ASTM G186-05(2021)
(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
SIGNIFICANCE AND USE
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 ammonia SCC, work-hardened brass is susceptible if its hardness exceeds about 54 HR 30T (55HRB) (Rockwell scale). Normal assembly of brass components should not induce sufficient work hardening to cause susceptibility to ammonia SCC. However, it is has been observed that over-tightening of the components will render them susceptible to SCC, and the problem becomes more severe in older components that have been tightened many times. In this test, the specimens are obtained in the hardened condition and are strained beyond the elastic limit to accelerate the tendency towards SCC.
5.2 It is normal practice to use LDFs to check pressurized systems to assure that leaking is not occurring. LDFs are usually aqueous solutions containing surfactants that will form bubbles at the site of a leak. If the LDF contains ammonia or other agent that can cause SCC in brass, serious damage can occur to the system that will compromise its safety and integrity.
5.3 It is important to test LDFs to assure that they do not cause SCC of brass and to assure that the use of these products does not compromise the integrity of the pressure containing system.
5.4 It has been found that corrosion of brass is necessary before SCC can occur. The reason for this is that the corrosion process results in cupric and cuprous ions accumulating in the electrolyte. Therefore, adding copper metal and cuprous oxide (Cu2O) to the aqueous solution accelerates the SCC process if agents that cause SCC are present. However, adding these components to a solution that does not cause SCC will not make stressed brass crack.
5.5 Repeated application of the solution to the specimen followed by a drying period causes the components in the solution to concentrate thereby further increasing the rate of cracking. This also simulates se...
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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.4 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.
General Information
Relations
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: G186 − 05 (Reapproved 2021)
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.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope G15TerminologyRelatingtoCorrosionandCorrosionTest-
ing (Withdrawn 2010)
1.1 This test method covers an accelerated test method for
G37Practice for Use of Mattsson’s Solution of pH 7.2 to
evaluating the tendency of gas leak detection fluids (LDFs) to
Evaluate the Stress-Corrosion Cracking Susceptibility of
cause stress corrosion cracking (SCC) of brass components in
Copper-Zinc Alloys
compressed gas service.
G38 Practice for Making and Using C-Ring Stress-
1.2 The values stated in inch-pound units are to be regarded
Corrosion Test Specimens
as standard. The values given in parentheses are mathematical
conversions to SI units that are provided for information only
3. Terminology
and are not considered standard.
3.1 Definitions of Terms Specific to This Standard:
1.3 This standard does not purport to address all of the
3.1.1 Gas Leak Detector Solutions—Also known as leak
safety concerns, if any, associated with its use. It is the
detection fluids, leak detector solutions, bubble solutions, and
responsibility of the user of this standard to establish appro-
soap solutions, designated in this standard as LDFs, are fluids
priate safety, health, and environmental practices and deter-
used to detect leaks in pressurized gas systems by the forma-
mine the applicability of regulatory limitations prior to use.
tion of bubbles at the leak site.
1.4 This international standard was developed in accor-
dance with internationally recognized principles on standard- 3.1.2 The terminology used herein, if not specifically de-
ization established in the Decision on Principles for the finedotherwise,shallbeinaccordancewithTerminologyG15.
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical 4. Summary of Test Method
Barriers to Trade (TBT) Committee.
4.1 This test method consists of three steps: The first step
consistsofrunningasampleofthetestspecimenstoverifythat
2. Referenced Documents
they are susceptible to stress corrosion cracking using Matts-
2.1 ASTM Standards:
son’sSolution(seePracticeG37).Thesecondstepistoexpose
B135SpecificationforSeamlessBrassTube[Metric]B0135
the specimens to a solution that does not cause SCC to verify
_B0135M
thatthetestenvironmentdoesnotcontaincomponentsthatcan
B135MSpecification for Seamless Brass Tube [Metric]
cause SCC to brass. The third step is to test the LDF to
(Withdrawn 2017)
determine if it causes SCC of the brass specimens within 15
D1193Specification for Reagent Water
wetting and evaporation cycles.
G1Practice for Preparing, Cleaning, and Evaluating Corro-
4.2 The specimen used in this test is a C-ring stressed to
sion Test Specimens
createatleast0.65%strainintheouterfibersofthespecimen.
