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ASTM G78-20

(Guide)

Standard Guide for Crevice Corrosion Testing of Iron-Base and Nickel-Base Stainless Alloys in Seawater and Other Chloride-Containing Aqueous Environments

Standard Guide for Crevice Corrosion Testing of Iron-Base and Nickel-Base Stainless Alloys in Seawater and Other Chloride-Containing Aqueous Environments

SIGNIFICANCE AND USE
4.1 This guide covers procedures for crevice-corrosion testing of iron-base and nickel-base stainless alloys in seawater. The guidance provided may also be applicable to crevice corrosion testing in other chloride containing natural waters and various laboratory prepared aqueous chloride environments.  
4.1.1 While this guide focuses on testing of iron-base and nickel-base stainless alloys, the procedures and evaluations methods described herein have been successfully applied to characterize the crevice corrosion performance of other alloy systems (see, for example, Aylor et al.3).
Note 1: In the case of copper alloys, the occurrence of crevice-related corrosion associated with different corrosion mechanisms takes place immediately adjacent to the crevice former rather than within the occlusion.  
4.2 This guide describes the use of a variety of crevice formers including the nonmetallic, segmented washer design referred to as the multiple crevice assembly (MCA) as described in 9.2.2.  
4.3 In-service performance data provide the most reliable determination of whether a material would be satisfactory for a particular end use. Translation of laboratory data from a single test program to predict service performance under a variety of conditions should be avoided. Terms, such as immunity, superior resistance, etc., provide only a general and relatively qualitative description of an alloy's corrosion performance. The limitations of such terms in describing resistance to crevice corrosion should be recognized.  
4.4 While the guidance provided is generally for the purpose of evaluating sheet and plate materials, it is also applicable for crevice-corrosion testing of other product forms, such as tubing and bars.  
4.5 The presence or absence of crevice corrosion under one set of conditions is no guarantee that it will or will not occur under other conditions. Because of the many interrelated metallurgical, environmental, and geometric factors known to affect crevice...
SCOPE
1.1 This guide covers information for conducting crevice-corrosion tests and identifies factors that may affect results and influence conclusions.  
1.2 These procedures can be used to identify conditions most likely to result in crevice corrosion and provide a basis for assessing the relative resistance of various alloys to crevice corrosion under certain specified conditions.  
1.3 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.  
1.4 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use. For a specific warning statement, see 7.1.  
1.5 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
31-Oct-2020
ICS
77.060 - Corrosion of metals
Technical Committee
G01 - Corrosion of Metals
Drafting Committee
G01.04 - Corrosion of Metals in Natural Atmospheric and Aqueous Environments
Current Stage
Ref Project

