1、Designation: G103 97 (Reapproved 2016)Standard Practice forEvaluating Stress-Corrosion Cracking Resistance of LowCopper 7XXX Series Al-Zn-Mg-Cu Alloys in Boiling 6 %Sodium Chloride Solution1This standard is issued under the fixed designation G103; the number immediately following the designation ind
2、icates 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.INTRODUCTIONContinuous immersion in boiling 6 % sodiu
3、m chloride solution historically was considered to be aneffective accelerated SCC testing medium for allAl-Zn-Mg-Cu alloys (1, 2),2but in more recent years,alternate immersion in 3.5 % sodium chloride solution (Practice G44) has become the favored testmedium for the high copper (1.2 to 2.6 % Cu) 7XX
4、X series alloys (3, 4). Evidence to date shows,however, that the boiling 6 % sodium chloride medium correlates better with outdoor atmosphericexposure than Practice G44 for the 7XXX series alloys containing little or no copper (5, 6, 7, 8).1. Scope1.1 This practice primarily covers the test medium w
5、hichmay be used with a variety of test specimens and methods ofapplying stress. Exposure times, criteria of failure, and so on,are variable and not specified.1.2 This stress-corrosion testing practice is intended forstatically loaded smooth non-welded or welded specimens of7XXX series Al-Zn-Mg-Cu al
6、loys containing less than 0.26 %copper.1.3 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 l
7、imitations prior to use. See Section 8 foradditional precautions.2. Referenced Documents2.1 ASTM Standards:3B580 Specification for Anodic Oxide Coatings on Alumi-numD1193 Specification for Reagent WaterG30 Practice for Making and Using U-Bend Stress-Corrosion Test SpecimensG38 Practice for Making an
8、d Using C-Ring Stress-Corrosion Test SpecimensG39 Practice for Preparation and Use of Bent-Beam Stress-Corrosion Test SpecimensG44 Practice for Exposure of Metals andAlloys byAlternateImmersion in Neutral 3.5 % Sodium Chloride SolutionG49 Practice for Preparation and Use of Direct TensionStress-Corr
9、osion Test SpecimensG58 Practice for Preparation of Stress-Corrosion Test Speci-mens for Weldments3. Summary of Practice3.1 Stressed specimens are totally and continuously im-mersed in boiling 6 % sodium chloride solution for up to 168 h.Various types of smooth test specimens and methods ofstressing
10、 may be used. Performance is based on time to visualcracking.4. Significance and Use4.1 This practice is normally used for stress-corrosionscreening for the development ofAl-Zn-Mg-Cu alloys contain-ing less than 0.26 % copper. Effects on stress-corrosion resis-tance due to variables such as composit
11、ion, thermo-mechanicalprocessing, other fabrication variables, and magnitude ofapplied stress may be compared.1This 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 edi
12、tion approved May 1, 2016. Published May 2016. Originallyapproved in 1989. Last previous edition approved in 2011 as G103 97 (2011).DOI: 10.1520/G0103-97R16.2The boldface numbers in parentheses refer to the list of references at the end ofthis standard.3For referenced ASTM standards, visit the ASTM
13、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.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United S
14、tates14.2 For a given mechanical method of stressing, the relativestress-corrosion resistance of the low copper Al-Zn-Mg-Cualloys in atmospheric exposure correlates better with perfor-mance in boiling 6 % sodium chloride solution than with otheraccelerated testing media (7-9). In addition, this prac
15、tice isrelatively rapid.4.3 This practice is not applicable to 2XXX (Al-Cu), 5XXX(Al-Mg), 6XXX (Al-Mg-Si), and the 7XXX (Al-Zn-Mg-Cu)series alloys containing more than 1.2 % copper.4.3.1 For 7XXX series alloys containing between 0.26 %and 1.2 % copper, there is no general agreement as to whetherthis
16、 practice or Practice G44 correlates better with stress-corrosion resistance in service (5-8, 10).5. Apparatus5.1 Fig. 1 illustrates one type of apparatus that has beenused.5.2 Materials of Construction:5.2.1 Materials of construction that come in contact with theboiling salt solution shall be such
