1、Designation: G36 94 (Reapproved 2018)Standard Practice forEvaluating Stress-Corrosion-Cracking Resistance of Metalsand Alloys in a Boiling Magnesium Chloride Solution1This standard is issued under the fixed designation G36; the number immediately following the designation indicates the year of origi
2、naladoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.Asuperscriptepsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice describes a procedure for conductingstress-corrosion cr
3、acking tests in a boiling magnesium chloridesolution. Although this test may be performed using variousconcentrations of magnesium chloride, this procedure covers atest solution held at a constant boiling temperature of 155.0 61.0C (311.0 6 1.8F). The boiling points of aqueous magne-sium chloride so
4、lutions at one atmosphere pressure as afunction of concentration are shown graphically in Fig. 1.2Asuggested test apparatus capable of maintaining solution con-centration and temperature within the prescribed limits forextended periods of time is also described herein.31.2 The boiling magnesium chlo
5、ride test is applicable towrought, cast, and welded stainless steels and related alloys. Itis a method for detecting the effects of composition, heattreatment, surface finish, microstructure, and stress on thesusceptibility of these materials to chloride stress corrosioncracking.41.3 This practice i
6、s concerned primarily with the testsolution, which may be used with a variety of stress corrosiontest specimens, surface finishes, and methods of applyingstress.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the us
7、er of this standard to establish appro-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.See Section 7 for specific safety precautions.1.5 This international standard was developed in accor-dance with internationally recognized
8、 principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:5D1193 Specification for Re
9、agent WaterG1 Practice for Preparing, Cleaning, and Evaluating Corro-sion Test SpecimensG15 Terminology Relating to Corrosion and Corrosion Test-ing (Withdrawn 2010)6G30 Practice for Making and Using U-Bend Stress-Corrosion Test Specimens3. Terminology3.1 DefinitionsFor definitions of terms used in
10、this prac-tice see Terminology G15.4. Summary of Practice4.1 A predetermined quantity of reagent grade magnesiumchloride and some distilled water are added to a container. Thecontainer and contents, with thermometer and condenseraffixed, are placed on a source of heat. When the magnesiumchloride sol
11、ution boils, it is adjusted to maintain the desiredconcentration and boiling point through the addition of smallquantities of either water or salt.4.2 After the solution has stabilized at the desired boilingpoint for the test, the stressed specimens are added. Dependingupon the intent of the test, t
12、he specimens should be given1This practice is under the jurisdiction of ASTM Committee G01 on Corrosionof Metals and is the direct responsibility of Subcommittee G01.06 on Environmen-tally Assisted Cracking.Current edition approved Oct. 1, 2018. Published November 2018. Originallyapproved in 1973. L
13、ast previous edition approved in 2013 as G36 94 (2013). DOI:10.1520/G0036-94R18.2Available data on the relationship of concentrations and boiling points ofmagnesium chloride solutions are critically reviewed and supplemented by I. B.Casale in “Boiling Points of Magnesium Chloride SolutionsTheir Appl
14、ication inStress Corrosion Studies,” Corrosion, Vol 23, 1967, pp. 31417.3The apparatus and test procedures for maintaining constant boiling tempera-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. 16.4The
15、 use of concentrated magnesium chloride solutions for determining thesusceptibility to stress corrosion cracking of austenitic and ferritic stainless steelsand related nickel-base alloys was first described by M. A. Scheil, Symposium onStress Corrosion Cracking of Metals, ASTM STP 64, ASTM, 1945, p.
