1、Designation: D7869 13D7869 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 ca
2、se 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 practice specifies the operating procedures for a controlled irradiance xenon arc lig
3、ht and water apparatus. Theprocedure uses one or more lamp(s) and optical filter(s) to produce irradiance similar to sunlight in the UV and visible range. Italso simulates the water absorption and stress cycles experienced by automotive exterior coatings under natural weatheringconditions. This prac
4、tice has also been found applicable to coatings on other transportation vehicles, such as aircraft, trucks andrail cars.1.2 This practice uses a xenon arc light source with specified optical filter(s). The spectral power distribution (SPD) for the lampand special daylight filter(s) is as specified i
5、n Annex A1. The irradiance level used in this practice varies between 0.40 and 0.80W/(m2nm) at 340 nm. Water is sprayed on the specimens during portions of several dark steps. The application of water is suchthat the coatings will absorb and desorb substantial amounts of water during testing. In add
6、ition, the cycling between wet/dry andwarm/cool will induce mechanical stresses into the materials. These test conditions are designed to simulate the physical andchemical stresses from environments in a subtropical climate, such as southern Florida.1.3 The values stated in SI units are to be regard
7、ed as standard. No other units of measurement are included in this standard.1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determi
8、ne the applicability of regulatorylimitations 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 SpectroscopyG113 Terminology Relating to Natural and Artificial Weathering Tests of Nonmetallic Mater
9、ialsG147 Practice for Conditioning and Handling of Nonmetallic Materials for Natural and Artificial Weathering TestsG151 Practice for Exposing Nonmetallic Materials in Accelerated Test Devices that Use Laboratory Light SourcesG155 Practice for Operating Xenon Arc Light Apparatus for Exposure of Non-
10、Metallic Materials3. Terminology3.1 Definitions applicable to this standard can be found in Terminology G113.3.2 transportation coatings, nexterior coatings used for vehicles subjected to natural weathering conditions such asautomobiles, aircraft, trucks, rail cars, etc.4. Summary of Practice4.1 Tes
11、t specimens are exposed to specific test conditions designed to simulate the physical and chemical stresses fromenvironments in a subtropical climate, such as southern Florida. The test conditions consist of a primary test cycle and a sub-cycle.The primary test cycle includes two long water exposure
12、s and a single, long light exposure with precise spectral match to daylightas described in AnnexA1. It is designed to reproduce water penetration failures, such as adhesion, blistering and diffusion of small1 This practice is under the jurisdiction of ASTM Committee D01 on Paint and Related Coatings
13、, Materials, and Applications and is the direct responsibility ofSubcommittee D01.27 on Accelerated Testing.Current edition approved June 1, 2013Feb. 1, 2017. Published June 2013March 2017. DOI: 10.1520/D7869-13.Originally approved in 2013. Last previous edition approvedin 2013 as D7869 13.DOI: 10.1
14、520/D7869-17.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standardsstandards Document Summary page on the ASTM website.This document is not an ASTM standard a
15、nd is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only
16、 the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1molecules (1).3 The sub-cycle consisting of shorter alternating water and light exposur
17、es is designed to simulate cyclic stressessuch as cracking and surface erosion. These two cycles are designed to replicate the common types of failures driven by theinteraction of photo-oxidation during daylight and hydrolysis during water exposure that are seen in a subtropical climate such asgloss
18、 loss, color change, adhesion, blistering and cracking (2).5. Significance and Use5.1 This test procedure is used to simulate the physical and environmental stresses that a coating for exterior transportationapplications (for example, automotive) is exposed to in a subtropical climate, such as south
