ASTM G37-98
(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
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 pos- sible 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 method may be applied to wrought brass products or components, brass castings, brass weldments, etc., 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 STP425.
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 and health practices and determine the applicability of regulatory limitations prior to use. (For more specific safety hazard statements see Section 8.)
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Designation: G 37 – 98
Standard Practice for
Use of Mattsson’s Solution of pH 7.2 to Evaluate the Stress-
Corrosion Cracking Susceptibility of Copper-Zinc Alloys
This standard is issued under the fixed designation G 37; 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.
1. Scope rations or methods of applying the stress. Test specimen
configurations that may be used are referenced in Practice G 30
1.1 This practice covers the preparation and use of Matts-
and STP 425.
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
D 1193 Specification for Reagent Water
deliberate alloying additions.
G 30 Practice for Making and Using the U-Bend Stress-
1.3 This practice is intended primarily where the test objec-
Corrosion 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
corrosion cracking susceptibility, if any, of a particular brass or
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
Other legitimate test objectives for which this test solution may
+
of pH 7.2. The copper is added as CuSO ·5H O and the NH
4 2 4
be used do, of course, exist. The tensile stresses present may be
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
1 2
This practice is under the jurisdiction of ASTM Committee G-1 on Corrosion Stress Corrosion Testing, ASTM STP 425, ASTM (Although currently out of
of Metals, and is the direct responsibility of Subcommittee G01.06 on Environmen- print, copies may be obtained from University Microfilms, Inc., 300 North Zeeb Rd.,
tally Assisted Cracking. Ann Arbor, MI 48106).
Current edition approved April 10, 1998. Published September 1998. Originally Annual Book of ASTM Standards, Vol 11.01.
e1 4
published as G 37-73. Last previous edition G 37-90 (Reapproved 1994) Annual Book of ASTM Standards, Vol 03.02.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
G37
long-term exposure to environments containing corrodents 6.2 Purity of Water— Reagent water Type IV (Specification
other than ammonia is not at present known. Examples of such D 1193) 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 It is not possible at present to specify any particular time
g-atom/L with respect to Cu and 1.0 g-mol/L with respect to
to failure (defined on the basis of any particular failure criteria) +
NH . The pH of the test solution shall be 7.2 + 0.3, −0.1 pH.
in pH 7.2 Mattsson’s solution of pH 7.2 that corresponds to a
7.2 The test solution shall be prepared by completely
distinction between acceptable and unacceptable stress-
dissolving 590.0 6 1.0 g of (NH ) SO in 4 L of water and by
4 2 4
corrosion behavior in brass alloys. Such particular correlations
completely dissolving 125.0 6 0.5 g of CuSO ·5H Oin1Lof
4 2
must be determined 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 mL of 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 Any suitable inert container may be used to hold the test
mended. Instead, the room air temperature should be controlled
solution and test specimens during exposure. Glass or plastic is
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-
humidity control
...
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