ASTM G44-99

Standard Practice for Exposure of Metals and Alloys by Alternate Immersion in Neutral 3.5% Sodium Chloride Solution

SCOPE
1.1 This practice covers procedures for making alternate immersion stress corrosion tests in 3.5% sodium chloride (NaCl) (Note 1). It is primarily for tests of aluminum alloys (Test Method G47) and ferrous alloys, but may be used for other metals. It sets forth the environmental conditions of the test and the means for controlling them.  Note 1-Alternate immersion stress corrosion exposures are sometimes made in substitute ocean water (without heavy metals) prepared in accordance with Specification D1141. The general requirements of this present practice are also applicable to such exposures except that the reagents used, the solution concentration, and the solution pH should be as specified in Specification D1141.
1.2 This practice applies only to tests in which the specimens are accessible to the surrounding air under conditions that permit drying. It does not cover tests in which specimens are placed in closed containers into which the solution is periodically pumped and the specimens not permitted to dry.  
1.3 This practice is intended for alloy development and for applications where the alternate immersion test is to serve as a control test on the quality of successive lots of the same material. Therefore, strict test conditions are stipulated for maximum assurance that variations in results are attributable to variations in the material being tested.
1.4 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-Dec-1999
• ICS: 77.060 - Corrosion of metals
• Technical Committee: G01 - Corrosion of Metals
• Drafting Committee: G01.06 - Environmentally Assisted Cracking

Relations

• Replaced By: ASTM G44-99(2005) - Standard Practice for Exposure of Metals and Alloys by Alternate Immersion in Neutral 3.5% Sodium Chloride Solution
• Effective Date: 01-May-2005
• Referred By: ASTM G168-17 - Standard Practice for Making and Using Precracked Double Beam Stress Corrosion Specimens
• Effective Date: 10-Dec-1999
• Referred By: ASTM F2660-20 - Standard Test Method for Qualifying Coatings for Use on F3125 Grade A490 Structural Bolts Relative to Environmental Hydrogen Embrittlement
• Effective Date: 10-Dec-1999
• Referred By: ASTM G47-22 - Standard Test Method for Determining Susceptibility to Stress-Corrosion Cracking of 2XXX and 7XXX Aluminum Alloy Products
• Effective Date: 10-Dec-1999
• Referred By: ASTM G64-99(2021) - Standard Classification of Resistance to Stress-Corrosion Cracking of Heat-Treatable Aluminum Alloys
• Effective Date: 10-Dec-1999
• Referred By: ASTM G39-99(2021) - Standard Practice for Preparation and Use of Bent-Beam Stress-Corrosion Test Specimens
• Effective Date: 10-Dec-1999
• Referred By: ASTM G49-85(2019) - Standard Practice for Preparation and Use of Direct Tension Stress-Corrosion Test Specimens
• Effective Date: 10-Dec-1999
• Referred By: ASTM F3043-15 - Standard Specification for “Twist Off” Type Tension Control Structural Bolt/Nut/Washer Assemblies, Alloy Steel, Heat Treated, 200 ksi Minimum Tensile Strength
• Effective Date: 10-Dec-1999
• Referred By: ASTM G30-22 - Standard Practice for Making and Using U-Bend Stress-Corrosion Test Specimens
• Effective Date: 10-Dec-1999
• Referred By: ASTM G139-05(2022) - Standard Test Method for Determining Stress-Corrosion Cracking Resistance of Heat-Treatable Aluminum Alloy Products Using Breaking Load Method
• Effective Date: 10-Dec-1999
• Referred By: ASTM D6361/D6361M-98(2020) - Standard Guide for Selecting Cleaning Agents and Processes
• Effective Date: 10-Dec-1999
• Referred By: ASTM G58-85(2015) - Standard Practice for Preparation of Stress-Corrosion Test Specimens for Weldments
• Effective Date: 10-Dec-1999
• Referred By: ASTM F3111-16 - Standard Specification for Heavy Hex Structural Bolt/Nut/Washer Assemblies, Alloy Steel, Heat Treated, 200 ksi Minimum Tensile Strength
• Effective Date: 10-Dec-1999
• Referred By: ASTM G103-97(2023)e1 - Standard Practice for Evaluating Stress-Corrosion Cracking Resistance of Low Copper 7XXX Series Al-Zn-Mg-Cu Alloys in Boiling 6 % Sodium Chloride Solution
• Effective Date: 10-Dec-1999

