1、Designation: G123 00 (Reapproved 2015)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 G123; the number immediately following the designation
2、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 () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers a procedure fo
3、r 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 style
4、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 many
5、 environments readily crack inPractice G36, but have not cracked during interlaboratorytesting (see Section 12) using 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 (ferrit
6、e-austenite) stainless 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 chlor
7、ide stress-corrosion 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 pur
8、port 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 specific hazardstatements, see Section 8
9、.2. Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent WaterE8 Test Methods for Tension Testing of Metallic MaterialsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodG15 Terminology Relating to Corrosion and Corrosion Test-ing (With
10、drawn 2010)3G16 Guide for Applying Statistics to Analysis of CorrosionDataG30 Practice for Making and Using U-Bend Stress-Corrosion Test SpecimensG36 Practice for Evaluating Stress-Corrosion-Cracking Re-sistance of Metals and Alloys in a Boiling MagnesiumChloride SolutionG49 Practice for Preparation
11、 and Use of Direct TensionStress-Corrosion Test SpecimensG107 Guide for Formats for Collection and Compilation ofCorrosion Data for Metals for Computerized DatabaseInput3. Terminology3.1 DefinitionsFor definitions of corrosion-related termsused in this test method, see Terminology G15.4. Summary of
12、Test Method4.1 Asolution of 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.1This test method is under the jurisdi
13、ction of ASTM Committee G01 onCorrosion of Metals and is the direct responsibility of Subcommittee G01.06 onEnvironmentally Assisted Cracking.Current edition approved Nov. 1, 2015. Published December 2015. Originallyapproved in 1994. Last previous edition approved in 2011 as G12300(2011). DOI:10.152
14、0/G0123-00R15.2For 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.3The last approved version of this historical s
15、tandard is referenced onwww.astm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14.2 The test may be continued for as many weeks asnecessary, but six weeks (about 1000 h) or less are expected tobe sufficient to crack susceptible m
16、aterials. Longer exposuresprovide greater assurance of resistance for those materialswhich do not crack.4.3 It is recommended that samples of a susceptiblematerial, for example, UNS S30400 or S31600 (Type 304 orType 316 stainless, respectively), be included as a control whenmore resistant materials
17、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 test of Practice G36. Theboiling magnesium
18、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 inwater, especially cooling waters that conta
19、in 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 conditions comprisingexposure to the water-li
20、ne 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 crackedannealed UNS S30400 and S31600 but not more
21、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 G36 as U-bends. Materials whichwithstand this sodium chloride test for a longer pe
22、riod 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 withmany corrosion tests. Acceptance crit
23、eria 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.6.1.2 Condenser, a four-bulb Allihn conde
24、nser with a 45/50ground-glass joint (water-cooled joint suggested), a waterjacket at least 20 cm (8 in.) long anda1to2.5cm(0.4 to0.95 in.) long drip tip is used. (Modified Allihn condenserswith no drip tip and condensers with longer drip tips mayproduce different results. These alternate Allihn cond
25、enserdesigns may be used if control samples of susceptible (forexample, UNS S31600) and resistant (for example, UNSN08020) materials are included in the study.)6.1.3 Hot Plate, capable of maintaining the solution at itsboiling point.7. Reagents7.1 Purity of ReagentsReagent grade chemicals shall beus
26、ed 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 provided it is first ascertained that the reagen
27、t is ofsufficiently high purity to permit its use without affectingresults.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 n
28、otlisted 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 Apparatus Used for Stress-Corrosion Cracking TestG123 00 (
29、2015)27.2 Purity of WaterSolutions shall be made with water ofpurity conforming to at leastType IVreagent water as specifiedin Specification D1193 (except that for this method limits forchlorides and sodium may be ignored).7.3 Sodium Chloride (NaCl)A solution of 25 % NaCl (bymass) acidified to pH 1.
30、5 with phosphoric acid (H3PO4)isused. The solution may be prepared by adding 750 g H2O(750 mL) 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 glassware.The pH must be determined prior to eac
31、h 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 Minimum personal protective equipment for handlin
32、gboiling 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 than one crack may splinterinto two or mor
33、e 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 corrosion crack-ing specimens may be used wi
34、th 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). (See AnnexA1.) Regardless of the specimenstyle, it is recommended that UNS S30400 or UNS S31600, orboth, be included as controls.9.
35、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) must allow a solution volume to specimen su
36、rfacearea 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 providedin AnnexA1. These procedures are based on Practice G30, butin addition
37、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 must be (1) in the plastic range and (2)
38、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 stresscorrosion cracking in the environment
39、. 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 shoulder washer (that is, zirconiaor anoth
40、er 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 20, and replace anyspecimens with cracks or other defects.NOTE 2The direction and intensity of the incident li
41、ght may affectcrack detection during the 20 examination.10.2 Degrease in a halogen-free solvent or laboratorydetergent, rinse as necessary, and dry. It is best practice tostress the specimens immediately before the beginning of thetest. Any storage of the specimens should be in a cleanenclosure. A d
42、esiccant such as silica gel may be used. Thespecific level of relative humidity is not important for thealloys of interest.10.3 Place duplicate specimens in each 1000-mL Erlen-meyer flask. Duplicate flasks (four specimens) are necessary toevaluate a given sample of the specific material, materialcon
43、dition, 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 specimen support should beavoided. The stressed are
44、a 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 two U-bends as described inAnnex A1, the solut
45、ion 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 110C (223 to 230F).10.8 After one week remove t
46、he flask from the hot plate,determine the final pH of the solution at room temperature, anddiscard the remaining solution. A final pH over about 2.56The sole source of supply of amphoteric alundum granules known to thecommittee at this time is Hengar Co., Philadelphia, PA. If you are aware ofalterna
47、tive 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.G123 00 (2015)3suggests that general corrosion or pitting of the specimen orfastening device ha
48、s occurred.ApH at this level 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 t
49、he fastener) at 20 forcracking. 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 residualstresses 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 specimens from the solutionmay be necessary