19、ern Florida. It has been found that sucha subtropical climate causes particularly severe deterioration of such coatings. The long water exposures and wet/dry cycling foundin southern Florida are particularly important for this deterioration, in addition to the high dosage of solar radiation (3). Thi
20、spractice was developed to address the deficiencies of historical tests used for transportation coatings, especially automotivecoatings (4).NOTE 1This test procedure was developed through eight years of cooperative testing between automotive and aerospace OEMs, material suppliers,and test equipment
21、manufacturers. See References for published papers on this research.6. Apparatus6.1 The xenon arc light and water apparatus shall comply with Practice G155.6.1.1 The xenon arc light and water apparatus shall have an uninsulated black panel thermometer as described in Practice G151unless otherwise ag
22、reed upon by contractual parties6.1.2 The xenon arc light and water apparatus must be able to control irradiance at 340 nm, relative humidity, uninsulated blackpanel temperature and chamber temperature, and provide water spray on the front of the specimens.6.2 Mass balancewith a resolution of at lea
23、st 0.1 g.7. Reagents and Materials7.1 Sponge. See Annex A2 for more detailed specifications.7.2 Purified Water, as specified in Practice G155 and 8.2.8. Apparatus Setup8.1 Maintain and calibrate the apparatus according to manufacturers instructions.8.2 Water SprayThe water for spray and humidificati
24、on shall be of the same quality listed in Practice G155 and shall leaveno objectionable deposits or stains on the exposed specimens. The water shall have less than 1 mg per litre (1 ppm) total dissolvedsolids and it shall have less than 0.1 mg per litre (0.1 ppm) silica.NOTE 2Silica levels should be
25、 determined using Test Method D4517 or equivalent.Acombination of deionization and reverse osmosis treatment caneffectively produce water with the desired purity. In certain cases some samples could exude materials into the chamber that can promote deleteriouseffects on other samples.8.3 Qualify the
26、 sponges used for the water uptake per the procedure in AnnexA2. For each xenon arc light and water apparatus,verify the water uptake capability in accordance with the procedure in Annex A3 before placing it into service and at least onceper year thereafter. Follow the recommendations of the manufac
27、turer of the xenon arc light and water apparatus for additionalchecks, if any.8.4 Fit the xenon arc light and water apparatus with a special daylight filter(s) in accordance with the requirements of AnnexA1.NOTE 3Contact the xenon arc light and water apparatus manufacturer for the proper optical fil
28、ter(s) required. Follow the manufacturersrecommendations for optical filter maintenance.8.5 Other optical filters may be used by mutual agreement between the contractual parties.NOTE 4Minor differences in the resultant spectral power distribution (especially in the short wavelength UV region) can ha
29、ve an impact on the testresults. Follow the manufacturers recommendations for xenon arc lamp and optical filter maintenance (5).9. Test Procedure9.1 Refer to Practice G147 for specimen preparation, conditioning and handling.All test specimens must be clean and free fromfingerprints or other surface
30、contaminants before testing. Prepare a specimen for exposure to fit the specimen mounting fixturebeing used, if any. Follow the manufacturers guidelines for specimen size and mounting.9.1.1 Seal any cut edges on the test specimens if required, as agreed between contractual parties. For example, (a)
31、rust andcorrosion products from the cut edges of metal panels may stain the test specimens, (b) by-products from the cut edges of plasticsubstrates may leach out and contaminate test specimens, and (c) other panels may not require any edge sealing at all.NOTE 5Air-dry primers, plastic barrier tapes
32、and silicone sealants have often been found suitable for edge sealing.3 The boldface numbers in parentheses refer to the list of references at the end of this standard.D7869 1729.2 Fill all unused specimen positions in the xenon arc light and water apparatus exposure area with inert specimens (forex
33、ample, anodized aluminum panels) to maintain desired airflow.NOTE 6Refer to the manufacturers instructions for proper operation of the apparatus.9.3 Program the xenon arc light and water apparatus to run the exposure cycle shown in Table 1 and in accordance withmanufacturers instructions. The durati