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ASTM G78-20 - Standard Guide for Crevice Corrosion Testing of Iron-Base and Nickel-Base Stainless Alloys in Seawater and Other Chloride-Containing Aqueous EnvironmentsASTM G78-20 - Standard Guide for Crevice Corrosion Testing of Iron-Base and Nickel-Base Stainless Alloys in Seawater and Other Chloride-Containing Aqueous Environments
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ASTM G78-20 - Standard Guide for Crevice Corrosion Testing of Iron-Base and Nickel-Base Stainless Alloys in Seawater and Other Chloride-Containing Aqueous Environments
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REDLINE ASTM G78-20 - Standard Guide for Crevice Corrosion Testing of Iron-Base and Nickel-Base Stainless Alloys in Seawater and Other Chloride-Containing Aqueous EnvironmentsREDLINE ASTM G78-20 - Standard Guide for Crevice Corrosion Testing of Iron-Base and Nickel-Base Stainless Alloys in Seawater and Other Chloride-Containing Aqueous Environments
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REDLINE ASTM G78-20 - Standard Guide for Crevice Corrosion Testing of Iron-Base and Nickel-Base Stainless Alloys in Seawater and Other Chloride-Containing Aqueous Environments
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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: G78 − 20
Standard Guide for
Crevice Corrosion Testing of Iron-Base and Nickel-Base
Stainless Alloys in Seawater and Other Chloride-Containing
1
Aqueous Environments
ThisstandardisissuedunderthefixeddesignationG78;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginal
adoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
Crevice corrosion of iron-base and nickel-base stainless alloys can occur when an occlusion or
crevice limits access of the bulk environment to a localized area of the metal surface. Localized
environmental changes in this stagnant area can result in the formation of acidic/high chloride
conditions that may result in initiation and propagation of crevice corrosion of susceptible alloys.
In practice, crevices can generally be classified into two categories: (1) naturally occurring, that is,
those created by biofouling, sediment, debris, deposits, etc. and (2) man-made, that is, those created
during manufacturing, fabrication, assembly, or service. Crevice formers utilized in laboratory and
field studies can represent actual geometric conditions encountered in some service applications. Use
of such crevice formers in service-type environments are not considered accelerated test methods.
The geometry of a crevice can be described by the dimensions of crevice gap and crevice depth.
Crevice gap is identified as the width or space between the metal surface and the crevice former.
Crevice depth is the distance from the mouth to the center or base of the crevice.
1. Scope 1.5 This international standard was developed in accor-
dance with internationally recognized principles on standard-
1.1 This guide covers information for conducting crevice-
ization established in the Decision on Principles for the
corrosion tests and identifies factors that may affect results and
Development of International Standards, Guides and Recom-
influence conclusions.
mendations issued by the World Trade Organization Technical
1.2 These procedures can be used to identify conditions
Barriers to Trade (TBT) Committee.
mostlikelytoresultincrevicecorrosionandprovideabasisfor
assessing the relative resistance of various alloys to crevice
2. Referenced Documents
corrosion under certain specified conditions. 2
2.1 ASTM Standards:
1.3 The values stated in SI units are to be regarded as
G1Practice for Preparing, Cleaning, and Evaluating Corro-
standard. The values given in parentheses after SI units are
sion Test Specimens
provided for information only and are not considered standard.
G4Guide for Conducting Corrosion Tests in Field Applica-
tions
1.4 This standard does not purport to address all of the
G46Guide for Examination and Evaluation of Pitting Cor-
safety concerns, if any, associated with its use. It is the
rosion
responsibility of the user of this standard to establish appro-
G48Test Methods for Pitting and Crevice Corrosion Resis-
priate safety, health, and environmental practices and deter-
tance of Stainless Steels and Related Alloys by Use of
mine the applicability of regulatory limitations prior to use.
Ferric Chloride Solution
For a specific warning statement, see 7.1.
G52PracticeforExposingandEvaluatingMetalsandAlloys
in Surface Seawater
1
This guide is under the jurisdiction ofASTM Committee G01 on Corrosion of
Metals and is the direct responsibility of Subcommittee G01.04 on Corrosion of
2
Metals in Natural Atmospheric and Aqueous Environments. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Nov. 1, 2020. Published November 2020. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1983. Last previous edition approved in 2015 as G78–15. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/G0078-20. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
G78−20
G193Terminology and Acronyms Relating to Corrosion 4.4 While the guidance provided is generally for the pur-
pose of evaluating sheet and plate materials, it is also appli-
3. Terminology
cableforcrevice-corrosiontestingofotherproductforms,such
3.1 Definitions of related terms can be found in Terminol- as tubing and bars.
ogy G193.
4.5 The presence or absence of crevice corrosion under one
set of conditions is no guarantee that it will or will not occur
4. Significance and Use
under other conditions. B
...

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: G78 − 15 G78 − 20
Standard Guide for
Crevice Corrosion Testing of Iron-Base and Nickel-Base
Stainless Alloys in Seawater and Other Chloride-Containing
1
Aqueous Environments
This standard is issued under the fixed designation G78; 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
Crevice corrosion of iron-base and nickel-base stainless alloys can occur when an occlusion or
crevice limits access of the bulk environment to a localized area of the metal surface. Localized
environmental changes in this stagnant area can result in the formation of acidic/high chloride
conditions that may result in initiation and propagation of crevice corrosion of susceptible alloys.
In practice, crevices can generally be classified into two categories: (1) naturally occurring, that is,
those created by biofouling, sediment, debris, deposits, etc. and (2) man-made, that is, those created
during manufacturing, fabrication, assembly, or service. Crevice formers utilized in laboratory and
field studies can represent actual geometric conditions encountered in some service applications. Use
of such crevice formers in service-type environments are not considered accelerated test methods.
The geometry of a crevice can be described by the dimensions of crevice gap and crevice depth.
Crevice gap is identified as the width or space between the metal surface and the crevice former.
Crevice depth is the distance from the mouth to the center or base of the crevice.
1. Scope
1.1 This guide covers information for conducting crevice-corrosion tests and identifies factors that may affect results and influence
conclusions.
1.2 These procedures can be used to identify conditions most likely to result in crevice corrosion and provide a basis for assessing
the relative resistance of various alloys to crevice corrosion under certain specified conditions.
1.3 The values stated in SI units are to be regarded as standard. The values given in parentheses are for information only. after
SI units are provided for information only and are not considered standard.
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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use. For a specific warning statement, see 7.1.
1.5 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.
1
This guide is under the jurisdiction of ASTM Committee G01 on Corrosion of Metals and is the direct responsibility of Subcommittee G01.04 on Corrosion of Metals
in Natural Atmospheric and Aqueous Environments.
Current edition approved June 1, 2015Nov. 1, 2020. Published July 2015November 2020. Originally approved in 1983. Last previous edition approved in 20122015 as
G78–01 (2012). –15. DOI: 10.1520/G0078-15.10.1520/G0078-20.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
G78 − 20
2. Referenced Documents
2
2.1 ASTM Standards:
G1 Practice for Preparing, Cleaning, and Evaluating Corrosion Test Specimens
G4 Guide for Conducting Corrosion Tests in Field Applications
G46 Guide for Examination and Evaluation of Pitting Corrosion
G48 Test Methods for Pitting and Crevice Corrosion Resistance of Stainless Steels and Related Alloys by Use of Ferric Chloride
Solution
G52 Practice for Exposing and Evaluating Metals and Alloys in Surface Seawater
G193 Terminology and Acronyms Relating to Corrosion
3. Terminology
3.1 Definitions of related terms can be found in Terminology G193.
4. Significance and Use
4.1 This guide covers procedures for crevice-corrosion testing of iron-base and nickel-base stainless alloys in seawater. The
guidance provided may also be applicable to crevice corrosion testing in other chloride containing natural waters and various
laboratory prepared aqueous chloride environments.
4.1.1 While this gu
...

