ASTM G102-23

Standard Practice for Calculation of Corrosion Rates and Related Information from Electrochemical Measurements

SIGNIFICANCE AND USE
3.1 Electrochemical corrosion rate measurements often provide results in terms of electrical current. Although the conversion of these current values into mass loss rates or penetration rates is based on Faraday’s Law, the calculations can be complicated for alloys and metals with elements having multiple valence values. This practice is intended to provide guidance in calculating mass loss and penetration rates for such alloys. Some typical values of equivalent weights for a variety of metals and alloys are provided.  
3.2 Electrochemical corrosion rate measurements may provide results in terms of electrical resistance. The conversion of these results to either mass loss or penetration rates requires additional electrochemical information. Some approaches for estimating this information are given.  
3.3 Use of this practice will aid in producing more consistent corrosion rate data from electrochemical results. This will make results from different studies more comparable and minimize calculation errors that may occur in transforming electrochemical results to corrosion rate values.
SCOPE
1.1 This practice covers the providing of guidance in converting the results of electrochemical measurements to rates of uniform corrosion. Calculation methods for converting corrosion current density values to either mass loss rates or average penetration rates are given for most engineering alloys. In addition, some guidelines for converting polarization resistance values to corrosion rates are provided.  
1.2 The values stated in SI units are to be regarded as standard. Other units of measurement are included in this standard because of their usage.  
1.3 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: 14-Feb-2023
• ICS: 77.060 - Corrosion of metals
• Technical Committee: G01 - Corrosion of Metals
• Drafting Committee: G01.11 - Electrochemical Measurements in Corrosion Testing

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: G102 − 23
Standard Practice for
Calculation of Corrosion Rates and Related Information
1
from Electrochemical Measurements
This standard is issued under the fixed designation G102; 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 3. Significance and Use
3.1 Electrochemical corrosion rate measurements often pro-
1.1 This practice covers the providing of guidance in
vide results in terms of electrical current. Although the con-
converting the results of electrochemical measurements to rates
version of these current values into mass loss rates or penetra-
of uniform corrosion. Calculation methods for converting
tion rates is based on Faraday’s Law, the calculations can be
corrosion current density values to either mass loss rates or
complicated for alloys and metals with elements having
average penetration rates are given for most engineering alloys.
multiple valence values. This practice is intended to provide
In addition, some guidelines for converting polarization resis-
guidance in calculating mass loss and penetration rates for such
tance values to corrosion rates are provided.
alloys. Some typical values of equivalent weights for a variety
1.2 The values stated in SI units are to be regarded as
of metals and alloys are provided.
standard. Other units of measurement are included in this
3.2 Electrochemical corrosion rate measurements may pro-
standard because of their usage.
vide results in terms of electrical resistance. The conversion of
1.3 This international standard was developed in accor-
these results to either mass loss or penetration rates requires
dance with internationally recognized principles on standard-
additional electrochemical information. Some approaches for
ization established in the Decision on Principles for the
estimating this information are given.
Development of International Standards, Guides and Recom-
3.3 Use of this practice will aid in producing more consis-
mendations issued by the World Trade Organization Technical
tent corrosion rate data from electrochemical results. This will
Barriers to Trade (TBT) Committee.
make results from different studies more comparable and
minimize calculation errors that may occur in transforming
2. Referenced Documents
electrochemical results to corrosion rate values.
2
2.1 ASTM Standards:
D2776 Methods of Test for Corrosivity of Water in the
4. Corrosion Current Density
Absence of Heat Transfer (Electrical Methods) (With-
3 4.1 Corrosion current values may be obtained from galvanic
drawn 1991)
cells and polarization measurements, including Tafel extrapo-
G1 Practice for Preparing, Cleaning, and Evaluating Corro-
lations or polarization resistance measurements. (See Refer-
sion Test Specimens
ence Test Method G5 and Test Method G59 for examples.) The
G5 Reference Test Method for Making Potentiodynamic
first step is to convert the measured or estimated current value
Anodic Polarization Measurements
to current density. This is accomplished by dividing the total
G59 Test Method for Conducting Potentiodynamic Polariza-
current by the geometric area of the electrode exposed to the
tion Resistance Measurements
solution. The surface roughness is generally not taken into
account when calculating the current density. It is assumed that
the current distributes uniformly across the area used in this
1
This practice is under the jurisdiction of ASTM Committee G01 on Corrosion
calculation. In the case of galvanic couples, the exposed area of
of Metals and is the direct responsibility of Subcommittee G01.11 on Electrochemi-
the anodic specimen should be used. This calculation may be
cal Measurements in Corrosion Testing.
expressed as follows:
Current edition approved Feb. 15, 2023. Published February 2023. Originally
1
approved in 1989. Last previous edition approved in 2015 as G102–89 (2015)ɛ .
I
cor
DOI: 10.1520/G0102-23.
i 5 (1)
cor
2
A
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
where:
Standards volume information, refer to the standard’s Document Summary page on
2
the ASTM website.
i = corrosion current density, μA/cm ,
cor
3
The last approved version of this historical standard is referenced on www.ast-
I = total anodic current, μA, and
cor
m.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

