ASTM G50-76(1997)e1

Standard Practice for Conducting Atmospheric Corrosion Tests on Metals

SCOPE
1.1 This practice defines conditions for exposure of metals and alloys to the weather. It sets forth the general procedures that should be followed in any atmospheric test. It is presented as an aid in conducting atmospheric corrosion tests so that some of the pitfalls of such testing may be avoided. As such, it is concerned mainly with panel exposures to obtain data for comparison purposes.  
1.2 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-Oct-1997
• Technical Committee: G01 - Corrosion of Metals
• Drafting Committee: G01.04 - Corrosion of Metals in Natural Atmospheric and Aqueous Environments

Relations

• Replaced By: ASTM G50-76(2003) - Standard Practice for Conducting Atmospheric Corrosion Tests on Metals
• Effective Date: 27-Aug-1976
• Referred By: ASTM G112-22 - Standard Guide for Conducting Exfoliation Corrosion Tests in Aluminum Alloys
• Effective Date: 10-Oct-1997
• Referred By: ASTM G7/G7M-21 - Standard Practice for Natural Weathering of Materials
• Effective Date: 10-Oct-1997
• Referred By: ASTM G39-99(2021) - Standard Practice for Preparation and Use of Bent-Beam Stress-Corrosion Test Specimens
• Effective Date: 10-Oct-1997
• Referred By: ASTM G101-04(2020) - Standard Guide for Estimating the Atmospheric Corrosion Resistance of Low-Alloy Steels
• Effective Date: 10-Oct-1997
• Referred By: ASTM G1-03(2017)e1 - Standard Practice for Preparing, Cleaning, and Evaluating Corrosion Test Specimens
• Effective Date: 10-Oct-1997
• Referred By: ASTM G92-20 - Standard Practice for Characterization of Atmospheric Test Sites
• Effective Date: 10-Oct-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-Oct-1997
• Referred By: ASTM D6577-15(2019) - Standard Guide for Testing Industrial Protective Coatings
• Effective Date: 10-Oct-1997
• Referred By: ASTM G168-17 - Standard Practice for Making and Using Precracked Double Beam Stress Corrosion Specimens
• Effective Date: 10-Oct-1997
• Referred By: ASTM G116-99(2020)e1 - Standard Practice for Conducting Wire-on-Bolt Test for Atmospheric Galvanic Corrosion
• Effective Date: 10-Oct-1997

Standards Content (Sample)

NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
e1
Designation: G 50 – 76 (Reapproved 1997)
AMERICAN SOCIETY FOR TESTING AND MATERIALS
100 Barr Harbor Dr., West Conshohocken, PA 19428
Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
Standard Practice for
Conducting Atmospheric Corrosion Tests on Metals
This standard is issued under the fixed designation G 50; 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 (e) indicates an editorial change since the last revision or reapproval.
e NOTE— Section 11 was added editorially in December 1997.
1. Scope influence. Also, as corrosivity may vary at a site from season to
season, exposures should be made either at the same time of
1.1 This practice defines conditions for exposure of metals
the year to minimize variability or these differences should be
and alloys to the weather. It sets forth the general procedures
established by multiple exposures.
that should be followed in any atmospheric test. It is presented
3.2 Control specimens should always be employed in
as an aid in conducting atmospheric corrosion tests so that
weathering tests. The control specimens should be from a
some of the pitfalls of such testing may be avoided. As such, it
material having established weathering characteristics. A sub-
is concerned mainly with panel exposures to obtain data for
stantial amount of corrosion data shall have been accumulated
comparison purposes.
for the control specimens. It is also good practice to retain
1.2 This standard does not purport to address all of the
samples of all materials exposed so that possible effects of
safety concerns, if any, associated with its use. It is the
long-term aging can be measured.
responsibility of whoever uses this standard to consult and
establish appropriate safety and health practices and deter-
4. Test Sites
mine the applicability of regulatory limitations prior to use.
4.1 Test sites should be chosen at a number of locations
2. Referenced Documents representative of the atmospheric environments where the
metals or alloys are likely to be used. If such information is not
2.1 ASTM Standards:
available, the selection should include sites typical of indus-
A 380 Practice for Cleaning, Descaling and Passivation of
trial, rural, and marine atmospheres.
Stainless Steel Parts, Equipment, and Systems
4.2 Exposure racks should be located in cleared, well-
D 2010/D 2010M Test Methods for Evaluation of Total
drained areas such that the exposed specimens will be sub-
Sulfation Activity in the Atmosphere by the Lead Dioxide
jected to the full effects of the atmosphere at the location of the
Technique
test site. Shadows of trees, buildings, or structures should not
G 1 Practice for Preparing, Cleaning, and Evaluating Cor-
fall on the specimens, and local contamination of the atmo-
rosion Test Specimens
sphere should be avoided, unless the specific influences of such
G 33 Practice for Recording Data from Atmospheric Cor-
conditions are intended to be assessed.
rosion Tests of Metallic-Coated Steel Specimens
4.3 In special cases, the exposure racks may be partially
G 46 Guide for Examination and Evaluation of Pitting
sheltered to allow accumulation of corrosive materials from the
Corrosion
air but at the same time prevent washing by rain. If sheltering
3. Significance and Use
is used, its purpose and configuration should be described in
detail.
3.1 The procedures described herein can be used to evaluate
4.4 If local pollution effects are to be investigated, the
the corrosion resistance of metals when exposed to the weather,
samples should be exposed at different distances from the
as well as to evaluate the relative corrosivity of the atmosphere
source and at different elevations. Where it is particularly
at specific locations. Because of the variability and complexity
important to obtain corrosion rates involving a micro-
of weather effects and the industrial and natural factors
environment, samples should be mounted directly on the
influencing the atmospheric corrosivity of a test site, a multi-
structure involved. Suitable attachment must be devised for
year exposure period should be considered to minimize their
each case.
5. Exposure Racks and Frames
This practice is under the jurisdiction of ASTM Committee G-1 on Corrosion
of Metals, and is the direct responsibility of Subcommittee G01.04 on Atmospheric
5.1 Test racks and frames should be constructed of a
Corrosion.
material that will remain intact for the entire proposed period
Current edition approved Aug. 27, 1976. Published March 1977.
Annual Book of ASTM Standards, Vol 01.03. of exposure. Galvanized pipe has been found adequate for rack
Annual Book of ASTM Standards, Vol 11.03.
construction in most environments (Note 1). Type 304 stainless
Annual Book of ASTM Standards, Vol 03.02.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
G50
steel is adequate as a frame material for all environments. For 5.7 A rack of the design and dimensions shown in Fig. 2 will
marine exposures, alloy 400 UNS No. N04400 or Type 316 give the correct exposure angle and can support the specimen
stainless steel has also been successfully used. Aluminum frame described in 5.4.
(5052 and 6061-T6) and copper frames also have given 5.8 The ground under the racks should be kept free of
satisfactory service in a wide range of environments. Care weeds, bushes, and debris. Organic herbicides, defoliants, or
should be observed in the use of copper frames, as corrosion pesticides should not be used for this purpose.
products splashed during rainfall might affect the corrosion of
6. Test Specimens
other metals such as aluminum or magnesium.
6.1 When the material to be tested is in sheet form, a
NOTE 1—If galvanized pipe is field-threaded, thread areas must be
specimen size of 4 by 6 in. (100 by 150 mm) is appropriate.
protected to ensure joint integrity for long exposure periods. In severe
Specimens may be larger, for example, 4 by 8 in. (100 by 200
environments, additional coatings may be required to provide corrosion-
mm), to suit a particular test; however, the specimens prefer-
free service.
ably should not be smaller than 4 by 6 in.
5.2 Racks and frames also may be constructed of wood.
6.2 To assure adequate rigidity of the specimens on the rack,
Insulators may be attached to wooden frames with aluminum
a minimum thickness of 0.030 in. (0.75 mm) is suggested. It
bronze, alloy 400, or stainless steel screws. In such a case, no
may be difficult to accommodate thicknesses greater than 0.250
wood sections should be used with dimensions less than 2 by
in. (6.25 mm) in the insulator grooves. (Special deep-throated
4 in. (50 by 100 mm), and at least two coats of an exterior
insulators can be obtained to accommodate thicker specimens,
grade paint or enamel over a suitable primer must be applied.
or the edges of thicker specimens can be machined to fit
Periodic maintenance will be required on all wood construc-
standard insulators.)
tion.
6.3 When it is desired to test samples of odd shapes, such as
5.3 Solid, glazed, electrical insulator knobs should be used
bolts, nuts, pipes, angles, assemblies, and structures, etc., a
to hold the specimens on the frames, using stainless steel, alloy
means of supporting them in the test racks must be devised. It
400, aluminum, nylon, or bronze bolts and nuts. Specimens
is important that the specimens be electrically insulated from
shall be mounted in the grooves of these insulators. In selecting
their respective supports and from each other to prevent
fasteners for use on specific frame materials, care should be
unintentional galvanic corrosion. However, if desired, galvanic
taken to avoid unfavorable galvanic relationships.
couples of dissimilar metals can be exposed on these frames.
5.4 A suitable frame for mounting the insulators is shown in
Efforts should be made to minimize crevices between speci-
Fig. 1. This frame will accommodate 70 standard 4 by 6-in.
mens and support materials.
(100 by 150-mm) specimens; other sizes can be mounted by
6.4 The total number of test specimens required should be
rearranging the insulators in the holes provided. It is acceptable
determined from a knowledge of the duration of the test and the
to slot the holes in the frames in such a manner that the
planned removals of the specimens for intermediate evalua-
mounting frames are adjustable for specimens of other sizes.
tions. Usually it should not be necessary to remove specimens
This is a convenience when it is not possible to prepare
prior to completing one year’s exposure, unless specific data
specimens of a preplanned size, and it is often helpful in fitting
are required for corrosion occurring during earlier stages of
the specimens snugly into the frames.
exposure. For reliable results, sufficient specimens should be
5.5 The racks should be designed to give exposure to as
used for multiple removals at each exposure period. Triplicate
large an area of the underside of the specimens as possible.
specimens for each examination period will usually satisfy this
Structural members of the rack should not be located directly
requirement. A suggested suitable removal schedule is 1, 2, 4,
under the specimens where they would shelter the underside of
8, and 16 years. Removal schedules for tests of different
the specimens.
periods of total exposure should be adjusted accordingly.
5.6 As most published data on atmospheric corrosion of
6.5 Included with each series of test specimens should be an
metals are based on an exposure angle of 30 deg from the
appropriate number of control specimens, as defined in 3.2.
horizontal, facing south, it is recommended that this angle be
used. Racks should be designed so that the lowest specimens
7. Preparation of Test Specimens
are at least 30 in. (760 mm) above the ground.
7.1 Specimens should be identified in a manner that will
NOTE 2—Maximum exposure to the sun may be obtained by exposing
endure for the life of the test. A good method is the use of a
specimens facing south (for the northern hemisphere) at an angle equal to
series of edge notches or drilled holes in the body of the
the latitude of the test site. Exposure at this angle will yield the lowest
specimen arranged according to some desired code. Another
corrosion rates for most materials. Although these corrosion rates will
method is to attach a stainless steel tag by means of an
change at other angles of exposure, the order of merit established for each
insulated cord and a suitably located hole. Numbers stamped
material will be the same.
NOTE 3—In special instances, i
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