ASTM G100-89(2021)

Standard Test Method for Conducting Cyclic Galvanostaircase Polarization

SIGNIFICANCE AND USE
3.1 In this test method, susceptibility to localized corrosion of aluminum is indicated by a protection potential (Eprot) determined by cyclic galvanostaircase polarization (1). The more noble this potential, the less susceptible is the alloy to initiation of localized corrosion. The results of this test method are not intended to correlate in a quantitative manner with the rate of propagation of localized corrosion that one might observe in service.  
3.2 The breakdown (Eb), and protection potentials (Eprot) determined by the cyclic GSCP method correlate with the constant potential corrosion test (immersion-glassware) result for aluminum (1, 6, 7). When the applied potential was more negative than the GSCP Eprot, no pit initiation was observed. When the applied potential was more positive than the GSCP Eprot, pitting occurred even when the applied potential was less negative than Eb.  
3.2.1 Severe crevice corrosion occurred when the separation of Eb and Eprot was 500 mV or greater and Eprot was less than −400 mV Vs. SCE (in 100 ppm NaCl) (1, 6, 8). For aluminum, Eprot determined by cyclic GSCP agrees with the repassivation potential determined by the scratch potentiostatic method (1, 9). Both the scratch potentiostatic method and the constant potential technique for determination of Eprot require much longer test times and are more involved techniques than the GSCP method.  
3.3 DeBerry and Viebeck (3-5) found that the breakdown potentials (Eb) (galvanodynamic polarization, similar to GSCP but no kinetic information) had a good correlation with the inhibition of localized corrosion of 304L stainless steel by surface active compounds. They attained accuracy and precision by avoiding the strong induction effect which they observed by the potentiodynamic technique.  
3.4 If this test method is followed using the specific alloy discussed it will provide (GSCP) measurements that will reproduce data developed at other times in other laboratories.  
3.5 Eb and Eprot...
SCOPE
1.1 This test method covers a procedure for conducting cyclic galvanostaircase polarization (GSCP) to determine relative susceptibility to localized corrosion (pitting and crevice corrosion) for aluminum alloy 3003-H14 (UNS A93003) (1).2 It may serve as guide for examination of other alloys (2-5). This test method also describes a procedure that can be used as a check for one's experimental technique and instrumentation.  
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this 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.

General Information

• Status: Published
• Publication Date: 31-Jul-2021
• ICS: 25.220.20 - Surface treatment
• Technical Committee: G01 - Corrosion of Metals
• Drafting Committee: G01.11 - Electrochemical Measurements in Corrosion Testing

Relations

• Refers: ASTM G69-20 - Standard Test Method for Measurement of Corrosion Potentials of Aluminum Alloys
• Effective Date: 01-May-2020
• Refers: ASTM G5-14 - Standard Reference Test Method for Making Potentiodynamic Anodic Polarization Measurements
• Effective Date: 01-Nov-2014
• Refers: ASTM G5-13e2 - Standard Reference Test Method for Making Potentiodynamic Anodic Polarization Measurements
• Effective Date: 01-Feb-2013
• Refers: ASTM G5-13 - Standard Reference Test Method for Making Potentiodynamic Anodic Polarization Measurements
• Effective Date: 01-Feb-2013
• Refers: ASTM G5-13e1 - Standard Reference Test Method for Making Potentiodynamic Anodic Polarization Measurements
• Effective Date: 01-Feb-2013
• Refers: ASTM G5-12 - Standard Reference Test Method for Making Potentiostatic and Potentiodynamic Anodic Polarization Measurements
• Effective Date: 15-Nov-2012
• Refers: ASTM G69-12 - Standard Test Method for Measurement of Corrosion Potentials of Aluminum Alloys
• Effective Date: 01-May-2012
• Refers: ASTM G1-03(2011) - Standard Practice for Preparing, Cleaning, and Evaluating Corrosion Test Specimens
• Effective Date: 01-Dec-2011
• Refers: ASTM G5-94(2011)e1 - Standard Reference Test Method for Making Potentiostatic and Potentiodynamic Anodic Polarization Measurements
• Effective Date: 15-Nov-2011
• Refers: ASTM G69-97(2009) - Standard Test Method for Measurement of Corrosion Potentials of Aluminum Alloys
• Effective Date: 01-May-2009
• Refers: ASTM D1193-06 - Standard Specification for Reagent Water
• Effective Date: 01-Mar-2006
• Refers: ASTM G5-94(2004) - Standard Reference Test Method for Making Potentiostatic and Potentiodynamic Anodic Polarization Measurements
• Effective Date: 01-Nov-2004
• Refers: ASTM G1-03 - Standard Practice for Preparing, Cleaning, and Evaluating Corrosion Test Specimens
• Effective Date: 01-Oct-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

Overview

ASTM G100-89(2021), “Standard Test Method for Conducting Cyclic Galvanostaircase Polarization,” establishes a reliable procedure for assessing the susceptibility of metals, particularly aluminum alloy 3003-H14 (UNS A93003), to localized corrosion such as pitting and crevice corrosion. Developed by ASTM International in compliance with globally recognized standardization principles, this method employs cyclic galvanostaircase polarization (GSCP) to determine critical potentials related to corrosion vulnerability. While most validated for aluminum, this standard also serves as a practical guide for evaluating other alloys, providing substantial value for corrosion engineers and laboratories.

