ASTM G7-97

Standard Practice for Atmospheric Environmental Exposure Testing of Nonmetallic Materials

SCOPE
1.1 This practice covers procedures to be followed for direct exposure of nonmetallic materials to the environment. When originators of a weathering test have the actual exposure conducted by a separate agency, the specific conditions for the exposure of test and control specimens should be clearly defined and mutually agreed upon between all parties.  
1.2 For exposures behind glass, refer to Practice G 24.  
1.3 The values stated in SI units are to be regarded as the standard. The inch-pound units given in parentheses are for information only.  
1.4 This practice is technically equivalent to the parts of ISO 877 that describe direct exposures of specimens to the environment.  
1.5 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 limitations prior to use.

General Information

• Status: Historical
• Publication Date: 09-Dec-1997
• ICS: 19.040 - Environmental testing
• Technical Committee: G03 - Weathering and Durability
• Drafting Committee: G03.02 - Natural and Environmental Exposure Tests

Relations

• Replaced By: ASTM G7-05 - Standard Practice for Atmospheric Environmental Exposure Testing of Nonmetallic Materials
• Effective Date: 01-Jan-2005
• Referred By: ASTM D3274-09(2021) - Standard Test Method for Evaluating Degree of Surface Disfigurement of Paint Films by Fungal or Algal Growth, or Soil and Dirt Accumulation
• Effective Date: 10-Dec-1997
• Referred By: ASTM D6577-15(2019) - Standard Guide for Testing Industrial Protective Coatings
• Effective Date: 10-Dec-1997
• Referred By: ASTM D6675-23 - Standard Practice for Salt-Accelerated Outdoor Cosmetic Corrosion Testing of Organic Coatings on Automotive Sheet Steel
• Effective Date: 10-Dec-1997
• Referred By: ASTM D1435-20 - Standard Practice for Outdoor Weathering of Plastics
• Effective Date: 10-Dec-1997
• Referred By: ASTM G147-17 - Standard Practice for Conditioning and Handling of Nonmetallic Materials for Natural and Artificial Weathering Tests
• Effective Date: 10-Dec-1997
• Referred By: ASTM G141-09(2021) - Standard Guide for Addressing Variability in Exposure Testing of Nonmetallic Materials
• Effective Date: 10-Dec-1997
• Referred By: ASTM G178-16(2023) - Standard Practice for Determining the Activation Spectrum of a Material (Wavelength Sensitivity to an Exposure Source) Using the Sharp Cut-On Filter or Spectrographic Technique
• Effective Date: 10-Dec-1997
• Referred By: ASTM D1014-18 - Standard Practice for Conducting Exterior Exposure Tests of Paints and Coatings on Metal Substrates
• Effective Date: 10-Dec-1997
• Referred By: ASTM D1006/D1006M-21 - Standard Practice for Conducting Exterior Exposure Tests of Hand and Factory Applied Paints on Wood and Wood Composite Materials
• Effective Date: 10-Dec-1997
• Referred By: ASTM G24-21 - Standard Practice for Conducting Exposures to Daylight Filtered Through Glass
• Effective Date: 10-Dec-1997
• Referred By: ASTM D7376-10a(2022) - Standard Practice for Outdoor Evaluation of Wet Stack Storage Conditions on Coil-Coated Metals
• Effective Date: 10-Dec-1997
• Referred By: ASTM C1900-20 - Standard Practice for Weathering and Evaluation of Laminated Glass
• Effective Date: 10-Dec-1997
• Referred By: ASTM C1589/C1589M-18(2023) - Standard Practice for Outdoor Weathering of Construction Seals and Sealants
• Effective Date: 10-Dec-1997
• Referred By: ASTM D7893-13(2018) - Standard Guide for Corrosion Test Panel Preparation, Testing, and Rating of Coil-Coated Building Products
• Effective Date: 10-Dec-1997

