1、Designation: G 35 98 (Reapproved 2004)Standard Practice forDetermining the Susceptibility of Stainless Steels andRelated Nickel-Chromium-Iron Alloys to Stress-CorrosionCracking in Polythionic Acids1This standard is issued under the fixed designation G 35; the number immediately following the designa
2、tion indicates the year of originaladoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscriptepsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice describes procedur
3、es for preparing andconducting the polythionic acid test at room temperature, 22 to25C (72 to 77F), to determine the relative susceptibility ofstainless steels or other related materials (nickel-chromiumironalloys) to intergranular stress corrosion cracking.1.2 This practice can be used to evaluate
4、stainless steels orother materials in the “as received” condition or after beingsubjected to high-temperature service, 482 to 815C (900 to1500F), for prolonged periods of time.1.3 This practice can be applied to wrought products,castings, and weld metal of stainless steels or other relatedmaterials
5、to be used in environments containing sulfur orsulfides. Other materials capable of being sensitized can alsobe tested in accordance with this test.1.4 This practice may be used with a variety of stresscorrosion test specimens, surface finishes, and methods ofapplying stress.1.5 This standard does n
6、ot 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 determine the applica-bility of regulatory limitations prior to use. For more specificprecautionary stateme
7、nts, see Section 7.2. Referenced Documents2.1 ASTM Standards:2D 1193 Specification for Reagent WaterG 1 Practice for Preparing, Cleaning, and Evaluating Cor-rosion Test SpecimensG 15 Terminology Relating to Corrosion and CorrosionTestingG 30 Practice for Making and Using U-Bend Stress-Corrosion Test
8、 Specimens3. Summary of Practice3.1 The stressed specimens are placed in the container alongwith a sensitized and stressed AISI Type 302 (UNS S30200) orType 304 (UNS S30400) stainless steel control specimen. Asufficient amount of the previously prepared polythionic acidsolution is added to the conta
9、iner to immerse the test speci-mens. A cover is placed on the container and the test is carriedout at room temperature.4. Significance and Use4.1 This environment provides a way of evaluating theresistance of stainless steels and related alloys to intergranularstress corrosion cracking. Failure is a
10、ccelerated by the presenceof increasing amounts of intergranular precipitate. Results forthe polythionic acid test have not been correlated exactly withthose of intergranular corrosion tests. Also, this test may not berelevant to stress corrosion cracking in chlorides or causticenvironments.4.2 The
11、polythionic acid environment may produce areas ofshallow intergranular attack in addition to the more localizedand deeper cracking mode of attack. Examination of failedspecimens is necessary to confirm that failure occurred bycracking rather than mechanical failure of reduced sections.5. Apparatus5.
12、1 Any suitable glass or other transparent, inert containercan be used to contain the acid solution and stressed specimensduring the period of test at room temperature, 22 to 25C (72to 77F). The container should be fitted with a removable topto reduce evaporation and to allow access to the stressedsp
13、ecimen (or specimens) for the periodic inspection.6. Reagents6.1 Purity of ReagentsThe polythionic acid solution shallbe prepared using reagent grade sulfurous acid and technicalgrade hydrogen sulfide; or, distilled water, commercial gradesulfur dioxide, and technical grade hydrogen sulfide.1This pr
14、actice 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, 2004. Published May 2004. Originallyapproved in 1988. Last previous edition approved in 1998 as
15、G 35 98.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact 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,
16、 PO Box C700, West Conshohocken, PA 19428-2959, United States.6.2 Purity of WaterReagent water Type IV (SpecificationD 1193) shall be used to prepare the test solutions.6.3 Wackenroders or Polythionic Acid Solution (1)3Aslow current of hydrogen sulfide is passed for an hour througha fritted glass tu
17、be into a flask containing chilled (0C, 32F)6 % sulfurous acid, after which the liquid is kept in thestoppered flask for 48 h at room temperature. This operation isrepeated until the liquid no longer gives off the odor of sulfurdioxide after standing at room temperature for a few hours.Note safety p
18、recautions in Section 7.6.3.1 In an alternative method (2), the polythionic acidsolution is prepared by passing a slow current of sulfur dioxidegas through a fritted glass bubbler submerged in a container ofdistilled water. This is continued until the solution becomessaturated and then the hydrogen
19、sulfide gas is slowly bubbledinto the sulfurous acid solution.6.3.2 The presence of polythionic acids in the solutionprepared in accordance with 6.3 or 6.3.1 can be checked byeither of the following methods. Polarography (3) can beemployed to identify the thionic acids, or the percent of acidpresent
