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ASTM G46-94(2005)

(Guide)

Standard Guide for Examination and Evaluation of Pitting Corrosion

Standard Guide for Examination and Evaluation of Pitting Corrosion

SIGNIFICANCE AND USE
It is important to be able to determine the extent of pitting, either in a service application where it is necessary to predict the remaining life in a metal structure, or in laboratory test programs that are used to select the most pitting-resistant materials for service.
SCOPE
1.1 This guide covers the selection of procedures that can be used in the identification and examination of pits and in the evaluation of pitting (See Terminology G 15) corrosion to determine the extent of its effect.
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
30-Apr-2005
ICS
77.060 - Corrosion of metals
Technical Committee
G01 - Corrosion of Metals
Drafting Committee
G01.05 - Laboratory Corrosion Tests
Current Stage
Ref Project

Relations

Replaces
ASTM G46-94(1999) - Standard Guide for Examination and Evaluation of Pitting Corrosion
Effective Date
01-May-2005
Replaced By
ASTM G46-94(2013) - Standard Guide for Examination and Evaluation of Pitting Corrosion
Effective Date
01-May-2013
Referred By
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
Effective Date
01-May-2005
Referred By
ASTM G33-99(2020) - Standard Practice for Recording Data from Atmospheric Corrosion Tests of Metallic-Coated Steel Specimens
Effective Date
01-May-2005
Referred By
ASTM G109-23 - Standard Test Methods for Determining Effects of Chemical Admixtures on Corrosion of Embedded Steel Reinforcement in Concrete Exposed to Chloride Environments
Effective Date
01-May-2005
Referred By
ASTM G31-21 - Standard Guide for Laboratory Immersion Corrosion Testing of Metals
Effective Date
01-May-2005
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
01-May-2005
Referred By
ASTM G48-11(2020)e1 - Standard Test Methods for Pitting and Crevice Corrosion Resistance of Stainless Steels and Related Alloys by Use of Ferric Chloride Solution
Effective Date
01-May-2005
Referred By
ASTM G87-02(2023) - Standard Practice for Conducting Moist SO<inf>2</inf> Tests
Effective Date
01-May-2005
Referred By
ASTM F1110-09(2020) - Standard Test Method for Sandwich Corrosion Test
Effective Date
01-May-2005
Referred By
ASTM G16-13(2019) - Standard Guide for Applying Statistics to Analysis of Corrosion Data
Effective Date
01-May-2005
Referred By
ASTM G107-95(2020)e1 - Standard Guide for Formats for Collection and Compilation of Corrosion Data for Metals for Computerized Database Input
Effective Date
01-May-2005
Referred By
ASTM D6208-07(2020) - Standard Test Method for Repassivation Potential of Aluminum and Its Alloys by Galvanostatic Measurement
Effective Date
01-May-2005
Referred By
ASTM G157-98(2018) - Standard Guide for Evaluating Corrosion Properties of Wrought Iron- and Nickel-Based Corrosion Resistant Alloys for Chemical Process Industries
Effective Date
01-May-2005
Referred By
ASTM G217-16(2022) - Standard Guide for Corrosion Monitoring in Laboratories and Plants with Coupled Multielectrode Array Sensor Method
Effective Date
01-May-2005

