1、Designation: G 37 98 (Reapproved 2004)Standard Practice forUse of Mattssons Solution of pH 7.2 to Evaluate the Stress-Corrosion Cracking Susceptibility of Copper-Zinc Alloys1This standard is issued under the fixed designation G 37; the number immediately following the designation indicates the year
2、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 covers the preparation and use of Matts-so
3、ns solution of pH 7.2 as an accelerated stress-corrosioncracking test environment for brasses (copper-zinc base al-loys). The variables (to the extent that these are known atpresent) that require control are described together with pos-sible means for controlling and standardizing these variables.1.
4、2 This practice is recommended only for brasses (copper-zinc base alloys). The use of this test environment is notrecommended for other copper alloys since the results may beerroneous, providing completely misleading rankings. This isparticularly true of alloys containing aluminum or nickel asdelibe
5、rate alloying additions.1.3 This practice is intended primarily where the test objec-tive is to determine the relative stress-corrosion crackingsusceptibility of different brasses under the same or differentstress conditions or to determine the absolute degree of stresscorrosion cracking susceptibil
6、ity, if any, of a particular brass orbrass component under one or more specific stress conditions.Other legitimate test objectives for which this test solution maybe used do, of course, exist. The tensile stresses present may beknown or unknown, applied or residual. The practice may beapplied to wro
7、ught brass products or components, brass cast-ings, brass weldments, and so forth, and to all brasses. Strictenvironmental test conditions are stipulated for maximumassurance that apparent variations in stress-corrosion suscepti-bility are attributable to real variations in the material beingtested
8、or in the tensile stress level and not to environmentalvariations.1.4 This practice relates solely to the preparation andcontrol of the test environment. No attempt is made torecommend surface preparation or finish, or both, as this mayvary with the test objectives. Similarly, no attempt is made tor
9、ecommend particular stress-corrosion test specimen configu-rations or methods of applying the stress. Test specimenconfigurations that may be used are referenced in Practice G 30and STP 425.21.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It
10、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 specificsafety hazard statements see Section 8.)2. Referenced Documents2.1 ASTM Standards:3D 1193 Specification f
11、or Reagent WaterG 30 Practice for Making and Using the U-Bend Stress-Corrosion Test Specimens3. Summary of Practice3.1 The practice consists of completely and continuouslyimmersing a stressed test specimen in an aqueous solutioncontaining 0.05 g-atom/L of Cu+and 1 g-mol/L of NH4+andof pH 7.2. The co
12、pper is added as CuSO45H2O and the NH4+as a mixture of NH4OH and (NH4)2SO4. The ratio of theselatter two compounds is adjusted to give the desired pH.Exposure time, criterion of failure, and so forth, are variableand not specifically recommended.4. Significance and Use4.1 This test environment is be
13、lieved to give an acceleratedranking of the relative or absolute degree of stress-corrosioncracking susceptibility for different brasses. It has been foundto correlate well with the corresponding service ranking inenvironments that cause stress-corrosion cracking which isthought to be due to the com
14、bined presence of traces of1This 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, 2004. Published May 2004. Originallyapproved in 1973. Last pr
15、evious edition approved in 1998 as G 37 98.2Stress Corrosion Testing, ASTM STP 425, ASTM (Although currently out ofprint, copies may be obtained from University Microfilms, Inc., 300 North Zeeb Rd.,Ann Arbor, MI 48106).3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact A
16、STM 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 States.moisture and ammonia vapor.
17、 The extent to which the accel-erated ranking correlates with the ranking obtained afterlong-term exposure to environments containing corrodentsother than ammonia is not at present known. Examples of suchenvironments may be severe marine atmospheres (Cl), severeindustrial atmospheres (predominantly
18、SO2), and super-heatedammonia-free steam.4.2 It is not possible at present to specify any particular timeto failure (defined on the basis of any particular failure criteria)in pH 7.2 Mattssons solution that corresponds to a distinctionbetween acceptable and unacceptable stress-corrosion behaviorin b
19、rass alloys. Such particular correlations must be determinedindividually.4.3 Mattssons solution of pH 7.2 may also cause stressindependent general and intergranular corrosion of brasses tosome extent. This leads to the possibility of confusing stress-corrosion failures with mechanical failures induc
20、ed bycorrosion-reduced net cross sections. This danger is particu-larly great with small cross section specimens, high appliedstress levels, long exposure periods and stress-corrosion resis-tant alloys. Careful metallographic examination is recom-mended for correct diagnosis of the cause of failure.
