1、Designation: G36 94 (Reapproved 2013)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 and health practices and determine the applica-bility of regulatory limitations prior to use. See Section 7 forspecific safety precautions.2. Referenced Documents2.1 ASTM Standards:5D1193 Specification for Reagent WaterG1 Practice for Preparing, C
8、leaning, and Evaluating Corro-sion Test SpecimensG15 Terminology Relating to Corrosion and Corrosion Test-ing (Withdrawn 2010)6G30 Practice for Making and Using U-Bend Stress-Corrosion Test Specimens3.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 this prac-tice see Terminology G15.4. S
9、ummary 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 solution boils, it is adjusted to maintain
10、 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, the specimens should be givenperiodic in
11、spections. 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 suscepti
12、bility for stainless steels and related1This 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 May 1, 2013. Published July 2013. Originally approvedin 1
13、973. Last previous edition approved in 2006 as G36 94 (2006). DOI:10.1520/G0036-94R13.2Available 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 SolutionsThei
14、r Application 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.
15、16.4The 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, 1
16、945, p. 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
17、volume 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 States1alloys in aqueous
18、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 Resistance to stress-corrosion cracking in boiling mag-nesiu
19、m 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 stainless alloys. This leads to the possibility of confusingstre
20、ss-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 resistantalloys, or a combination thereof are being used. Carefulexam
21、ination 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 stressed specimenwhile maintaining a constant temperature a
22、nd 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 the boiling point of thesolution with a reduction in the time
23、 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 shall beused in all tests. Unless otherwise indicated, it is in
24、tended 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 the reagent is ofsufficiently high purity to permit its use wi
25、thout 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 6 1.0C (311.0 61.8F) is used in this test. A second 25 weigh
26、t 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 Erlenmeyer flask or other container, weigh 600 g ofreagent grade MgC
27、l26H2O 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 condenser in place, leavingoff the trap. Hook up the cooling wa
28、ter 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). Use extreme caution whenadding the water to the boiling ma
29、gnesium 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 ofMgCl26H2O through the condenser until a temperature of 155.0C(311.
30、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.8. Safety Precautions8.1 When cold, magnesium chloride can be handled withthe minimum protecti
31、ve equipment of rubber gloves andgoggles. Maximum protective measures should be taken toprevent boiling magnesium chloride from coming into contactwith the skin. Severe burns can result as the hot magnesium7Reagent Chemicals, American Chemical Society Specifications , AmericanChemical Society, Washi
32、ngton, 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. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.FIG. 1 Boi
33、ling Points of Aqueous Magnesium Chloride Solutionsat One Atmosphere as a Function of Concentration2G36 94 (2013)2chloride adheres to the skin forming a crust which causes deepburns. The severity of the burns can be reduced by takingproper and immediate first aid measures and by contacting aphysicia
34、n.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 heating or boiling of magnesium chloride shouldbe done in a shiel
35、ded 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 gloves.8.1.4 Disposal of the magnesium chloride should be ac
36、com-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 thesolid layer of magnesium chloride can cause sufficient stress
37、esthrough 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 theapplied stress does not cause mechanical rupture when thecross s
38、ection 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 deleterious effects of the corrosion products of onealloy o
39、n 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 design for two types of test specimens thatcan be used with the s
40、uggested 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 by adding a known quantity ofreagent grade MgCl26H2O, reagent
41、 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 solution reaches the constant-boilingtemperature of 155 6 1.0C (31
42、1.0 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 immersion, vapor phase exposure,or a combination of immersion and
43、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 necessary to determine the time when cracks firstappear and
44、 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 ofpolished and etched cross sections at higher magnifications ar
45、enecessary 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 specimens whose cross sections have beenreduced by general or p
46、itting 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 containing alloy; stainless steels; stress-corrosion cracking
47、8For 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.) Se
48、e alsoSection 2 of this practice.G36 94 (2013)3APPENDIX(Nonmandatory Information)X1. TEST APPARATUSX1.1 The following test apparatus is suggested for its abilityto maintain a constant temperature and solution concentrationover a long period of time. Use of this apparatus is notmandatory and is prese
49、nted here only as a guide.X1.2 The suggested test apparatus is shown in Fig. X1.1 andthe design details are given below:X1.2.1 Flaskthe 1-L Erlenmeyer flask (Fig. X1.2) has aground-glass 45/50 outer joint at the mouth and a 10/30ground-glass outer joint to hold the thermometer.NOTE X1.1Other flasks or containers may be used. For tests requiringa larger container, a 3-L round bottom flask with a 71/60 ground-glassouter joint can also be used. The height of the condenser (X1.2.2) and thedimensions of the trap (Fig. X1.3) can be the same as for the 1-LErl
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