16、 395.(Although currently out of print, copies may be obtained from University Micro-films, Inc., 300 North Zeeb Rd., Ann Arbor, MI 48106.)5For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume
17、information, refer to the standards Document Summary page onthe ASTM website.6The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standar
18、d was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1periodic
19、 inspections. If the duration of test exceeds 7 days, thesolution should either be changed or the suggested or similartest apparatus used.5. Significance and Use5.1 For most applications, this environment provides anaccelerated method of ranking the relative degree of stress-corrosion cracking susce
20、ptibility for stainless steels and relatedalloys in aqueous chloride-containing environments. Materialsthat normally provide acceptable resistance in hot chlorideservice may crack in this test. The test may not be relevant tostress-corrosion cracking in polythionic acid or caustic envi-ronments.5.2
21、Resistance to stress-corrosion cracking in boiling mag-nesium chloride (155.0C (311.0F) should, where possible,be correlated to resistance in service for the materials ofinterest. However, such correlations may not always be pos-sible.5.3 Boiling magnesium chloride may also cause pitting ofmany stai
22、nless alloys. This leads to the possibility of confusingstress-corrosion failures with mechanical failures induced bycorrosion-reduced net cross sections. This danger is particu-larly great when small cross section samples, high appliedstress levels, long exposure periods, stress-corrosion resistant
23、alloys, or a combination thereof are being used. Carefulexamination is recommended for correct diagnosis of the causeof failure.6. Apparatus6.1 Any inert, transparent apparatus with provisions for athermometer and water-cooled condenser can be used, pro-vided that it has been designed to contain the
24、 stressed specimenwhile maintaining a constant temperature and concentration ofthe magnesium chloride solution by minimizing or preventinglosses of condensate and water vapor during prolonged periodsof test. Small losses of water from a solution of magnesiumchloride will lead to large increases in t
25、he boiling point of thesolution with a reduction in the time to failure of a specimen bystress corrosion cracking.Asuggested apparatus, shown in Fig.X1.1, meets these requirements. Design details of this appara-tus are given in Appendix X1.7. Reagents7.1 Purity of ReagentsReagent grade chemicals sha
26、ll beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.7Other grades may beused, provided it is first ascertained that th
27、e reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.7.2 Purity of WaterReagent water Type IV (SpecificationD1193) shall be used to prepare the test solutions.7.3 Magnesium Chloride (MgCl26H2O)A solution ofmagnesium chloride that boils at 155.0
28、 6 1.0C (311.0 61.8F) is used in this test. A second 25 weight percent solutionof magnesium chloride is required for the trap if the testduration exceeds seven days without a solution change and thesuggested apparatus is used.7.3.1 To prepare about 400 mL of the test solution for use ina 1-L Erlenme
29、yer flask or other container, weigh 600 g ofreagent grade MgCl26H2O and add this to the flask containinga thermometer along with 15 mL of reagent water.7.3.2 Add 10 to 15 boiling chips or other boiling aids.7.3.3 Heat by placing the flask on a hot plate or othersuitable source of heat and put the co
30、ndenser in place, leavingoff the trap. Hook up the cooling water supply to the condenser.7.3.4 When the solution boils vigorously and there is nomore dripping of condensate, slowly add small quantities (4 to5 mL) of reagent water at the top of the condenser to reduce thetemperature to 155.0C (311.0F
31、). Use extreme caution whenadding the water to the boiling magnesium chloride solution.Cool water can form a layer on top of the magnesium chloride,and when it reaches the bottom of the flask, bumping can occur.Use a protective shield.NOTE 1If too much water has been added, add some crystals ofMgCl2
32、6H2O through the condenser until a temperature of 155.0C(311.0F) is attained.7.4 To prepare the 25 weight percent solution for the trap(Fig. X1.3), place 53.4 g of MgCl26H2O and 46.6 mL ofreagent water in a flask and allow the crystals to dissolve atroom temperature.7Reagent Chemicals, American Chem
33、ical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Ph
34、armacopeial Convention, Inc. (USPC), Rockville,MD.FIG. 1 Boiling Points of Aqueous Magnesium Chloride Solutionsat One Atmosphere as a Function of Concentration2G36 94 (2018)28. Safety Precautions8.1 When cold, magnesium chloride can be handled withthe minimum protective equipment of rubber gloves an
