ASTM G44-21

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

SIGNIFICANCE AND USE
4.1 The 3.5 % NaCl alternate immersion procedure is a general, all-purpose procedure that produces valid comparisons for most metals, particularly when specimens are exposed at high levels of applied stress or stress intensity.  
4.2 While the alternate immersion test is an accelerated test and is considered to be representative of certain natural conditions, it is not intended to predict performance in specialized chemical environments in which a different mode of cracking may be operative. For example, it does not predict the performance of aluminum alloys in highly acidic environments such as heated inhibited red fuming nitric acid (IRFNA). For such cases, the results of the alternate immersion test are of doubtful significance until a relationship has been established between it and anticipated service environments.  
4.3 While this practice is applicable in some degree to all metals, it is not equally discriminative of all alloys, even within the same metal system. Consequently, information should be established to allow comparisons of performances of the alloy of interest in the alternate immersion test and in natural environments.
Note 2: The alternate immersion concept can be useful for exposure of corrosion specimens in other solutions because the procedure and apparatus provide a controlled set of conditions. Details of this are beyond the scope of this practice.
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 exhibiting susceptibility to chloride ions. 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 Practice 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 Practice D1141.  
1.2 This practice can be used for both stressed and unstressed corrosion specimens. Historically, it has been used for stress-corrosion cracking testing, but is often used for other forms of corrosion, such as uniform, pitting, intergranular, and galvanic.  
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 The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided for information only and are not considered standard.  
1.5 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 30-Apr-2021
• ICS: 77.040.30 - Chemical analysis of metals
• Technical Committee: G01 - Corrosion of Metals
• Drafting Committee: G01.06 - Environmentally Assisted Cracking

Relations

• Refers: ASTM G47-98(2019) - Standard Test Method for Determining Susceptibility to Stress-Corrosion Cracking of 2XXX and 7XXX Aluminum Alloy Products
• Effective Date: 15-Jun-2019
• Refers: ASTM G1-03(2011) - Standard Practice for Preparing, Cleaning, and Evaluating Corrosion Test Specimens
• Effective Date: 01-Dec-2011
• Refers: ASTM G47-98(2011) - Standard Test Method for Determining Susceptibility to Stress-Corrosion Cracking of 2XXX and 7XXX Aluminum Alloy Products
• Effective Date: 01-Sep-2011
• Refers: ASTM D1141-98(2008) - Standard Practice for the Preparation of Substitute Ocean Water
• Effective Date: 15-Jul-2008
• Refers: ASTM D1193-06 - Standard Specification for Reagent Water
• Effective Date: 01-Mar-2006
• Refers: ASTM G47-98(2004) - Standard Test Method for Determining Susceptibility to Stress-Corrosion Cracking of 2XXX and 7XXX Aluminum Alloy Products
• Effective Date: 01-May-2004
• Refers: ASTM G1-03 - Standard Practice for Preparing, Cleaning, and Evaluating Corrosion Test Specimens
• Effective Date: 01-Oct-2003
• Refers: ASTM D1141-98(2003) - Standard Practice for the Preparation of Substitute Ocean Water
• Effective Date: 10-Aug-2003
• Refers: ASTM D1193-99e1 - Standard Specification for Reagent Water
• Effective Date: 10-Feb-1999
• Refers: ASTM D1193-99 - Standard Specification for Reagent Water
• Effective Date: 10-Feb-1999
• Refers: ASTM D1141-98e1 - Standard Practice for the Preparation of Substitute Ocean Water
• Effective Date: 03-Feb-1999
• Refers: ASTM G1-90(1999)e1 - Standard Practice for Preparing, Cleaning, and Evaluating Corrosion Test Specimens
• Effective Date: 01-Jan-1999
• Refers: ASTM G47-98 - Standard Test Method for Determining Susceptibility to Stress-Corrosion Cracking of 2XXX and 7XXX Aluminum Alloy Products
• Effective Date: 10-Apr-1998

Overview

ASTM G44-21: Standard Practice for Exposure of Metals and Alloys by Alternate Immersion in Neutral 3.5 % Sodium Chloride Solution is an international standard developed by ASTM International. It outlines procedures for exposing metal and alloy specimens to alternate cycles of immersion and drying in a neutral 3.5% sodium chloride (NaCl) solution to evaluate their susceptibility to corrosion, particularly under stress. This accelerated corrosion testing method is widely recognized for its ability to provide valid comparative data for a range of metals, especially aluminum and ferrous alloys.

