ASTM G186-05
(Test Method)Standard Test Method for Determining Whether Gas-Leak-Detector Fluid Solutions Can Cause Stress Corrosion Cracking of Brass Alloys
Standard Test Method for Determining Whether Gas-Leak-Detector Fluid Solutions Can Cause Stress Corrosion Cracking of Brass Alloys
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 and health practices and to determine the applicability of regulatory limitations prior to use.
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Designation: G186 – 05
Standard Test Method for
Determining Whether Gas-Leak-Detector Fluid Solutions
Can Cause Stress Corrosion Cracking of Brass Alloys
This standard is issued under the fixed designation G186; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3.1.1 Gas Leak Detector Solutions—Also known as leak
detection fluids, leak detector solutions, bubble solutions, and
1.1 This test method covers an accelerated test method for
soap solutions, designated in this standard as LDFs, are fluids
evaluating the tendency of gas leak detection fluids (LDFs) to
used to detect leaks in pressurized gas systems by the forma-
cause stress corrosion cracking (SCC) of brass components in
tion of bubbles at the leak site.
compressed gas service.
3.1.2 The terminology used herein, if not specifically de-
1.2 The values stated in inch-pound units are to be regarded
fined otherwise, shall be in accordance with Terminology G15.
as standard. The values given in parentheses are mathematical
conversions to SI units that are provided for information only
4. Summary of Test Method
and are not considered standard.
4.1 This test method consists of three steps: The first step
1.3 This standard does not purport to address all of the
consistsofrunningasampleofthetestspecimenstoverifythat
safety concerns, if any, associated with its use. It is the
they are susceptible to stress corrosion cracking using Matts-
responsibility of the user of this standard to establish appro-
son’s Solution (see Practice G37).The second step is to expose
priate safety and health practices and to determine the
the specimens to a solution that does not cause SCC to verify
applicability of regulatory limitations prior to use.
that the test environment does not contain components that can
2. Referenced Documents cause SCC to brass. The third step is to test the LDF to
determine if it causes SCC of the brass specimens within 15
2.1 ASTM Standards:
wetting and evaporation cycles.
B135 Specification for Seamless Brass Tube
4.2 The specimen used in this test is a C-ring stressed to
B135M Specification for Seamless Brass Tube [Metric]
create at least 0.65% strain in the outer fibers of the specimen.
D1193 Specification for Reagent Water
4.3 Macroscopic examination of the specimens is carried
G1 Practice for Preparing, Cleaning, and Evaluating Corro-
out after every second wetting cycle and if cracking is
sion Test Specimens
suspected the specimen is examined at higher magnifications
G15 Terminology Relating to Corrosion and Corrosion
for confirmation. Metallographic sectioning through the
Testing
stressed area is used to verify minor cracking at the end of the
G37 Practice for Use of Mattsson’s Solution of pH to
fifteen cycles.
Evaluate the Stress-Corrosion Cracking Susceptibility of
4.4 LDFs that cause SCC in any specimens within 15
Copper-Zinc Alloys
wetting cycles are considered to have failed this test and not
G38 Practice for Making and Using C-Ring Stress-
suitable for use in pressurized gas systems with brass compo-
Corrosion Test Specimens
nents.
3. Terminology
5. Significance and Use
3.1 Definitions of Terms Specific to This Standard:
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
This test method is under the jurisdiction of ASTM Committee G01 on
ammonia SCC, work-hardened brass is susceptible if its
Corrosion of Metals, and is the direct responsibility of Subcommittee G01.06 on
hardnessexceedsabout54HR30T(55HRB)(Rockwellscale).
Environmentally Assisted Cracking.
Normal assembly of brass components should not induce
Current edition approved July 1, 2005. Published July 2005. DOI: 10.1520/
G0186-05.
sufficient work hardening to cause susceptibility to ammonia
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
SCC. However, it is has been observed that over-tightening of
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
the components will render them susceptible to SCC, and the
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. problem becomes more severe in older components that have
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
G186 – 05
been tightened many times. In this test, the specimens are committee on Analytical Reagents of the American Chemical
obtained in the hardened condition and are strained beyond the Society, where such specifications are applicable, shall be
elastic limit to accelerate the tendency towards SCC. used.