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:G7–97
Standard Practice for
Atmospheric Environmental Exposure Testing of
Nonmetallic Materials
ThisstandardisissuedunderthefixeddesignationG7;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginal
adoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscript
epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope AdjunctNo.12-700070-00 A Test Rack
2.3 ISO Standards:
1.1 Thispracticecoversprocedurestobefollowedfordirect
ISO877 Plastics—Methods of Exposure to DirectWeather-
exposure of nonmetallic materials to the environment. When
ing; to Weathering Using Glass-Filtered Daylight, and to
originators of a weathering test have the actual exposure
Intensified Weathering by Daylight Using Fresnel Mir-
conducted by a separate agency, the specific conditions for the
rors
exposure of test and control specimens should be clearly
defined and mutually agreed upon between all parties.
3. Terminology
1.2 For exposures behind glass, refer to Practice G24.
3.1 Definitions—The definitions given inTerminology E41
1.3 The values stated in SI units are to be regarded as the
and Terminology G113 are applicable to this practice.
standard. The inch-pound units given in parentheses are for
information only.
4. Significance and Use
1.4 This practice is technically equivalent to the parts of
4.1 The relative durability of materials in natural exposures
ISO 877 that describe direct exposures of specimens to the
canbeverydifferentdependingonthelocationoftheexposure
environment.
because of differences in ultraviolet (UV) radiation, time of
1.5 This standard does not purport to address all of the
wetness, temperature, pollutants, and other factors. Therefore,
safety concerns, if any, associated with its use. It is the
it cannot be assumed that results from one exposure in a single
responsibility of the user of this standard to establish appro-
location will be useful for determining relative durability in a
priate safety and health practices and determine the applica-
different location. Exposures in several locations with different
bility of regulatory limitations prior to use.
climates which represent a broad range of anticipated service
conditions are recommended.
2. Referenced Documents
4.2 Because of year-to-year climatological variations, re-
2.1 ASTM Standards:
2 sults from a single exposure test cannot be used to predict the
E41 Terminology Relating to Conditioning
absolute rate at which a material degrades. Several years of
E824 Test Method for Transfer of Calibration from Refer-
3 repeat exposures are needed to get an “average” test result for
ence to Field Pyranometers
a given location.
E913 Test Method for Calibration of Reference Pyranom-
3 4.3 Solar ultraviolet radiation varies considerably as a
eters with Axis Vertical by the Shading Method
functionoftimeofyear.Thiscancauselargedifferencesinthe
E941 Test Method for Calibration of Reference Pyranom-
3 apparent rate of degradation in many polymers. Comparing
eters with Axis Tilted by the Shading Method
results for materials exposed for short periods (less than one
G24 Practice for Conducting Exposures to Daylight Fil-
2 year) is not recommended unless materials are exposed at the
tered Through Glass
same time in the same location.
G 113 Terminology Relating to Natural and Artificial
2 4.4 Defining cxposure periods in terms of total solar or
Weathering Tests of Nonmetallic Materials
solar-ultraviolet radiant energy can reduce variability in results
2.2 ASTM Adjunct:
from separate exposures. Solar ultraviolet measurements may
be made using instruments which record broadband UV (e.g.
This practice is under the jurisdiction ofASTM Committee G-3 on Durability
ofNonmetallicMaterialsandisthedirectresponsibilityofSubcommitteeG03.02on
Natural Environmental Testing.
Current edition approved Dec. 10, 1997. Published February 1998. Originally Available from ASTM Headquarters, 100 Barr Harbor Dr., West Consho-
published as G7–69T. Last previous editionG7–96. hocken, PA 19428. Request ADJG0007.
2 5
Annual Book of ASTM Standards, Vol 14.02. Available from the American National Standards Institute (ANSI), 1430
Annual Book of ASTM Standards, Vol 12.02. Broadway, New York, NY 10018.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
G7
295 6385nm)ornarrowbandUV,asdefinedinSections7.2.4 5.4 Exposure Orientation—Unless otherwise specified, ex-
and 7.2.5. An inherent limitation in solar-radiation measure- posure racks shall be oriented so that specimens face the
ments is that they do not reflect the effects of temperature and equator. Specimens can be exposed at a number of different
moisture, which are often as important as solar radiation. orientations or “exposure angles” in order to simulate end-use
conditions of the material being evaluated. Typical exposure
