ASTM G66-99

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Designation:G66–99
Standard Test Method for
Visual Assessment of Exfoliation Corrosion Susceptibility of
5XXX Series Aluminum Alloys (ASSET Test)
ThisstandardisissuedunderthefixeddesignationG 66;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginal
adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.Asuperscript
epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 5. Significance and Use
5.1 This test method provides a reliable prediction of the
1.1 This test method covers a procedure for continuous
immersion exfoliation corrosion testing of 5XXX series exfoliation corrosion behavior of Al-Mg alloys in marine
aluminum-magnesium alloys containing 2.0 % or more mag- environments. The test is useful for alloy development studies
nesium. and quality control of mill products such as sheet and plate.
1.2 This test method applies only to wrought products.
6. Apparatus
1.3 The values stated in SI units are to be regarded as the
standard. 6.1 Any suitable glass or plastic container can be used to
contain the solution and specimens during the test period.
1.4 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the Depending upon the shape and size of the specimens, rods or
racks of glass, plastic, or other inert substance shall be used to
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica- support the specimens above the bottom of the container. The
container should be fitted with a removable cover to reduce
bility of regulatory limitations prior to use.
evaporation.
2. Referenced Documents
7. Reagents
2.1 ASTM Standards:
D 1193 Specification for Reagent Water 7.1 Purity of Reagents—Reagent grade chemicals shall be
used in all tests.
G 15 Terminology Relating to Corrosion and Corrosion
Testing 7.2 Purity of Water—Distilled or deionized water conform-
ing to Specification D 1193. Type IV shall be used to prepare
3. Terminology
the test solution except chloride ion sodium limits can be
3.1 Definitions: disregarded.
3.1.1 exfoliation—corrosion that proceeds laterally from the
8. Test Solution
sites of initiation along planes parallel to the surface, generally
at grain boundaries, forming corrosion products that force 8.1 Preparation of Test Solution:
8.1.1 The test solution shall have the following composi-
metal away from the body of the material, giving rise to a
layered appearance (see Terminology G 15). tion:
NH Cl (1.0 M)
4. Summary of Test Method
NH NO (0.25 M)
4 3
(NH ) C H O (0.01 M)
4 2 4 4 6
4.1 Specimens are immersed for 24 h at 65 6 1°C (150 6
H O (0.09 M)
2 2
2°F) in a solution containing ammonium chloride, ammonium
8.1.2 Dissolve 53.5 g ammonium chloride (NH Cl), 20.0 g
nitrate, ammonium tartrate, and hydrogen peroxide. The sus-
ammonium nitrate (NH NO ), 1.8 g ammonium tartrate
4 3
ceptibility to exfoliation is determined by visual examination
((NH ) C H O ), and 10 mL of 30 % stock solution hydrogen
4 2 4 4 6
using performance ratings established by reference to standard
photographs.
AluminumAssociation Technical Report T1,“ Exfoliation Corrosion Testing of
This test method is under the jurisdiction of ASTM Committee G01 on Aluminum Alloys 5086 and 5456”.
Corrosion of Metals and is the direct responsibility of Subcommittee G01.05 on Sprowls, D. O., Walsh, J. D. and Shumaker, M. B., “Simplified Exfoliation
Laboratory Corrosion Tests. This method was developed by a joint task group with TestingofAluminumAlloys”, Localized Corrosion—Cause of Metal Failure, ASTM
The Aluminum Assoc., Inc. STP 516, ASTM, 1972, pp 38–65.
Current edition approved Apr. 10, 1999. Published June 1999. Originally Summerson T. J., Interim Report, Aluminum Association Task Group on
published as G 66 – 80. Last previous edition G 66 – 95. Exfoliation and Stress Corrosion Cracking of Aluminum Alloys for Boat Stock;
Annual Book of ASTM Standards, Vol 11.01. ProceedingsTri-Service Corrosion Military Equipment Conference, October 29–31,
Annual Book of ASTM Standards, Vol 03.02. 1974; Technical Report AFML-TR-75-42, Vol. II, p. 193–221, February 1, 1975.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
G66–99
peroxide (H O ) in a small amount of water. After dissolving, 12.3 Immerse the specimens vertically with the top edge of
2 2
mix the components together thoroughly and adjust the final the specimens at least 25 mm (1 in.) below the surface of the
dilution to 1 L. solution and the bottom edge at least 25 mm above the bottom
of the container.
NOTE 1—If a stock solution of the above chemicals is to be stored,the
12.4 Immerse the specimens in the test solution continu-
hydrogen peroxide should not be added until the solution is heated for the
ously for 24 h.
test.
12.5 Rinse the specimens gently in running tap water
8.2 The solution will have a typical pH of 5.2 to 5.4.
immediately after removal from the solution, then soak in
8.3 The solution shall be used in sufficient quantity to
concentrated nitric acid at room temperature until they appear
provide a volume-to-exposed specimen surface area ratio of at
clean, again rinse in water, and air dry.
2 2
least 100 L/m (65 mL/in. ).
12.5.1 Air-blast drying is to be avoided in order to prevent
8.4 The temperature of the solution shall be maintained at
mechanical removal of exfoliated metal.
65 6 1°C (150 6 2°F).
13. Rating of Specimens
9. Sampling
13.1 The following codes and classifications shall be used
9.1 The procedure for sampling mill products is covered in
for reporting the visual appearance of corroded specimens.
product specifications, or otherwise, and is considered outside
Code Classification
the scope of this standard.
N No appreciable attack
P Pitting
10. Test Specimen
E Exfoliation
10.1 While this test method can be used with any form of
13.2 Descriptions of the various classifications, which are
specimen or part that can be immersed in the test solution, it is
illustrated in Figs. 1 and 2, are as follows:
preferred that specimens be at least 40 by 100 mm (1.5 by 4.0
13.2.1 N (no appreciable attack)—Surface may be etched or
in.) with the metal working direction in the 40-mm (1.5-in.)
discolored.
dimension.
13.2.2 P (Pitting)—Includes discrete pitting or pit-
10.2 The specimens should be sawed or machined to mini-
blistering. In the latter case, attack results in a
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