ASTM G3-14

Standard Practice for Conventions Applicable to Electrochemical Measurements in Corrosion Testing

SIGNIFICANCE AND USE
3.1 This practice provides guidance for reporting, displaying, and plotting electrochemical corrosion data and includes recommendations on signs and conventions. Use of this practice will result in the reporting of electrochemical corrosion data in a standard format, facilitating comparison between data developed at different laboratories or at different times. The recommendations outlined in this standard may be utilized when recording and reporting corrosion data obtained from electrochemical tests such as potentiostatic and potentiodynamic polarization, polarization resistance, electrochemical impedance and admittance measurements, galvanic corrosion, and open circuit potential measurements.
SCOPE
1.1 This practice covers conventions for reporting and displaying electrochemical corrosion data. Conventions for potential, current density, electrochemical impedance and admittance, as well as conventions for graphical presentation of such data are included.  
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. See also 7.4.  
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: 14-Dec-2014
• ICS: 77.060 - Corrosion of metals
• Technical Committee: G01 - Corrosion of Metals
• Drafting Committee: G01.11 - Electrochemical Measurements in Corrosion Testing

Relations

• Replaces: ASTM G3-13 - Standard Practice for Conventions Applicable to Electrochemical Measurements in Corrosion Testing
• Effective Date: 15-Dec-2014
• Replaced By: ASTM G3-14(2019) - Standard Practice for Conventions Applicable to Electrochemical Measurements in Corrosion Testing
• Effective Date: 01-May-2019
• Referred By: ASTM G119-09(2021) - Standard Guide for Determining Synergism Between Wear and Corrosion
• Effective Date: 15-Dec-2014
• Referred By: ASTM C876-22b - Standard Test Method for Corrosion Potentials of Uncoated Reinforcing Steel in Concrete
• Effective Date: 15-Dec-2014
• Referred By: ASTM G69-20 - Standard Test Method for Measurement of Corrosion Potentials of Aluminum Alloys
• Effective Date: 15-Dec-2014
• Referred By: ASTM G106-89(2023) - Standard Practice for Verification of Algorithm and Equipment for Electrochemical Impedance Measurements
• Effective Date: 15-Dec-2014
• Referred By: ASTM G185-06(2020)e1 - Standard Practice for Evaluating and Qualifying Oil Field and Refinery Corrosion Inhibitors Using the Rotating Cylinder Electrode
• Effective Date: 15-Dec-2014
• Referred By: ASTM G150-18 - Standard Test Method for Electrochemical Critical Pitting Temperature Testing of Stainless Steels and Related Alloys
• Effective Date: 15-Dec-2014
• Referred By: ASTM G61-86(2018) - Standard Test Method for Conducting Cyclic Potentiodynamic Polarization Measurements for Localized Corrosion Susceptibility of Iron-, Nickel-, or Cobalt-Based Alloys
• Effective Date: 15-Dec-2014
• Referred By: ASTM F1113-87(2017) - Standard Test Method for Electrochemical Measurement of Diffusible Hydrogen in Steels (Barnacle Electrode)
• Effective Date: 15-Dec-2014
• Referred By: ASTM D6208-07(2020) - Standard Test Method for Repassivation Potential of Aluminum and Its Alloys by Galvanostatic Measurement
• Effective Date: 15-Dec-2014
• Referred By: ASTM G116-99(2020)e1 - Standard Practice for Conducting Wire-on-Bolt Test for Atmospheric Galvanic Corrosion
• Effective Date: 15-Dec-2014
• Referred By: ASTM A955/A955M-20c - Standard Specification for Deformed and Plain Stainless Steel Bars for Concrete Reinforcement
• Effective Date: 15-Dec-2014
• Referred By: ASTM F2129-19a - Standard Test Method for Conducting Cyclic Potentiodynamic Polarization Measurements to Determine the Corrosion Susceptibility of Small Implant Devices
• Effective Date: 15-Dec-2014
• Referred By: ASTM G170-06(2020)e1 - Standard Guide for Evaluating and Qualifying Oilfield and Refinery Corrosion Inhibitors in the Laboratory
• Effective Date: 15-Dec-2014