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ASTM G46-94(2005) - Standard Guide for Examination and Evaluation of Pitting CorrosionASTM G46-94(2005) - Standard Guide for Examination and Evaluation of Pitting Corrosion
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ASTM G46-94(2005) - Standard Guide for Examination and Evaluation of Pitting Corrosion
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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: G46 − 94(Reapproved 2005)
Standard Guide for
1
Examination and Evaluation of Pitting Corrosion
ThisstandardisissuedunderthefixeddesignationG46;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginal
adoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 4. Identification and Examination of Pits
4.1 VisualInspection—Avisualexaminationofthecorroded
1.1 Thisguidecoverstheselectionofproceduresthatcanbe
used in the identification and examination of pits and in the metal surface is usually beneficial, and this is done under
evaluation of pitting (See Terminology G15) corrosion to ordinary light, with or without the use of a low-power
determine the extent of its effect. magnifying glass, to determine the extent of corrosion and the
apparentlocationofpits.Itisoftenadvisabletophotographthe
1.2 This standard does not purport to address all of the
corroded surface at this point so that it can be compared with
safety concerns, if any, associated with its use. It is the
the clean surface after the removal of corrosion products.
responsibility of the user of this standard to establish appro-
4.1.1 If the metal specimen has been exposed to an un-
priate safety and health practices and determine the applica-
knownenvironment,thecompositionofthecorrosionproducts
bility of regulatory limitations prior to use.
may be of value in determining the cause of corrosion. Follow
recommended procedures in the removal of particulate corro-
2. Referenced Documents
sion products and reserve them for future identification (see
2
2.1 ASTM Standards:
NACE RP-01-73).
E3Guide for Preparation of Metallographic Specimens
4.1.2 To expose the pits fully, use recommended cleaning
G1Practice for Preparing, Cleaning, and Evaluating Corro-
procedures to remove the corrosion products and avoid solu-
sion Test Specimens
tions that attack the base metal excessively (see Practice G1).
G15TerminologyRelatingtoCorrosionandCorrosionTest-
It may be advisable during cleaning to probe the pits with a
3
ing (Withdrawn 2010)
pointed tool to determine the extent of undercutting or subsur-
G16Guide for Applying Statistics to Analysis of Corrosion
face corrosion (Fig. 1). However, scrubbing with a stiff bristle
Data
brush will often enlarge the pit openings sufficiently by
2.2 National Association of Corrosion Engineers Standard:
removal of corrosion products, or undercut metal to make the
NACE RP-01-73Collection and Identification of Corrosion pits easier to evaluate.
4
Products
4.1.3 Examine the cleaned metal surface under ordinary
lighttodeterminetheapproximatesizeanddistributionofpits.
3. Significance and Use
Follow this procedure by a more detailed examination through
a microscope using low magnification (20×).
3.1 It is important to be able to determine the extent of
4.1.4 Determine the size, shape, and density of pits.
pitting, either in a service application where it is necessary to
4.1.4.1 Pits may have various sizes and shapes. A visual
predict the remaining life in a metal structure, or in laboratory
examinationofthemetalsurfacemayshowaround,elongated,
test programs that are used to select the most pitting-resistant
or irregular opening, but it seldom provides an accurate
materials for service.
indication of corrosion beneath the surface. Thus, it is often
necessary to cross section the pit to see its actual shape and to
determine its true depth. Several variations in the cross-
1
This guide is under the jurisdiction ofASTM Committee G01 on Corrosion of
sectioned shape of pits are shown in Fig. 1.
Metals and is the direct responsibility of Subcommittee G01.05 on Laboratory
4.1.4.2 It is a tedious job to determine pit density by
Corrosion Tests.
Current edition approved May 1, 2005. Published May 2005. Originally
counting pits through a microscope eyepiece, but the task can
approvedin1976.Lastpreviouseditionapprovedin1999asG46–94(1999).DOI:
be made easier by the use of a plastic grid. Place the grid,
10.1520/G0046-94R05.
containing3to6-mmsquares,onthemetalsurface.Countand
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
record the number of pits in each square, and move across the
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
grid in a systematic manner until all the surface has been
the ASTM website.
covered. This approach minimizes eyestrain because the eyes
3
The last approved version of this historical standard is referenced on
can be taken from the field of view without fear of losing the
www.astm.org.
4
Insert in Materials Protection and Performance, Vol 12, June 1973, p. 65. area of intere
...