21、 Alterna-tively, unstressed control specimens may be exposed toevaluate the extent to which stress independent corrosiondegrades mechanical properties.5. Apparatus5.1 Any suitable inert container may be used to hold the testsolution and test specimens during exposure. Glass or plastic ishighly recom
22、mended. The container should be fitted with aremovable top to reduce evaporation during test, thus prevent-ing dust and other particulate matter from entering the envi-ronment, and facilitating periodic inspection of the specimens.The top should not, however, be airtight, but instead shouldpermit re
23、asonably free access of laboratory air to the surface ofthe environment. The container and top should not be trans-parent and should be fully opaque to light.5.2 Specimen holders should be designed to insulate elec-trically the test specimens from each other and from any otherbare metal. They should
24、 also be completely inert to the testenvironment so that leaching of soluble components or directreaction with the test environment will not interfere with thetest. The shape and form of the specimen holders and supportsshould be such that they do not interfere with free access to thetest environmen
25、t to the test specimen and its stressed surfaces.6. Reagents and Materials6.1 Reagent grade copper sulfate crystals (CuSO45H2O),ammonium sulfate crystals (NH4)2SO4), and concentratedammonium hydroxide solution (NH4OH) (28 to 30 % NH3assayed and 0.90 sp gr) conforming to the specifications of theComm
26、ittee on Analytical Reagents of the American ChemicalSociety shall be used.46.2 Purity of Water Reagent water Type IV (SpecificationD 1193) shall be used to prepare the test solution.7. Test Solution7.1 The concentration of the test solution shall be 0.05g-atom/L with respect to Cu+and 1.0 g-mol/L w
27、ith respect toNH4+. The pH of the test solution shall be 7.2 + 0.3, 0.1 pH.7.2 The test solution shall be prepared by completelydissolving 590.0 6 1.0 g of (NH4)2SO4in 4 L of water and bycompletely dissolving 125.0 6 0.5 g of CuSO45H2Oin1Lofwater. These two solutions should then be thoroughly mixeda
28、nd 71.0 6 0.2 mL of NH4OH solution added, preferably witha buret. Finally, the whole should be diluted to 10.0 6 0.1 Land allowed to age for 48 to 96 h in the test container prior touse. It is not recommended that the solution be stored forextended periods or used without the specified aging. Smalle
29、ror larger volumes of solution can be prepared using lesseramounts of reagents in the same proportions.7.3 After aging, the pH of the test solution should bemeasured. If outside the range specified above, the pH may beadjusted to within the range 7.1 to 7.5 by the addition of freshpH 4 or pH 10 Matt
30、ssons solution. Addition of NH4OH orH2SO4to adjust pH is not recommended since the concentra-tion of the various soluble ions can be considerably altered.7.4 Temperature control of the test solution is not recom-mended. Instead, the room air temperature should be controlledat 21 6 3C (70 6 5F) and t
31、he test solution allowed to reachits equilibrium temperature with the air. No room air relativehumidity control is recommended and temperature recording isnot mandatory.7.5 The volume of test solution used should be sufficientlylarge to avoid any appreciable change in corrosivity due toeither exhaus
32、tion of corrosive constituents or accumulation ofcorrosion products. An arbitrary minimum ratio between thevolume of test solution and the exposed specimen surface areaof 3 L/dm2(30 mL/cm2) is recommended.7.6 The test solution should be changed after every 7 daysof specimen exposure time by transfer
33、ring the test specimens toa new batch of 48-h aged test solution. Evaporation lossesshould be replenished with reagent water Type IV (Specifica-tion D 1193) as frequently as deemed necessary. As far aspossible, the air above the solution should be static to minimizewater and ammonia evaporation. For
34、ced ventilation should beavoided. It has not been found necessary to check or adjust thepH of the test solution during test after the initial 48-h agingperiod.4Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of rea
35、gents 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. Pharmaceupeial Convention, Inc. (USPC), Rockville,MD.G 37 98 (2004)28. Hazards8.1 The test solution presents n
