ASTM G36-94(2000)
(Practice)Standard Practice for Evaluating Stress-Corrosion-Cracking Resistance of Metals and Alloys in a Boiling Magnesium Chloride Solution
Standard Practice for Evaluating Stress-Corrosion-Cracking Resistance of Metals and Alloys in a Boiling Magnesium Chloride Solution
SCOPE
1.1 This practice describes a procedure for conducting stress-corrosion cracking tests in a boiling magnesium chloride solution. Although this test may be performed using various concentrations of magnesium chloride, this procedure covers a test solution held at a constant boiling temperature of 155.0 + 1.0°C (311.0 + 1.8°F). The boiling points of aqueous magnesium chloride solutions at one atmosphere pressure as a function of concentration are shown graphically in Fig. 1. A suggested test apparatus capable of maintaining solution concentration and temperature within the prescribed limits for extended periods of time is also described herein.
1.2 The boiling magnesium chloride test is applicable to wrought, cast, and welded stainless steels and related alloys. It is a method for detecting the effects of composition, heat treatment, surface finish, microstructure, and stress on the susceptibility of these materials to chloride stress corrosion cracking.
1.3 This practice is concerned primarily with the test solution, which may be used with a variety of stress corrosion test specimens, surface finishes, and methods of applying stress.
1.4 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. See Section 7 for specific safety precautions.
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Designation: G 36 – 94 (Reapproved 2000)
Standard Practice for
Evaluating Stress-Corrosion-Cracking Resistance of Metals
and Alloys in a Boiling Magnesium Chloride Solution
ThisstandardisissuedunderthefixeddesignationG 36;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginal
adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.Asuperscript
epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This practice describes a procedure for conducting
stress-corrosion cracking tests in a boiling magnesium chloride
solution. Although this test may be performed using various
concentrations of magnesium chloride, this procedure covers a
test solution held at a constant boiling temperature of 155.0 6
1.0°C (311.0 6 1.8°F). The boiling points of aqueous magne-
sium chloride solutions at one atmosphere pressure as a
function of concentration are shown graphically in Fig. 1. A
suggested test apparatus capable of maintaining solution con-
centration and temperature within the prescribed limits for
extended periods of time is also described herein.
1.2 The boiling magnesium chloride test is applicable to
wrought, cast, and welded stainless steels and related alloys. It
is a method for detecting the effects of composition, heat
treatment, surface finish, microstructure, and stress on the
susceptibility of these materials to chloride stress corrosion
cracking.
1.3 This practice is concerned primarily with the test solu-
tion, which may be used with a variety of stress corrosion test
specimens, surface finishes, and methods of applying stress.
1.4 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 appro-
priate safety and health practices and determine the applica- FIG. 1 Boiling Points of Aqueous Magnesium Chloride Solutions
at One Atmosphere as a Function of Concentration
bility of regulatory limitations prior to use. See Section 7 for
specific safety precautions.
2. Referenced Documents
2.1 ASTM Standards:
1 5
This practice is under the jurisdiction of ASTM Committee G-1 on Corrosion D 1193 Specification for Reagent Water
of Metals, and is the direct responsibility of Subcommittee G01.06 on Stress
G 1 Practice for Preparing, Cleaning, and Evaluating Cor-
Corrosion Cracking and Corrosion Fatigue.
rosion Test Specimens
Current edition approved Feb. 15, 1994. Published April 1994. Originally
G 15 Terminology Relating to Corrosion and Corrosion
published as G 36 – 73. Last previous edition G 36 – 87.
Available data on the relationship of concentrations and boiling points of
Testing
magnesium chloride solutions are critically reviewed and supplemented by I. B.
G 30 Practice for Making and Using U-Bend Stress-
Casale in “Boiling Points of Magnesium Chloride Solutions—Their Application in
Corrosion Test Specimens
Stress Corrosion Studies,” Corrosion, Vol 23, 1967, pp. 314–17.
The apparatus and test procedures for maintaining constant boiling tempera-
3. Terminology
tures of magnesium chloride solutions for stress corrosion tests are described by M.
A. Streicher and A. J. Sweet in Corrosion, Vol 25, 1969, pp. 1–6.
3.1 Definitions: For definitions of terms used in this practice
The use of concentrated magnesium chloride solutions for determining the
see Terminology G 15.
susceptibility to stress corrosion cracking of austenitic and ferritic stainless steels
and related nickel-base alloys was first described by M. A. Scheil, Symposium on
Stress Corrosion Cracking of Metals, ASTM STP 64, ASTM, 1945, p. 395.
(Although currently out of print, copies may be obtained from University Micro- Annual Book of ASTM Standards, Vol 11.01.
films, Inc., 300 North Zeeb Rd., Ann Arbor, MI 48106.) 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.
G36
4. Summary of Practice where such specifications are available. Other grades may be
used, provided it is first ascertained that the reagent is of
4.1 A predetermined quantity of reagent grade magnesium
sufficiently high purity to permit its use without lessening the
chloride and some distilled water are added to a container. The
accuracy of the determination.
container and contents, with thermometer and condenser af-
7.2 Purity of Water—Reagent water Type IV (Specification
fixed, are placed on a source of heat. When the magnesium
D 1193) shall be used to prepare the test solutions.
chloride solution boils, it is adjusted to maintain the desired
7.3 Magnesium Chloride (MgCl ·6H O)—A solution of
concentration and boiling point through the addition of small 2 2
magnesium chloride that boils at 155.0 6 1.0°C (311.0 6
quantities of either water or salt.