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:G44–99
Standard Practice for
Exposure of Metals and Alloys by Alternate Immersion in
Neutral 3.5% Sodium Chloride Solution
ThisstandardisissuedunderthefixeddesignationG 44;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.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope D 1193 Specification for Reagent Water
E 3 Methods of Preparation of Metallographic Specimens
1.1 This practice covers procedures for making alternate
G 1 Practice for Preparing, Cleaning, and Evaluating Cor-
immersion stress corrosion tests in 3.5 % sodium chloride
rosion Test Specimens
(NaCl) (Note 1). It is primarily for tests of aluminum alloys
G 16 Guide forApplying Statistics toAnalysis of Corrosion
(Test Method G 47) and ferrous alloys, but may be used for
Data
other metals exhibiting susceptibility to chloride ions. It sets
G 47 Test Method for Determining Susceptibility to Stress-
forththeenvironmentalconditionsofthetestandthemeansfor
Corrosion Cracking of High-Strength Aluminum Alloy
controlling them.
Products
NOTE 1—Alternate immersion stress corrosion exposures are some-
times made in substitute ocean water (without heavy metals) prepared in
3. Summary of Practice
accordance with Specification D 1141. The general requirements of this
3.1 The alternate immersion test utilizes a 1-h cycle that
present practice are also applicable to such exposures except that the
includes a 10-min period in an aqueous solution of 3.5 %
reagentsused,thesolutionconcentration,andthesolutionpHshouldbeas
sodium chloride (NaCl) followed by a 50-min period out of the
specified in Specification D 1141.
solution, during which the specimens are allowed to dry. This
1.2 This practice can be used for both stressed and un-
1-h cycle is continued 24 h/day for the total number of days
stressed corrosion specimens. Historically, it has been used for
recommended for the particular alloy being tested. Typically,
stress-corrosion cracking testing, but is often used for other
aluminumandferrousalloysareexposedfrom20to90daysor
forms of corrosion, such as uniform, pitting, intergranular, and
longer, depending upon the resistance of the alloy to corrosion
galvanic.
by saltwater.
1.3 This practice is intended for alloy development and for
applications where the alternate immersion test is to serve as a
4. Significance and Use
control test on the quality of successive lots of the same
4.1 The 3.5 % NaCl alternate immersion procedure is a
material. Therefore, strict test conditions are stipulated for
general,all-purposeprocedurethatproducesvalidcomparisons
maximumassurancethatvariationsinresultsareattributableto
for most metals, particularly when specimens are exposed at
variations in the material being tested.
high levels of applied stress or stress intensity.
1.4 This standard does not purport to address all of the
4.2 While the alternate immersion test is an accelerated test
safety concerns, if any, associated with its use. It is the
and is considered to be representative of certain natural
responsibility of the user of this standard to establish appro-
conditions, it is not intended to predict performance in special-
priate safety and health practices and determine the applica-
ized chemical environments in which a different mode of
bility of regulatory limitations prior to use.
cracking may be operative. For example, it does not predict the
performance of aluminum alloys in highly acidic environments
2. Referenced Documents
such as heated inhibited red fuming nitric acid (IRFNA). For
2.1 ASTM Standards:
2 such cases, the results of the alternate immersion test are of
D 1141 Specification for Substitute Ocean Water
doubtful significance until a relationship has been established
between it and anticipated service environments.
This recommended practice is under the jurisdiction ofASTM Committee G-1
on Corrosion of Metals, and is the direct responsibility of Subcommittee G01.06 on
Stress-Corrosion Cracking and Corrosion Fatigue.
Current edition approved Dec. 10, 1999. Published January 2000. Originally Annual Book of ASTM Standards, Vol 11.01.
published as G 44 – 75. Last previous edition G 44 – 94. Annual Book of ASTM Standards, Vol 03.01.
2 5
Annual Book of ASTM Standards, Vol 11.02. Annual Book of ASTM Standards, Vol 03.02.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
G44
4.3 While this practice is applicable in some degree to all 6.3.2 Use of inert plastics or glass is recommended where
metals,itisnotequallydiscriminativeofallalloys,evenwithin feasible.
the same metal system. Consequently, information should be 6.3.3 Metallic materials of construction should be selected
established to allow comparisons of performances of the alloy from alloys that are recommended for marine use and of the
of interest in the alternate immersion test and in natural same general type as the metals being tested. Preferably, all
environments. metal parts should be protected with a suitable corrosion-
resistant coating that also satisfies paragraph 6.3.1.
NOTE 2—The alternate immersion concept can be useful for exposure
6.4 Specimen Holders:
of corrosion specimens in other solutions because the procedure and