20、 in the solution can be determined by wet techniques(4). The simplest method of checking the solution for poly-thionic acids is to expose a stressed and sensitized sample ofAISI Type 302 stainless steel. The sample should fail bycracking in less than 1 h. Alternatively, Type 304 sheet (0.07%carbon)
21、which has been sensitized and exposed as a U-bendshould crack in 1 h (5). Detection of cracks can be facilitatedby closing the legs of the U-bend and examining with a 203binocular microscope.7. Safety Precautions7.1 Hydrogen sulfide should be handled with extreme cau-tion. The characteristic odor of
22、 hydrogen sulfide cannot alwaysbe used as an alarm system because the olfactory nervesbecome deadened when exposed to a concentration of a fewparts per million of this gas. The maximum allowable concen-tration in the air for an 8-h work day is 10 ppm, which is wellabove the level detectable by smell
23、. Exposure to high concen-trations of hydrogen sulfide can be fatal. For additionalinformation on the toxicity of hydrogen sulfide, consult Ref(6).7.2 Normal laboratory precautions should be observed whenhandling the sulfurous or polythionic acid solutions. Hydrogensulfide should only be used in a h
24、ood observing the aboveprecautions.8. Test Specimens8.1 Any type of stress corrosion test specimen can be usedwith this test solution. For a comprehensive discussion of thevarious types of test specimens available, see Ref (7), as wellas Practices G 1 and G 30, and Terminology G 15.8.2 The AISI Type
25、 302 control specimens should be sensi-tized by heating in a furnace for4hat650C (1200F) andthen allowing to air cool. The AISI Type 304 control specimensshould be sensitized by heating in a furnace for2hat677C(1250F) and then allowing to air cool.9. Procedure9.1 Prepare the polythionic acid test so
26、lution as described in6.3 and 6.3.1.9.2 Prior to usage, filter the acid solution to remove theexcess sulfur and test for the presence of polythionic acids. Thesimplest method of testing for the acid is to expose a stressedspecimen of sensitized AISI Type 302 or Type 304 stainlesssteel. The specimen
27、should fail by cracking in less than 1 h.9.3 Place the stressed specimens in the container along withthe sensitized and stressed AISI Type 302 or Type 304 stainlesssteel control sample. Add a sufficient amount of polythionicacid solution to the container to immerse the test specimens.Close the conta
28、iner and carry out the test at room temperature.Record starting time for the test.10. Report10.1 Record starting time, type of specimen, stress, and typeof exposure. A distinction must be made in the type ofexposure; that is, complete immersion, vapor phase exposure,or a combination of immersion and
29、 vapor phase. The timerequired to initiate cracks, the rate of crack growth, and time tofailure may be of importance, depending upon the purpose ofthe test.10.1.1 Periodic removal of specimens from the solutionmay be necessary to determine the time when cracks firstappear and the rate of crack propa
30、gation. Microscopicalexamination of polished surfaces is required to detect crackinitiation. All stressed surfaces should be examined at magni-fications up to 203 at the completion of this test. Metallo-graphic examination of exposed surfaces and of polished andetched cross sections at higher magnif
31、ications are necessary toestablish the type of cracking.10.1.2 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 pitting corrosion or both. Such failuresusually show
32、 evidence of ductility. Duplicate tests with thickerspecimens should be made in cases of doubt.11. Keywords11.1 accelerated test; nickel-chromium-iron alloys; poly-thionic acids; stainless steels; stress-corrosion cracking3The boldface numbers in parentheses refer to the reports and papers appearing
33、in the list of references at the end of this practice.G 35 98 (2004)2REFERENCES(1) Debus, H., “Chemical Investigation of Wackenroders Solution,”Journal of the Chemical Society, London, Transactions, Vol 53, 1888,p. 278 (paper XXV).(2) Samans, C. H., “Stress Corrosion Cracking Susceptibility of Stain
34、lessSteels and Nickel-Base Alloys in Polythionic Acids and Acid CopperSulfate Solution,” Corrosion, Vol 20, August 1964, pp. 256t262t.(3) Murayama, T., “Polarography of Polythionates,” Journal of ChemicalSociety of Japan, Pure Chemistry Section, Vol 74, No. 5, 1953, pp.349352.(4) Jay, P. R., “Determ
35、ination of Polythionic Acids,” Analytical Chemis-try, Vol 25, No. 2, 1953, pp. 288290.(5) Crum, J. R., Adkins, M. E., and Lipscomb, W. G., “Performance ofHigh Nickel Alloys in Refinery and Petrochemical Environments,”Materials Performance, Vol. 25, No. 7, July, 1986, pp. 2733.(6) Chemical Safety Dat
36、a Sheet SD-36, Manufacturing Chemists Associa-tion, 1825 Connecticut Ave., N.W., Washington, DC 20009.(7) “Stress Corrosion Testing Methods,” Stress Corrosion Testing, ASTMSTP 425, ASTM Testing Mats. (Out of print. Send orders directly toUniversity Microfilms, Inc., 300 North Zeeb Rd., Ann Arbor, MI
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40、Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).G 35 98 (2004)3
