least 2 L of water at room temperature (23 63C) for a minimum of 1 min. or until it has reached fullsaturation. Different types of sponges will take different timesto reach full saturation.A2.2.2 Wrin
47、g sponge tightly by hand as shown in Fig. A2.1until no water drips are observed over a period of 15 seconds.Weigh it to the nearest 0.1 g on a calibrated balance capable ofat least 100.0 g total weight. The preferred type of sponge forthis test method will weigh between 20.0 and 30.0 g afterremoving
48、 excess water.A2.2.3 Tare the balance to zero and remove the dampsponge from the balance. Subsequent weighing of the spongewill thus record only the additional water absorbed into thesponge.A2.3 Weigh a saturated sponge.A2.3.1 Saturate the sponge again in a minimum 2 L of roomtemperature water by ke
49、eping the sponge totally immersed fora minimum of 1 min.A2.3.2 After a minimum of 1 min., remove the sponge fromthe water and lightly hold it vertically over the water containeras shown in Fig.A2.2. Continue holding it until the sponge hasat most, one water drop per 15 seconds coming from thebottom of the sponge.A2.3.3 Turn the sponge horizontally as shown in Fig. A2.3to prevent any more water loss and place it on the taredbalance. This will show the add
