1、Designation: G 123 00 (Reapproved 2005)Standard Test Method forEvaluating Stress-Corrosion Cracking of Stainless Alloyswith Different Nickel Content in Boiling Acidified SodiumChloride Solution1This standard is issued under the fixed designation G 123; the number immediately following the designatio
2、n indicates the year oforiginal adoption or, 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 a procedure
3、 for conductingstress-corrosion cracking tests in an acidified boiling sodiumchloride solution. This test method is performed in 25 % (bymass) sodium chloride acidified to pH 1.5 with phosphoricacid. This test method is concerned primarily with the testsolution and glassware, although a specific sty
4、le of U-bend testspecimen is suggested.1.2 This test method is designed to provide better correla-tion with chemical process industry experience for stainlesssteels than the more severe boiling magnesium chloride test ofPractice G36. Some stainless steels which have providedsatisfactory service in m
5、any environments readily crack inPractice G36, but have not cracked during interlaboratorytesting2using this sodium chloride test method.1.3 This boiling sodium chloride test method was used in aninterlaboratory test program to evaluate wrought stainlesssteels, including duplex (ferrite-austenite) s
6、tainless and analloy with up to about 33 % nickel. It may also be employed toevaluate these types of materials in the cast or weldedconditions.1.4 This test method detects major effects of composition,heat treatment, microstructure, and stress on the susceptibilityof materials to chloride stress-cor
7、rosion cracking. Small dif-ferences between samples such as heat-to-heat variations of thesame grade are not likely to be detected.1.5 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.6 This standard does not purport to addres
8、s 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 specific hazardstatements, see Section 8.2. Referenced
9、 Documents2.1 ASTM Standards:3D 1193 Specification for Reagent WaterE8 Test Methods for Tension Testing of Metallic MaterialsE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodG15 Terminology Relating to Corrosion and CorrosionTestingG16 Guide forApplyin
10、g Statistics toAnalysis of CorrosionDataG30 Practice for Making and Using U-Bend Stress Corro-sion Test SpecimensG36 Practice for Evaluating Stress-Corrosion-CrackingResistance of Metals and Alloys in a Boiling MagnesiumChloride SolutionG49 Practice for Preparation and Use of Direct TensionStress Co
11、rrosion Test SpecimensG 107 Guide for Formats for Collection and Compilation ofCorrosion Data for Metals for Computerized DatabaseInput3. Terminology3.1 Definitions:3.1.1 For definitions of corrosion-related terms used in thistest method, see Terminology G15.4. Summary of Test Method4.1 Asolution of
12、 25 % sodium chloride (by mass) in reagentwater is mixed, and the pH is adjusted to 1.5 with phosphoricacid. The solution is boiled and U-bends (or other stressedspecimens) are exposed in fresh solution for successive one-week periods.4.2 The test may be continued for as many weeks asnecessary, but
13、six weeks (about 1000 h) or less are expected to1This test method is 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 Oct. 1, 2005. Published October 2005. Originall
14、yapproved in 1994. Last previous edition approved in 2000 as G 123 00.2Supporting data (including UNS S30400, S31600, S32550, and N08020) havebeen filed at ASTM International Headquarters and may be obtained by requestingResearch Report RR: G01-1013.3For referenced ASTM standards, visit the ASTM web
15、site, 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, PO Box C700, West Conshohocken, PA 19428-2959, United Sta
16、tes.be sufficient to crack susceptible materials. Longer exposuresprovide greater assurance of resistance for those materialswhich do not crack.4.3 It is recommended that samples of a susceptible mate-rial, for example, UNS S30400 or S31600 (Type 304 or Type316 stainless, respectively), be included
17、as a control whenmore resistant materials are evaluated.5. Significance and Use5.1 This test method is designed to compare alloys and maybe used as one method of screening materials prior to service.In general, this test method is more useful for stainless steelsthan the boiling magnesium chloride t
18、est of Practice G36. Theboiling magnesium chloride test cracks materials with thenickel levels found in relatively resistant austenitic and duplexstainless steels, thus making comparisons and evaluations formany service environments difficult.5.2 This test method is intended to simulate cracking inw