17、that they are not affected bythe corrodent to an extent that they can cause contamination ofthe solution and change its corrosiveness.5.2.2 Use of glass or aluminum containers and condensers isrecommended.5.2.3 Metallic materials of construction should be limited tocopper free aluminum alloys, which
18、 may be anodized toprovide electrical contact resistance.5.3 Specimen HoldersThe specimen holders should bedesigned to electrically insulate the specimens from each otherand from other bare metal. An anodized aluminum holder hasbeen found to be appropriate. (Satisfactory anodic coating maybe Type A
19、or B, Specification B580.) Periodic ohmeter checksmay be made to confirm electrical isolation of specimen andanodized holder.5.4 Heater for Solution:5.4.1 Heaters must be of sufficient capacity that boilingtemperature can be maintained and solution can be broughtback up to a boil within 10 min after
20、 the introduction of testspecimens.5.4.1.1 Quartz immersion heaters may be used.5.4.1.2 Hot plate resistance heaters may be used.6. Reagents and Solution Conditions6.1 Reagent grade sodium chloride (NaCl) shall be used. Itshall conform to the specifications of the Committee onAnalytical Reagents of
21、the American Chemical Society, wheresuch specifications are applicable.U bend specimens (Practice G39) stressed in an anodized aluminum fixture (right photo) are placed in a pyrex battery jar (left photo), which is placed over a mag-netic stirrer. The 6 % salt solution is heated to boiling by means
22、of two quartz immersion heaters. A powerstat controls the heat output of the quartz heaters. A coldwater circulating aluminum condenser tube is placed just below the aluminum cover to prevent evaporation losses. Stressed specimens are placed in the jar after thesolution comes to a boil. Specimens ar
23、e examined in place for visual evidence of cracking.FIG. 1 Boiling 6 % NaClStress-Corrosion Testing PracticeG103 97 (2016)26.2 The 6 % NaCl solution shall be prepared using distilledor deionized water conforming to the purity requirements ofSpecification D1193, Type IV reagent water, except that val
24、uesfor chloride and sodium shall be disregarded.6.3 ConcentrationThe salt solutions shall be prepared bydissolving 6.0 6 0.1 parts by weight of NaCl in 94.0 parts ofwater.6.4 Solution pH, shall be between 6.4 and 7.2. The pH maybe adjusted by the addition of dilute reagent grade HCl orNaOH solutions
25、. (See Practice G44.)6.5 Minimum VolumeThe volume of solution should belarge enough to avoid any appreciable change in its corrosive-ness through exhaustion of corrosive constituents, or theaccumulation of corrosion products or other constituents thatmight significantly affect further corrosion. A m
26、inimum ratiobetween the volume of solution and total exposed area ofspecimens of 20 mL/in.2(3 mL/cm2) is recommended.6.6 Reflux condensers are required in order to preventevaporation losses. Condenser material can be glass or copper-free aluminum alloy.6.7 Solution should be boiling throughout the e
27、xposure,except for the first few minutes after specimens are immersed.6.8 Replacement of SolutionNew solution should be usedfor each new set of specimens. Solution should not be changedduring exposure.7. Test Specimens7.1 Type and SizeNo single configuration of test specimenis applicable for the man
28、y complex shapes and sizes ofproducts that can be evaluated. Bent beams (G39) and U bends(G30) are useful for thin products while C-rings (G38)ortension specimens (G49) are more suitable for thicker productsand for short transverse testing. Guidance for selection ofappropriate specimens for evaluati
29、ng weldments is given inPractice G58.7.2 Stressing Direction and Magnitude of StressAny ofthe three primary grain directions may be used. The magnitudeof stress can be either within the elastic range or beyond. Themethod of stressing the specimens should be reproducible andin accordance to standard
30、procedures for the type of specimenselected.7.3 Surface PreparationThe specimen surface should befree of oil, grease, and dirt. This usually entails cleaning withorganic solvents such as alcohol or acetone.7.4 There is no need to provide compensation for thermalexpansion effects on applied stress.8.
