1、Designation: G 186 05Standard Test Method forDetermining Whether Gas-Leak-Detector Fluid SolutionsCan Cause Stress Corrosion Cracking of Brass Alloys1This standard is issued under the fixed designation G 186; the number immediately following the designation indicates the year oforiginal adoption or,
2、 in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers an accelerated test method forevaluating the tendency o
3、f gas leak detection fluids (LDFs) tocause stress corrosion cracking (SCC) of brass components incompressed gas service.1.2 The values stated in inch-pound units are to be regardedas standard. The values given in parentheses are mathematicalconversions to SI units that are provided for information o
4、nlyand are not considered standard.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and to determine theapplicability of regulatory limi
5、tations prior to use.2. Referenced Documents2.1 ASTM Standards:2B 135 Specification for Seamless Brass TubeB 135M Specification for Seamless Brass Tube MetricD 1193 Specification for Reagent WaterG1 Practice for Preparing, Cleaning, and Evaluating Cor-rosion Test SpecimensG15 Terminology Relating to
6、 Corrosion and CorrosionTestingG37 Practice for Use of Mattssons Solution of pH 7.2 toEvaluate the Stress-Corrosion Cracking Susceptibility ofCopper-Zinc AlloysG38 Practice for Making and Using C-ring Stress-Corrosion Test Specimens3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1
7、.1 Gas Leak Detector SolutionsAlso known as leakdetection fluids, leak detector solutions, bubble solutions, andsoap solutions, designated in this standard as LDFs, are fluidsused to detect leaks in pressurized gas systems by the forma-tion of bubbles at the leak site.3.1.2 The terminology used here
8、in, if not specifically de-fined otherwise, shall be in accordance with Terminology G15.4. Summary of Test Method4.1 This test method consists of three steps: The first stepconsists of running a sample of the test specimens to verify thatthey are susceptible to stress corrosion cracking using Matts-
9、sons Solution (see Practice G37). The second step is to exposethe specimens to a solution that does not cause SCC to verifythat the test environment does not contain components that cancause SCC to brass. The third step is to test the LDF todetermine if it causes SCC of the brass specimens within 15
10、wetting and evaporation cycles.4.2 The specimen used in this test is a C-ring stressed tocreate at least 0.65% strain in the outer fibers of the specimen.4.3 Macroscopic examination of the specimens is carriedout after every second wetting cycle and if cracking issuspected the specimen is examined a
11、t higher magnificationsfor confirmation. Metallographic sectioning through thestressed area is used to verify minor cracking at the end of thefifteen cycles.4.4 LDFs that cause SCC in any specimens within 15wetting cycles are considered to have failed this test and notsuitable for use in pressurized
12、 gas systems with brass compo-nents.5. Significance and Use5.1 Brass components are routinely used in compressed gasservice for valves, pressure regulators, connectors and manyother components. Although soft brass is not susceptible toammonia SCC, work-hardened brass is susceptible if itshardness ex
13、ceeds about 54 HR 30T (55HRB) (Rockwell scale).Normal assembly of brass components should not inducesufficient work hardening to cause susceptibility to ammoniaSCC. However, it is has been observed that over-tightening ofthe components will render them susceptible to SCC, and the1This test method is
14、 under the jurisdiction of ASTM Committee G01 onCorrosion of Metals, and is the direct responsibility of Subcommittee G01.06 onEnvironmentally Assisted Cracking.Current edition approved July 1, 2005. Published July 2005.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact
15、ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.problem becomes more sever
16、e in older components that havebeen tightened many times. In this test, the specimens areobtained in the hardened condition and are strained beyond theelastic limit to accelerate the tendency towards SCC.5.2 It is normal practice to use LDFs to check pressurizedsystems to assure that leaking is not
17、occurring. LDFs areusually aqueous solutions containing surfactants that will formbubbles at the site of a leak. If the LDF contains ammonia orother agent that can cause SCC in brass, serious damage canoccur to the system that will compromise its safety andintegrity.5.3 It is important to test LDFs
18、to assure that they do notcause SCC of brass and to assure that the use of these productsdoes not compromise the integrity of the pressure containingsystem.5.4 It has been found that corrosion of brass is necessarybefore SCC can occur. The reason for this is that the corrosionprocess results in cupr
19、ic and cuprous ions accumulating in theelectrolyte. Therefore, adding copper metal and cuprous oxide(Cu2O) to the aqueous solution accelerates the SCC process ifagents that cause SCC are present. However, adding thesecomponents to a solution that does not cause SCC will notmake stressed brass crack.