4.3 Macroscopic examination of the specimens is carried
This test method is under the jurisdiction of ASTM Committee G01 on
out after every second wetting cycle and if cracking is
Corrosion of Metals and is the direct responsibility of Subcommittee G01.06 on
suspected the specimen is examined at higher magnifications
Environmentally Assisted Cracking.
for confirmation. Metallographic sectioning through the
Current edition approved May 1, 2021. Published May 2021. Originally
approved in 2005. Last previous edition approved in 2016 as G186–05 (2016). stressed area is used to verify minor cracking at the end of the
DOI: 10.1520/G0186-05R21.
fifteen cycles.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
4.4 LDFs that cause SCC in any specimens within 15
Standards volume information, refer to the standard’s Document Summary page on
wetting cycles are considered to have failed this test and not
the ASTM website.
suitable for use in pressurized gas systems with brass compo-
The last approved version of this historical standard is referenced on
www.astm.org. nents.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
G186 − 05 (2021)
5. Significance and Use 6.3 In this test, the susceptibility of the C-ring specimens to
crack in a particular test solution can be affected by the temper
5.1 Brass components are routinely used in compressed gas
of the brass alloy; therefore, it is crucial that the C-rings be
service for valves, pressure regulators, connectors and many
fabricated from hard drawn temper brass tubing that meets the
other components. Although soft brass is not susceptible to
minimum specified hardness requirements.
ammonia SCC, work-hardened brass is susceptible if its
hardnessexceedsabout54HR30T(55HRB)(Rockwellscale).
7. Reagents and Materials
Normal assembly of brass components should not induce
7.1 Reagent grade cuprous oxide (Cu O) and USP/FCC
sufficient work hardening to cause susceptibility to ammonia
grade glycerin (C H O ) conforming to specifications of the
3 8 3
SCC. However, it is has been observed that over-tightening of
committee on Analytical Reagents of the American Chemical
the components will render them susceptible to SCC, and the
Society, where such specifications are applicable, shall be
problem becomes more severe in older components that have
used.
been tightened many times. In this test, the specimens are
obtainedinthehardenedconditionandarestrainedbeyondthe 7.2 Finepurecopperpowderwithparticlesize<68µmshall
be used.
elastic limit to accelerate the tendency towards SCC.
5.2 It is normal practice to use LDFs to check pressurized 7.3 Solutionsusingwatershallbepreparedusingdistilledor
systems to assure that leaking is not occurring. LDFs are deionized water conforming to the purity requirements of
usually aqueous solutions containing surfactants that will form Specification D1193, Type IV reagent water.
bubbles at the site of a leak. If the LDF contains ammonia or
7.4 Leakdetectorsolutionsshallmeetmanufacturer’sspeci-
other agent that can cause SCC in brass, serious damage can
fications.
occur to the system that will compromise its safety and
7.5 Mattsson’s Solution shall be freshly prepared according
integrity.
to Practice G37.
5.3 It is important to test LDFs to assure that they do not
8. Hazards
causeSCCofbrassandtoassurethattheuseoftheseproducts
does not compromise the integrity of the pressure containing
8.1 Consult Material Safety Data Sheets (MSDS) for all
system.
chemicals both reagent and commercial before testing to gain
5.4 It has been found that corrosion of brass is necessary a full understanding of any potential hazards.
before SCC can occur.The reason for this is that the corrosion
8.2 The test solutions present no undue safety hazard. It is
process results in cupric and cuprous ions accumulating in the
recommended, however, that appropriate personnel protection
electrolyte. Therefore, adding copper metal and cuprous oxide
equipment such as resistant gloves and shatterproof eyewear
(Cu O) to the aqueous solution accelerates the SCC process if
withsideshieldsbewornwhenthechemicalsorspecimensare
agents that cause SCC are present. However, adding these
handled.
components to a solution that does not cause SCC will not
8.3 The solutions contain copper and are thus considered
make stressed brass crack.
poisonous so they should not be ingested.
5.5 Repeated application of the solution to the specimen
8.4 Ammonium sulfate, (NH ) SO , in the Mattsson’s solu-
4 2 4
followed by a drying period causes the components in the
tion has been reported to be allergenic. Repeated short-time
solution to concentrate thereby further increasing the rate of
skin contact with the solution over extended periods of time
cracking. This also simulates service where a system may be
should be avoided.
tested many times during its life. These features of the test
method accelerate the test and allow an answer to be obtained 8.5 The fumes given off by the Mattsson’s test solution
more rapidly. contain ammonia. The least detectable ammonia odor corre-
spondstoaconcentrationof50ppm;100ppmcanbetolerated
5.6 This test method applies only to brasses. Successful
for several hours without serious disturbance; 700 ppm causes
passage of this test does not assure that the LDF will be
immediate eye irritation; and greater than 5000 ppm can be
acceptable for use on other alloy systems such as stainless
lethal. The mixing and the actual testing with Mattsson’s
steels or aluminum alloys.
solution should therefore be run in a well-ventilated area.
6. Interferences
9. Test Solutions
6.1 When conducting this test, it is very important that the
9.1 Control Solution (benign water solution)—Add2.5gCu
air not be contaminated with ammonia vapors. Reagent bottles
powder and 2.5 g Cu O to 1000 mLof H O. Then add 10 mL
2 2
withammoniumhydroxideorotherteststhatinvolveammonia
of glycerin to solution. Shake solution vigorously to thor-
or its compounds including amines must not be in the vicinity
oughly mix contents.
of these tests. This also includes Mattsson’s test solution.