The standard is primarily applicable to stress-corrosion cracking assessments, but it can also be utilized for evaluating uniform, pitting, intergranular, and galvanic corrosion. ASTM G44-21 establishes rigorous and repeatable test conditions, making it a valuable tool in alloy development, quality control, and material comparison.

Key Topics

• Accelerated Corrosion Testing: Uses a controlled cycle of 10 minutes’ immersion in 3.5% NaCl solution followed by 50 minutes’ air drying, repeated around the clock.
• Specimen Versatility: Suitable for testing both stressed and unstressed corrosion specimens and applicable to a range of metals and alloys susceptible to chloride-induced corrosion.
• Strict Environmental Controls: Specifies conditions for solution preparation, pH (6.4 to 7.2), temperature (27°C ± 1°C), and humidity (45% ± 10%) to ensure test consistency and reliability.
• Quality and Comparative Assessment: Designed for alloy development and control testing of material lots to ensure that observed performance variations are due to material differences rather than test inconsistencies.
• Limitations: Not intended to predict performance in highly specialized chemical environments or for alloys with unique corrosion mechanisms outside the chloride system.
• Apparatus Design: Describes requirements for specimen holders and immersion mechanisms to avoid contamination and ensure proper exposure of specimens.

Applications

Organizations across industries use ASTM G44-21 for:

• Alloy Development: Comparing corrosion resistance between various aluminum and ferrous alloy compositions to guide material selection or innovation.
• Quality Control: Routine monitoring of successive production lots in manufacturing by using alternate immersion testing as a control measure.
• Comparative Analysis: Evaluating the relative performance of new or modified metal products against established benchmarks under standardized, accelerated corrosion conditions.
• Research and Testing: Academic and industrial laboratories use this standard to simulate marine or salt-spray corrosion environments and to generate data that correlates with natural exposure.
• Corrosion Prevention: Identification of unsuitable alloys for chloride-rich service environments, enabling proactive design and maintenance decisions.
• Supplementary Assessment: Supports other more specific standards when assessing general suitability in environments where chloride-induced corrosion is a concern.

Related Standards

ASTM G44-21 references and complements several other key ASTM standards focused on corrosion and material testing, such as:

• ASTM D1141: Standard Practice for the Preparation of Substitute Ocean Water, often used when ocean water exposure is required for comparative purposes.
• ASTM D1193: Specification for Reagent Water, which details requirements for water purity in test solution preparation.
• ASTM G1: Practice for Preparing, Cleaning, and Evaluating Corrosion Test Specimens, ensuring proper pre- and post-test specimen handling.
• ASTM G16: Guide for Applying Statistics to Analysis of Corrosion Data, supporting robust data interpretation.
• ASTM G47: Test Method for Determining Susceptibility to Stress-Corrosion Cracking of 2XXX and 7XXX Aluminum Alloy Products.

