1、Designation: G 157 98 (Reapproved 2005)Standard Guide forEvaluating Corrosion Properties of Wrought Iron- andNickel-Based Corrosion Resistant Alloys for ChemicalProcess Industries1This standard is issued under the fixed designation G 157; the number immediately following the designation indicates th
2、e 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 guide covers an evaluation approach that is
3、de-signed to provide information on the corrosion properties ofwrought iron- and nickel-based alloys for the chemical processindustries. This guide incorporates test conditions for generalcorrosion measurements in a variety of environments, crevicecorrosion resistance in chloride environments, and s
4、tress cor-rosion cracking resistance in chloride environments.1.2 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is t
5、heresponsibility of the user of this standard to establish appro-priate safety and health practices and to determine theapplicability of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 1193 Specification for Reagent WaterG1 Practice for Preparing, Cleaning, and Evalu
6、ating Cor-rosion Test SpecimensG15 Terminology Relating to Corrosion and CorrosionTestingG30 Practice for Making and Using U-Bend Stress-Corrosion Test SpecimensG36 Practice for Evaluating Stress-Corrosion-CrackingResistance of Metals and Alloys in a Boiling MagnesiumChloride SolutionG46 Guide for E
7、xamination and Evaluation of PittingCorrosionG48 Test Methods for Pitting and Crevice Corrosion Re-sistance of Stainless Steels and Related Alloys by Use ofFerric Chloride SolutionG 123 Test Method for Evaluating Stress-Corrosion Crack-ing of Stainless Alloys with Different Nickel Content inBoiling
8、Acidified Sodium Chloride Solution3. Terminology3.1 Terms such as crevice corrosion, stress corrosion crack-ing, and corrosion rate are defined in Terminology G 15.4. Significance and Use4.1 This guide is intended to provide a series of evaluationsthat will assist engineers dealing with chemical env
9、ironmentsin selecting appropriate alloys (1-3). In chemical environments,an important issue for determining general corrosion resistanceis the temperature at which an alloy transitions from corrosionat a low rate to corrosion at a much higher rate. Otherimportant concerns include the tendency toward
10、s crevicecorrosion and stress corrosion cracking resistance, especially inhot chloride-containing aqueous environments.4.2 This guide is also intended for alloy developers to assistthem in choosing environments and test methods that are ofparticular interest to the chemical process industries.4.3 Th
11、e use of this approach will allow direct comparisonsto be made among alloys from various suppliers and, thereby,to assist engineers in selecting the most appropriate materialsfor further testing to determine suitability in their application.5. General Corrosion Resistance5.1 The general corrosion re
12、sistance of nickel- and iron-based alloys is determined in 14 test solutions at varioustemperatures to determine the lowest temperature at which thecorrosion rate exceeds 0.13 mm/y (5 mpy). The test solutionsare listed in Table 1. A suggested procedure is provided inAppendix X1. The test is run on t
13、hree coupons of metal foreach environment. The tests are run for two 48-h exposures1This guide is under the jurisdiction of ASTM Committee G01 on Corrosion ofMetals and is the direct responsibility of Subcommittee G01.05 on LaboratoryCorrosion Tests.Current edition approved Oct. 1, 2005. Published O
14、ctober 2005. Originallyapproved in 1998. Last previous edition approved in 1998 as G 157 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 S
15、ummary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.with one specimen exposed for the total 96 h. Welded speci-mens may be used if results are required on weldments.5.2 The corrosion rates are based on mass
16、 loss measure-ments with appropriate conversion to thickness loss as shownin Appendix X1.5.3 The results of the tests in each solution should bereported on a summary results sheet. A typical format is shownin Fig. 1 and Fig. 2.6. Six Percent Ferric Chloride Solution Critical CreviceCorrosion Tempera
17、ture6.1 The crevice corrosion resistance of each alloy is to beevaluated as described in Test Methods G 48, Method D. Thestandard exposure period of 72 h is to be used. Mass lossresults are also to be obtained and reported in this environment.6.2 The results of this test are to be reported as discus
18、sed inTest Methods G 48. The results should also be entered on thesummary results sheet shown in Fig. 3.7. Chloride Stress Corrosion Resistance7.1 The resistance to chloride stress corrosion cracking is animportant characteristic of alloys used in the chemical processindustries. Two environments are
19、 provided to evaluate andreport chloride stress corrosion cracking behavioracidifiedsodium chloride and magnesium chloride. The magnesiumchloride environment is highly acidic and, as a consequence,tends to cause many suitably resistant alloys to fail. Theacidified sodium chloride environment gives r
20、esults closer toexperience in cooling water and process water environments.7.2 Acidified Sodium Chloride TestTest Method G 123should be used to evaluate all alloys for resistance to chloridestress corrosion cracking. The specimen design suggested inTest Method G 123 should be used, if possible. This