20、5.5 Repeated application of the solution to the specimenfollowed by a drying period causes the components in thesolution to concentrate thereby further increasing the rate ofcracking. This also simulates service where a system may betested many times during its life. These features of the testmethod
21、 accelerate the test and allow an answer to be obtainedmore rapidly.5.6 This test method applies only to brasses. Successfulpassage of this test does not assure that the LDF will beacceptable for use on other alloy systems such as stainlesssteels or aluminum alloys.6. Interferences6.1 When conductin
22、g this test, it is very important that theair not be contaminated with ammonia vapors. Reagent bottleswith ammonium hydroxide or other tests that involve ammoniaor its compounds including amines must not be in the vicinityof these tests. This also includes Mattssons test solution.6.2 Cross contamina
23、tion may result in false stress corrosioncracking results therefore concurrent exposure tests with dif-ferent leak detector solutions should be conducted in such away that any set of samples does not influence the results ofany of the other samples.6.3 In this test, the susceptibility of the C-ring
24、specimens tocrack in a particular test solution can be affected by the temperof the brass alloy; therefore, it is crucial that the C-rings befabricated from hard drawn temper brass tubing that meets theminimum specified hardness requirements.7. Reagents and Materials7.1 Reagent grade cuprous oxide (
25、Cu2O) and USP/FCCgrade glycerin (C3H8O3) conforming to specifications of thecommittee on Analytical Reagents of the American ChemicalSociety, where such specifications are applicable,3shall beused.7.2 Fine pure copper powder with particle size 68 m shallbe used.7.3 Solutions using water shall be pre
26、pared using distilled ordeionized water conforming to the purity requirements ofSpecification D 1193, Type IV reagent water.7.4 Leak detector solutions shall meet manufacturers speci-fications.7.5 Mattssons Solution shall be freshly prepared accordingto Practice G37.8. Hazards8.1 Consult Material Sa
27、fety Data Sheets (MSDS) for allchemicals both reagent and commercial before testing to gaina full understanding of any potential hazards.8.2 The test solutions present no undue safety hazard. It isrecommended, however, that appropriate personnel protectionequipment such as resistant gloves and shatt
28、erproof eyewearwith side shields be worn when the chemicals or specimens arehandled.8.3 The solutions contain copper and are thus consideredpoisonous so they should not be ingested.8.4 Ammonium sulfate, (NH4)2SO4, in the Mattssons solu-tion has been reported to be allergenic. Repeated short-timeskin
29、 contact with the solution over extended periods of timeshould be avoided.8.5 The fumes given off by the Mattssons test solutioncontain ammonia. The least detectable ammonia odor corre-sponds to a concentration of 50 ppm; 100 ppm can be toleratedfor several hours without serious disturbance; 700 ppm
30、 causesimmediate eye irritation; and greater than 5000 ppm can belethal. The mixing and the actual testing with Mattssonssolution should therefore be run in a well-ventilated area.9. Test Solutions9.1 Control Solution (benign water solution)Add 2.5 g Cupowder and 2.5 g Cu2O to 1000 ml of H2O. Then a
31、dd 10ml ofglycerin to solution. Shake solution vigorously to thoroughlymix contents.9.2 Leak Detector SolutionsAdd 2.5 g Cu powder and 2.5gCu2O to 1000 ml of each manufacturers solution to betested. Shake solutions vigorously to thoroughly mix contents.NOTE 1Some of the solids will settle out of the
32、 solutions in betweencycles, therefore, it is very important to shake the solutions vigorouslyprior to their use in the wetting cycle.3Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For Suggestions on the testing of reagents notlisted by the Am
33、erican Chemical Society, see Annual Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.G18605210. Test Specimen10.1 Type and SizeAn unnotched C-ring in accordancewith Pra
34、ctice G38shall be used (Fig. 1). C-rings shall have anouter diameter (OD) between 1.0 to 2.0 in. (25.4 to 50.8 mm)and thickness between 0.065 to 0.25 in. (1.65 to 6.4 mm).Widths shall be fixed at 0.75 in. (19.0 mm).10.2 Alloy Composition and TemperTest specimens shallbe fabricated from copper alloy
35、(UNS C27200) seamless tubewith a H80 hard-drawn temper. The hard drawn temper shallhave a minimum hardness of 70 on the 30T Rockwell scalewhich corresponds to minimum tensile strength of 66 ksi (455MPa). Refer to Specifications B 135 and B 135M for tubeinformation.10.3 Surface FinishSpecimens shall
