ASTM G7/G7M-21
(Practice)Standard Practice for Natural Weathering of Materials
Standard Practice for Natural Weathering of Materials
SIGNIFICANCE AND USE
4.1 The relative durability of materials in natural exposures can be very different depending on the location of the exposure because of differences in ultraviolet (UV) radiation, relative humidity, time of wetness, temperature, wet-dry cycling, freeze-thaw cycling, pollutants, and other factors. Therefore, it cannot be assumed that results from one exposure in a single location will be useful for determining relative durability in a different location. Exposures in several locations with different climates which represent a broad range of anticipated service conditions are recommended.
4.2 Because of year-to-year climatological variations, results from a single exposure test cannot be used to predict the absolute rate at which a material degrades. Several exposures, repeated over several years are needed to get a representative test result for a given location.
4.3 Solar UV radiation varies considerably as a function of time of year. This can cause large differences in the apparent rate of degradation in many materials. Comparing results for materials exposed for short periods (less than one year) is not recommended unless materials are exposed at the same time in the same location.
4.4 The duration of natural weathering tests is often based on time (24 months for example). The variability between different exposures can be reduced by using a duration based on total solar or solar UV radiant exposure. Solar UV measurements are typically made using instruments which record broadband UV (for example, 295 to 385 nm), as described in 7.2.4. An inherent limitation in timing a weathering test based solely on solar-radiation measurements is that temperature and moisture may also influence the rate or type of degradation.
4.5 The design of the exposure rack, the location of the specimen on the exposure rack, and the type, color, and emissivity of adjacent specimens can affect specimen temperature and time of wetness. In order to minimize variability caused by t...
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1.1 This practice covers procedures to be followed for direct exposure of materials to the environment. Typically, this testing is performed on exposure racks tilted at a commonly-used tilt angle from the horizontal (such as 5 or 45 degrees) and facing the equator. Other exposure orientations can be used.
1.2 This practice is not intended for the corrosion testing of bare metals, or for testing behind glass.
1.2.1 For corrosion testing, refer to Practice G50
1.2.2 For exposures behind glass, refer to Practice G24
1.3 Units—The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used independently of the other, and values from the two systems shall not be combined.
1.4 This practice is technically equivalent to the parts of ISO 877-1 and -2 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
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This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: G7/G7M − 21
Standard Practice for
1
Natural Weathering of Materials
This standard is issued under the fixed designation G7/G7M; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope* 2. Referenced Documents
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1.1 Thispracticecoversprocedurestobefollowedfordirect 2.1 ASTM Standards:
exposure of materials to the environment. Typically, this
D3614 Guide for Laboratories Engaged in Sampling and
testing is performed on exposure racks tilted at a commonly-
Analysis of Atmospheres and Emissions
usedtiltanglefromthehorizontal(suchas5or45degrees)and
E772 Terminology of Solar Energy Conversion
facing the equator. Other exposure orientations can be used.
E824 Test Method for Transfer of Calibration From Refer-
ence to Field Radiometers
1.2 This practice is not intended for the corrosion testing of
G24 Practice for Conducting Exposures to Daylight Filtered
bare metals, or for testing behind glass.
Through Glass
1.2.1 For corrosion testing, refer to Practice G50
G50 Practice for Conducting Atmospheric Corrosion Tests
1.2.2 For exposures behind glass, refer to Practice G24
on Metals
1.3 Units—The values stated in either SI units or inch- G113 Terminology Relating to Natural andArtificial Weath-
pound units are to be regarded separately as standard. The ering Tests of Nonmetallic Materials
G130 Test Method for Calibration of Narrow- and Broad-
values stated in each system are not necessarily exact equiva-
lents; therefore, to ensure conformance with the standard, each Band Ultraviolet Radiometers Using a Spectroradiometer
system shall be used independently of the other, and values G167 Test Method for Calibration of a Pyranometer Using a
from the two systems shall not be combined.