5.2 It is normal practice to use LDFs to check pressurized 7.2 Fine pure copper powder with particle size <68 µm shall
systems to assure that leaking is not occurring. LDFs are be used.
usually aqueous solutions containing surfactants that will form 7.3 Solutionsusingwatershallbepreparedusingdistilledor
bubbles at the site of a leak. If the LDF contains ammonia or deionized water conforming to the purity requirements of
other agent that can cause SCC in brass, serious damage can Specification D1193, Type IV reagent water.
occur to the system that will compromise its safety and 7.4 Leakdetectorsolutionsshallmeetmanufacturer’sspeci-
integrity. fications.
5.3 It is important to test LDFs to assure that they do not 7.5 Mattsson’s Solution shall be freshly prepared according
cause SCC of brass and to assure that the use of these products to Practice G37.
does not compromise the integrity of the pressure containing
8. Hazards
system.
5.4 It has been found that corrosion of brass is necessary 8.1 Consult Material Safety Data Sheets (MSDS) for all
before SCC can occur. The reason for this is that the corrosion chemicals both reagent and commercial before testing to gain
process results in cupric and cuprous ions accumulating in the a full understanding of any potential hazards.
electrolyte. Therefore, adding copper metal and cuprous oxide 8.2 The test solutions present no undue safety hazard. It is
recommended, however, that appropriate personnel protection
(Cu O) to the aqueous solution accelerates the SCC process if
agents that cause SCC are present. However, adding these equipment such as resistant gloves and shatterproof eyewear
with side shields be worn when the chemicals or specimens are
components to a solution that does not cause SCC will not
make stressed brass crack. handled.
8.3 The solutions contain copper and are thus considered
5.5 Repeated application of the solution to the specimen
followed by a drying period causes the components in the poisonous so they should not be ingested.
8.4 Ammonium sulfate, (NH ) SO , in the Mattsson’s solu-
solution to concentrate thereby further increasing the rate of
4 2 4
cracking. This also simulates service where a system may be tion has been reported to be allergenic. Repeated short-time
skin contact with the solution over extended periods of time
tested many times during its life. These features of the test
method accelerate the test and allow an answer to be obtained should be avoided.
8.5 The fumes given off by the Mattsson’s test solution
more rapidly.
5.6 This test method applies only to brasses. Successful contain ammonia. The least detectable ammonia odor corre-
sponds to a concentration of 50 ppm; 100 ppm can be tolerated
passage of this test does not assure that the LDF will be
acceptable for use on other alloy systems such as stainless for several hours without serious disturbance; 700 ppm causes
immediate eye irritation; and greater than 5000 ppm can be
steels or aluminum alloys.
lethal. The mixing and the actual testing with Mattsson’s
6. Interferences
solution should therefore be run in a well-ventilated area.
6.1 When conducting this test, it is very important that the
9. Test Solutions
air not be contaminated with ammonia vapors. Reagent bottles
with ammonium hydroxide or other tests that involve ammonia
9.1 Control Solution (benign water solution)—Add2.5gCu
or its compounds including amines must not be in the vicinity
powder and 2.5 g Cu O to 1000 ml of H O. Then add 10ml of
2 2
of these tests. This also includes Mattsson’s test solution.
glycerin to solution. Shake solution vigorously to thoroughly
6.2 Cross contamination may result in false stress corrosion
mix contents.
cracking results therefore concurrent exposure tests with dif-
9.2 Leak Detector Solutions—Add 2.5 g Cu powder and 2.5
ferent leak detector solutions should be conducted in such a
gCu O to 1000 ml of each manufacturer’s solution to be
way that any set of samples does not influence the results of
tested. Shake solutions vigorously to thoroughly mix contents.
any of the other samples.
NOTE 1—Some of the solids will settle out of the solutions in between
6.3 In this test, the susceptibility of the C-ring specimens to
cycles, therefore, it is very important to shake the solutions vigorously
crack in a particular test solution can be affected by the temper
prior to their use in the wetting cycle.
of the brass alloy; therefore, it is crucial that the C-rings be
fabricated from hard drawn temper brass tubing that meets the
Reagent Chemicals, American Chemical Society Specifications, American
minimum specified hardness requirements.
Chemical Society, Washington, DC. For Suggestions on the testing of reagents not
listed by the American Chemical Society, see Annual Standards for Laboratory
7. Reagents and Materials
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
7.1 Reagent grade cuprous oxide (Cu O) and USP/FCC
2 and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
grade glycerin (C H O ) conforming to specifications of the MD.
3 8 3
G186 – 05
the surface and handle with gloves to prevent fingerprinting and the
10. Test Specimen
transfer of contaminants.