By following ASTM G44-21, laboratories, manufacturers, and researchers gain a consistent, reproducible method for accelerated corrosion testing of metals and alloys under conditions representative of many real-world chloride exposures. This helps optimize materials’ performance, safety, and longevity while meeting rigorous international quality standards.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: G44 − 21
Standard Practice for
Exposure of Metals and Alloys by Alternate Immersion in
Neutral 3.5 % Sodium Chloride Solution
ThisstandardisissuedunderthefixeddesignationG44;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginal
adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.Asuperscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope 1.6 This international standard was developed in accor-
dance with internationally recognized principles on standard-
1.1 This practice covers procedures for making alternate
ization established in the Decision on Principles for the
immersion stress corrosion tests in 3.5 % sodium chloride
Development of International Standards, Guides and Recom-
(NaCl) (Note 1). It is primarily for tests of aluminum alloys
mendations issued by the World Trade Organization Technical
(Test Method G47) and ferrous alloys, but may be used for
Barriers to Trade (TBT) Committee.
other metals exhibiting susceptibility to chloride ions. It sets
forththeenvironmentalconditionsofthetestandthemeansfor
2. Referenced Documents
controlling them.
2.1 ASTM Standards:
NOTE 1—Alternate immersion stress corrosion exposures are some-
D1141 Practice for the Preparation of Substitute Ocean
times made in substitute ocean water (without heavy metals) prepared in
Water
accordance with Practice D1141. The general requirements of this present
D1193 Specification for Reagent Water
practice are also applicable to such exposures except that the reagents
used, the solution concentration, and the solution pH should be as G1 Practice for Preparing, Cleaning, and Evaluating Corro-
specified in Practice D1141.
sion Test Specimens
G47 Test Method for Determining Susceptibility to Stress-
1.2 This practice can be used for both stressed and un-
Corrosion Cracking of 2XXX and 7XXX Aluminum
stressed corrosion specimens. Historically, it has been used for
Alloy Products
stress-corrosion cracking testing, but is often used for other
forms of corrosion, such as uniform, pitting, intergranular, and
3. Summary of Practice
galvanic.
3.1 The alternate immersion test utilizes a 1 h cycle that
1.3 This practice is intended for alloy development and for
includes a 10 min period in an aqueous solution of 3.5 %
applications where the alternate immersion test is to serve as a
sodium chloride (NaCl) followed by a 50 min period out of the
control test on the quality of successive lots of the same
solution, during which the specimens are allowed to dry. This
material. Therefore, strict test conditions are stipulated for
1 h cycle is continued 24 h/day for the total number of days
maximumassurancethatvariationsinresultsareattributableto
recommended for the particular alloy being tested. Typically,
variations in the material being tested.
aluminum and ferrous alloys are exposed from 20 days to 90
1.4 The values stated in SI units are to be regarded as
days or longer, depending upon the resistance of the alloy to
standard. The values given in parentheses after SI units are
corrosion by saltwater.
provided for information only and are not considered standard.
4. Significance and Use
1.5 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the 4.1 The 3.5 % NaCl alternate immersion procedure is a
responsibility of the user of this standard to establish appro-
general,all-purposeprocedurethatproducesvalidcomparisons
priate safety, health, and environmental practices and deter- for most metals, particularly when specimens are exposed at
mine the applicability of regulatory limitations prior to use.
high levels of applied stress or stress intensity.
4.2 While the alternate immersion test is an accelerated test
and is considered to be representative of certain natural
This practice is under the jurisdiction of ASTM Committee G01 on Corrosion
of Metals and is the direct responsibility of Subcommittee G01.06 on Environmen-
tally Assisted Cracking. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved May 1, 2021. Published June 2021. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 1975. Last previous edition approved in 2013 as G44 – 99 (2013). DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/G0044-21. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
G44−21
conditions, it is not intended to predict performance in special- elapse from the time the first portion of any specimen is