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FIG. 1 Typical Stressed U-bends  
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SCOPE
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1.3 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.  
1.3.1 Exception—In X1.2.1, mils per year (MPY) are regarded as standard for the target corrosion rate.  
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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.5 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.

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ASTM
ASTM G39-99(2021)(Practice)
Standard Practice for Preparation and Use of Bent-Beam Stress-Corrosion Test Specimens

SIGNIFICANCE AND USE
5.1 The bent-beam specimen is designed for determining the stress-corrosion behavior of alloy sheets and plates in a variety of environments. The bent-beam specimens are designed for testing at stress levels below the elastic limit of the alloy. For testing in the plastic range, U-bend specimens should be employed (see Practice G30). Although it is possible to stress bent-beam specimens into the plastic range, the stress level cannot be calculated for plastically-stressed three- and four-point loaded specimens as well as the double-beam specimens. Therefore, the use of bent-beam specimens in the plastic range is not recommended for general use.
SCOPE
1.1 This practice covers procedures for designing, preparing, and using bent-beam stress-corrosion specimens.  
1.2 Different specimen configurations are given for use with different product forms, such as sheet or plate. This practice is applicable to specimens of any metal that are stressed to levels less than the elastic limit of the material, and therefore, the applied stress can be accurately calculated or measured (see Note 1). Stress calculations by this practice are not applicable to plastically stressed specimens.  
Note 1: It is the nature of these practices that only the applied stress can be calculated. Since stress-corrosion cracking is a function of the total stress, for critical applications and proper interpretation of results, the residual stress (before applying external stress) or the total elastic stress (after applying external stress) should be determined by appropriate nondestructive methods, such as X-ray diffraction (1).2  
1.3 Test procedures are given for stress-corrosion testing by exposure to gaseous and liquid environments.  
1.4 The bent-beam test is best suited for flat product forms, such as sheet, strip, and plate. For plate material the bent-beam specimen is more difficult to use because more rugged specimen holders must be built to accommodate the specimens. A double-beam modification of a four-point loaded specimen to utilize heavier materials is described in 10.5.  
1.5 The exposure of specimens in a corrosive environment is treated only briefly since other practices deal with this aspect, for example, Practices D1141, G30, G36, G44, G50, and G85. The experimenter is referred to ASTM Special Technical Publication 425 (2).  
1.6 The bent-beam practice generally constitutes a constant strain (deflection) test. Once cracking has initiated, the state of stress at the tip of the crack as well as in uncracked areas has changed, and therefore, the known or calculated stress or strain values discussed in this practice apply only to the state of stress existing before initiation of cracks.  
1.7 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.  
1.8  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. (For more specific safety hazard information see Section 7 and 12.1.)  
1.9 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.