19、ater, especially cooling waters that contain chloride. It is notintended to simulate cracking that occurs at high temperatures(greater than 200C or 390F) with chloride or hydroxide.NOTE 1The degree of cracking resistance found in full-immersiontests may not be indicative of that for some service con
20、ditions comprisingexposure to the water-line or in the vapor phase where chlorides mayconcentrate.5.3 Correlation with service experience should be obtainedwhen possible. Different chloride environments may rankmaterials in a different order.5.4 In interlaboratory testing, this test method crackedan
21、nealed UNS S30400 and S31600 but not more resistantmaterials, such as annealed duplex stainless steels or highernickel alloys, for example, UNS N08020 (for example 20Cb-34stainless). These more resistant materials are expected to crackwhen exposed to Practice G36as U-bends. Materials whichwithstand
22、this sodium chloride test for a longer period thanUNS S30400 or S31600 may be candidates for more severeservice applications.5.5 The repeatability and reproducibility data from Section12 and Appendix X1 must be considered prior to use. Inter-laboratory variation in results may be expected as occurs
23、withmany corrosion tests. Acceptance criteria are not part of thistest method and if needed are to be negotiated by the user andthe producer.6. Apparatus6.1 The glassware used for this test method is shown in Fig.1 and is as follows:6.1.1 Flask1000-mL Erlenmeyer flask with a 45/50ground-glass joint.
24、6.1.2 Condenser, a four-bulb Allihn condenser with a 45/50ground-glass joint (water-cooled joint suggested), a waterjacket at least 20 cm (8 in.) long anda1to2.5cm(0.4 to 0.95in.) long drip tip is used. (Modified Allihn condensers with nodrip tip and condensers with longer drip tips may producediffe
25、rent results. These alternate Allihn condenser designs maybe used if control samples of susceptible (for example, UNSS31600) and resistant (for example, UNS N08020) materialsare included in the study.)6.1.3 Hot Plate, capable of maintaining the solution at itsboiling point.7. Reagents7.1 Purity of R
26、eagentsReagent grade chemicals shall 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.5Other grades may beused provide
27、d it is first ascertained that the reagent is ofsufficiently high purity to permit its use without affectingresults.7.2 Purity of WaterSolutions shall be made with water ofpurity conforming to at leastType IVreagent water as specifiedin Specification D 1193 (except that for this method limits forchl
28、orides and sodium may be ignored).420Cb-3 is a registered trademark of Carpenter Technology Corp., Reading, PA.5Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society
29、, 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 Apparatus Used for Stress-Corrosion Cracking TestG 123 00 (2005)27.3 Sodium Chloride (NaCl)A soluti
30、on of 25 % NaCl (bymass) acidified to pH 1.5 with phosphoric acid (H3PO4)isused. The solution may be prepared by adding 750 g H2O (750mL) to 250 g NaCl, and adjusting to pH 1.5 with H3PO4.Varying quantities of solution may be prepared and largeramounts may be stored indefinitely in appropriate glass
31、ware.The pH must be determined prior to each use.8. Hazards8.1 Normal precautions for handling boiling liquid shouldbe observed.8.2 All heating or boiling of the NaCl solution should bedone in an area where personnel are not likely to accidentallybump the flask. A hooded area is preferred.8.3 Minimu
32、m personal protective equipment for handlingboiling sodium chloride should include safety glasses orgoggles, face shield, laboratory coat, and rubber gloves.(WarningU-bends (and other highly stressed test speci-mens) may be susceptible to high rates of crack propagationand a specimen containing more
33、 than one crack may splinterinto two or more pieces. This may also occur due to a crackedrestraining bolt. Due to the highly stressed condition in aU-bend specimen, these pieces may leave the specimen at highvelocity and can be dangerous.)9. Test Specimens9.1 U-bends are preferred but other stress c
34、orrosion crack-ing specimens may be used with this test solution. Thespecimen style chosen should provide sufficient stress to crackless resistant materials (for example, UNS S30400 or S31600)in 1000 h or less). (SeeAnnexA1.) Regardless of the specimenstyle, it is recommended that UNS S30400 or UNS
35、S31600, orboth, be included as controls.9.2 The test specimen must be thick enough so that theapplied stress does not cause mechanical rupture of lessresistant materials if the cross section is reduced by pitting orgeneral corrosion.9.3 The size of alternate specimens (other than those inAnnex A1) m
