1、Designation: G 103 97 (Reapproved 2005)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 G 103; the number immediately following the designation i
2、ndicates 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 (e) indicates an editorial change since the last revision or reapproval.INTRODUCTIONContinuous immersion in boiling 6 % so
3、dium 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)
4、7XXX series alloys (3, 4). Evidence to date shows,however, that the boiling 6 % sodium chloride medium correlates better with outdoor atmosphericexposure than Practice G44for the 7XXX series alloys containing little or no copper (5, 6, 7, 8).1. Scope1.1 This practice primarily covers the test medium
5、 whichmay 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
6、alloys containing less than 0.26 %copper.1.3 This standard may involve hazardous materials, opera-tions, and equipment. This standard does not purport toaddress all of the safety concerns, if any, associated with itsuse. It is the responsibility of the user of this standard toestablish appropriate s
7、afety and health practices and deter-mine the applicability of regulatory limitations prior to use.See Section 8 for additional precautions.2. Referenced Documents2.1 ASTM Standards:3B 580 Specification for Anodic Oxide Coatings on Alumi-numD 1193 Specification for Reagent WaterG30 Practice for Maki
8、ng and Using U-Bend Stress-Corrosion Test SpecimensG38 Practice for Making and Using C-Ring Stress-Corrosion Test SpecimensG39 Practice for Preparation and Use of Bent-Beam Stress-Corrosion Test SpecimensG44 Practice for Exposure of Metals and Alloys by Alter-nate Immersion in Neutral 3.5 % Sodium C
9、hloride Solu-tionG49 Practice for Preparation and Use of Direct TensionStress-Corrosion Test SpecimensG58 Practice for Preparation of Stress-Corrosion TestSpecimens for Weldments1This practice is under the jurisdiction of ASTM Committee G01 on Corrosionof Metals and is the direct responsibility of S
10、ubcommittee G01.06 on Environmen-tally Assisted Cracking.Current edition approved Oct. 1, 2005. Published October 2005. Originallyapproved in 1989. Last previous edition approved in 1997 as G 103 97.2The boldface numbers in parentheses refer to the list of references at the end ofthis standard.3For
11、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.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700,
12、 West Conshohocken, PA 19428-2959, United States.3. Summary of Practice3.1 Stressed specimens are totally and continuously im-mersed in boiling 6 % sodium chloride solution for up to 168h. Various types of smooth test specimens and methods ofstressing may be used. Performance is based on time to vis
13、ualcracking.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 composition, thermo-mechanicalprocessing, other fabricati
14、on variables, and magnitude ofapplied stress may be compared.4.2 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 other
15、accelerated testing media (7-9). In addition, this practice 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 %
16、copper, there is no general agreement as to whetherthis 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
17、in contact with theboiling salt solution shall be such 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
18、 should be limited tocopper free aluminum alloys, which 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
19、appropriate. (Satisfactory anodic coating maybe Type A or B, Specification B 580.) Periodic ohmeter checksmay be made to confirm electrical isolation of specimen andanodized holder.5.4 Heater for Solution:U bend specimens (Practice G39) stressed in an anodized aluminum fixture (right photo) are plac
20、ed 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 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
21、aluminum cover to prevent evaporation losses. Stressed specimens are placed in the jar afterthe solution comes to a boil. Specimens are examined in place for visual evidence of cracking.FIG. 1 Boiling 6 % NaClStress-Corrosion Testing PracticeG 103 97 (2005)25.4.1 Heaters must be of sufficient capaci
22、ty that boilingtemperature can be maintained and solution can be broughtback up to a boil within 10 min after 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 ch
23、loride (NaCl) shall be used. Itshall conform to the specifications of the Committee onAnalytical Reagents of the American Chemical Society, wheresuch specifications are applicable.6.2 The 6 % NaCl solution shall be prepared using distilledor deionized water conforming to the purity requirements ofSp
24、ecification D 1193, Type IV reagent water, except thatvalues for 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
25、 the addition of dilute reagent grade HCl orNaOH solutions. (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 constitu
26、ents thatmight significantly affect further corrosion. A minimum 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 alum
27、inum alloy.6.7 Solution should be boiling throughout the exposure,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 sing
28、le configuration of test specimenis applicable for the many 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 prod-ucts and for short transverse testing.
29、 Guidance for selection ofappropriate specimens for evaluating 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 sp
30、ecimens should be reproducible andin accordance to standard 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 co
31、mpensation for thermalexpansion effects on applied stress.8. 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 Imm
32、erse specimens as soon as possible after stressing(delays between 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
33、or theinitiation of gas evolution from the surface in areas 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 s
34、alt solution,then the time out of solution should be kept to 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
35、configuration and size of the test specimen, and thepurpose 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 al
36、l exposures, including type and size ofspecimen, orientation 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 appli
37、cable specifi-cations.10.1.3 Any deviation from the procedures outlined above.11. Keywords11.1 accelerated test environment; aluminum-zinc-magnesium-copper alloys; boiling sodium chloride solution;continuous immersionG 103 97 (2005)3REFERENCES(1) Sager, G. F., Brown, R. H., and Mears, R. B., “Tests
38、for DeterminingSusceptibility to Stress-Corrosion Cracking,” ASTM-AIME Symposiumon 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,
39、 R. H., “What Every Engineer ShouldKnow About Stress Corrosion of Aluminum,” 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., andCraig, H. L., Jr., “Evaluation of a Proposed Standard Method ofTesting
40、 for Susceptibility to Stress-Corrosion Cracking of HighStrength 7XXX SeriesAluminumAlloy Products,” Stress CorrosionNew Approaches, ASTM STP 610, 1976, pp. 331.(5) Romans, H. B., “Stress Corrosion Test Environments and Test Dura-tions,” ASTM STP 425, 1967, pp. 182208.(6) Lifka, B. W. and Sprowls, D
41、. O., “Stress Corrosion Testing ofAluminumAlloy 7079-T6 in Various Environments,” Stress CorrosionTesting, 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.
42、, 1971, pp. 275277.(8) Summerson, T. J., Letter to Aluminum 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 S
43、TP 425, 1967.(10) King, W. L., “Boiling Salt Tests of 7016 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 stand
44、ard are expressly advised that determination of the validity 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 andi
45、f not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, wh
46、ich you may attend. If you feel that your comments have not 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 copies) 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).G 103 97 (2005)4