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ASTM
ASTM G37-98(2021)(Practice)
Standard Practice for Use of Mattsson's Solution of pH 7.2 to Evaluate the Stress-Corrosion Cracking Susceptibility of Copper-Zinc Alloys

SIGNIFICANCE AND USE
4.1 This test environment is believed to give an accelerated ranking of the relative or absolute degree of stress-corrosion cracking susceptibility for different brasses. It has been found to correlate well with the corresponding service ranking in environments that cause stress-corrosion cracking which is thought to be due to the combined presence of traces of moisture and ammonia vapor. The extent to which the accelerated ranking correlates with the ranking obtained after long-term exposure to environments containing corrodents other than ammonia is not at present known. Examples of such environments may be severe marine atmospheres (Cl−), severe industrial atmospheres (predominantly SO2), and super-heated ammonia-free steam.  
4.2 It is not possible at present to specify any particular time to failure (defined on the basis of any particular failure criteria) in pH 7.2 Mattsson’s solution that corresponds to a distinction between acceptable and unacceptable stress-corrosion behavior in brass alloys. Such particular correlations must be determined individually.  
4.3 Mattsson's solution of pH 7.2 may also cause stress independent general and intergranular corrosion of brasses to some extent. This leads to the possibility of confusing stress-corrosion failures with mechanical failures induced by corrosion-reduced net cross sections. This danger is particularly great with small cross section specimens, high applied stress levels, long exposure periods and stress-corrosion resistant alloys. Careful metallographic examination is recommended for correct diagnosis of the cause of failure. Alternatively, unstressed control specimens may be exposed to evaluate the extent to which stress independent corrosion degrades mechanical properties.
SCOPE
1.1 This practice covers the preparation and use of Mattsson’s solution of pH 7.2 as an accelerated stress-corrosion cracking test environment for brasses (copper-zinc base alloys). The variables (to the extent that these are known at present) that require control are described together with possible means for controlling and standardizing these variables.  
1.2 This practice is recommended only for brasses (copper-zinc base alloys). The use of this test environment is not recommended for other copper alloys since the results may be erroneous, providing completely misleading rankings. This is particularly true of alloys containing aluminum or nickel as deliberate alloying additions.  
1.3 This practice is intended primarily where the test objective is to determine the relative stress-corrosion cracking susceptibility of different brasses under the same or different stress conditions or to determine the absolute degree of stress corrosion cracking susceptibility, if any, of a particular brass or brass component under one or more specific stress conditions. Other legitimate test objectives for which this test solution may be used do, of course, exist. The tensile stresses present may be known or unknown, applied or residual. The practice may be applied to wrought brass products or components, brass castings, brass weldments, and so forth, and to all brasses. Strict environmental test conditions are stipulated for maximum assurance that apparent variations in stress-corrosion susceptibility are attributable to real variations in the material being tested or in the tensile stress level and not to environmental variations.  
1.4 This practice relates solely to the preparation and control of the test environment. No attempt is made to recommend surface preparation or finish, or both, as this may vary with the test objectives. Similarly, no attempt is made to recommend particular stress-corrosion test specimen configurations or methods of applying the stress. Test specimen configurations that may be used are referenced in Practice G30 and STP 425.2  
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included ...

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ASTM
ASTM G186-05(2021)(Test Method)
Standard Test Method for Determining Whether Gas-Leak-Detector Fluid Solutions Can Cause Stress Corrosion Cracking of Brass Alloys

SIGNIFICANCE AND USE
5.1 Brass components are routinely used in compressed gas service for valves, pressure regulators, connectors and many other components. Although soft brass is not susceptible to ammonia SCC, work-hardened brass is susceptible if its hardness exceeds about 54 HR 30T (55HRB) (Rockwell scale). Normal assembly of brass components should not induce sufficient work hardening to cause susceptibility to ammonia SCC. However, it is has been observed that over-tightening of the components will render them susceptible to SCC, and the problem becomes more severe in older components that have been tightened many times. In this test, the specimens are obtained in the hardened condition and are strained beyond the elastic limit to accelerate the tendency towards SCC.  
5.2 It is normal practice to use LDFs to check pressurized systems to assure that leaking is not occurring. LDFs are usually aqueous solutions containing surfactants that will form bubbles at the site of a leak. If the LDF contains ammonia or other agent that can cause SCC in brass, serious damage can occur to the system that will compromise its safety and integrity.  
5.3 It is important to test LDFs to assure that they do not cause SCC of brass and to assure that the use of these products does not compromise the integrity of the pressure containing system.  
5.4 It has been found that corrosion of brass is necessary before SCC can occur. The reason for this is that the corrosion process results in cupric and cuprous ions accumulating in the electrolyte. Therefore, adding copper metal and cuprous oxide (Cu2O) to the aqueous solution accelerates the SCC process if agents that cause SCC are present. However, adding these components to a solution that does not cause SCC will not make stressed brass crack.  
5.5 Repeated application of the solution to the specimen followed by a drying period causes the components in the solution to concentrate thereby further increasing the rate of cracking. This also simulates se...
SCOPE
1.1 This test method covers an accelerated test method for evaluating the tendency of gas leak detection fluids (LDFs) to cause stress corrosion cracking (SCC) of brass components in compressed gas service.  
1.2 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.  
1.3 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.  
1.4 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.

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