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ASTM G50-76(2003)

(Practice)

Standard Practice for Conducting Atmospheric Corrosion Tests on Metals

Standard Practice for Conducting Atmospheric Corrosion Tests on Metals

SIGNIFICANCE AND USE
The procedures described herein can be used to evaluate the corrosion resistance of metals when exposed to the weather, as well as to evaluate the relative corrosivity of the atmosphere at specific locations. Because of the variability and complexity of weather effects and the industrial and natural factors influencing the atmospheric corrosivity of a test site, a multi-year exposure period should be considered to minimize their influence. Also, as corrosivity may vary at a site from season to season, exposures should be made either at the same time of the year to minimize variability or these differences should be established by multiple exposures.
Control specimens should always be employed in weathering tests. The control specimens should be from a material having established weathering characteristics. A substantial amount of corrosion data shall have been accumulated for the control specimens. It is also good practice to retain samples of all materials exposed so that possible effects of long-term aging can be measured.
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 whoever uses this standard to consult and establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

General Information

Status
Historical
Publication Date
26-Aug-1976
ICS
77.060 - Corrosion of metals
Technical Committee
G01 - Corrosion of Metals
Drafting Committee
G01.04 - Corrosion of Metals in Natural Atmospheric and Aqueous Environments
Current Stage
Ref Project

Relations

Replaces
ASTM G50-76(1997)e1 - Standard Practice for Conducting Atmospheric Corrosion Tests on Metals
Effective Date
27-Aug-1976
Replaced By
ASTM G50-10 - Standard Practice for Conducting Atmospheric Corrosion Tests on Metals
Effective Date
01-Sep-2010
Referred By
ASTM G7/G7M-21 - Standard Practice for Natural Weathering of Materials
Effective Date
27-Aug-1976
Referred By
ASTM D6675-23 - Standard Practice for Salt-Accelerated Outdoor Cosmetic Corrosion Testing of Organic Coatings on Automotive Sheet Steel
Effective Date
27-Aug-1976
Referred By
ASTM G92-20 - Standard Practice for Characterization of Atmospheric Test Sites
Effective Date
27-Aug-1976
Referred By
ASTM G101-04(2020) - Standard Guide for Estimating the Atmospheric Corrosion Resistance of Low-Alloy Steels
Effective Date
27-Aug-1976
Referred By
ASTM G112-22 - Standard Guide for Conducting Exfoliation Corrosion Tests in Aluminum Alloys
Effective Date
27-Aug-1976
Referred By
ASTM G168-17 - Standard Practice for Making and Using Precracked Double Beam Stress Corrosion Specimens
Effective Date
27-Aug-1976
Referred By
ASTM G39-99(2021) - Standard Practice for Preparation and Use of Bent-Beam Stress-Corrosion Test Specimens
Effective Date
27-Aug-1976
Referred By
ASTM G1-03(2017)e1 - Standard Practice for Preparing, Cleaning, and Evaluating Corrosion Test Specimens
Effective Date
27-Aug-1976
Referred By
ASTM G116-99(2020)e1 - Standard Practice for Conducting Wire-on-Bolt Test for Atmospheric Galvanic Corrosion
Effective Date
27-Aug-1976
Referred By
ASTM D6577-15(2019) - Standard Guide for Testing Industrial Protective Coatings
Effective Date
27-Aug-1976