34、on of the test in terms of number of cycles, hours, or radiant dosage shall be agreed uponby contractual parties.9.4 Specimens shall be repositioned at a minimum of every two weeks of operation to improve uniformity of exposure. SeePractice G151, Appendix X2 for more specific guidance and figures on
35、 repositioning of specimens in both rotating rack and flatarray xenon arc light and water apparatus.9.4.1 Specimens in a rotating rack apparatus shall be repositioned to the position immediately above it; specimens in the topposition shall be repositioned to the bottom position.9.4.2 Specimens in a
36、flat array apparatus shall be repositioned to the position immediately to the left; specimens in the left-mostposition shall be repositioned to the right-most position, with front-back and back-front repositioning if applicable.TABLE 1 Exposure CycleStep Number Step Minutes FunctionIrradiance SetPoi
37、ntA at 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 42C 50 %5 150 dark + spray 40C 95 %6 30 dark + spray 40C 95 %7 20 light 0.40 50C 42C
38、 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 24 h = 1 cycle).A The set point is the target condition for the sensor used at the operational control point and is programmed by the user. When the exposure cycl
39、e 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 operational fluctuation during equilibrium conditions for the exposure cycle above is 0
40、.02 W/(m2nm) for irradiance, 2.5C for black paneltemperature, 2C for chamber air temperature, and 10 % for relative humidity.D7869 173NOTE 7Specimen repositioning in 9.4.1 and 9.4.2 is required to compensate for variations in light, water, relative humidity and temperature withinthe test chamber.9.5
41、 The test shall be interrupted for repositioning and specimen evaluations only during a step without water spray.10. Report10.1 The test report shall conform to Practice G151. The report shall also include the average of three water collectionmeasurements for each position in the xenon arc light and
42、 water apparatus, in accordance with Annex A3.11. Keywords11.1 accelerated; automotive; coatings; durability; exposure test; irradiance; lightfastness; weathering; xenon arcANNEXES(Mandatory Information for Equipment Manufacturers)A1. DAYLIGHT FILTER IRRADIANCE LIMITS BY WAVELENGTH(Mandatory Informa
43、tion for Equipment Manufacturers)A1.1 Conformance to the spectral power distribution in TableA1.1 is a design parameter for a xenon-arc source with the differentoptical filters provided. Manufacturers of equipment claiming conformance to this standard shall be responsible for determiningconformance
44、to the spectral power distribution table for all lamp/filter combinations provided, and provide information onmaintenance procedures to minimize any spectral changes that may occur during normal use.(Mandatory Information)A2. SPONGE QUALIFICATION PROCEDURE(Mandatory Information)A2.1 Cut a section of
45、 the homogeneous sponge material to a maximum size of 57 mm wide, 127 mm long and 19 mm thick. Bothsides of the sponge shall have the same water absorbance capability. Do not use multi-layer sponges.A2.2 Weigh a damp sponge.Wavelength BandTotal Irradiance Over IndicatedWavelength Band(W/m2)(nm) Mini
46、mum Maximum 290 0.00 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/m2
47、 normalized to 0.80 W/(m2nm) at 340 nm.D7869 174A2.2.1 Thoroughly saturate the cut sponge with water by soaking it in at least 2 L of water at room temperature (23 6 3C) fora minimum of 1 min. or until it has reached full saturation. Different types of sponges will take different times to reach full
48、saturation.A2.2.2 Remove as much water as possible from the sponge through wringing Wring sponge tightly by hand as shown in Fig.A2.1.until no water drips are observed over a period of 15 seconds. Weigh it to the nearest 0.1 g on a calibrated balance capable of atleast 100.0 g total weight. The pref
49、erred type of sponge for this test method will weigh between 20.0 and 30.0 g after removingexcess water.A2.2.3 Tare the balance to zero and remove the damp sponge from the balance. Subsequent weighing of the sponge will thusrecord only the additional water absorbed into the sponge.A2.3 Weigh a saturated sponge.A2.3.1 Saturate the sponge again in a minimum 2 L of room temperature water by keeping the sponge totally immersed for aminimum of 1 min.A2.3.2 After a minimum of 1 min., remove the sp