6.4.1 Specimen holders should be designed to electrically
apparatus provide a controlled set of conditions. Details of this are beyond
insulatethespecimensfromeachotherandfromanyotherbare
the scope of this practice.
metal. When this is not possible, as in the case of certain
5. Interferences
stressing bolts or jigs, the bare metal contacting the specimen
should be isolated from the corrodent by a suitable coating.
5.1 A disadvantage of the 3.5 % NaCl alternate immersion
Protective coatings should be of a type that will not leach
test for stres-corrosion cracking tests of certain high-strength
inhibiting or accelerating ions or protective oils over the
aluminum alloys is the severe pitting that develops in the
noncoated portions of the specimen. Coatings containing
specimens. Such pitting can interfere with the initiation of
chromates are to be particularly avoided.
stress-corrosion cracks and may cause mechanical failures that
complicate the interpretation of the stress corrosion test results.
NOTE 3—Coatings that have been satisfactorily used by several labo-
This is particularly a problem with copper-bearing aluminum
ratories are described in Appendix X1.
alloys when tested with specimens of small cross section.
6.4.2 The shape and form of specimen supports and holders
Thorough metallographic examination of the specimens is
should be such that:
necessary for proper diagnosis of the cause of failure and
6.4.2.1 They avoid, as much as possible, any interference of
separation of stress corrosion failures from those caused by
free contact of the specimen with the salt solution.
mechanical overload.
6.4.2.2 They do not obstruct air flow over the specimen,
5.2 An advantage of the substitute ocean water (Note 1) is
thereby retarding the drying rate.
that it causes less pitting corrosion of aluminum alloys than the
6.4.2.3 They do not retain a pool of solution in contact with
3.5 % NaCl solution.
the specimen after the immersion period.
6.4.2.4 Drainage from one specimen does not directly con-
6. Apparatus
tact any other specimen.
6.1 Method of Cycling—Any suitable mechanism may be
used to accomplish the immersion portion of the cycle pro-
7. Reagents
vided that: (1) it achieves the specified rate of immersion and
7.1 Reagent grade sodium chloride (NaCl) shall be used
removal, and (2) the apparatus is constructed of suitable inert
conforming to the specifications of the Committee onAnalyti-
materials. The usual methods of immersion are:
cal Reagents of the American Chemical Society, where such
6.1.1 Specimens placed on a movable rack that is periodi-
specifications are applicable (see Note 1).
cally lowered into a stationary tank containing the solution.
7.2 The solution shall be prepared using distilled or deion-
6.1.2 Specimens placed on a hexagonal Ferris wheel ar-
ized water conforming to the purity requirements of Specifi-
rangement which rotates every 10 min through 60° and,
cation D 1193, Type IV reagent water except that for this
thereby, passes the specimens through a stationary tank of
practice the values for chloride and sodium shall be disre-
solution. Use of a Ferris wheel continuously rotating at a rate
garded.
of 1 revolution per hour is not recommended for very large
specimens for which the rate of immersion would be slower
8. Solution Conditions
than that specified in 6.2.
8.1 Concentration—The salt solution shall be prepared by
6.1.3 Specimens placed in a stationary tray open to the
dissolving 3.5 6 0.1 parts by weight of NaCl in 96.5 parts of
atmosphere and having the solution moved by air pressure,
water.
nonmetallic pump, or gravity drain from a reservoir to the tray.
8.2 Solution pH:
6.2 Rate of Immersion—The rate of immersion and removal
8.2.1 The pH of the salt solution, when freshly prepared,
of the specimens from the solution should be as rapid as
shall be within the range from 6.4 to 7.2. Only diluted, reagent
possible without jarring them. For purposes of standardization,
gradehydrochloricacid(HCl)orreagentgradesodiumhydrox-
anarbitrarylimitshallbeadoptedsuchthatnomorethan2min
ide (NaOH) shall be used to adjust the pH.
elapse from the time the first portion of any specimen is
covered (or uncovered) until it is fully covered (or uncovered)
by solution.
6.3 Materials of Construction:
Reagent Chemicals, American Chemical Society Specifications, American
Chemical Society, Washington, DC. For suggestions on the testing of reagents not
6.3.1 Materialsofconstructionthatcomeincontactwiththe
listed by the American Chemical Society, see Analar Standards for Laboratory
salt solution shall be such that they are not affected by the
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
corrodent to an extent that they can cause contamination of the
and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
solution and change its corrosiveness. MD.
G44
conditioning equipment which could result in systematic excursions
8.2.2 Experience has shown that periodic adjustment of pH
outside the temperature and humidity control ranges. Occasional excur-
is not necessary when the minimum volume of solution is met
sio
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