21、 design isbased on the Practice G 30 U-bend and the tests should becarried out with at least triplicate specimens for a period of1000 h. The results are to be reported as described in TestMethod G 123 and entered on the summary results sheet. SeeFig. 3.7.3 Magnesium Chloride Test, OptionalAlloys tha
22、t do notcrack in the acidified sodium chloride environment may betested in a magnesium chloride test. The test environment isTABLE 1 Fourteen Environments for Evaluating GeneralCorrosion ResistanceCorrodent Formula Concentration, %AHydrochloric Acid HCl 0.2, 1.0, 5.0Sulfuric Acid H2SO410, 60, 96BNit
23、ric Acid HNO310, 70BPhosphoric Acid H3PO485BFormic Acid HCOOH 50Acetic Acid CH3COOH 80Sodium Hydroxide NaOH 50Hydrochloric Acid + HCl + FeCl31.0 HCl + 0.3 FeCl3CFerric ChlorideAcetic Acid + CH3COOH + (CH3CO)2O 50/50Acetic AnhydrideAAll chemicals are ACS reagent grade mixed with Specification D 1193
24、Type 4reagent water.BUndiluted reagent grade acid may be used.CFerric chloride concentration calculated on anhydrous basis.FIG. 1 Summary Results Form - Alloy DescriptionFIG. 2 Summary Results Form - General Corrosion ResistanceFIG. 3 Summary Results Form - Localized CorrosionPerformanceG 157 98 (20
25、05)2described in Practice G 36. U-bend specimens similar to thosesuggested in Test Method G 123 should be used with triplicatereplication. The test should be run for 30 days or until crackingis observed. The specimens should be removed at convenientintervals not to exceed three days during exposure
26、and exam-ined for cracking. The time to first crack is reported. Metallo-graphic sectioning is to be carried out on at least one of eachset of replicates at the end of the exposure to document thecrack morphology or, in the case of surviving specimens, thatno microcracks are present. The result of t
27、his test is to bereported on the summary results sheet (Fig. 3).8. Report8.1 The results of these tests are to be reported as specifiedin the test method referenced. The summary results sheetsshown in Figs. 1-3 provide a convenient form to present theresults in a consistent format.9. Keywords9.1 che
28、mical process industry; crevice corrosion; generalcorrosion; iron-base corrosion resistant alloys; nickel-basecorrosion resistant alloys; stress corrosion crackingAPPENDIX(Nonmandatory Information)X1. SUGGESTED LABORATORY TESTING OF IRON- AND NICKEL-BASED ALLOYS FOR CORROSION RESISTANCE INSELECTED M
29、EDIA FOR GENERAL CORROSION PERFORMANCEX1.1 ScopeX1.1.1 This test method describes a suggested procedure forcorrosion tests to determine the relative resistance of wroughtiron- and nickel-based alloys to corrosion in selected media.These tests are intended to provide corrosion data suitable forprelim
30、inary evaluation prior to testing for specific chemicalapplications.X1.1.2 Each alloy is tested in the as-manufactured condi-tion; as-welded specimens may be included. (See X1.3.10.2 forwhen only the as-welded condition need be tested.)X1.1.3 Specimen evaluation procedures provide for massloss measu
31、rements for evaluation of general corrosion and lowpower surface microscopic examination for presence of local-ized corrosion, such as pitting, stress corrosion, intergranularattack, end-grain corrosion, and preferential weld attack.X1.2 ApparatusX1.2.1 A 1000 mL Erlenmeyer flask equipped with a ref
32、luxcondenser, a sparger with a fitted glass disc for deaeratingcertain solutions, a specimen support system, and a means forcontrolling the temperature of the contents of the flask arerecommended for all tests.X1.2.2 All components of the apparatus described in X1.2.1which are in contact with the te
33、st environment (liquid and gasphases) are to be made of glass or polytetrafluoroethylene(PTFE) or other inert nonconductive material.X1.2.3 The temperature-regulating device used for tests attemperatures other than the boiling temperature should becapable of controlling the temperature of the conten
34、ts of theflask to within 61C of the selected test temperature.X1.2.4 The specimen support system should be designed sothat the specimen is separated from the flask and its internalcomponents. The specimen is to be maintained in a verticalposition, totally immersed in the test solution. One desirable
35、support system is to use an individual glass cradle for eachspecimen.X1.2.5 A nitrogen sparging system, which is used for initialdeaeration in tests at temperatures below boiling and innon-oxidizing solutions, should be capable of sparging nitro-gen at the rate of 100 mL/min. A device to prevent bac
36、kflow oftest solution into the gas supply system should be included.X1.3 Test SpecimensX1.3.1 The specimens should be made from sheet, plate, orstrip produced by commercial methods.X1.3.2 Material from which the specimens are made shouldbe in the annealed condition, the final heat treatment beingdon
37、e after any cold rolling. Temperature of the final heattreatment and method of cooling should be reported.X1.3.3 Thickness of the sheet materials used for specimensshould be between 1.5 and 4.8 mm (0.06 and 0.188 in.). Widthof the specimens should be 20 mm (0.8 in.) and the length 50mm (2.0 in.).X1.