ized chemical environments in which a different mode of covered (or uncovered) until it is fully covered (or uncovered)
cracking may be operative. For example, it does not predict the by solution.
performance of aluminum alloys in highly acidic environments
6.3 Materials of Construction:
such as heated inhibited red fuming nitric acid (IRFNA). For
6.3.1 Materialsofconstructionthatcomeincontactwiththe
such cases, the results of the alternate immersion test are of
salt solution shall be such that they are not affected by the
doubtful significance until a relationship has been established
corrodent to an extent that they can cause contamination of the
between it and anticipated service environments.
solution and change its corrosiveness.
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
metal parts should be protected with a suitable corrosion-
environments.
resistant coating that also satisfies paragraph 6.3.1.
NOTE2—Thealternateimmersionconceptcanbeusefulforexposureof
corrosion specimens in other solutions because the procedure and appa-
6.4 Specimen Holders:
ratus provide a controlled set of conditions. Details of this are beyond the
6.4.1 Specimen holders should be designed to electrically
scope of this practice.
insulatethespecimensfromeachotherandfromanyotherbare
metal. When this is not possible, as in the case of certain
5. Interferences
stressing bolts or jigs, the bare metal contacting the specimen
5.1 A disadvantage of the 3.5 % NaCl alternate immersion
should be isolated from the corrodent by a suitable coating.
test for stress-corrosion cracking tests of certain high-strength
Protective coatings should be of a type that will not leach
aluminum alloys is the severe pitting that develops in the
inhibiting or accelerating ions or protective oils over the
specimens. Such pitting can interfere with the initiation of
noncoated portions of the specimen. Coatings containing
stress-corrosion cracks and may cause mechanical failures that
chromates are to be particularly avoided.
complicatetheinterpretationofthestress-corrosiontestresults.
6.4.2 The shape and form of specimen supports and holders
This is particularly a problem with copper-bearing aluminum
should be such that:
alloys when tested with specimens of small cross section.
6.4.2.1 They avoid, as much as possible, any interference of
Thorough metallographic examination of the specimens is
free contact of the specimen with the salt solution;
necessary for proper diagnosis of the cause of failure and
6.4.2.2 They do not obstruct air flow over the specimen,
separation of stress corrosion failures from those caused by
thereby retarding the drying rate;
mechanical overload.
6.4.2.3 They do not retain a pool of solution in contact with
5.2 An advantage of the substitute ocean water (Note 1)is
the specimen after the immersion period; and
that it causes less pitting corrosion of aluminum alloys than the
6.4.2.4 Drainage from one specimen does not directly con-
3.5 % NaCl solution.
tact any other specimen.
6. Apparatus
7. Reagents
6.1 Method of Cycling—Any suitable mechanism may be
7.1 Reagent grade sodium chloride (NaCl) shall be used
used to accomplish the immersion portion of the cycle pro-
conforming to the specifications of the Committee onAnalyti-
vided that: (1) it achieves the specified rate of immersion and
cal Reagents of the American Chemical Society, where such
removal, and (2) the apparatus is constructed of suitable inert 3
specifications are applicable (see Note 1).
materials. The usual methods of immersion are:
7.2 The solution shall be prepared using distilled or deion-
6.1.1 Specimens placed on a movable rack that is periodi-
ized water conforming to the purity requirements of Specifi-
cally lowered into a stationary tank containing the solution.
cation D1193, Type IV reagent water except that for this
6.1.2 Specimens placed on a hexagonal Ferris wheel ar-
practice the values for chloride and sodium shall be disre-
rangement which rotates every 10 min through 60° and,
garded.
thereby, passes the specimens through a stationary tank of
solution. Use of a Ferris wheel continuously rotating at a rate
8. Solution Conditions
of 1 revolution per hour is not recommended for very large
8.1 Concentration—The salt solution shall be prepared by
specimens for which the rate of immersion would be slower
dissolving 3.5 6 0.1 parts by weight of NaCl in 96.5 parts of
than that specified in 6.2.
water.
6.1.3 Specimens placed in a stationary tray open to the
atmosphere and having the solution moved by air pressure,
nonmetallic pump, or gravity drain from a reservoir to the tray.
Reagent Chemicals, American Chemical Society Specifications, American
