ASTM G103-97(2011)
(Practice)Standard Practice for Evaluating Stress-Corrosion Cracking Resistance of Low Copper 7XXX Series Al-Zn-Mg-Cu Alloys in Boiling 6% Sodium Chloride Solution
Standard Practice for Evaluating Stress-Corrosion Cracking Resistance of Low Copper 7XXX Series Al-Zn-Mg-Cu Alloys in Boiling 6% Sodium Chloride Solution
SIGNIFICANCE AND USE
This practice is normally used for stress-corrosion screening for the development of Al-Zn-Mg-Cu alloys containing less than 0.26 % copper. Effects on stress-corrosion resistance due to variables such as composition, thermo-mechanical processing, other fabrication variables, and magnitude of applied stress may be compared.
For a given mechanical method of stressing, the relative stress-corrosion resistance of the low copper Al-Zn-Mg-Cu alloys in atmospheric exposure correlates better with performance in boiling 6 % sodium chloride solution than with other accelerated testing media (7-9). In addition, this practice is relatively rapid.
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 whether this practice or Practice G 44 correlates better with stress-corrosion resistance in service (5-8, 10).
SCOPE
1.1 This practice primarily covers the test medium which may be used with a variety of test specimens and methods of applying stress. Exposure times, criteria of failure, and so on, are variable and not specified.
1.2 This stress-corrosion testing practice is intended for statically loaded smooth non-welded or welded specimens of 7XXX series Al-Zn-Mg-Cu alloys containing less than 0.26 % copper.
This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. See Section for additional precautions.
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Standards Content (Sample)
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Designation: G103 − 97(Reapproved 2011)
Standard Practice for
Evaluating Stress-Corrosion Cracking Resistance of Low
Copper 7XXX Series Al-Zn-Mg-Cu Alloys in Boiling 6 %
Sodium Chloride Solution
This standard is issued under the fixed designation G103; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
Continuous immersion in boiling 6 % sodium chloride solution historically was considered to be an
effectiveacceleratedSCCtestingmediumforallAl-Zn-Mg-Cualloys (1, 2), butinmorerecentyears,
alternate immersion in 3.5 % sodium chloride solution (Practice G44) has become the favored test
medium for the high copper (1.2 to 2.6 % Cu) 7XXX series alloys (3, 4). Evidence to date shows,
however, that the boiling 6 % sodium chloride medium correlates better with outdoor atmospheric
exposure than Practice G44 for the 7XXX series alloys containing little or no copper (5, 6, 7, 8).
1. Scope B580 Specification for Anodic Oxide Coatings on Alumi-
num
1.1 This practice primarily covers the test medium which
D1193 Specification for Reagent Water
may be used with a variety of test specimens and methods of
G30 Practice for Making and Using U-Bend Stress-
applying stress. Exposure times, criteria of failure, and so on,
Corrosion Test Specimens
are variable and not specified.
G38 Practice for Making and Using C-Ring Stress-
1.2 This stress-corrosion testing practice is intended for
Corrosion Test Specimens
statically loaded smooth non-welded or welded specimens of
G39 Practice for Preparation and Use of Bent-Beam Stress-
7XXX seriesAl-Zn-Mg-Cu alloys containing less than 0.26 %
Corrosion Test Specimens
copper.
G44 PracticeforExposureofMetalsandAlloysbyAlternate
1.3 This standard does not purport to address all of the Immersion in Neutral 3.5 % Sodium Chloride Solution
safety concerns, if any, associated with its use. It is the
G49 Practice for Preparation and Use of Direct Tension
responsibility of the user of this standard to establish appro- Stress-Corrosion Test Specimens
priate safety and health practices and determine the applica-
G58 Practice for Preparation of Stress-CorrosionTest Speci-
bility of regulatory limitations prior to use. See Section 8 for mens for Weldments
additional precautions.