38、3.4 Specimens are to be cut to size by a machiningoperation. If sheared specimens are used, the sheared edges areto be removed by grinding or machining; the amount of metalremoved by machining should equal the thickness of thespecimen.X1.3.5 All specimens should be abraded to provide auniform surfac
39、e finish free of scale and dirt, and to remove anysharp edges or burrs due to machining or drilling operations.The final step in this abrading operation should be done withwet No. 80 or dry No. 120 grit abrasive paper. Exercise care toavoid overheating the surface. This step should be omittedwhen th
40、e intent of the test is to evaluate mill finish or othersurface conditions.X1.3.6 Specimens should be stamped with identifying let-ters and numbers, using clean, hardened steel stamps.X1.3.7 Specimens should be measured prior to test and thetotal exposed area, including edges, calculated and reporte
41、d tothe closest 65 mm2(0.1 in.2).X1.3.8 Following the abrasive treatment, the specimensshould be cleaned with a magnesium oxide paste or detergentsolution to remove any residual dirt or grease, rinsed in water,and dipped in acetone and air dried.G 157 98 (2005)3X1.3.9 The dried specimens should be w
42、eighed to anaccuracy of at least 60.2 mg. Weighed specimens should bestored in a desiccator for at least 24 h before use.X1.3.10 Two kinds of specimens may be used: (1)asmanufactured specimens and (2) as-welded specimens.X1.3.10.1 As-Manufactured SpecimensThese specimensshould be prepared according
43、to the procedure described inX1.3.1-X1.3.9.X1.3.10.2 As-Welded SpecimensThe principal reason forusing these specimens is to evaluate the corrosion resistance ofthe weld deposit. However, where the corrosion resistance ofthe weld deposit is equal to, or better than, that of the parentmetal, a welded
44、specimen can be used in lieu of the as-manufactured specimen and thus avoid running an additionaltest. The welded specimens should be prepared from materialdescribed in X1.3.1 and X1.3.2. The minimum thickness ofmaterial for these specimens should be 3.0 mm (0.12 in.). Theweld should be made so that
45、 it will be in the center of thespecimen and be parallel to the long direction of the specimen.The weld should be a gas-tungsten arc (GTAW) with fillermetal. The filler metal and welding procedure should corre-spond to that recommended by the manufacturer for fabricationof process equipment. The wel
46、d bead should be ground ormachined flush with the base metal. The final preparation of thespecimen should be as specified in X1.3.3-X1.3.9. Thereshould be no post-weld heat treatment.X1.4 Test SolutionsX1.4.1 Test solution should be prepared accurately fromreagent grade chemicals conforming to the S
47、pecifications ofthe Committee onAnalytical Reagents of theAmerican Chemi-cal Society,3and Specification D 1193 Type IV reagent water.X1.4.2 The compositions of the various test solutions aregiven in Table 1.X1.4.3 The sparging gas, employed to deaerate non-oxidizing solutions to be used in tests at
48、temperatures belowthe boiling point, should be nitrogen with a purity of at least99.9 % and with an oxygen content of less than 0.02 %.X1.4.4 Procedure for Preparing Solutions:X1.4.4.1 Hydrochloric Acid SolutionUse hydrochloricacid 36.5 to 38 %, specific gravity 1.185 to 1.192. Prepare 1200mL of eac
49、h solution using the volumes shown as follows:Desired % mL Concentrated HCl mL Reagent H2O0.2 5.4 11971.0 27.2 11845.0 139 1125Add water to a 1.5 L beaker, then carefully and slowly addthe reagent acid to the beaker while stirring the mixture. Whencool, measure 600 mL into each flask for the test.X1.4.4.2 Sulfuric Acid SolutionUse sulfuric acid 95 to98 %, specific gravity 1.84 min. Prepare 800 mL of eachsolution using volumes shown as follows:Desired % mL Concentrated Acid mL Reagent H2O10 72 114860 608 680Add water to a 1.5 L beaker, then carefully and slowly addconcentrat
