ASTM G37-98(2021)
(Practice)Standard Practice for Use of Mattsson's Solution of pH 7.2 to Evaluate the Stress-Corrosion Cracking Susceptibility of Copper-Zinc Alloys
Standard Practice for Use of Mattsson's Solution of pH 7.2 to Evaluate the Stress-Corrosion Cracking Susceptibility of Copper-Zinc Alloys
SIGNIFICANCE AND USE
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 ...
General Information
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Standards Content (Sample)
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: G37 − 98 (Reapproved 2021)
Standard Practice for
Use of Mattsson’s Solution of pH 7.2 to Evaluate the Stress-
Corrosion Cracking Susceptibility of Copper-Zinc Alloys
ThisstandardisissuedunderthefixeddesignationG37;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginal
adoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope rations or methods of applying the stress. Test specimen
configurations that may be used are referenced in PracticeG30
1.1 This practice covers the preparation and use of Matts-
and STP425.
son’s solution of pH 7.2 as an accelerated stress-corrosion
cracking test environment for brasses (copper-zinc base al-
1.5 The values stated in SI units are to be regarded as
loys). The variables (to the extent that these are known at
standard. No other units of measurement are included in this
present) that require control are described together with pos-
standard.
sible means for controlling and standardizing these variables.
1.6 This standard does not purport to address all of the
1.2 This practice is recommended only for brasses (copper-
safety concerns, if any, associated with its use. It is the
zinc base alloys). The use of this test environment is not
responsibility of the user of this standard to establish appro-
recommended for other copper alloys since the results may be
priate safety, health, and environmental practices and deter-
erroneous, providing completely misleading rankings. This is
mine the applicability of regulatory limitations prior to use.
particularly true of alloys containing aluminum or nickel as
(For more specific safety hazard statements see Section 8.)
deliberate alloying additions.
1.7 This international standard was developed in accor-
1.3 This practice is intended primarily where the test objec- dance with internationally recognized principles on standard-
tive is to determine the relative stress-corrosion cracking ization established in the Decision on Principles for the
susceptibility of different brasses under the same or different
Development of International Standards, Guides and Recom-
stress conditions or to determine the absolute degree of stress mendations issued by the World Trade Organization Technical
corrosioncrackingsusceptibility,ifany,ofaparticularbrassor
Barriers to Trade (TBT) Committee.
brass component under one or more specific stress conditions.
Otherlegitimatetestobjectivesforwhichthistestsolutionmay
2. Referenced Documents
beuseddo,ofcourse,exist.Thetensilestressespresentmaybe
2.1 ASTM Standards:
known or unknown, applied or residual. The practice may be
D1193Specification for Reagent Water
applied to wrought brass products or components, brass
G30 Practice for Making and Using U-Bend Stress-
castings, brass weldments, and so forth, and to all brasses.
Corrosion Test Specimens
Strict environmental test conditions are stipulated for maxi-
mum assurance that apparent variations in stress-corrosion
3. Summary of Practice
susceptibility are attributable to real variations in the material
being tested or in the tensile stress level and not to environ-
3.1 The practice consists of completely and continuously
mental variations.
immersing a stressed test specimen in an aqueous solution
++ +
containing 0.05 g-atom/L of Cu and 1 g-mol/L of NH and
1.4 This practice relates solely to the preparation and
+
of pH 7.2. The copper is added as CuSO ·5H O and the NH
control of the test environment. No attempt is made to 4 2 4
as a mixture of NH OH and (NH ) SO . The ratio of these
recommend surface preparation or finish, or both, as this may 4 4 2 4
latter two compounds is adjusted to give the desired pH.
vary with the test objectives. Similarly, no attempt is made to
Exposure time, criterion of failure, and so forth, are variable
recommend particular stress-corrosion test specimen configu-
and not specifically recommended.
This practice is under the jurisdiction ofASTM Committee G01 on Corrosion
of Metals and is the direct responsibility of Subcommittee G01.06 on Environmen- STP425, Stress Corrosion Testing, ASTM International.
tally Assisted Cracking. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved May 1, 2021. Published May 2021. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approvedin1973.Lastpreviouseditionapprovedin2016asG37–98(2016).DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/G0037-98R21. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
G37 − 98 (2021)
4. Significance and Use assayed and 0.90 sp gr) conforming to the specifications of the
Committee on Analytical Reagents of the American Chemical
4.1 This test environment is believed to give an accelerated
Society shall be used.
ranking of the relative or absolute degree of stress-corrosion
cracking susceptibility for different brasses. It has been found 6.2 Purity of Water—Reagent water Type IV (Specification
to correlate well with the corresponding service ranking in D1193) shall be used to prepare the test solution.
environments that cause stress-corrosion cracking which is
thought to be due to the combined presence of traces of
7. Test Solution
moisture and ammonia vapor. The extent to which the accel-
7.1 The concentration of the test solution shall be 0.05
erated ranking correlates with the ranking obtained after
++
g-atom/Lwith respect to Cu and 1.0 g-mol/Lwith respect to
long-term exposure to environments containing corrodents +
NH . The pH of the test solution shall be 7.2+0.3,−0.1 pH.
otherthanammoniaisnotatpresentknown.Examplesofsuch
−
7.2 The test solution shall be prepared by completely
environments may be severe marine atmospheres (Cl ), severe
dissolving 590.0g 6 1.0 g of (NH ) SO in 4L of water and
industrial atmospheres (predominantly SO ), and super-heated 4 2 4
by completely dissolving 125.0g 6 0.5 g of CuSO ·5HOin
4 2
ammonia-free steam.
1L of water. These two solutions should then be thoroughly
4.2 Itisnotpossibleatpresenttospecifyanyparticulartime
mixed and 71.0mL 6 0.2 mL of NH OH solution added,
tofailure(definedonthebasisofanyparticularfailurecriteria)
preferably with a buret. Finally, the whole should be diluted to
in pH 7.2 Mattsson’s solution that corresponds to a distinction
10.0L 6 0.1 L and allowed to age for 48h to 96 h in the test
betweenacceptableandunacceptablestress-corrosionbehavior
container prior to use. It is not recommended that the solution
inbrassalloys.Suchparticularcorrelationsmustbedetermined
be stored for extended periods or used without the specified
individually.
aging. Smaller or larger volumes of solution can be prepared
4.3 Mattsson’s solution of pH 7.2 may also cause stress
using lesser amounts of reagents in the same proportions.
independent general and intergranular corrosion of brasses to
7.3 After aging, the pH of the test solution should be
some extent. This leads to the possibility of confusing stress-
measured. If outside the range specified above, the pH may be
corrosion failures with mechanical failures induced by
adjusted to within the range 7.1 to 7.5 by the addition of fresh
corrosion-reduced net cross sections. This danger is particu-
pH 4 or pH 10 Mattsson’s solution. Addition of NH OH or
larly great with small cross section specimens, high applied
H SO to adjust pH is not recommended since the concentra-
2 4
stress levels, long exposure periods and stress-corrosion resis-
tion of the various soluble ions can be considerably altered.
tant alloys. Careful metallographic examination is recom-
7.4 Temperature control of the test solution is not recom-
mended for correct diagnosis of the cause of failure.
mended.Instead,theroomairtemperatureshouldbecontrolled
Alternatively, unstressed control specimens may be exposed to
at 21°C 6 3°C and the test solution allowed to reach its
evaluate the extent to which stress independent corrosion
equilibrium temperature with the air. No room air relative
degrades mechanical properties.
humiditycontrolisrecommendedandtemperaturerecordingis
not mand
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