Key Topics

• Cyclic Galvanostaircase Polarization (GSCP): A method for electrochemical testing that involves incrementally changing the current to reveal critical protection and breakdown potentials, essential for localized corrosion assessment.
• Protection Potential (Eprot): Indicates the potential above which pitting or crevice corrosion is likely. A more noble Eprot implies lower susceptibility.
• Breakdown Potential (Eb): The potential at which the material becomes vulnerable to pit initiation.
• Corrosion Testing Correlations: Both Eprot and Eb as measured by GSCP align well with results from established methods like constant potential immersion tests and the scratch potentiostatic approach, but GSCP is notably faster and less complex.
• Precision & Reproducibility: The method, when followed according to the ASTM G100 protocol, ensures reproducibility of corrosion data across different labs and timeframes, supporting reliability in comparison studies.
• Electrochemical Measurements: Involves use of inert cells, specified electrodes (working, reference, and auxiliary), controlled environments, and precise solution concentrations, ensuring accuracy and comparability of results.

Applications

• Materials Selection: Offers a practical way to compare the relative corrosion resistance of aluminum alloys and potentially other metals, informing design and alloy selection for applications in harsh environments such as marine, processing, and chemical industries.
• Quality Control: Laboratories and manufacturers use GSCP to validate the corrosion resistance of metal batches, ensuring conformance to performance specifications.
• Instrumentation Verification: The method provides an effective check for experimental setup integrity, including proper functioning of corrosion testing equipment and protocols.
• Research and Development: Enables systematic study of corrosion inhibitors, alloy modifications, and environmental factors on localized corrosion, benefiting material scientists and engineers.
• Standardization and Compliance: Following ASTM G100 supports alignment with internationally recognized test procedures, facilitating acceptance by stakeholders in project specifications and regulatory documentation.

Related Standards

For comprehensive corrosion testing and improved electrochemical measurement practices, the following related ASTM standards are often referenced:

• ASTM G1 – Practice for Preparing, Cleaning, and Evaluating Corrosion Test Specimens
• ASTM G5 – Reference Test Method for Making Potentiodynamic Anodic Polarization Measurements
• ASTM G59 – Test Method for Conducting Potentiodynamic Polarization Resistance Measurements
• ASTM G69 – Test Method for Measurement of Corrosion Potentials of Aluminum Alloys
• ASTM D1193 – Specification for Reagent Water

Keywords: aluminum corrosion, galvanostaircase polarization, GSCP, localized corrosion testing, ASTM G100, pitting corrosion, crevice corrosion, protection potential, electrochemical measurement, material testing standards

By following ASTM G100-89(2021), laboratories and engineers gain a robust, repeatable procedure for assessing localized corrosion susceptibility, improving material selection, and supporting research into corrosion prevention for metals in demanding environments.