10.1 Type and Size—An unnotched C-ring in accordance
with Practice G38 shall be used (Fig. 1). C-rings shall have an
11. Test Setup and Apparatus
outer diameter (OD) between 1.0 to 2.0 in. (25.4 to 50.8 mm)
11.1 C-ring Test Assembly—Individual C-ring specimens
and thickness between 0.065 to 0.25 in. (1.65 to 6.4 mm).
shall be placed apex down in a glass-fiber-wick covered dish
Widths shall be fixed at 0.75 in. (19.0 mm).
(Fig. 3)
10.2 Alloy Composition and Temper—Test specimens shall
11.2 Exposure Dish—The individual dishes shall be made
be fabricated from copper alloy (UNS C27200) seamless tube
out of a material that will not react with the chemicals being
with a H80 hard-drawn temper. The hard drawn temper shall
used for the exposure (for example, glass, polystyrene, poly-
have a minimum hardness of 70 on the 30T Rockwell scale
carbonate). The required dish dimensions are 2.36- to 3.94-in.
which corresponds to minimum tensile strength of 66 ksi (455
(60- to 100-mm) diameter and 0.59- to 0.79-in. (15- to 20-mm)
MPa). Refer to Specifications B135 and B135M for tube
height.
information.
11.3 Wick Material—Borosilicateglasswickmaterialwitha
10.3 Surface Finish—Specimens shall have a 120-grit fin-
fiber diameter of about 0.3 mil (8 µm) shall be used.
ish. Grind marks shall be in the circumferential direction.
11.4 Number of Specimens—Five individual C-ring speci-
10.4 Restraining hardware—Nuts, bolts, and flat washers
men test assemblies will be used for each leak detector or
shall be made from a metal resistant to the chemicals used in
control solution to be tested.
this test (for example, Type 316 stainless steel, UNS S31600).
11.5 Test Assembly Arrangement—Individual exposure
Insulation washers shall be made from a hard resistant material
dishes shall be laid out such that there is at least a 1.0 ft (305
to prevent relaxation of the stressed C-ring specimen (for
mm) separation between groups of specimens (Fig. 4). The
example, alumina). Refer to Fig. 1.
control solution specimens shall always be positioned in the
10.5 Pre-test Condition—C-rings will be un-stressed prior
center of the test group.
to testing.
10.6 Stressing Method—Constant-strain stressing method
12. Calibration and Standardization
shall be used in stressing the C-rings (refer to Practice G38).
12.1 When a new batch of specimens is to be used, it is
Tensile stress will be introduced on the exterior of the ring by
necessary to first test a representative number of C-rings from
tightening a bolt centered on the diameter of the ring.
the batch with Mattsson’s solution.
10.7 Surface Preparation—The specimen surface should be
12.2 Mattsson’s Solution test must produce cracking of the
free of oil, grease, and dirt. This usually entails cleaning with
test specimens before any further testing is carried out.
organic solvent such as acetone followed by an alcohol rinse.
12.3 If cracking is not produced during the predescribed
Mattsson’s solution test the following variables need to be
NOTE 2—Every precaution shall be taken to maintain the integrity of
thesurfaceafterthefinalpreparation.Avoidroughhandlingthatcouldmar verified before rejecting the batch of C-rings.
FIG. 1 C-ring Specimen
G186 – 05
FIG. 2 Caliper Measurement of C-ring’s Deflection
FIG. 3 C-ring Specimen Ready for Exposure to Test Solution
12.3.1 Specimen material hardness shall exceed 70 HR 30T 12.4 Follow steps in Annex Section Annex A1 to test the
(Rockwell scale).
C-rings in Mattsson’s Solution.
12.3.2 Strain should be checked with a strain gauge if
hardness is sufficient.
12.3.3 Mattsson’s solution should be checked to make sure
it conforms to Practice G37.
G186 – 05
FIG. 4 Arrangement and Spacing of Specimens for Multiple Solution Testing
13. Air Conditions 14.2.2 Individual specimens should be assembled as shown
in Fig. 1.
13.1 Temperature—Airtemperatureshallbemaintainedina
14.2.3 Constant strain stressing method shall be used in
range of 70 – 80°F (21 – 27°C) throughout the entire test
stressing the C-rings. Tensile stress will be introduced on the
duration.
exterior of the ring by tightening the bolt centered on the
13.2 Relative Humidity—Percent relative humidity of the
diameter of the ring.
air shall be maintained in a range of 15 to 60 % throughout the
14.2.4 Tighten the restraining bolt and nut until the deflec-
entire test cycle.
tion required to produce a total strain of 0.65% on the outer
13.3 Air Circulation
fiber of the C-ring specimen is achieved.
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