Chemical Society, Washington, DC. For suggestions on the testing of reagents not
6.2 Rate of Immersion—The rate of immersion
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: G44 − 99 (Reapproved 2013) G44 − 21
Standard Practice for
Exposure of Metals and Alloys by Alternate Immersion in
Neutral 3.5 % Sodium Chloride Solution
This standard is issued under the fixed designation G44; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. 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 exhibiting
susceptibility to chloride ions. 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 SpecificationPractice 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 SpecificationPractice D1141.
1.2 This practice can be used for both stressed and unstressed corrosion specimens. Historically, it has been used for
stress-corrosion cracking testing, but is often used for other forms of corrosion, such as uniform, pitting, intergranular, and
galvanic.
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 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.after
SI units are provided for information only and are not considered standard.
1.5 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
This practice is under the jurisdiction of ASTM Committee G01 on Corrosion of Metals and is the direct responsibility of Subcommittee G01.06 on Environmentally
Assisted Cracking.
Current edition approved May 1, 2013May 1, 2021. Published July 2013June 2021. Originally approved in 1975. Last previous edition approved in 20052013 as G44 – 99
(2005).(2013). DOI: 10.1520/G0044-99R13.10.1520/G0044-21.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’sstandard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
G44 − 21
D1141 Practice for the Preparation of Substitute Ocean Water
D1193 Specification for Reagent Water
E3 Guide for Preparation of Metallographic Specimens
G1 Practice for Preparing, Cleaning, and Evaluating Corrosion Test Specimens
G16 Guide for Applying Statistics to Analysis of Corrosion Data
G47 Test Method for Determining Susceptibility to Stress-Corrosion Cracking of 2XXX and 7XXX Aluminum Alloy Products
3. Summary of Practice
3.1 The alternate immersion test utilizes a 1-h1 h cycle that includes a 10-min10 min period in an aqueous solution of 3.5 %
sodium chloride (NaCl) followed by a 50-min50 min period out of the solution, during which the specimens are allowed to dry.
This 1-h1 h cycle is continued 24 h/day for the total number of days recommended for the particular alloy being tested. Typically,
aluminum and ferrous alloys are exposed from 2020 days to 90 days or longer, depending upon the resistance of the alloy to
corrosion by saltwater.
4. Significance and Use
4.1 The 3.5 % NaCl alternate immersion procedure is a general, all-purpose procedure that produces valid comparisons for most
metals, particularly when specimens are exposed at high levels of applied stress or stress intensity.
4.2 While the alternate immersion test is an accelerated test and is considered to be representative of certain natural conditions,
it is not intended to predict performance in specialized chemical environments in which a different mode of cracking may be
operative. For example, it does not predict the performance of aluminum alloys in highly acidic environments such as heated
inhibited red fuming nitric acid (IRFNA). For such cases, the results of the alternate immersion test are of doubtful significance
until a relationship has been established between it and anticipated service environments.
4.3 While this practice is applicable in some degree to all metals, it is not equally discriminative of all alloys, even within the same
metal system. Consequently, information should be established to allow comparisons of performances of the alloy of interest in
the alternate immersion test and in natural environments.
NOTE 2—The alternate immersion concept can be useful for exposure of corrosion specimens in other solutions because the procedure and apparatus
provide a controlled set of conditions. Details of this are beyond the scope of this practice.
5. Interferences
5.1 A disadvantage of the 3.5 % NaCl alternate immersion test for stress-corrosion cracking tests of certain high-strength
aluminum alloys is the severe pitting that develops in the specimens. Such pitting can interfere with the initiation of
stress-corrosion cracks and may cause mechanical failures that complicate the interpretation of the stress-corrosion test results.
This is particularly a problem with copper-bearing aluminum alloys when tested with specimens of small cross section. Thorough
metallographic examination of the specimens is necessary for proper diagnosis of the cause of failure and separation of stress