36、have a 120-grit fin-ish. Grind marks shall be in the circumferential direction.10.4 Restraining hardwareNuts, bolts, and flat washersshall be made from a metal resistant to the chemicals used inthis test (for example, Type 316 stainless steel, UNS S31600).Insulation washers shall be made from a hard
37、 resistant materialto prevent relaxation of the stressed C-ring specimen (forexample, alumina). Refer to Fig. 1.10.5 Pre-test ConditionC-rings will be un-stressed priorto testing.10.6 Stressing MethodConstant-strain stressing methodshall be used in stressing the C-rings (refer to Practice G38).Tensi
38、le stress will be introduced on the exterior of the ring bytightening a bolt centered on the diameter of the ring.10.7 Surface PreparationThe specimen surface should befree of oil, grease, and dirt. This usually entails cleaning withorganic solvent such as acetone followed by an alcohol rinse.NOTE 2
39、Every precaution shall be taken to maintain the integrity ofthe surface after the final preparation.Avoid rough handling that could marthe surface and handle with gloves to prevent fingerprinting and thetransfer of contaminants.11. Test Setup and Apparatus11.1 C-ring Test AssemblyIndividual C-ring s
40、pecimensshall be placed apex down in a glass-fiber-wick covered dish(Fig. 3)11.2 Exposure DishThe individual dishes shall be madeout of a material that will not react with the chemicals beingused for the exposure (for example, glass, polystyrene, poly-carbonate). The required dish dimensions are 2.3
41、6- to 3.94-in.(60- to 100-mm) diameter and 0.59- to 0.79-in. (15- to 20-mm)height.11.3 Wick MaterialBorosilicate glass wick material with afiber diameter of about 0.3 mil (8 m) shall be used.11.4 Number of SpecimensFive individual C-ring speci-men test assemblies will be used for each leak detector
42、orcontrol solution to be tested.11.5 Test Assembly ArrangementIndividual exposuredishes shall be laid out such that there is at least a 1.0 ft (305mm) separation between groups of specimens (Fig. 4). Thecontrol solution specimens shall always be positioned in thecenter of the test group.12. Calibrat
43、ion and Standardization12.1 When a new batch of specimens is to be used, it isnecessary to first test a representative number of C-rings fromthe batch with Mattssons solution.12.2 Mattssons Solution test must produce cracking of thetest specimens before any further testing is carried out.12.3 If cra
44、cking is not produced during the predescribedMattssons solution test the following variables need to beverified before rejecting the batch of C-rings.FIG. 1 C-ring SpecimenG18605312.3.1 Specimen material hardness shall exceed 70 HR 30T(Rockwell scale).12.3.2 Strain should be checked with a strain ga
45、uge ifhardness is sufficient.12.3.3 Mattssons solution should be checked to make sureit conforms to Practice G37.12.4 Follow steps in Annex Section Annex A1 to test theC-rings in Mattssons Solution.FIG. 2 Caliper Measurement of C-rings DeflectionFIG. 3 C-ring Specimen Ready for Exposure to Test Solu
46、tionG18605413. Air Conditions13.1 TemperatureAir temperature shall be maintained in arange of 70 80F (21 27C) throughout the entire testduration.13.2 Relative HumidityPercent relative humidity of theair shall be maintained in a range of 15 to 60 % throughout theentire test cycle.13.3 Air Circulation
47、13.3.1 Air circulation is considered to be very important totesting since it affects the rate at which the solutions lose waterby evaporation. Optimum conditions for air circulation havenot been established, but recommendations described in 13.3.2shall be considered.13.3.2 The most important conside
48、ration is to achievemoderate evaporation of the test solutions in a 2-3 day timeperiod.13.3.3 Stagnant air conditions should be avoided.13.3.4 Testing in a ventilated enclosure may be required toachieve adequate circulation.NOTE 3Care should be taken to avoid overnight and weekendchanges in operatio
49、n of the laboratory heating, ventilation, and airconditioning equipment which could result in systematic excursionsoutside the desired temperature, humidity, and air circulation ranges.14. Procedure14.1 Leak detector fluid and control solutions are testedconcurrently. No Mattssons solution tests shall be conductedwhile control or test solutions are in progress.14.2 Stressing of the C-rings:14.2.1 The specimens shall be stressed the same way forexposures in the leak detector fluid and control solutions.14.2.2 Individual specimens should be