31、 Safety Precautions8.1 Care should be taken in order to avoid burns from hotsurfaces.8.2 Appropriate eye protection equipment should be used.9. Procedure9.1 Allow solution to boil for a minimum of 10 min beforespecimens are immersed.9.2 Immerse specimens as soon as possible after stressing(delays be
32、tween stressing and testing should be avoided unlessthe stressed specimens are kept in a desiccator at a relativehumidity less than 5 %).9.3 Inspection Method and FrequencySpecimen surfacesshould be examined for visual evidence of cracking or theinitiation of gas evolution from the surface in areas
33、of higheststress. (Usually gassing is noted before cracking becomesvisible.) It is preferred that these inspections be done in situ,which can be accomplished with glass reaction vessels. If thespecimens have to be removed from the boiling salt solution,then the time out of solution should be kept to
34、 a minimum, nomore than 5 min.9.4 Time to first gassing and the first visual evidence ofcracking shall be recorded.9.5 Duration of ExposureThe duration of exposure shallbe determined by the inherent resistance to corrosion of thealloy, the configuration and size of the test specimen, and thepurpose
35、of the test. Common practice is a maximum of 168 h.9.6 Final ExaminationGive all specimens a final inspec-tion for evidence of cracking at the termination of the expo-sure.10. Report10.1 Report the following information:10.1.1 Details of all exposures, including type and size ofspecimen, orientation
36、 of specimen and number of replicates,solution volume to surface area ratio, stress level, and time ofexposure, and time to failure.10.1.2 Identification of alloy, temper, product form, thick-ness of materials exposed and reference to applicable specifi-cations.10.1.3 Any deviation from the procedur
37、es outlined above.11. Keywords11.1 accelerated test environment; aluminum-zinc-magnesium-copper alloys; boiling sodium chloride solution;continuous immersionG103 97 (2016)3REFERENCES(1) Sager, G. F., Brown, R. H., and Mears, R. B., “Tests for DeterminingSusceptibility to Stress-Corrosion Cracking,”
38、ASTM-AIME Sympo-sium on Stress-Corrosion Cracking of Metals, 1944, pp. 255272.(2) Dix, E. H., Jr., “Aluminum-Zinc-Magnesium Alloys: Their Develop-ment and Commercial Production,” Trans. ASM 42, 1950, pp.10571127.(3) Sprowls, D. O. and Brown, R. H., “What Every Engineer ShouldKnowAbout Stress Corrosi
39、on ofAluminum,” Metal Progress, Vol 81,No. 4, 1962, pp. 7985 and Vol 81, No. 5, 1962, pp. 7783.(4) Sprowls, D. O., Summerson, T. J., Ugiansky, G. M., Epstein, S. G.,and Craig, H. L., Jr., “Evaluation of a Proposed Standard Method ofTesting for Susceptibility to Stress-Corrosion Cracking of HighStren
40、gth 7XXX Series Aluminum Alloy Products,” StressCorrosionNew Approaches, ASTM STP 610, 1976, pp. 331.(5) Romans, H. B., “Stress Corrosion Test Environments and TestDurations,” ASTM STP 425, 1967, pp. 182208.(6) Lifka, B. W. and Sprowls, D. O., “Stress Corrosion Testing ofAluminum Alloy 7079-T6 in Va
41、rious Environments,” Stress Corro-sion Testing, ASTM STP 425, 1967, pp. 342362.(7) Craig, H. L., Jr., Sprowls, D. O., and Piper, D. E., Chapter 10 in theHandbook on Corrosion Testing and Evaluation, W. H. Ailor, Ed.,John Wiley and Sons, Inc., 1971, pp. 275277.(8) Summerson, T. J., Letter to Aluminum
42、 Association Task Group onCorrosion Testing of 7029 and 7021 Aluminum Alloy Bumpers,February 2, 1980.(9) Helfrich, W. J., “Influence of Stress and Temperature on the ShortTransverse Stress Corrosion Resistance of Al-4.2Zn-2.5Mg Alloy,”ASTM STP 425, 1967.(10) King, W. L., “Boiling Salt Tests of 7016
43、and 7029 Alloy Bumpers,”Alcoa Research Laboratory Report, September 9, 1981.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validit
44、y of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comment
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46、 received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copi
47、es) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the Copyright Clearance Center, 222Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http:/ 97 (2016)4