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ASTM G50-76(2003) - Standard Practice for Conducting Atmospheric Corrosion Tests on MetalsASTM G50-76(2003) - Standard Practice for Conducting Atmospheric Corrosion Tests on Metals
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ASTM G50-76(2003) - Standard Practice for Conducting Atmospheric Corrosion Tests on Metals
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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:G50–76 (Reapproved 2003)
Standard Practice for
1
Conducting Atmospheric Corrosion Tests on Metals
This standard is issued under the fixed designation G50; the number immediately following the designation indicates the year of original
adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.Asuperscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope year exposure period should be considered to minimize their
influence.Also, as corrosivity may vary at a site from season to
1.1 This practice defines conditions for exposure of metals
season, exposures should be made either at the same time of
and alloys to the weather. It sets forth the general procedures
the year to minimize variability or these differences should be
that should be followed in any atmospheric test. It is presented
established by multiple exposures.
as an aid in conducting atmospheric corrosion tests so that
3.2 Control specimens should always be employed in
some of the pitfalls of such testing may be avoided.As such, it
weathering tests. The control specimens should be from a
is concerned mainly with panel exposures to obtain data for
material having established weathering characteristics. A sub-
comparison purposes.
stantial amount of corrosion data shall have been accumulated
1.2 This standard does not purport to address all of the
for the control specimens. It is also good practice to retain
safety concerns, if any, associated with its use. It is the
samples of all materials exposed so that possible effects of
responsibility of whoever uses this standard to consult and
long-term aging can be measured.
establish appropriate safety and health practices and deter-
mine the applicability of regulatory limitations prior to use.
4. Test Sites
2. Referenced Documents 4.1 Test sites should be chosen at a number of locations
2
representative of the atmospheric environments where the
2.1 ASTM Standards:
metals or alloys are likely to be used. If such information is not
A380 Practice for Cleaning, Descaling, and Passivation of
available, the selection should include sites typical of indus-
Stainless Steel Parts, Equipment, and Systems
trial, rural, and marine atmospheres.
D2010/D2010M Test Methods for Evaluation of Total Sul-
4.2 Exposure racks should be located in cleared, well-
fation Activity in the Atmosphere by the Lead Dioxide
drained areas such that the exposed specimens will be sub-
Technique
jected to the full effects of the atmosphere at the location of the
G1 Practice for Preparing, Cleaning, and Evaluating Corro-
test site. Shadows of trees, buildings, or structures should not
sion Test Specimens
fall on the specimens, and local contamination of the atmo-
G33 Practice for Recording Data from Atmospheric Corro-
sphereshouldbeavoided,unlessthespecificinfluencesofsuch
sion Tests of Metallic-Coated Steel Specimens
conditions are intended to be assessed.
G46 Guide for Examination and Evaluation of Pitting
4.3 In special cases, the exposure racks may be partially
Corrosion
shelteredtoallowaccumulationofcorrosivematerialsfromthe
3. Significance and Use
air but at the same time prevent washing by rain. If sheltering
is used, its purpose and configuration should be described in
3.1 The procedures described herein can be used to evaluate
detail.
thecorrosionresistanceofmetalswhenexposedtotheweather,
4.4 If local pollution effects are to be investigated, the
as well as to evaluate the relative corrosivity of the atmosphere
samples should be exposed at different distances from the
at specific locations. Because of the variability and complexity
source and at different elevations. Where it is particularly
of weather effects and the industrial and natural factors
important to obtain corrosion rates involving a micro-
influencing the atmospheric corrosivity of a test site, a multi-
environment, samples should be mounted directly on the
structure involved. Suitable attachment must be devised for
1
This practice is under the jurisdiction of ASTM Committee G01 on Corrosion
each case.
of Metals, and is the direct responsibility of Subcommittee G01.04 onAtmospheric
Corrosion.
5. Exposure Racks and Frames
Current edition approved Aug. 27, 1976. Published March 1977. DOI: 10.1520/
G0050-76R03.
5.1 Test racks and frames should be constructed of a
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
material that will remain intact for the entire proposed period
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
of exposure. Galvanized pipe has been found adequate for rack
Standards volume information, refer to the standard’s Document Summary page on
construction in most environments (Note 1).Type 304 stainless
the ASTM website.
Copyright © ASTM
...