36、o undue safety hazard. It isrecommended, however, that rubber gloves and shatterproofgoggles be worn during inspection.8.2 The solution contains copper and is poisonous andshould not be ingested.8.3 Should any of the solution come into contact with theeyes, qualified medical aid should be obtained i
37、mmediately.8.4 (NH4)2SO4has been reported to be allergenic. Repeatedshort-time skin contact with the solution over extended periodsof time should be avoided.8.5 The fumes given off by the test solution contain ammo-nia. The least detectable ammonia odor corresponds to aconcentration of 50 ppm; 100 p
38、pm can be tolerated for severalhours without serious disturbance; 700 ppm causes immediateeye irritation; and greater than 5000 ppm can be lethal. The testshould therefore be run in a well ventilated area.9. Calibration and Standardization9.1 When a new test facility is established, calibration test
39、sshould be conducted to determine how the results obtainedcompare with published data.9.2 A suitable supply of control material which can beexposed periodically to confirm the reproducibility of the testprocedure should be available.10. Procedure10.1 Completely and continuously immerse the test spec
40、i-mens in the test solution with the exception of periodicwithdrawals for inspection or measurement. Gently rinse thespecimens in distilled water after each withdrawal and whenthe test solution is being changed.10.2 The duration of the test will be determined solely bythe material being tested. High
41、ly susceptible alloys or highlystressed alloys may fail with extreme rapidity. Moderatelystressed alloys may take considerable time to fail. Generally,failures are not observed after periods of greater than 1000 h.It is therefore recommended that this be the longest duration ofthe test.11. Cleaning1
42、1.1 After completion of the test, rinse the specimens wellin distilled water and air dry.11.2 Any other cleaning may be performed, depending ontest objective and method of failure determination.12. Report12.1 The report shall include the following:12.1.1 Chemical composition, thermal treatments, mec
43、hani-cal treatments, and mechanical properties of the material,12.1.2 Microstructure and grain size of the material,12.1.3 Size, type, and orientation of the test specimens,12.1.4 Surface treatment and preparation procedures of thetest specimens,12.1.5 In configurations where the stress level is kno
44、wn, theapplied tensile stress,12.1.6 Ratio of test solution volume to exposed specimensurface area,12.1.7 Total duration of the test and the frequency ofinspection periods,12.1.8 Measured pH of the test solution and the NH4+content if determined analytically,12.1.9 Criterion used for definition of f
45、ailure,12.1.10 Number of specimens tested,12.1.11 Details of the solution container, specimen loadingjigs, and so forth, where these are in any way exceptional,12.1.12 Method used to clean the test specimens afterexposure, and12.1.13 Any intentional or inadvertent deviations from therecommended test
46、 procedures and any other information thatthe investigator considers pertinent.13. Keywords13.1 accelerated stress-corrosion cracking test environment;continuous immersion; copper-ammonium sulfate solution;copper-zinc alloysANNEX(Mandatory Information)A1. PREPARATION OF MATTSSONS SOLUTION OF pH 4 AN
47、D pH 10A1.1 The preparation of Mattssons solution of pH 4 andpH 10 is provided in this annex to enable the pH of Mattssonssolution, pH 7.2, to be adjusted correctly.A1.2 Mattssons Solution of pH 4:66 g (NH4)2SO412.5 g CuSO45H2O plus reagent water Type IV (Specifica-tion D 1193) to make 1 L.A1.2.1 Pr
48、oceed as for Mattssons solution of pH 7.2. ThepH is insensitive to composition and adjustment should not berequired. The solution should be 1 M with respect to NH3and0.05 M with respect to Cu+.A1.3 Mattssons Solution of pH 10:15.2 g (NH4)2SO412.5 g CuSO45H2OG 37 98 (2004)352 mL of concentrated ammon
49、ium hydroxide solution(NH4OH) (28 to 30 % NH3assayed and 0.90 sp gr) plusreagent water Type IV (Specification D1193) to make 1L.A1.3.1 Proceed as for Mattssons solution of pH 7.2. ThepH is insensitive to composition and adjustment should not berequired. The solution should be 1 M with respect to NH3and0.05 M with respect to Cu+.A1.4 Both of the above solutions should be aged for 48 to96 h before use.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of thi