corrosion failures from those caused by mechanical overload.
5.2 An advantage of the substitute ocean water (Note 1) is that it causes less pitting corrosion of aluminum alloys than the 3.5 %
NaCl solution.
6. Apparatus
6.1 Method of Cycling—Any suitable mechanism may be used to accomplish the immersion portion of the cycle provided that:
(1) it achieves the specified rate of immersion and removal, and (2) the apparatus is constructed of suitable inert materials. The
usual methods of immersion are:
6.1.1 Specimens placed on a movable rack that is periodically lowered into a stationary tank containing the solution.
6.1.2 Specimens placed on a hexagonal Ferris wheel arrangement which rotates every 10 min through 60° and, thereby, passes
the specimens through a stationary tank of solution. Use of a Ferris wheel continuously rotating at a rate of 1 revolution per hour
is not recommended for very large specimens for which the rate of immersion would be slower than that specified in 6.2.
G44 − 21
6.1.3 Specimens placed in a stationary tray open to the atmosphere and having the solution moved by air pressure, nonmetallic
pump, or gravity drain from a reservoir to the tray.
6.2 Rate of Immersion—The rate of immersion and removal of the specimens from the solution should be as rapid as possible
without jarring them. For purposes of standardization, an arbitrary limit shall be adopted such that no more than 2 min 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:
6.3.1 Materials of construction that come in contact with the salt solution shall be such that they are not affected by the corrodent
to an extent that they can cause contamination of the solution and change its corrosiveness.
6.3.2 Use of inert plastics or glass is recommended where feasible.
6.3.3 Metallic materials of construction should be selected from alloys that are recommended for marine use and of the same
general type as the metals being tested. Preferably, all metal parts should be protected with a suitable corrosion-resistant coating
that also satisfies paragraph 6.3.1.
6.4 Specimen Holders:
6.4.1 Specimen holders should be designed to electrically insulate the specimens from each other and from any other bare metal.
When this is not possible, as in the case of certain stressing bolts or jigs, the bare metal contacting the specimen should be isolated
from the corrodent by a suitable coating. Protective coatings should be of a type that will not leach inhibiting or accelerating ions
or protective oils over the noncoated portions of the specimen. Coatings containing chromates are to be particularly avoided.
NOTE 3—Coatings that have been satisfactorily used by several laboratories are described in Appendix X1.
6.4.2 The shape and form of specimen supports and holders should be such that:
6.4.2.1 They avoid, as much as possible, any interference of free contact of the specimen with the salt solution;
6.4.2.2 They do not obstruct air flow over the specimen, thereby retarding the drying rate;
6.4.2.3 They do not retain a pool of solution in contact with the specimen after the immersion period; and
6.4.2.4 Drainage from one specimen does not directly contact any other specimen.
7. Reagents
7.1 Reagent grade sodium chloride (NaCl) shall be used conforming to the specifications of the Committee on Analytical Reagents
of the American Chemical Society, where such specifications are applicable (see Note 1).
7.2 The solution shall be prepared using distilled or deionized water conforming to the purity requirements of Specification D1193,
Type IV reagent water except that for this practice the values for chloride and sodium shall be disregarded.
8. Solution Conditions
8.1 Concentration—The salt solution shall be prepared by dissolving 3.5 6 0.1 parts by weight of NaCl in 96.5 parts of water.
8.2 Solution pH:
Reagent Chemicals, American Chemical Society Specifications, American Chemical Society, Washington, DC. For suggestions on the testing of reagents not listed by
the American Chemical Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and National
Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, MD.
G44 − 21
8.2.1 The pH of the salt solution, when freshly prepared, shall be within the range from 6.4 to 7.2. Only diluted, reagent grade
hydrochloric acid (HCl) or reagent grade sodium hydroxide (NaOH) shall be used to adjust the pH.
8.2.2 Experience has shown that periodic adjustment of pH is not necessary when the minimum volume of solution is met and
the solution is replaced at the specified interval. For a new testing facility, however, it is recommended that daily pH measurements
be made for one week to verify stable operation a
...