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4.1 Polythionic acids are chemically described as H2SxO6, where x is usually 3, 4, or 5 (1)3 though can be more than 50 (2). These acid environments provide a way of evaluating the resistance of stainless steels and related alloys to intergranular stress corrosion cracking. Failure is accelerated by the presence of increasing amounts of intergranular precipitate. Results for the polythionic acid test have not been correlated exactly with those of intergranular corrosion tests (Test Methods G28). Also, this test may not be relevant to stress corrosion cracking in chlorides or caustic environments.  
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5.1 Autoclave tests are commonly used to evaluate the corrosion performance of metallic and non-metallic materials under simulated HP and HTHP service conditions. Examples of service environments in which HP and HTHP corrosion tests have been used include chemical processing, petroleum production and refining, food processing, pressurized cooling water, electric power systems, and aerospace propulsion.  
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1.3 The primary purpose for this guide is to promote consistency of corrosion test results. Furthermore, this guide will aid in the comparison of corrosion data between laboratories or testing organizations that utilize different equipment.  
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4.1 It is important to be able to determine the extent of pitting, either in a service application in which it is necessary to predict the remaining life in a metal structure, or in laboratory test programs that are used to select the most pitting-resistant materials for service. The purpose of the study is crucial in determining the appropriate examination and evaluation steps.  
4.2 Some typical purposes of laboratory tests include, but are not limited to, evaluating performance of alloys, determining whether an alloy is resistant to the environment, evaluating how environmental conditions including corrosion inhibitor affect or prevent pitting, and evaluating whether a lot of metal is sufficiently resistant for its use in a particular application or environment.  
4.3 Some typical purposes of field studies include, but are not limited to, determining if pits are likely to grow and cause leak or release of process fluid, and assisting a determination of whether to replace or repair damage from pits (remaining life assessment).
SCOPE
1.1 This guide covers the selection of procedures that can be used in the examination and evaluation of pitted metals. These procedures include both nondestructive and destructive approaches.  
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1.3.1 Exception—In X1.2.1, mils per year (MPY) are regarded as standard for the target corrosion rate.  
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4.1 This test environment is believed to give an accelerated ranking of the relative or absolute degree of stress-corrosion cracking susceptibility for different brasses. It has been found to correlate well with the corresponding service ranking in environments that cause stress-corrosion cracking which is thought to be due to the combined presence of traces of moisture and ammonia vapor. The extent to which the accelerated ranking correlates with the ranking obtained after long-term exposure to environments containing corrodents other than ammonia is not at present known. Examples of such environments may be severe marine atmospheres (Cl−), severe industrial atmospheres (predominantly SO2), and super-heated ammonia-free steam.  
4.2 It is not possible at present to specify any particular time to failure (defined on the basis of any particular failure criteria) in pH 7.2 Mattsson’s solution that corresponds to a distinction between acceptable and unacceptable stress-corrosion behavior in brass alloys. Such particular correlations must be determined individually.  
4.3 Mattsson's solution of pH 7.2 may also cause stress independent general and intergranular corrosion of brasses to some extent. This leads to the possibility of confusing stress-corrosion failures with mechanical failures induced by corrosion-reduced net cross sections. This danger is particularly great with small cross section specimens, high applied stress levels, long exposure periods and stress-corrosion resistant alloys. Careful metallographic examination is recommended for correct diagnosis of the cause of failure. Alternatively, unstressed control specimens may be exposed to evaluate the extent to which stress independent corrosion degrades mechanical properties.
SCOPE
1.1 This practice covers the preparation and use of Mattsson’s solution of pH 7.2 as an accelerated stress-corrosion cracking test environment for brasses (copper-zinc base alloys). The variables (to the extent that these are known at present) that require control are described together with possible means for controlling and standardizing these variables.  
1.2 This practice is recommended only for brasses (copper-zinc base alloys). The use of this test environment is not recommended for other copper alloys since the results may be erroneous, providing completely misleading rankings. This is particularly true of alloys containing aluminum or nickel as deliberate alloying additions.  
1.3 This practice is intended primarily where the test objective is to determine the relative stress-corrosion cracking susceptibility of different brasses under the same or different stress conditions or to determine the absolute degree of stress corrosion cracking susceptibility, if any, of a particular brass or brass component under one or more specific stress conditions. Other legitimate test objectives for which this test solution may be used do, of course, exist. The tensile stresses present may be known or unknown, applied or residual. The practice may be applied to wrought brass products or components, brass castings, brass weldments, and so forth, and to all brasses. Strict environmental test conditions are stipulated for maximum assurance that apparent variations in stress-corrosion susceptibility are attributable to real variations in the material being tested or in the tensile stress level and not to environmental variations.  
1.4 This practice relates solely to the preparation and control of the test environment. No attempt is made to recommend surface preparation or finish, or both, as this may vary with the test objectives. Similarly, no attempt is made to recommend particular stress-corrosion test specimen configurations or methods of applying the stress. Test specimen configurations that may be used are referenced in Practice G30 and STP 425.2  
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included ...

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ASTM
ASTM G186-05(2021)(Test Method)
Standard Test Method for Determining Whether Gas-Leak-Detector Fluid Solutions Can Cause Stress Corrosion Cracking of Brass Alloys

SIGNIFICANCE AND USE
5.1 Brass components are routinely used in compressed gas service for valves, pressure regulators, connectors and many other components. Although soft brass is not susceptible to ammonia SCC, work-hardened brass is susceptible if its hardness exceeds about 54 HR 30T (55HRB) (Rockwell scale). Normal assembly of brass components should not induce sufficient work hardening to cause susceptibility to ammonia SCC. However, it is has been observed that over-tightening of the components will render them susceptible to SCC, and the problem becomes more severe in older components that have been tightened many times. In this test, the specimens are obtained in the hardened condition and are strained beyond the elastic limit to accelerate the tendency towards SCC.  
5.2 It is normal practice to use LDFs to check pressurized systems to assure that leaking is not occurring. LDFs are usually aqueous solutions containing surfactants that will form bubbles at the site of a leak. If the LDF contains ammonia or other agent that can cause SCC in brass, serious damage can occur to the system that will compromise its safety and integrity.  
5.3 It is important to test LDFs to assure that they do not cause SCC of brass and to assure that the use of these products does not compromise the integrity of the pressure containing system.  
5.4 It has been found that corrosion of brass is necessary before SCC can occur. The reason for this is that the corrosion process results in cupric and cuprous ions accumulating in the electrolyte. Therefore, adding copper metal and cuprous oxide (Cu2O) to the aqueous solution accelerates the SCC process if agents that cause SCC are present. However, adding these components to a solution that does not cause SCC will not make stressed brass crack.  
5.5 Repeated application of the solution to the specimen followed by a drying period causes the components in the solution to concentrate thereby further increasing the rate of cracking. This also simulates se...
SCOPE
1.1 This test method covers an accelerated test method for evaluating the tendency of gas leak detection fluids (LDFs) to cause stress corrosion cracking (SCC) of brass components in compressed gas service.  
1.2 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.  
1.3 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.  
1.4 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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