1、Designation: G37 98 (Reapproved 2016)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 G37; the number immediately following the designation indicates the year of
2、 originaladoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.Asuperscriptepsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice covers the preparation and use of Matts-sons solu
3、tion 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.1.2 This
4、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 asdeliberate al
5、loying 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 susceptibility, if
6、 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 wrought br
7、ass products or components, brasscastings, brass weldments, and so forth, and to all brasses.Strict environmental test conditions are stipulated for maxi-mum assurance that apparent variations in stress-corrosionsusceptibility are attributable to real variations in the materialbeing tested or in the
8、 tensile stress level and not to environ-mental variations.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 torecommen
9、d particular stress-corrosion test specimen configu-rations or methods of applying the stress. Test specimenconfigurations that may be used are referenced in Practice G30and STP 425.21.5 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisst
10、andard.1.6 This standard does not 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 mo
11、re specificsafety hazard statements see Section 8.)2. Referenced Documents2.1 ASTM Standards:3D1193 Specification for Reagent WaterG30 Practice for Making and Using U-Bend Stress-Corrosion Test Specimens3. Summary of Practice3.1 The practice consists of completely and continuouslyimmersing a stresse
12、d 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 copper 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
13、 so forth, are variableand not specifically recommended.4. Significance and Use4.1 This test environment is believed 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 correspo
14、nding service ranking inenvironments that cause stress-corrosion cracking which isthought to be due to the combined 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 As
15、sisted Cracking.Current edition approved May 1, 2016. Published May 2016. Originallyapproved in 1973. Last previous edition approved in 2011 as G37 98 (2011). DOI:10.1520/G0037-98R16.2STP425, Stress Corrosion Testing, ASTM International.3For referenced ASTM standards, visit the ASTM website, www.ast
16、m.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.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1moisture a
17、nd ammonia vapor. 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 atmosphere
18、s (predominantly 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-corro
19、sion behaviorin brass 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 mechanic
20、al failures induced 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
21、cause of failure.Alternatively, 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
22、 ishighly recommended. The container should be fitted with aremovable top to reduce evaporation during test, thus prevent-ing dust and other particulate matter from entering theenvironment, and facilitating periodic inspection of the speci-mens. The top should not, however, be airtight, but insteads
23、hould permit reasonably free access of laboratory air to thesurface of the environment. The container and top should notbe transparent 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 meta
24、l. They should 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 thet
25、est environment 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 specificati
26、ons of theCommittee on Analytical Reagents of the American ChemicalSociety shall be used.46.2 Purity of WaterReagent water Type IV (SpecificationD1193) 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
27、.0 g-mol/L with 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 thoro
28、ughly mixedand 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 a
29、ging. Smalleror 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 o
30、r pH 10 Mattssons 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 and
31、 the test solution allowed to reach itsequilibrium 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 exha
32、ustion 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 transf
33、erring the test specimens toa new batch of 48-h aged test solution. Evaporation lossesshould be replenished with reagent water Type IV (Specifica-tion D1193) as frequently as deemed necessary. As far aspossible, the air above the solution should be static to minimizewater and ammonia evaporation. Fo
34、rced ventilation should be4Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and th
35、e United States Pharmacopeiaand National Formulary, U.S. Pharmaceupeial Convention, Inc. (USPC), Rockville,MD.G37 98 (2016)2avoided. It has not been found necessary to check or adjust thepH of the test solution during test after the initial 48-h agingperiod.8. 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 and pH10 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 D1193)tomake1L.A1.2.1 Proceed
48、 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 CuSO45H2OG37 98 (2016)352 mL of concentrated ammonium hy
49、droxide solution(NH4OH) (28 to 30 % NH3assayed and 0.90 sp gr) plusreagent water Type IV (Specification D1193)tomake1L.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 this standar