--
...

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.
´1
Designation: G102 − 89 (Reapproved 2015) G102 − 23
Standard Practice for
Calculation of Corrosion Rates and Related Information
1
from Electrochemical Measurements
This standard is issued under the fixed designation G102; 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
ε NOTE—Editorially corrected the legend below Eq 1 in 4.1 in November 2015.
1. Scope
1.1 This practice covers the providing of guidance in converting the results of electrochemical measurements to rates of uniform
corrosion. Calculation methods for converting corrosion current density values to either mass loss rates or average penetration rates
are given for most engineering alloys. In addition, some guidelines for converting polarization resistance values to corrosion rates
are provided.
1.2 The values stated in SI units are to be regarded as standard. No other Other units of measurement are included in this
standard.standard because of their usage.
1.3 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.
2. Referenced Documents
2
2.1 ASTM Standards:
3
D2776 Methods of Test for Corrosivity of Water in the Absence of Heat Transfer (Electrical Methods) (Withdrawn 1991)
G1 Practice for Preparing, Cleaning, and Evaluating Corrosion Test Specimens
G5 Reference Test Method for Making Potentiodynamic Anodic Polarization Measurements
G59 Test Method for Conducting Potentiodynamic Polarization Resistance Measurements
3. Significance and Use
3.1 Electrochemical corrosion rate measurements often provide results in terms of electrical current. Although the conversion of
these current values into mass loss rates or penetration rates is based on Faraday’sFaraday’s Law, the calculations can be
complicated for alloys and metals with elements having multiple valence values. This practice is intended to provide guidance in
calculating mass loss and penetration rates for such alloys. Some typical values of equivalent weights for a variety of metals and
alloys are provided.
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 Nov. 1, 2015Feb. 15, 2023. Published December 2015February 2023. Originally approved in 1989. Last previous edition approved in 20102015
1
as G102–89 (2010).(2015)ɛ . DOI: 10.1520/G0102-89R15E01. 10.1520/G0102-23.
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’sstandard’s Document Summary page on the ASTM website.
3
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

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G102 − 23
3.2 Electrochemical corrosion rate measurements may provide results in terms of electrical resistance. The conversion of these
results to either mass loss or penetration rates requires additional electrochemical information. Some approaches for estimating this
information are given.
3.3 Use of this practice will aid in producing more consistent corrosion rate data from electrochemical results. This will make
results from different studies more comparable and minimize calculation errors that may occur in transforming electrochemical
results to corrosion rate values.
4. Corrosion Current Density
4.1 Corrosion current values may be obtained from galvanic cells and polarization measurements, including Tafel extrapolations
or polarization resistance measurements. (See Reference Test Method G5 and Practice Test Method G59 for examples.) The first
step is to convert the measured or estimated current value to current density. This is accomplished by dividing the total current
by the geometric area of the electrode exposed to the solution. The surface roughness is generally not taken into account when
calcu
...