ASTM G108-94(2015)

Standard Test Method for Electrochemical Reactivation (EPR) for Detecting Sensitization of AISI Type 304 and 304L Stainless Steels

SIGNIFICANCE AND USE
5.1 This test method describes an EPR test method for quantitatively determining the relative degree of sensitization in AISI Type 304 and 304L stainless steels. The EPR test has found wide use as a means to provide a numerical level of sensitization in studies of the effects of sensitization on intergranular corrosion and intergranular stress corrosion cracking behavior. The results of this test method correlate with other test methods (for example, Practices A262 and Test Methods G28) that are commonly used to assess sensitization in stainless steels.  
5.2 The EPR test can also be used for product acceptance, service evaluation, regulatory statutes, and manufacturing controls providing that both the supplier and user have agreed upon appropriate acceptance criteria and a sensitizing treatment. The test is not intended for design purposes since the test conditions accelerate corrosion in a manner that does not simulate any actual service environment.  
5.3 The EPR test involves the measurement of the amount of charge resulting from the corrosion of the chromium-depleted regions surrounding the precipitated chromium carbide particles. Most of these particles in a sensitized microstructure are located at the grain boundaries. However, discrete particles located within grains (referred to as intragranular precipitates) will also contribute to the total measured charge. (See Fig. 2.) Therefore, it is important to examine the alloy microstructure following an EPR test to determine the relative proportion of corrosion sites associated with intergranular versus intragranular precipitates. Sites of intergranular attack will appear similar to grain boundary ditching as defined in Practice A of Practices A262.  
Note 1: The calculation of Pa is based on the assumptions illustrated at left. Mild cases of sensitization usually result in a combination of intergranular attack and pitting as illustrated at right (6).
SCOPE
1.1 This test method covers a laboratory procedure for conducting an electrochemical reactivation (EPR) test on AISI Type 304 and 304L (UNS No. S30400 and S30403, respectively) stainless steels. This test method can provide a nondestructive means of quantifying the degree of sensitization in these steels (1, 2, 3).2 This test method has found wide acceptance in studies of the effects of sensitization on intergranular corrosion and intergranular stress corrosion cracking behavior (see Terminology G15). The EPR technique has been successfully used to evaluate other stainless steels and nickel base alloys (4), but the test conditions and evaluation criteria used were modified in each case from those cited in this test method.  
1.2 The values stated in SI units are to be regarded as the standard. The inch-pound units given in parentheses are for information only.  
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 and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 31-Oct-2015
• ICS: 77.140.20 - Stainless steels
• Technical Committee: G01 - Corrosion of Metals
• Drafting Committee: G01.11 - Electrochemical Measurements in Corrosion Testing

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: G108 − 94 (Reapproved 2015)
Standard Test Method for
Electrochemical Reactivation (EPR) for Detecting
1
Sensitization of AISI Type 304 and 304L Stainless Steels
This standard is issued under the fixed designation G108; 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.
1. Scope E112 Test Methods for Determining Average Grain Size
G1 Practice for Preparing, Cleaning, and Evaluating Corro-
1.1 This test method covers a laboratory procedure for
sion Test Specimens
conducting an electrochemical reactivation (EPR) test on AISI
G3 Practice for Conventions Applicable to Electrochemical
Type 304 and 304L (UNS No. S30400 and S30403, respec-
Measurements in Corrosion Testing
tively) stainless steels. This test method can provide a nonde-
G5 Reference Test Method for Making Potentiodynamic
structive means of quantifying the degree of sensitization in
2 Anodic Polarization Measurements
these steels (1, 2, 3). This test method has found wide
G15 Terminology Relating to Corrosion and Corrosion Test-
acceptance in studies of the effects of sensitization on inter-
4
ing (Withdrawn 2010)
granular corrosion and intergranular stress corrosion cracking
G28 Test Methods for Detecting Susceptibility to Inter-
behavior (see Terminology G15). The EPR technique has been
granular Corrosion in Wrought, Nickel-Rich, Chromium-
successfully used to evaluate other stainless steels and nickel
Bearing Alloys
base alloys (4), but the test conditions and evaluation criteria
G61 Test Method for Conducting Cyclic Potentiodynamic
used were modified in each case from those cited in this test
Polarization Measurements for Localized Corrosion Sus-
method.
ceptibility of Iron-, Nickel-, or Cobalt-Based Alloys
1.2 The values stated in SI units are to be regarded as the
standard. The inch-pound units given in parentheses are for
3. Terminology
information only.
3.1 Definitions of Terms Specific to This Standard:
1.3 This standard does not purport to address all of the
3.1.1 integrated charge (Q)—the charge measured, in
safety concerns, if any, associated with its use. It is the
coulombs, during reactivation as given by the time integral of
responsibility of the user of this standard to establish appro-
current density below the reactivation peak of the curve.
priate safety and health practices and determine the applica-
3.1.2 maximum anodic current density (I )—the current
r
bility of regulatory limitations prior to use.
density measured at the peak of the anodic curve during
reactivation.
2. Referenced Documents
3.1.3 normalized charge (P )—the integrated current nor-
3 a
2.1 ASTM Standards:
malized to the specimen size and grain size. P represents the
a
A262 Practices for Detecting Susceptibility to Intergranular
2
charge (in coulombs/cm ) of the grain-boundary area. The
Attack in Austenitic Stainless Steels
method for calculating P is given in 9.2.
a
D1193 Specification for Reagent Water
3.1.4 reactivation—in the electrochemical reactivation
E3 Guide for Preparation of Metallographic Specimens
(EPR) test, the potential sweep from the passivation potential
E7 Terminology Relating to Metallography
returning to the corrosion potential.
3.1.5 scan rate—the rate at which the electrical potential
1
applied to a specimen in a polarization test is changed.
This test method is under the jurisdiction of ASTM Committee G01 on
Corrosion of Metals and is the direct responsibility of Subcommittee G01.11 on
Electrochemical Measurements in Corrosion Testing.
4. Summary of Test Method
Current edition approved Nov. 1, 2015. Published December 2015. Originally
4.1 The EPR test is accomplished by a potentiodynamic
approved in 1992. Last previous edition approved in 2010 as G108–94(2010). DOI:
10.1520/G0108-94R15.
sweep from the passive to the active regions of electrochemical
2
The boldface numbers in parentheses refer to a list of references at the end of
potentials in a process referred to as reactivation. The EPR test
this standard.
3
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
4
Standards volume information, refer to the standard’s Document Summary page on The last approved version of this historical standard is referenced on
the ASTM website. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
G108 − 94 (2015)
measures the amount of charge associated with the corrosion of activated and show higher Q and I
...