6.2 Cross contamination may result in false stress corrosion
Reagent Chemicals, American Chemical Society Specifications, American
Chemical Society, Washington, DC. For Suggestions on the testing of reagents not
cracking results therefore concurrent exposure tests with dif-
listed by the American Chemical Society, see Annual Standards for Laboratory
ferent leak detector solutions should be conducted in such a
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
way that any set of samples does not influence the results of
and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
any of the other samples. MD.
G186 − 05 (2021)
9.2 Leak Detector Solutions—Add 2.5 g Cu powder and this test (for example, Type 316 stainless steel, UNS S31600).
2.5g Cu O to 1000 mL of each manufacturer’s solution to be Insulationwashersshallbemadefromahardresistantmaterial
tested. Shake solutions vigorously to thoroughly mix contents.
to prevent relaxation of the stressed C-ring specimen (for
example, alumina). Refer to Fig. 1.
NOTE 1—Some of the solids will settle out of the solutions in between
cycles, therefore, it is very important to shake the solutions vigorously
10.5 Pre-test Condition—C-rings will be unstressed prior to
prior to their use in the wetting cycle.
testing.
10. Test Specimen
10.6 Stressing Method—Constant-strain stressing method
10.1 Type and Size—An unnotched C-ring in accordance
shall be used in stressing the C-rings (refer to Practice G38).
with Practice G38 shall be used (Fig. 1). C-rings shall have an
Tensile stress will be introduced on the exterior of the ring by
outer diameter (OD) between 1.0in. to 2.0 in. (25.4mm to
tightening a bolt centered on the diameter of the ring.
50.8mm)andthicknessbetween0.065in.to0.25in.(1.65mm
to 6.4 mm). Widths shall be fixed at 0.75 in. (19.0 mm). 10.7 Surface Preparation—The specimen surface should be
free of oil, grease, and dirt. This usually entails cleaning with
10.2 Alloy Composition and Temper—Test specimens shall
organic solvent such as acetone followed by an alcohol rinse.
be fabricated from copper alloy (UNS C27200) seamless tube
with a H80 hard-drawn temper. The hard drawn temper shall
NOTE2—Everyprecautionshallbetakentomaintaintheintegrityofthe
have a minimum hardness of 70 on the 30T Rockwell scale
surfaceafterthefinalpreparation.Avoidroughhandlingthatcouldmarthe
which corresponds to minimum tensile strength of 66 ksi
surface and handle with gloves to prevent fingerprinting and the transfer
(455MPa). Refer to Specifications B135 and B135M for tube of contaminants.
information.
11. Test Setup and Apparatus
10.3 SurfaceFinish—Specimensshallhavea120gritfinish.
Grind marks shall be in the circumferential direction.
11.1 C-ring Test Assembly—Individual C-ring specimens
shall be placed apex down in a glass-fiber-wick covered dish
10.4 Restraining Hardware—Nuts, bolts, and flat washers
shall be made from a metal resistant to the chemicals used in (Fig. 2).
FIG. 1 C-ring Specimen
G186 − 05 (2021)
FIG. 2 C-ring Specimen Ready for Exposure to Test Solution
11.2 Exposure Dish—The individual dishes shall be made 12.3.3 Mattsson’s solution should be checked to make sure
out of a material that will not react with the chemicals being it conforms to Practice G37.
used for the exposure (for example, glass, polystyrene, poly-
12.4 Follow steps in Annex A1 to test the C-rings in
carbonate). The required dish dimensions are 2.36in. to
Mattsson’s Solution.
3.94in. (60mm to 100mm) diameter and 0.59in. to 0.79in.
(15mm to 20mm) height.
13. Air Conditions
11.3 Wick Material—Borosilicateglasswickmaterialwitha
13.1 Temperature—Airtemperatureshallbemaintainedina
fiber diameter of about 0.3 mil (8 µm) shall be used.
range of 70°F to 80°F (21°C to 27°C) throughout the entire
11.4 Number of Specimens—Five individual C-ring speci-
test duration.
men test assemblies will be used for each leak detector or
control solution to be tested.
13.2 Relative Humidity—Percentrelativehumidityoftheair
shall be maintained in a range of 15% to 60% throughout the
11.5 Test Assembly Arrangement—Individual exposure
entire test cycle.
dishes shall be laid out such that there is at least a 1.0 ft
(305mm) separation between groups of specimens (Fig. 3).
13.3 Air Circulation:
The control solution specimens shall always be positioned in
13.3.1 Air circulation is considered to be very important to
the center of the test group.
testingsinceitaffectstherateatwhichthesolutionslosewater
12. Calibration and Standardization
by evaporation. Optimum conditions for air circulation have
not been established, but recommendations described in 13.3.2
12.1 When a new batch of specimens is to be used, it is
shall be considered.
necessary to first test a representative number of C-rings from
13.3.2 The most important consideration is to achieve
the batch with Mattsson’s solution.
moderate evaporation of the test solutions in a 2 day to 3 day
12.2 Mattsson’s Solution test must produce cracking of the
ti
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