4.5 The design of the exposure rack, the location of the
angles are as follows:
specimen on the exposure rack, and the type or color of
5.4.1 Latitude Angle—Exposure rack is positioned so that
adjacent specimens can affect specimen temperature and time
the exposed surface of specimens are at an angle from the
of wetness. In order to minimize variability caused by these
horizontal that is equal to the geographical latitude of the
factors, it is recommended that test specimens, control speci-
exposure site.
mens, and any applicable weathering reference material be
5.4.2 45°—Exposure rack is positioned so that the exposed
placed on a single test panel or on test panels placed adjacent
specimens are at an angle of 45° from the horizontal. This is
to each other during exposure.
the most commonly used exposure orientation.
4.6 It is strongly recommended that at least one control
5.4.3 90°—Exposure rack is positioned so that the exposed
material be part of any exposure evaluation. The control
specimens are at an angle of 90° from the horizontal.
material should meet the requirements of Terminology G113,
5.4.4 5°—Exposure rack is positioned so that the exposed
and should be of similar composition and construction com-
specimens are at an angle of 5° from the horizontal.This angle
pared to test specimens. It is preferable to use two control
is preferred over horizontal exposure to avoid standing water
materials, one with relatively good durability and one with
on specimens being exposed. This exposure angle typically
relatively poor durability. Unless otherwise specified, use at
receives the highest levels of solar radiation during mid-
least two replicate specimens of each test and control material
summer and is used to test materials that would normally be
beingexposed.Controlmaterialsincludedaspartofatestshall
used in horizontal or nearly horizontal applications.
be used for the purpose of comparing the performance of test
materials relative to the controls.
NOTE 1—Exposures conducted at less than the site latitude typically
receive more ultraviolet radiation than exposures conducted at larger
5. Test Sites, Location of Test Fixtures, and Exposure angles.
Orientation
5.4.5 Any other angle that is mutually agreed on by all
5.1 Test Sites—Exposures can be conducted in any type of interested parties may be used. In some instances, exposures
facing directly away from the equator or some other specific
climate. However, in order to get more rapid indications of
outdoor durability, exposures are often conducted in locations directionmaybedesired.Thetestreportshallcontaintheexact
angle and specimen orientation of any exposure condition
that receive high levels of solar radiation, temperature, and
moisture. Typically, these conditions are found in hot desert outside of those described in 5.4.1-5.4.4.
and subtropical or tropical climates. Known attributes of the 5.5 Specimen Backing—Three types of specimen backing
use environment should be represented by the locations se- can be used. Comparisons between materials should only be
lectedforoutdoordurabilityevaluation.Forexample,iftheuse made with exposures conducted with the same specimen
environment for the product being evaluated will include backing.
freeze/thawcycling,specimenexposureinanortherntempera- 5.5.1 Unbacked Exposures—Specimens are exposed so that
ture climate is recommended. In addition, exposures are often the portion of the test specimen being evaluated is subjected to
conducted in areas where specimens are subjected to salt air the effects of the weather on all sides.
(seashore) or industrial pollutants. 5.5.2 Backed Exposures—Specimens are attached to a solid
substrate so that only the front surface is exposed. Surface
5.1.1 Unless otherwise specified, test fixtures or racks shall
temperatures of specimens in backed exposures will be higher
belocatedinclearedareas.Theareabeneathandinthevicinity
than for specimens subjected to unbacked exposures. In some
of the test fixtures should be characterized by low reflectance
cases,thesubstrateispaintedblack,whichproducessignificant
and by ground cover typical of the climatological area where
differences in surface temperature compared to exposures
the exposures are being conducted. In desert areas, the ground
conducted on unpainted substrate. This can cause large differ-
is often gravel to control dust and in most temperate areas, the
encesindegradationrateswhencomparedtobackedexposures
ground cover should be low-cut grass. The type of ground
conducted on unpainted substrates.
cover at the exposure site shall be indicated in the test report.
5.5.3 Black Box Exposure—Specimens are attached to the
If test fixtures are placed on a rooftop, specimens may be
front face of a black painted aluminum box (see 6.2.3). The
subjected to different environmental conditions than at ground
