ASTM G37-98(2004)
(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
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.
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’solution that corresponds to a distinction between acceptable and unacceptable stress-corrosion behavior in brass alloys. Such particular correlations must be determined individually.
Mattsson’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 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 G 30 and STP 425.
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...
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Designation:G37–98 (Reapproved 2004)
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
configurationsthatmaybeusedarereferencedinPracticeG30
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
1.5 This standard does not purport to address all of the
cracking test environment for brasses (copper-zinc base al-
safety concerns, if any, associated with its use. It is the
loys). The variables (to the extent that these are known at
responsibility of the user of this standard to establish appro-
present) that require control are described together with pos-
priate safety and health practices and determine the applica-
sible means for controlling and standardizing these variables.
bility of regulatory limitations prior to use. (For more specific
1.2 This practice is recommended only for brasses (copper-
safety hazard statements see Section 8.)
zinc base alloys). The use of this test environment is not
recommended for other copper alloys since the results may be
2. Referenced Documents
erroneous, providing completely misleading rankings. This is
2.1 ASTM Standards:
particularly true of alloys containing aluminum or nickel as
D1193 Specification for Reagent Water
deliberate alloying additions.
G30 Practice for Making and Using U-Bend Stress-
1.3 This practice is intended primarily where the test objec-
Corrosion Test Specimens
tive is to determine the relative stress-corrosion cracking
susceptibility of different brasses under the same or different
3. Summary of Practice
stress conditions or to determine the absolute degree of stress
3.1 The practice consists of completely and continuously
corrosioncrackingsusceptibility,ifany,ofaparticularbrassor
immersing a stressed test specimen in an aqueous solution
brass component under one or more specific stress conditions.
++ +
containing 0.05 g-atom/L of Cu and 1 g-mol/L of NH and
Otherlegitimatetestobjectivesforwhichthistestsolutionmay
+
of pH 7.2. The copper is added as CuSO ·5H O and the NH
4 2 4
beuseddo,ofcourse,exist.Thetensilestressespresentmaybe
as a mixture of NH OH and (NH ) SO . The ratio of these
4 4 2 4
known or unknown, applied or residual. The practice may be
latter two compounds is adjusted to give the desired pH.
applied to wrought brass products or components, brass cast-
Exposure time, criterion of failure, and so forth, are variable
ings, brass weldments, and so forth, and to all brasses. Strict
and not specifically recommended.
environmental test conditions are stipulated for maximum
assurance that apparent variations in stress-corrosion suscepti-
4. Significance and Use
bility are attributable to real variations in the material being
4.1 This test environment is believed to give an accelerated
tested or in the tensile stress level and not to environmental
ranking of the relative or absolute degree of stress-corrosion
variations.
cracking susceptibility for different brasses. It has been found
1.4 This practice relates solely to the preparation and
to correlate well with the corresponding service ranking in
control of the test environment. No attempt is made to
environments that cause stress-corrosion cracking which is
recommend surface preparation or finish, or both, as this may
thought to be due to the combined presence of traces of
vary with the test objectives. Similarly, no attempt is made to
moisture and ammonia vapor. The extent to which the accel-
recommend particular stress-corrosion test specimen configu-
erated ranking correlates with the ranking obtained after
Stress Corrosion Testing, ASTM STP 425, ASTM (Although currently out of
This practice is under the jurisdiction ofASTM Committee G01 on Corrosion print,copiesmaybeobtainedfromUniversityMicrofilms,Inc.,300NorthZeebRd.,
of Metals, and is the direct responsibility of Subcommittee G01.06 on Environmen- Ann Arbor, MI 48106).
tally Assisted Cracking. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved May 1, 2004. Published May 2004. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1973. Last previous edition approved in 1998 as G37–98. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/G0037-98R04. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
G37–98 (2004)
long-term exposure to environments containing corrodents 6.2 Purity of Water—ReagentwaterTypeIV(Specification
otherthanammoniaisnotatpresentknown.Examplesofsuch D1193) shall be used to prepare the test solution.
−
environments may be severe marine atmospheres (Cl ), severe
industrial atmospheres (predominantly SO ), and super-heated 7. Test Solution
ammonia-free steam.
7.1 The concentration of the test solution shall be 0.05
++
4.2 Itisnotpossibleatpresenttospecifyanyparticulartime
g-atom/Lwith respect to Cu and 1.0 g-mol/Lwith respect to
tofailure(definedonthebasisofanyparticularfailurecriteria) +
NH . The pH of the test solution shall be 7.2+0.3,−0.1 pH.
in pH 7.2 Mattsson’s solution that corresponds to a distinction
7.2 The test solution shall be prepared by completely
betweenacceptableandunacceptablestress-corrosionbehavior
dissolving 590.0 6 1.0 g of (NH ) SO in 4 Lof water and by
4 2 4
inbrassalloys.Suchparticularcorrelationsmustbedetermined
completely dissolving 125.0 6 0.5 g of CuSO ·5HOin1Lof
4 2
individually.
water. These two solutions should then be thoroughly mixed
4.3 Mattsson’s solution of pH 7.2 may also cause stress
and 71.0 6 0.2 mLof NH OH solution added, preferably with
independent general and intergranular corrosion of brasses to
a buret. Finally, the whole should be diluted to 10.0 6 0.1 L
some extent. This leads to the possibility of confusing stress-
and allowed to age for 48 to 96 h in the test container prior to
corrosion failures with mechanical failures induced by
use. It is not recommended that the solution be stored for
corrosion-reduced net cross sections. This danger is particu-
extended periods or used without the specified aging. Smaller
larly great with small cross section specimens, high applied
or larger volumes of solution can be prepared using lesser
stress levels, long exposure periods and stress-corrosion resis-
amounts of reagents in the same proportions.
tant alloys. Careful metallographic examination is recom-
7.3 After aging, the pH of the test solution should be
mended for correct diagnosis of the cause of failure. Alterna-
measured. If outside the range specified above, the pH may be
tively, unstressed control specimens may be exposed to
adjusted to within the range 7.1 to 7.5 by the addition of fresh
evaluate the extent to which stress independent corrosion
pH 4 or pH 10 Mattsson’s solution. Addition of NH OH or
degrades mechanical properties.
H SO to adjust pH is not recommended since the concentra-
2 4
tion of the various soluble ions can be considerably altered.
5. Apparatus
7.4 Temperature control of the test solution is not recom-
5.1 Anysuitableinertcontainermaybeusedtoholdthetest
mended.Instead,theroomairtemperatureshouldbecontrolled
solutionandtestspecimensduringexposure.Glassorplasticis
at 21 6 3°C (70 6 5°F) and the test solution allowed to reach
highly recommended. The container should be fitted with a
its equilibrium temperature with the air. No room air relative
removable top to reduce evaporation during test, thus prevent-
humiditycontrolisrecommendedandtemperaturerecordingis
ing dust and other particulate matter from entering the envi-
not mandatory.
ronment, and facilitating periodic inspection of
...
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