Pyrheliometer
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2.2 ISO Standards:
1.4 This practice is technically equivalent to the parts of
ISO 877-1 and -2 that describe direct exposures of specimens ISO 877 Plastics—Methods of Exposure to Direct Weath-
to the environment. ering;toWeatheringUsingGlass-FilteredDaylight,andto
Intensified Weathering by Daylight Using Fresnel Mirrors
1.5 This standard does not purport to address all of the
ISO 9370 Plastics—Instrumental Determination of Radiant
safety concerns, if any, associated with its use. It is the
Exposure in Weathering Tests—General Guidance and
responsibility of the user of this standard to establish appro-
Basic Test Method
priate safety, health, and environmental practices and deter-
ISO 9060:2018 Solar Energy – Specification and Classifica-
mine the applicability of regulatory limitations prior to use.
tion of Instruments for Measuring Hemispherical Solar
1.6 This international standard was developed in accor-
and Direct Solar Radiation
dance with internationally recognized principles on standard-
2.3 Other Standards:
ization established in the Decision on Principles for the
WMO – No. 8, “Guide to Meteorological Instruments and
Development of International Standards, Guides and Recom-
Methods of Observation,” seventh edition, World Meteo-
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee. rological Organization, Geneva, Switzerland, 2008
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This practice is under the jurisdiction ofASTM Committee G03 on Weathering For referenced ASTM standards, visit the ASTM website, www.astm.org, or
and Durability and is the direct responsibility of Subcommittee G03.02 on Natural contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
and Environmental Exposure Tests. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved July 1, 2021. Published August 2021. Originally the ASTM website.
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approved in 1969. Last previous edition approved in 2013 as G7/G7M – 13. DOI: Available from American National Standards Institute (ANSI), 25 W. 43rd St.,
10.1520/G0007_G0007M-21. 4th Floor, New York, NY 10036, http://www.ansi.org.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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G7/G7M − 21
3. Terminology materials exposed for short periods (less than one year) is not
recommended unless materials are exposed at the same time in
3.1 Definitions—The definitions given in Terminologies
the same location.
G1
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This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: G7/G7M − 13 G7/G7M − 21
Standard Practice for
Atmospheric Environmental Exposure Testing of
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Nonmetallic Natural Weathering of Materials
This standard is issued under the fixed designation G7/G7M; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope 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 must be clearly defined and mutually agreed upon between all parties.Typically, this testing is
performed on exposure racks tilted at a commonly-used tilt angle from the horizontal (such as 5 or 45 degrees) and facing the
equator. Other exposure orientations can be used.
1.2 For exposures behind glass, refer to PracticeThis practice is not intended for the G24.corrosion testing of bare metals, or for
testing behind glass.
1.2.1 For corrosion testing, refer to Practice G50
1.2.2 For exposures behind glass, refer to Practice G24
1.3 Units—The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in
each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used
independently of the other, and values from the two systems shall not be combined.
1.4 This practice is technically equivalent to the parts of ISO 877 877-1 and -2 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
1
This practice is under the jurisdiction of ASTM Committee G03 on Weathering and Durability and is the direct responsibility of Subcommittee G03.02 on Natural and
Environmental Exposure Tests.
Current edition approved June 1, 2013July 1, 2021. Published June 2013August 2021. Originally approved in 1969. Last previous edition approved in 20112013 as
G7/G7M – 11.G7/G7M – 13. DOI: 10.1520/G0007_G0007M-13.10.1520/G0007_G0007M-21.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1
---------------------- Page: 1 ----------------------
G7/G7M − 21
2. Referenced Documents
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2.1 ASTM Standards:
D3614 Guide for Laboratories Engaged in Sampling and Analysis of Atmospheres and Emissions
E41E772 Terminology Relating to Conditioningof Solar Energy Conversion (Withdrawn 2019)
E824 Test Method for Transfer of Calibration From Reference to Field Radiometers
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E913 Method for Calibration of Reference Pyranometers With Axis Vertical by the Shading Method (Withdrawn 2005)
3
E941 Test Method for Calibration of Reference Pyranometers With Axis Tilted by the Shading Method (Withdrawn 2005)
G24 Practice for Conducting Exposures to Daylight Filtered Through Glass
G50 Practice for Conducting Atmospheric Corrosion Tests on Metals
G113 Terminology Relating to Natural and Artificial Weathering Tests of Nonmetallic Materials
G130 Test Method for Calibration of Narrow- and Broad-Band Ultraviolet Radiometers Using a Spectroradiometer
G167 Test Method for Calibration of a Pyranometer Using a Pyrheliometer
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2.2 ISO Standards:
ISO 877 Plastics—Methods of Exposure to Direct Weathering; to Weathering Using Glass-Filtered Daylight, and to Intensified
Weathering by Daylight Using Fresnel Mirrors
ISO 9370 Plastics—Instrumental Determination of Radiant Exposure in Weathering Tests—General Guidance and Basic Test
Method
ISO 9060:2018 Solar Energy – Specification and Classificat
...
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