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4.1 Polythionic acids are chemically described as H2SxO6, where x is usually 3, 4, or 5 (1)3 though can be more than 50 (2). These acid environments provide a way of evaluating the resistance of stainless steels and related alloys to intergranular stress corrosion cracking. Failure is accelerated by the presence of increasing amounts of intergranular precipitate. Results for the polythionic acid test have not been correlated exactly with those of intergranular corrosion tests (Test Methods G28). Also, this test may not be relevant to stress corrosion cracking in chlorides or caustic environments.  
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1.3 This practice can be applied to wrought products, castings, and weld metal of stainless steels or other related materials to be used in environments containing sulfur or sulfides. Other materials capable of being sensitized can also be tested in accordance with this test.  
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Standard Practice for Conducting Moist SO2 Tests

SIGNIFICANCE AND USE
3.1 Moist air containing sulfur dioxide quickly produces easily visible corrosion on many metals in a form resembling that occurring in industrial environments. It is therefore a test medium well suited to detect pores or other sources of weakness in protective coatings and deficiencies in corrosion resistance associated with unsuitable alloy composition or treatments.  
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5.1 The U-bend specimen may be used for any metal alloy sufficiently ductile to be formed into the U-shape without mechanically cracking. The specimen is most easily made from strip or sheet but can be machined from plate, bar, castings, or weldments; wire specimens may be used also.  
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FIG. 1 Typical Stressed U-bends  
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5.1 Autoclave tests are commonly used to evaluate the corrosion performance of metallic and non-metallic materials under simulated HP and HTHP service conditions. Examples of service environments in which HP and HTHP corrosion tests have been used include chemical processing, petroleum production and refining, food processing, pressurized cooling water, electric power systems, and aerospace propulsion.  
5.2 For the applications of corrosion testing listed in 5.1, the service environment involves handling corrosive and potentially hazardous media under conditions of high pressure or high temperature, or both. The temperature and pressure, among other parameters, usually drive the composition and properties of the aqueous phase and, hence, the severity of the corrosion process. Consequently, the laboratory evaluation of corrosion severity cannot be performed in conventional low pressure glassware without making potentially invalid assumptions as to the potential effects of high temperature and pressure on corrosion severity.  
5.3 Therefore, there is a substantial need to provide standardized methods by which corrosion testing can be performed under HP and HTHP. In many cases, however, the standards used for exposure of specimens in conventional low-pressure glassware experiments cannot be followed due to the limitations of access, volume, and visibility arising from the construction of high-pressure test cells. This guide refers to existing corrosion standards and practices, as applicable, and then goes further in areas in which specific guidelines for performing HP and HTHP corrosion testing are needed.
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1.1 This guide covers procedures, specimens, and equipment for conducting laboratory corrosion tests on metallic materials under conditions of high pressure (HP) or the combination of high temperature and high pressure (HTHP). See 3.2 for definitions of high pressure and temperature.  
1.2 The procedures and methods in this guide are applicable for conducting mass loss corrosion, localized corrosion, and electrochemical tests as well as for use in environmentally induced cracking tests that need to be conducted under HP or HTHP conditions.  
1.3 The primary purpose for this guide is to promote consistency of corrosion test results. Furthermore, this guide will aid in the comparison of corrosion data between laboratories or testing organizations that utilize different equipment.  
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.

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ASTM G46-21(Guide)
Standard Guide for Examination and Evaluation of Pitting Corrosion

SIGNIFICANCE AND USE
4.1 It is important to be able to determine the extent of pitting, either in a service application in which it is necessary to predict the remaining life in a metal structure, or in laboratory test programs that are used to select the most pitting-resistant materials for service. The purpose of the study is crucial in determining the appropriate examination and evaluation steps.  
4.2 Some typical purposes of laboratory tests include, but are not limited to, evaluating performance of alloys, determining whether an alloy is resistant to the environment, evaluating how environmental conditions including corrosion inhibitor affect or prevent pitting, and evaluating whether a lot of metal is sufficiently resistant for its use in a particular application or environment.  
4.3 Some typical purposes of field studies include, but are not limited to, determining if pits are likely to grow and cause leak or release of process fluid, and assisting a determination of whether to replace or repair damage from pits (remaining life assessment).
SCOPE
1.1 This guide covers the selection of procedures that can be used in the examination and evaluation of pitted metals. These procedures include both nondestructive and destructive approaches.  
1.2 The procedures covered in this guide include those that may be used in laboratory evaluations of corroded metal specimens and field examinations and inspections.  
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.  
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ASTM G39-99(2021)(Practice)
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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 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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