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: G3 − 14
Standard Practice for
Conventions Applicable to Electrochemical Measurements
1
in Corrosion Testing
This standard is issued under the fixed designation G3; the number immediately following the designation indicates the year of original
adoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope impedance and admittance measurements, galvanic corrosion,
and open circuit potential measurements.
1.1 This practice covers conventions for reporting and
displaying electrochemical corrosion data. Conventions for
4. Sign Convention for Electrode Potential
potential, current density, electrochemical impedance and
4.1 The Stockholm sign invariant convention is recom-
admittance, as well as conventions for graphical presentation
mended for use in reporting the results of specimen potential
of such data are included.
measurements in corrosion testing. In this convention, the
1.2 The values stated in SI units are to be regarded as
positivedirectionofelectrodepotentialimpliesanincreasingly
standard. No other units of measurement are included in this
oxidizing condition at the electrode in question. The positive
standard. See also 7.4.
direction has also been denoted as the noble direction because
1.3 This standard does not purport to address all of the
thecorrosionpotentialsofmostnoblemetals,suchasgold,are
safety concerns, if any, associated with its use. It is the
more positive than the nonpassive base metals. On the other
responsibility of the user of this standard to establish appro-
hand,thenegativedirection,oftencalledtheactivedirection,is
priate safety and health practices and determine the applica-
associated with reduction and consequently the corrosion
bility of regulatory limitations prior to use.
potentials of active metals, such as magnesium. This conven-
tionwasadoptedunanimouslybythe1953InternationalUnion
2. Referenced Documents
of Pure and Applied Chemistry as the standard for electrode
2 3
2.1 ASTM Standards:
potential (1).
IEEE/ASTM SI 10Standard for Use of the International
4.2 In the context of a specimen electrode of unknown
System of Units (SI) (the Modern Metric System)
potential in an aqueous electrolyte, consider the circuit shown
in Fig. 1 with a reference electrode connected to the ground
3. Significance and Use
terminal of an electrometer. If the electrometer reads on scale
3.1 This practice provides guidance for reporting,
when the polarity switch is negative, the specimen electrode
displaying, and plotting electrochemical corrosion data and
potential is negative (relative to the reference electrode).
includes recommendations on signs and conventions. Use of
Conversely, if the electrometer reads on scale when polarity is
this practice will result in the reporting of electrochemical
positive, the specimen potential is positive. On the other hand,
corrosion data in a standard format, facilitating comparison
if the specimen electrode is connected to the ground terminal,
between data developed at different laboratories or at different
the potential will be positive if the meter is on scale when the
times. The recommendations outlined in this standard may be
polarity switch is negative, and vice versa.
utilized when recording and reporting corrosion data obtained
NOTE 1—In cases where the polarity of a measuring instrument is in
from electrochemical tests such as potentiostatic and potentio-
doubt, a simple verification test can be performed as follows: connect the
dynamic polarization, polarization resistance, electrochemical
measuring instrument to a dry cell with the lead previously on the
referenceelectrodetothenegativebatteryterminalandtheleadpreviously
1 on the specimen electrode to the positive battery terminal. Set the range
This practice is under the jurisdiction ofASTM Committee G01 on Corrosion
switchtoaccommodatethedrycellvoltage.Themeterdeflectionwillnow
ofMetalsandisthedirectresponsibilityofSubcommitteeG01.11onElectrochemi-
show the direction of positive potential.
cal Measurements in Corrosion Testing.
Also, the corrosion potential of magnesium or zinc should be negative
Current edition approved Dec. 15, 2014. Published December 2014. Originally
ina1 N NaCl solution if measured against a saturated standard calomel
approved in 1968. Last previous edition approved in 2013 as G3–13. DOI:
10.1520/G0003-14. electrode (SCE).
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
3
Standards volume information, refer to the standard’s Document Summary page on The boldface numbers in parentheses refer to a list of references at the end of
the ASTM website. this standard.
Copyri
...

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: G3 − 13 G3 − 14
Standard Practice for
Conventions Applicable to Electrochemical Measurements
1
in Corrosion Testing
This standard is issued under the fixed designation G3; 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 practice covers conventions for reporting and displaying electrochemical corrosion data. Conventions for potential,
current density, electrochemical impedance and admittance, as well as conventions for graphical presentation of such data are
included.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
See also 7.4.
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
2
2.1 ASTM Standards:
IEEE/ASTM SI 10 Standard for Use of the International System of Units (SI) (the Modern Metric System)
3. Significance and Use
3.1 This practice provides guidance for reporting, displaying, and plotting electrochemical corrosion data and includes
recommendations on signs and conventions. Use of this practice will result in the reporting of electrochemical corrosion data in
a standard format, facilitating comparison between data developed at different laboratories or at different times. The
recommendations outlined in this standard may be utilized when recording and reporting corrosion data obtained from
electrochemical tests such as potentiostatic and potentiodynamic polarization, polarization resistance, electrochemical impedance
and admittance measurements, galvanic corrosion, and open circuit potential measurements.
4. Sign Convention for Electrode Potential
4.1 The Stockholm sign invariant convention is recommended for use in reporting the results of specimen potential
measurements in corrosion testing. In this convention, the positive direction of electrode potential implies an increasingly oxidizing
condition at the electrode in question. The positive direction has also been denoted as the noble direction because the corrosion
potentials of most noble metals, such as gold, are more positive than the nonpassive base metals. On the other hand, the negative
direction, often called the active direction, is associated with reduction and consequently the corrosion potentials of active metals,
such as magnesium. This convention was adopted unanimously by the 1953 International Union of Pure and Applied Chemistry
3
as the standard for electrode potential (1).
4.2 In the context of a specimen electrode of unknown potential in an aqueous electrolyte, consider the circuit shown in Fig.
1 with a reference electrode connected to the ground terminal of an electrometer. If the electrometer reads on scale when the
polarity switch is negative, the specimen electrode potential is negative (relative to the reference electrode). Conversely, if the
1
This practice 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 Dec. 1, 2013Dec. 15, 2014. Published December 2013December 2014. Originally approved in 1968. Last previous edition approved in 20102013
as G3–89 (2010). –13. DOI: 10.1520/G0003-13.10.1520/G0003-14.
2
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.
3
The boldface numbers in parentheses refer to a list of references at the end of this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

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G3 − 14
NOTE 1—The electrode potential of specimen is negative as shown.
FIG. 1 Schematic Diagram of an Apparatus to Measure Electrode Potential of a Specimen
electrometer reads on scale when polarity is positive, the specimen potential is positive. On the other hand, if the specimen
electrode is connected to the groun
...