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: G108 − 94 (Reapproved 2010) G108 − 94 (Reapproved 2015)
Standard Test Method for
Electrochemical Reactivation (EPR) for Detecting
1
Sensitization of AISI Type 304 and 304L Stainless Steels
This standard is issued under the fixed designation G108; 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.
1. Scope
1.1 This test method covers a laboratory procedure for conducting an electrochemical reactivation (EPR) test on AISI Type 304
and 304L (UNS No. S30400 and S30403, respectively) stainless steels. This test method can provide a nondestructive means of
2
quantifying the degree of sensitization in these steels (1, 2, 3). This test method has found wide acceptance in studies of the effects
of sensitization on intergranular corrosion and intergranular stress corrosion cracking behavior (see Terminology G15). The EPR
technique has been successfully used to evaluate other stainless steels and nickel base alloys (4), but the test conditions and
evaluation criteria used were modified in each case from those cited in this test method.
1.2 The values stated in SI units are to be regarded as the standard. The inch-pound units given in parentheses are for
information only.
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 and health practices and determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
3
2.1 ASTM Standards:
A262 Practices for Detecting Susceptibility to Intergranular Attack in Austenitic Stainless Steels
D1193 Specification for Reagent Water
E3 Guide for Preparation of Metallographic Specimens
E7 Terminology Relating to Metallography
E112 Test Methods for Determining Average Grain Size
G1 Practice for Preparing, Cleaning, and Evaluating Corrosion Test Specimens
G3 Practice for Conventions Applicable to Electrochemical Measurements in Corrosion Testing
G5 Reference Test Method for Making Potentiodynamic Anodic Polarization Measurements
4
G15 Terminology Relating to Corrosion and Corrosion Testing (Withdrawn 2010)
G28 Test Methods for Detecting Susceptibility to Intergranular Corrosion in Wrought, Nickel-Rich, Chromium-Bearing Alloys
G61 Test Method for Conducting Cyclic Potentiodynamic Polarization Measurements for Localized Corrosion Susceptibility of
Iron-, Nickel-, or Cobalt-Based Alloys
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 integrated charge (Q)—the charge measured, in couloumbs,coulombs, during reactivation as given by the time integral of
current density below the reactivation peak of the curve.
3.1.2 maximum anodic current density (I )—the current density measured at the peak of the anodic curve during reactivation.
r
1
This test method is under the jurisdiction of ASTM Committee G01 on Corrosion of Metals and is the direct responsibility of Subcommittee G01.11 on Electrochemical
Measurements in Corrosion Testing.
Current edition approved May 1, 2010Nov. 1, 2015. Published May 2010December 2015. Originally approved in 1992. Last previous edition approved in 20042010 as
ε1
G108–94(2004)G108–94(2010). . DOI: 10.1520/G0108-94R10.10.1520/G0108-94R15.
2
The boldface numbers in parentheses refer to a list of references at the end of this standard.
3
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’s Document Summary page on the ASTM website.
4
The last approved version of this historical standard is referenced on www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
G108 − 94 (2015)
3.1.3 normalized charge (P )—the integrated current normalized to the specimen size and grain size. P represents the charge
a a
2
(in coulombs/cm ) of the grain-boundary area. The method for calculating P is given in 9.2.
a
3.1.4 reactivation—in the electrochemical reactivation (EPR) test, the potential sweep from the passivation potential returning
to the corrosion potential.
3.1.5 scan rate—the rate at which the electrical potential applied to a
...