3. Summary of Practice
2. Referenced Documents
3.1 Stressed specimens are totally and continuously im-
2.1 ASTM Standards: mersedinboiling6 %sodiumchloridesolutionforupto168 h.
Various types of smooth test specimens and methods of
stressing may be used. Performance is based on time to visual
This practice is under the jurisdiction of ASTM Committee G01 on Corrosion
cracking.
of Metals and is the direct responsibility of Subcommittee G01.06 on Environmen-
tally Assisted Cracking.
4. Significance and Use
Current edition approved March 1, 2011. Published April 2011. Originally
approved in 1989. Last previous edition approved in 2005 as G103–97(2005). DOI:
4.1 This practice is normally used for stress-corrosion
10.1520/G0103-97R11.
screening for the development ofAl-Zn-Mg-Cu alloys contain-
The boldface numbers in parentheses refer to the list of references at the end of
this standard.
ing less than 0.26 % copper. Effects on stress-corrosion resis-
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
tance due to variables such as composition, thermo-mechanical
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
processing, other fabrication variables, and magnitude of
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
applied stress may be compared.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
G103 − 97 (2011)
4.2 For a given mechanical method of stressing, the relative 5.2.3 Metallic materials of construction should be limited to
stress-corrosion resistance of the low copper Al-Zn-Mg-Cu copper free aluminum alloys, which may be anodized to
alloys in atmospheric exposure correlates better with perfor- provide electrical contact resistance.
mance in boiling 6 % sodium chloride solution than with other
5.3 Specimen Holders—The specimen holders should be
accelerated testing media (7-9). In addition, this practice is
designed to electrically insulate the specimens from each other
relatively rapid.
and from other bare metal. An anodized aluminum holder has
4.3 This practice is not applicable to 2XXX (Al-Cu), 5XXX
been found to be appropriate. (Satisfactory anodic coating may
(Al-Mg), 6XXX (Al-Mg-Si), and the 7XXX (Al-Zn-Mg-Cu)
be TypeAor B, Specification B580.) Periodic ohmeter checks
series alloys containing more than 1.2 % copper.
may be made to confirm electrical isolation of specimen and
4.3.1 For 7XXX series alloys containing between 0.26 %
anodized holder.
and 1.2 % copper, there is no general agreement as to whether
5.4 Heater for Solution:
this practice or Practice G44 correlates better with stress-
5.4.1 Heaters must be of sufficient capacity that boiling
corrosion resistance in service (5-8, 10).
temperature can be maintained and solution can be brought
back up to a boil within 10 min after the introduction of test
5. Apparatus
specimens.
5.1 Fig. 1 illustrates one type of apparatus that has been
5.4.1.1 Quartz immersion heaters may be used.
used.
5.4.1.2 Hot plate resistance heaters may be used.
5.2 Materials of Construction:
5.2.1 Materialsofconstructionthatcomeincontactwiththe
6. Reagents and Solution Conditions
boiling salt solution shall be such that they are not affected by
the corrodent to an extent that they can cause contamination of 6.1 Reagent grade sodium chloride (NaCl) shall be used. It
the solution and change its corrosiveness. shall conform to the specifications of the Committee on
5.2.2 Useofglassoraluminumcontainersandcondensersis Analytical Reagents of theAmerican Chemical Society, where
recommended. such 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 of two quartz immersion heaters. A powerstat controls the heat output of the quartz heaters. A cold
water circulating aluminum condenser tube is placed just below the aluminum cover to prevent evaporation losses. Stressed specimens are placed in the jar after the
solution comes to a boil. Specimens are examined in place for visual evidence of cracking.
FIG. 1 Boiling 6 % NaCl—Stress-Corrosion Testing Practice
G103 − 97 (2011)
6.2 The 6 % NaCl solution shall be prepared using distilled 8. Safety Precautions
or deionized water conforming to the purity requirements of
8.1 Care should be taken in order to avoid burns from hot
Specification D1193,Type IVreagent water, except that va
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