35、dgoggles. Maximum protective measures should be taken toprevent boiling magnesium chloride from coming into contactwith the skin. Severe burns can result as the hot magnesiumchloride adheres to the skin forming a crust which causes deepburns. The severity of the burns can be reduced by takingproper
36、and immediate first aid measures and by contacting aphysician.8.1.1 In the advent of a spill or accident, the hot magnesiumchloride should be quickly flushed from the skin with largequantities of cold water to minimize the burning, followed byimmediate first aid and medical attention.8.1.2 All heati
37、ng or boiling of magnesium chloride shouldbe done in a shielded area with protection by hood or shield, orboth.8.1.3 Minimum personal protective equipment for handlingboiling magnesium chloride should include safety glasses orgoggles, face shield, laboratory coat, and rubber gloves withcotton inner
38、gloves.8.1.4 Disposal of the magnesium chloride should be accom-plished in accordance with the material safety data suppliedwith the chemical or by the chemical manufacturer or supplier.8.1.5 Do not remelt the solidified magnesium chloride.Localized melting adjacent to the heat source and below thes
39、olid layer of magnesium chloride can cause sufficient stressesthrough volume expansion to crack the containing vessel.9. Test Specimens9.1 Any type of stress corrosion test specimen can be usedwith this test solution.8See Practice G1 and G30.9.2 The test specimen must be thick enough so that theappl
40、ied stress does not cause mechanical rupture when thecross section is reduced by pitting or general corrosion.9.3 Whenever possible, only one specimen should be testedin each flask. If more than one specimen is tested in a flask, thespecimens should be of the same alloy in order to avoid thepossible
41、 deleterious effects of the corrosion products of onealloy on the performance of the other alloy.9.4 The test specimens must be kept from direct contactwith heated surfaces by glass supports. Metal specimen holdersused for stressing specimens should also be supported on glassrods or tubes. The desig
42、n for two types of test specimens thatcan be used with the suggested apparatus can be found infootnote 3.10. Procedure10.1 Collect the apparatus and test specimens in preparationfor the test. If the suggested test apparatus is used, assemble asoutlined in Appendix X1.10.2 Prepare the test solution b
43、y adding a known quantity ofreagent grade MgCl26H2O, reagent water, and some boilingaids to the container fitted with a thermometer and water-cooled condenser.After applying heat, adjust the concentrationof the solution by slowly adding small quantities (4 to 5 mL)of distilled water until the soluti
44、on reaches the constant-boilingtemperature of 155 6 1.0C (311.0 6 1.8F). Now place thepreviously prepared test specimens in the container.11. Report11.1 Record starting time, type of specimen, stress, and typeexposure. A clear distinction must be made in the type ofexposure; that is, complete immers
45、ion, vapor phase exposure,or a combination of immersion and exposure to the vaporphase. The time required to initiate cracks, the rate of crackgrowth, and the time to failure may be of importance, depend-ing upon the purpose of the test.11.1.1 Periodic removal of the specimen from the solutionmay be
46、 necessary to determine the time when cracks firstappear and the rate of crack propagation. Microscopic exami-nation of polished surfaces is required to detect crack initiation.All stressed surfaces should be examined at magnifications upto 20. Metallographic examination of exposed surfaces and ofpo
47、lished and etched cross sections at higher magnifications arenecessary at the end of the test to establish the type of cracking:transgranular, intergranular, or mixed.11.1.2 Ruptured specimens should also be examined forevidence of mechanical failure resulting from the action ofapplied stress on spe
48、cimens whose cross sections have beenreduced by general or pitting corrosion, or both. Such failuresusually show evidence of ductility. Duplicate tests with thickerspecimens should be made in case of doubt.12. Keywords12.1 accelerated test; apparatus; boiling magnesium chlo-ride; glassware; nickel c
49、ontaining alloy; stainless steels; stress-corrosion cracking8For a comprehensive discussion of the various types of test specimensavailable, see “Stress Corrosion Testing Methods,” Stress Corrosion Testing, ASTMSTP 425, ASTM. (Although currently out of print, copies may be obtained fromUniversity Microfilms, Inc., 300 North Zeeb Rd., Ann Arbor, MI 48106.) See alsoSection 2 of this practice.G36 94 (2018)3APPENDIX(Nonmandatory Information)X1. TEST APPARATUSX1.1 The following test apparatus is suggested for its abilityto maintain a constant temperature and
