ASTM G69-97

Standard Test Method for Measurement of Corrosion Potentials of Aluminum Alloys

SCOPE
1.1 This test method is a procedure for measurement of the corrosion potential (see Note 1) of an aluminum alloy in an aqueous solution of sodium chloride with enough hydrogen peroxide added to provide an ample supply of cathodic reactant.  
Note 1-The corrosion potential is sometimes referred to as the open-circuit solution or rest potential.
1.2 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.

General Information

• Status: Historical
• Publication Date: 09-Oct-1997
• Technical Committee: G01 - Corrosion of Metals
• Drafting Committee: G01.11 - Electrochemical Measurements in Corrosion Testing

Relations

• Replaced By: ASTM G69-97(2003) - Standard Test Method for Measurement of Corrosion Potentials of Aluminum Alloys
• Effective Date: 10-Oct-1997
• Referred By: ASTM G100-89(2021) - Standard Test Method for Conducting Cyclic Galvanostaircase Polarization
• Effective Date: 10-Oct-1997
• Referred By: ASTM C1187-20a - Standard Guide for Establishing Surveillance Test Program for Boron-based Neutron Absorbing Material Systems for Use in Nuclear Fuel Storage Racks in Pool Environment
• Effective Date: 10-Oct-1997
• Referred By: ASTM G215-17 - Standard Guide for Electrode Potential Measurement
• Effective Date: 10-Oct-1997
• Referred By: ASTM B918/B918M-20a - Standard Practice for Heat Treatment of Wrought Aluminum Alloys
• Effective Date: 10-Oct-1997
• Referred By: ASTM G110-92(2022)e2 - Standard Practice for Evaluating Intergranular Corrosion Resistance of Heat Treatable Aluminum Alloys by Immersion in Sodium Chloride + Hydrogen Peroxide Solution
• Effective Date: 10-Oct-1997

Standards Content (Sample)

NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: G 69 – 97
Standard Test Method for
Measurement of Corrosion Potentials of Aluminum Alloys
This standard is issued under the fixed designation G 69; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope alloys, especially those of the 2XXX and 7XXX types, which
contain copper and zinc as major alloying elements. Its uses
1.1 This test method is a procedure for measurement of the
include the determination of the effectiveness of solution heat
corrosion potential (see Note 1) of an aluminum alloy in an
treatment and annealing (1), of the extent of precipitation
aqueous solution of sodium chloride with enough hydrogen
during artificial aging (4) and welding (5), and of the extent of
peroxide added to provide an ample supply of cathodic
diffusion of alloying elements from the core into the cladding
reactant.
of alclad products (2).
NOTE 1—The corrosion potential is sometimes referred to as the
open-circuit solution or rest potential.
4. Apparatus
1.2 This standard does not purport to address all of the
4.1 The apparatus consists of an inert container for the test
safety concerns, if any, associated with its use. It is the
solution, a mechanical support for the test specimens that
responsibility of the user of this standard to establish appro-
insulates them electrically from each other and from ground,
priate safety and health practices and determine the applica-
saturated calomel electrode (SCE) (see Note 3), wires and
bility of regulatory limitations prior to use.
accessories for electrical connections, and equipment for the
measurement of potential.
2. Referenced Documents
NOTE 3—Saturated calomel electrodes are available from several
2.1 ASTM Standards:
manufacturers. It is a good practice to ensure the proper functioning of the
D 1193 Specification for Reagent Water
reference electrode by measuring its potential against one or more
reference electrodes. The potential difference should not exceed 2 or 3
3. Significance and Use
mV.
3.1 The corrosion potential of an aluminum alloy depends 12
4.2 A high-impedence (>10 V) voltmeter is suitable for
upon the amounts of certain alloying elements that the alloy
measurement of the potential. Measurement of this potential
contains in solid solution. Copper and zinc, which are two of
should be carried out to within 6 1 mV. Automatic data
the major alloying elements for aluminum, have the greatest
recording systems may be used to permit the simultaneous
effect with copper shifting the potential in the noble or positive
measurement of many specimens and the continuous recording
direction, and zinc in the active or negative direction. For
of corrosion potentials.
example, commercially unalloyed aluminum (1100 alloy) has
a potential of −750 mV when measured in accordance with this
5. Reagents
practice, 2024–T3 alloy with nearly all of its nominal 4.3 %
5.1 Purity of Reagents—Reagent grade chemicals shall be
copper in solid solution, a potential of −600 to −620 mV (Note
used in all tests. Unless otherwise indicated, it is intended that
2), and 7072 alloy with nearly all of its nominal 1.0 % zinc in
all reagents shall conform to the specifications of the Commit-
solid solution, a potential of − 885 mV (SCE) (1-3).
tee on Analytical Reagents of the American Chemical Society,
where such specifications are available. Other grades may be
NOTE 2—The potential depends upon the rate of quenching.
used, provided it is first ascertained that the reagent is of
3.2 Because it reflects the amount of certain alloying ele-
sufficiently high purity to permit its use without lessening the
ments in solid solution, the corrosion potential is a useful tool
accuracy of the determination.
for characterizing the metallurgical condition of aluminum
5.2 Purity of Water—The water shall be distilled or deion-
ized conforming to the purity requirements of Specification
D 1193, Type IV reagent water.
This practice is under the jurisdiction of Committee G-1 on Corrosion of Metals
and is the direct responsibility of Subcommittee G01.11 on Electrochemical
Measurements in Corrosion Testing.
Round-robin test conducted by G01.11 (unpublished results).
Current edition approved Oct. 10, 1997. Published December 1997. Originally
Reagent Chemicals, American Chemical Society Specifications, American
e1
published as G 69 – 81. Last previous edition G 69 – 81 (1994) .
Chemical Society, Washington, DC. For suggestions on the testing of reagents not
Annual Book of ASTM Standards, Vol 11.01. listed by the American Chemical Society, see Analar Standards for Laboratory
All alloy designations are those of the Aluminum Association. Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
The boldface numbers in parentheses refer to the references at the end of this and National Formulary, U.S. Pharmaceutical Convention, Inc. (USPC), Rockville,
standard. MD.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
G69
5.3 Sodium Chloride (NaCl). cleaned, or degreased, in an inert solvent (for example, acetone
5.4 Hydrogen Peroxide (H O ) (30 %)—In case of uncer- or perchloroethylene).
2 2
tainty (for example, whenever freshly opened reagent is not 8.6 All parts of a specimen and its electrical connection to
used), the concentration of hydrogen peroxide in the reagent be exposed in the test solution, except for the area of the
shall be confirmed by chemical analysis as described in Annex specimen prepared for measurement, are masked off. Any
A1. In no case shall reagent containing less than 20 % material that masks a surface physically and electrically and
hydrogen peroxide be used. that is inert in the test solution may be used (see Annex A2).
6. Solution Conditions
9. Procedure
6.1 The test solution shall consist of 58.5 6 0.1 g of NaCl
9.1 For corrosion potential measurements, the test speci-
and 9 6 1 mL of 30 % hydrogen peroxide reagent per 1 L of
mens and the reference electrode are immersed in the appro-
aqueous solution. (This solution is 1 M with respect to
priate quantity of test solution; the test specimens are con-
concentration of sodium chloride.)
nected to the positive terminal of the equipment for measuring
6.2 The hydrogen peroxide reagent shall be added just
potential, and the reference electrode to the negative terminal.
before measurements are made because it decomposes upon
9.2 Care should be taken to ensure that all the unmasked
standing.
area of each test specimen prepared for measurement is
6.3 Freshly prepared solution shall be used for each set of
exposed to the test solution and that any other unmasked area
measurements.
is not exposed. Care should also be taken to ensure that any
6.4 Not less than 500 mL of solution shall be used for each
unmasked portion of the electrical connection is outside the test
set of measurements.
solution.
6.5 The total exposed area of all the specimens of the same
9.3 The potential of each specimen shall be measured at
composition in each set of measurements shall not exceed 100
5-min intervals for a period of1hor recorded continuously
mm per 100 mL of solution.
using the output of a high-impedance voltmeter.
6.6 The temperature of the test solution shall be maintained
9.4 The potential of each specimen shall be reported as the
at 25 6 2°C.
average of the values for the last 30 min of measurement (that
is, for the last 7 measurements).
7. Test Specimen
9.5 Duplicate specimens shall be measured.
7.1 For measurement alone, specimen size is unimportant
9.6 The average of the values for duplicate specimens shall
provided that the area for measurement is at least 25 mm , but
be used if the values agree within 5 mV. If they do not agree
for convenience the specimen, wherever possible, should be
within 5 mV at least one additio
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