1.8°F) is used in this test.Asecond 25 weight percent solution
4.2 After the solution has stabilized at the desired boiling
of magnesium chloride is required for the trap if the test
point for the test, the stressed specimens are added. Depending
duration exceeds seven days without a solution change and the
upon the intent of the test, the specimens should be given
suggested apparatus is used.
periodic inspections. If the duration of test exceeds 7 days, the
7.3.1 To prepare about 400 mLof the test solution for use in
solution should either be changed or the suggested or similar
a 1-L Erlenmeyer flask or other container, weigh 600 g of
test apparatus used.
reagent grade MgCl ·6H O and add this to the flask containing
2 2
a thermometer along with 15 mL of reagent water.
5. Significance and Use
7.3.2 Add 10 to 15 boiling chips or other boiling aids.
5.1 For most applications, this environment provides an
7.3.3 Heat by placing the flask on a hot plate or other
accelerated method of ranking the relative degree of stress-
suitable source of heat and put the condenser in place, leaving
corrosion cracking susceptibility for stainless steels and related
offthetrap.Hookupthecoolingwatersupplytothecondenser.
alloys in aqueous chloride-containing environments. Materials
7.3.4 When the solution boils vigorously and there is no
that normally provide acceptable resistance in hot chloride
more dripping of condensate, slowly add small quantities (4 to
service may crack in this test. The test may not be relevant to
5mL)ofreagentwateratthetopofthecondensertoreducethe
stress-corrosion cracking in polythionic acid or caustic envi-
temperature to 155.0°C (311.0°F). Use extreme caution when
ronments.
adding the water to the boiling magnesium chloride solution.
5.2 Resistance to stress-corrosion cracking in boiling mag-
Cool water can form a layer on top of the magnesium chloride,
nesium chloride (155.0°C (311.0°F)) should, where possible,
andwhenitreachesthebottomoftheflask,bumpingcanoccur.
be correlated to resistance in service for the materials of
Use a protective shield.
interest. However, such correlations may not always be pos-
sible.
NOTE 1—If too much water has been added, add some crystals of
5.3 Boiling magnesium chloride may also cause pitting of
MgCl ·6H O through the condenser until a temperature of 155.0°C
(311.0°F) is attained.
many stainless alloys.This leads to the possibility of confusing
stress-corrosion failures with mechanical failures induced by
7.4 To prepare the 25 weight percent solution for the trap
corrosion-reduced net cross sections. This danger is particu-
(Fig. X1.3), place 53.4 g of MgCl ·6H O and 46.6 mL of
2 2
larly great when small cross section samples, high applied
reagent water in a flask and allow the crystals to dissolve at
stress levels, long exposure periods, stress-corrosion resistant
room temperature.
alloys, or a combination thereof are being used. Careful
examination is recommended for correct diagnosis of the cause
8. Safety Precautions
of failure.
8.1 When cold, magnesium chloride can be handled with
the minimum protective equipment of rubber gloves and
6. Apparatus
goggles. Maximum protective measures should be taken to
6.1 Any inert, transparent apparatus with provisions for a
prevent boiling magnesium chloride from coming into contact
thermometer and water-cooled condenser can be used, pro-
with the skin. Severe burns can result as the hot magnesium
videdthatithasbeendesignedtocontainthestressedspecimen
chloride adheres to the skin forming a crust which causes deep
while maintaining a constant temperature and concentration of
burns. The severity of the burns can be reduced by taking
the magnesium chloride solution by minimizing or preventing
proper and immediate first aid measures and by contacting a
losses of condensate and water vapor during prolonged periods
physician.
of test. Small losses of water from a solution of magnesium
8.1.1 In the advent of a spill or accident, the hot magnesium
chloride will lead to large increases in the boiling point of the
chloride should be quickly flushed from the skin with large
solutionwithareductioninthetimetofailureofaspecimenby
quantities of cold water to minimize the burning, followed by
stress corrosion cracking.Asuggested apparatus, shown in Fig.
immediate first aid and medical attention.
X1.1, meets these requirements. Design details of this appara-
tus are given in Appendix X1.
7. Reagents
Reagent Chemicals, American Chemical Society Specifications, American
Chemical Society, Washington, DC. For suggestions on the testing of reagents not
7.1 Purity of Reagents—Reagent grade chemicals shall be
listed by the American Chemical Society, see Analar Standards for Laboratory
used in all tests. Unless otherwise indicated, it is intended that
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
all reagents shall conform to the specifications of the Commit-
and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
tee onAnalytical Reagents of theAmerican Chemical Society, MD.
G36
8.1.2 All heating or boiling of magnesium chloride should 10. Procedure
be done in a shielded area with protection by hood or shield, or
10.1 Collect the apparatus and test specimens in preparation
both.
for the test. If the suggested test apparatus is used, assemble as
8.1.3 Minimum personal protective equipment for handling outlined in Appendix X1.
boiling magnesium chloride should include safety glasses or 10.2 Preparethetestsolutionbyaddingaknownquantityof
goggles, face shield, laboratory coat, and rubber gloves with reagent grade MgCl ·6H O, reagent water, and some boiling
2 2
aids to the container fitted with a thermometer and water-
cotton inner gloves.
cooled condenser.After applying heat, adjust the concentration
8.1.4 Disposal
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