specimens form the top surface of the box. If there are not
level. These differences may affect test results.
enough test specimens to completely cover the top surface,
5.2 The lowest row of specimens on a test fixture or rack
open areas shall be filled with black painted sheet metal panels
shall be positioned at a height above the ground to avoid
so that the box is completely closed.
contactwithvegetationandtopreventdamagethatmightoccur
duringareamaintenance.Aminimumheightof0.45m(18in.)
6. Construction of Test Fixtures (Exposure Racks)
above the ground is recommended.
5.3 Test fixtures shall be placed in a location so that there is 6.1 Materials of Construction—All materials used for test
no shadow on any specimen when the sun’s angle of elevation fixtures shall be noncorrodible without surface treatment.
is greater than 20°. AluminumAlloys6061T6or6063T6havebeenfoundsuitable
G7
for use in most locations. Properly primed and coated steel is
suitable for use in desert areas. Monel has been found suitable
in highly corrosive areas. Untreated wood is acceptable in
desertareasbutmayposemaintenanceproblemsinotherareas.
(See Fig. 1.)
6.1.1 For backed exposures (see 6.2.2 and Fig. 2), use
exterior-grade plywood to form a solid surface to which
specimens are directly attached. Replace the plywood when
there is any evidence of delamination or fiber separation.
Medium-density overlay (MDO) or high-density overlay
(HDO) plywood are satisfactory substrates and require less
frequentreplacementthanplywoodwithnooverlay.Theedges
oftheplywoodshouldbesealedwithadurablepainttoprevent
delamination.
6.2 Test Fixture Design—Test racks shall be constructed to
hold specimens or specimen holders of any convenient width
and length. Racks shall be constructed so that any contamina-
tion from specimens higher on the fixture cannot run down
onto specimens in lower positions. Test racks should be
designed to provide backed or unbacked exposures, whichever
best simulates end-use conditions.
FIG. 3 Black Box
6.2.1 Unbacked Exposures—Test racks shall be constructed
sothatmostofthetestspecimenisexposedtotheeffectsofthe
mentshallnotpreventexpansionandcontractionofspecimens
weather on all sides. Specimens are attached to the test fixture
caused by temperature or moisture. Use fastening devices for
at the top or bottom, or both, using clamping devices, properly
attaching specimens to the test fixture that will not corrode or
spaced slots, or mechanical fasteners. The method of attach-
degrade and contaminate the specimens. Aluminum, properly
galvanized steel, or stainless steel fasteners are recommended.
6.2.2 Backed Exposures—Test racks shall be constructed so
Detailed drawings for an acceptable test rack may be obtained from ASTM
that specimens are attached to a plywood substrate. The
Headquarters. Request ADJG0007.
NOTE 1—Detailed drawings of this test rack may be obtained fromASTM Headquarters, 100 Barr Harbor Dr., W. Conshohocken, PA19428. Request
Adjunct No. 12-700070-00.
FIG. 1 Typical Exposure Rack
G7
FIG. 2 Backed Exposure Rack
FIG. 4 Black Box in Use
this type produce higher specimen temperatures than those that would be
thickness of the plywood and type of coating used shall be
seen on backed exposures conducted according to this practice.
agreed upon by all interested parties and must be reported.
6.2.3 Black Box Exposures—An aluminum box 0.23 m (9
NOTE 2—Backed exposures as described in this standard are not
in.) deep with the outside surface painted black. The top
insulatedexposures.Forsomeapplicationssuchasoutdoorexposuretests
surface is open and fitted with mounting strips to hold
for roofing products, a layer of insulation material is attached behind the
solid substrate to which specimens are attached. Insulated exposures of specimens firmly in place. Two types of black boxes are in
G7
common usage. One measures approximately 1.5 m (5 ft) high −1). If requested, a certificate of calibration shall be provided
and1.8m(6ft)wideandtheothermeasures1.7m(5.5ft)high with all total solar ultraviolet irradiance measurements.
and3.7m(12ft)wide.Fig.3showsthedesignanddimensions
7.2.5 Narrow-Band Solar Ultraviolet Radiation—
for an acceptable black box. Fig. 4 shows a black box in use. Narrowband radiometers can be used to measure specific
wavelength bands of solar ultraviolet radiation. Unless other-
, ,
7 8 9
7. Instrumentation
wise specified, (for example, when measuring solar UV radia-
tion with a wavelength greater than 315 nm), narrow-band UV
7.1 Instruments for determining climatological data during
radiometers shall, when used to time or monitor outdoor
the exposure period should be operated in the immediate
exposure testing, have response functions in the UV-B region
vicinity of the test racks. Data obtained shall be reported if
defined as 280
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