36、ust allow a solution volume to specimen surfacearea ratio of at least 5:1 mL/cm2(33 mL/in.2).9.4 Aminimum of four replicates (two per flask) is requiredbecause of the variability typical in stress-corrosion testing.9.5 Methods of fabricating U-bend specimens are providedinAnnexA1. These procedures a
37、re based on Practice G30, butin addition provide a specimen that fits through a 45/50ground-glass joint. Assurance that the legs are stressed suffi-ciently by the bolt is also provided.9.5.1 Other methods of producing U-bends described inPractice G30 may be used; however, during exposure theU-bends
38、must be (1) in the plastic range and (2) stressed to themaximum applied tensile load experienced during fabrication.The same method must be used to fabricate all the U-bends ina given study.9.5.2 The bolt, nut, and flat washer must be made of amaterial resistant to general corrosion, pitting, and st
39、resscorrosion cracking in the environment. UNS N10276 (AlloyC-276) is recommended because some other materials (forexample, titanium or UNS N06600 Alloy 600) may beattacked resulting in an increase in solution pH.9.5.3 The metallic fastener must be electrically isolatedfrom the specimen by a rigid s
40、houlder washer (that is, zirconiaor another material that will not be compressed during the test).9.5.4 The extended end of the bolt may require cutting to fitinto the test vessel.10. Procedure10.1 Stress the specimens, examine at 203, and replace anyspecimens with cracks or other defects.NOTE 2The
41、direction and intensity of the incident light may affectcrack detection during the 203 examination.10.2 Degrease in a halogen-free solvent or laboratory deter-gent, rinse as necessary, and dry. It is best practice to stress thespecimens immediately before the beginning of the test. Anystorage of the
42、 specimens should be in a clean enclosure. Adesiccant such as silica gel may be used. The specific level ofrelative humidity is not important for the alloys of interest.10.3 Place duplicate specimens in each 1000-mL Erlenm-eyer flask. Duplicate flasks (four specimens) are necessary toevaluate a give
43、n sample of the specific material, materialcondition, etc. (The specimens may be placed in the flasks afterthe solution has been added, if convenient.)10.4 The specimens in each flask must be kept separate andcompletely submerged. Tight crevices between the stressed(bend) area and any means of speci
44、men support should beavoided. The stressed area should be free from direct contactwith heated surfaces. Specimens may be supported on glassrods or tubes or by glass fixtures.10.5 Drop boiling chips6into the flasks.10.6 Add 600 mL of 25 % NaCl solution, pH 1.5, to eachflask. When each flask contains
45、two U-bends as described inAnnex A1, the solution volume to sample surface area ratio is5:1 mL/cm2(33 mL/in.2).10.7 Place the flasks on a hot plate and insert the condenser.Begin recording the test duration when the solution beginsboiling. The boiling point during interlaboratory testing was106 to 1
46、10C (223 to 230F).10.8 After one week remove the flask from the hot plate,determine the final pH of the solution at room temperature, anddiscard the remaining solution. A final pH over about 2.5suggests that general corrosion or pitting of the specimen orfastening device has occurred.ApH at this lev
47、el is expected toreduce the test severity and may delay or preclude failures ofUNS S31600. More rapid cracking of UNS S31600 appearslikely with a final pH of about 2 or less.10.9 Rinse and dry the specimens. Examine the bend area,legs, and area adjacent to the crevice (at the fastener) at 203for cra
48、cking. See Note 3. Record location of cracks.Additionalexposures or metallographic evaluation may be used to deter-mine if questionable indications are, in fact, stress-corrosioncracks.NOTE 3Any cracking at the fastener is very likely due to residual6The sole source of supply of amphoteric alundum g
49、ranules known to thecommittee at this time is Hengar Co., Philadelphia, PA. If you are aware ofalternative suppliers, please provide this information to ASTM InternationalHeadquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee,1which you may attend.G 123 00 (2005)3stresses and more aggressive solution which may be formed in crevices. Ifcrevices are expected in service (due to design of service equipment ordeposits), a U-bend specimen employing a crevice on the bend may beevaluated.10.10 Periodic removal of the