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: G100 − 89 (Reapproved 2021)
Standard Test Method for
Conducting Cyclic Galvanostaircase Polarization
This standard is issued under the fixed designation G100; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope G59TestMethodforConductingPotentiodynamicPolariza-
tion Resistance Measurements
1.1 This test method covers a procedure for conducting
G69Test Method for Measurement of Corrosion Potentials
cyclic galvanostaircase polarization (GSCP) to determine rela-
of Aluminum Alloys
tive susceptibility to localized corrosion (pitting and crevice
corrosion) for aluminum alloy 3003-H14 (UNSA93003) (1).
3. Significance and Use
It may serve as guide for examination of other alloys (2-5).
3.1 In this test method, susceptibility to localized corrosion
Thistestmethodalsodescribesaprocedurethatcanbeusedas
of aluminum is indicated by a protection potential (E )
prot
a check for one’s experimental technique and instrumentation.
determined by cyclic galvanostaircase polarization (1). The
1.2 The values stated in SI units are to be regarded as
more noble this potential, the less susceptible is the alloy to
standard. No other units of measurement are included in this
initiationoflocalizedcorrosion.Theresultsofthistestmethod
standard.
are not intended to correlate in a quantitative manner with the
1.3 This standard does not purport to address all of the
rate of propagation of localized corrosion that one might
safety concerns, if any, associated with its use. It is the observe in service.
responsibility of the user of this standard to establish appro-
3.2 The breakdown (E ), and protection potentials (E )
b prot
priate safety, health, and environmental practices and deter-
determined by the cyclic GSCP method correlate with the
mine the applicability of regulatory limitations prior to use.
constant potential corrosion test (immersion-glassware) result
1.4 This international standard was developed in accor-
for aluminum (1, 6, 7). When the applied potential was more
dance with internationally recognized principles on standard-
negative than the GSCP E , no pit initiation was observed.
prot
ization established in the Decision on Principles for the
When the applied potential was more positive than the GSCP
Development of International Standards, Guides and Recom-
E ,pittingoccurredevenwhentheappliedpotentialwasless
prot
mendations issued by the World Trade Organization Technical
negative than E .
b
Barriers to Trade (TBT) Committee.
3.2.1 Severecrevicecorrosionoccurredwhentheseparation
of E and E was 500 mV or greater and E was less
b prot prot
2. Referenced Documents
than−400 mV Vs. SCE (in 100 ppm NaCl) (1, 6, 8). For
2.1 ASTM Standards:
aluminum, E determined by cyclic GSCP agrees with the
prot
D1193Specification for Reagent Water
repassivationpotentialdeterminedbythescratchpotentiostatic
G1Practice for Preparing, Cleaning, and Evaluating Corro-
method (1, 9). Both the scratch potentiostatic method and the
sion Test Specimens
constant potential technique for determination of E require
prot
G5Reference Test Method for Making Potentiodynamic
much longer test times and are more involved techniques than
Anodic Polarization Measurements
the GSCP method.
3.3 DeBerry and Viebeck (3-5) found that the breakdown
This test method is under the jurisdiction of ASTM Committee G01 on
potentials (E ) (galvanodynamic polarization, similar to GSCP
b
Corrosion of Metals and is the direct responsibility of Subcommittee G01.11 on
but no kinetic information) had a good correlation with the
Electrochemical Measurements in Corrosion Testing.
inhibition of localized corrosion of 304L stainless steel by
Current edition approved Aug. 1, 2021. Published August 2021. Originally
approvedin1989.Lastpreviouseditionapprovedin2015asG100–89(2015).DOI:
surface active compounds. They attained accuracy and preci-
10.1520/G0100-89R21.
sion by avoiding the strong induction effect which they
The boldface numbers in parentheses refer to a list of references at the end of
observed by the potentiodynamic technique.
this standard.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
3.4 If this test method is followed using the specific alloy
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
discussed it will provide (GSCP) measurements that will
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. reproduce data developed at other times in other laboratories.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
G100 − 89 (2021)
NOTE 2—The current staircase signal was generated manually in the
roundrobinbecauseautomatedsystemorsoftwarewasnotavailablewhen
this project was started.
4.3 Electrodes:
4.3.1 Working Electrode—For generating data to be com-
paredtothereferencedataincludedherein,usetype3003-H14
(UNSA93003)A1 in sheet form. Cut 1.55 cm diameter circles
and prepare in accordance with Practice G1 using 600grit
diamond slurry on a flat lapping machine. Install in flat
specimen holder using PTFE gasket (no crevice type) (Note 1)
so that 1 cm is exposed to the test solution.Apply 29 m-g of
torque.
4.3.2 Auxiliary Electrodes—Graphite, (ultrafine grade)
(Note 3).
NOTE 3—Coarse grades of graphite should be avoided because they
absorb solute impurities. Ultrafine grades are available from spectro-
graphic supply companies.
4.3.3 Reference Electrode—Saturated calomel (Note 1). It
should be checked against another reference which has not
been exposed to test solutions and they should be within 3 mV
of each other. Test Method G69 round robin test conducted by
G01.11 (unpublished results) indicate that potential difference
should not exceed 2mV or 3 mV. The reference electrode is
connected to the test bridge solution which consists of 75%
saturated KCl, prepared by adding 1 part (by volume) of
distilled water to 3 parts saturated KCl. When the bridge is in
active use, the bridge solution should be replaced once each
FIG. 1 Schematic Wiring Diagram for Galvanostaircase Polariza-
day and the bridge tip immersed in this solution when not in
tion
use. Any test solution that does not deposit films may also be
usedinthebridge.(TheVYCOR tip should notbeallowedto
go to dryness.)
3.5 E and E obtainedarebasedontheresultsfromeight
b prot
different laboratories that followed the standard procedure
4.4 Magnetic Stirrer.
using aluminum alloy 3003-H14 (UNS A93003). E and E
b prot
are included with statistical analysis to indicate the acceptable 5. Procedure
range.
5.1 Test solution, 3000ppm 6 30 ppm (0.0513 M) NaCl.
For example, transfer 6.000 g reagent grade NaCl to a 2L
4. Apparatus
volumetric flask. Dissolve in ASTM Type IV water (deminer-
4.1 Cell—The cell should be constructed of inert materials alized or distilled) and dilute to the mark. (See Specification
such as borosilicate glass and PTFE fluorocarbon. It should
D1193.)
have ports for the insertion of a working electrode (1 cm flat
5.2 Assemble cell with the electrodes described in Section
specimen holder (Note 1) is very convenient), two auxiliary
4.Placethereferencebridgeprobeabout2p
...