ASTM G82-98(2021)e1
(Guide)Standard Guide for Development and Use of a Galvanic Series for Predicting Galvanic Corrosion Performance
Standard Guide for Development and Use of a Galvanic Series for Predicting Galvanic Corrosion Performance
SIGNIFICANCE AND USE
4.1 When two dissimilar metals in electrical contact are exposed to a common electrolyte, one of the metals can undergo increased corrosion while the other can show decreased corrosion. This type of accelerated corrosion is referred to as galvanic corrosion. Because galvanic corrosion can occur at a high rate, it is important that a means be available to alert the user of products or equipment that involve the use of dissimilar metal combinations in an electrolyte of the possible effects of galvanic corrosion.
4.2 One method that is used to predict the effects of galvanic corrosion is to develop a galvanic series by arranging a list of the materials of interest in order of observed corrosion potentials in the environment and conditions of interest. The metal that will suffer increased corrosion in a galvanic couple in that environment can then be predicted from the relative position of the two metals in the series.
4.3 Types of Galvanic Series:
4.3.1 One type of Galvanic Series lists the metals of interest in order of their corrosion potentials, starting with the most active (electronegative) and proceeding in order to the most noble (electropositive). The potentials themselves (versus an appropriate reference half-cell) are listed so that the potential difference between metals in the series can be determined. This type of Galvanic Series has been put in graphical form as a series of bars displaying the range of potentials exhibited by the metal listed opposite each bar. Such a series is illustrated in Fig. 1.
4.4 Use of a Galvanic Series:
4.4.1 Generally, upon coupling two metals in the Galvanic Series, the more active (electronegative) metal will have a tendency to undergo increased corrosion while the more noble (electropositive) metal will have a tendency to undergo reduced corrosion.
4.4.2 Usually, the further apart two metals are in the series, and thus the greater the potential difference between them, the greater is the driving force f...
SCOPE
1.1 This guide covers the development of a galvanic series and its subsequent use as a method of predicting the effect that one metal can have upon another metal can when they are in electrical contact while immersed in an electrolyte. Suggestions for avoiding known pitfalls 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.
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. Specific precautionary statements are given in Section 5.
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
Relations
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.
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Designation: G82 − 98 (Reapproved 2021)
Standard Guide for
Development and Use of a Galvanic Series for Predicting
Galvanic Corrosion Performance
ThisstandardisissuedunderthefixeddesignationG82;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginal
adoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
ε NOTE—Replaced Terminology G15 with Terminology G193, and other editorial changes made throughout in Jan. 2021.
1. Scope G193Terminology and Acronyms Relating to Corrosion
1.1 This guide covers the development of a galvanic series
3. Terminology
and its subsequent use as a method of predicting the effect that
3.1 Definitions of terms used in this guide are from Termi-
one metal can have upon another metal can when they are in
nology G193.
electrical contact while immersed in an electrolyte. Sugges-
tions for avoiding known pitfalls are included. 3.2 active, n—the negative (decreasingly oxidizing) direc-
tion of electrode potential.
1.2 The values stated in SI units are to be regarded as
3.3 corrosion potential, n—the potential of a corroding
standard. No other units of measurement are included in this
surface in an electrolyte relative to a reference electrode
standard.
measured under open-circuit conditions.
1.3 This standard does not purport to address all of the
3.4 galvanic corrosion, n—accelerated corrosion of a metal
safety concerns, if any, associated with its use. It is the
because of an electrical contact with a more noble metal or
responsibility of the user of this standard to establish appro-
nonmetallic conductor in a corrosive electrolyte.
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
3.5 galvanic series, n—a list of metals and alloys arranged
Specific precautionary statements are given in Section 5.
according to their relative corrosion potentials in a given
1.4 This international standard was developed in accor-
environment.
dance with internationally recognized principles on standard-
3.6 noble, n—the positive (increasingly oxidizing) direction
ization established in the Decision on Principles for the
of electrode potential.
Development of International Standards, Guides and Recom-
3.7 passive, n—the state of the metal surface characterized
mendations issued by the World Trade Organization Technical
by low corrosion rates in a potential region that is strongly
Barriers to Trade (TBT) Committee.
oxidizing for the metal.
2. Referenced Documents 3.8 polarization, n—the change from the open-circuit elec-
trode potential as the result of the passage of current.
2.1 ASTM Standards:
G3Practice for Conventions Applicable to Electrochemical
4. Significance and Use
Measurements in Corrosion Testing
4.1 When two dissimilar metals in electrical contact are
G16Guide for Applying Statistics to Analysis of Corrosion
exposed to a common electrolyte, one of the metals can
Data
undergo increased corrosion while the other can show de-
G71Guide for Conducting and Evaluating Galvanic Corro-
creasedcorrosion.Thistypeofacceleratedcorrosionisreferred
sion Tests in Electrolytes
toasgalvaniccorrosion.Becausegalvaniccorrosioncanoccur
at a high rate, it is important that a means be available to alert
the user of products or equipment that involve the use of
This guide is under the jurisdiction ofASTM Committee G01 on Corrosion of
dissimilar metal combinations in an electrolyte of the possible
Metals and is the direct responsibility of Subcommittee G01.11 on Electrochemical
Measurements in Corrosion Testing.
effects of galvanic corrosion.
Current edition approved Jan. 1, 2021. Published January 2021. Originally
4.2 Onemethodthatisusedtopredicttheeffectsofgalvanic
approved in 1983. Last previous edition approved in 2014 as G82–98(2014). DOI:
10.1520/G0082-98R21E01.
corrosion is to develop a galvanic series by arranging a list of
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
the materials of interest in order of observed corrosion poten-
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
tials in the environment and conditions of interest. The metal
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. that will suffer increased corrosion in a galvanic couple in that
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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G82 − 98 (2021)
environmentcanthenbepredictedfromtherelativepositionof predictions of galvanic corrosion rate. A more precise deter-
the two metals in the series. mination of the effect of galvanic coupling can be obtained by
themeasurementofthecorrosioncurrentsinvolvedasoutlined
4.3 Types of Galvanic Series:
3,4
in Guide G71.
4.3.1 OnetypeofGalvanicSeriesliststhemetalsofinterest
5.6 SomepublishedGalvanicSeries,suchasthoseinFig.1
in order of their corrosion potentials, starting with the most
active (electronegative) and proceeding in order to the most and Fig. 2, consider the possibility of there being more than
one potential range for the same material, depending on
noble (electropositive). The potentials themselves (versus an
appropriate reference half-cell) are listed so that the potential whether the material is in the active or the passive state.
Knowledge of conditions affecting passivity of these materials
differencebetweenmetalsintheseriescanbedetermined.This
type of Galvanic Series has been put in graphical form as a is necessary to determine which potential range to use in a
particular application.
series of bars displaying the range of potentials exhibited by
themetallistedoppositeeachbar.Suchaseriesisillustratedin
5.7 Galvanic corrosion behavior is affected by many factors
Fig. 1.
besides corrosion potentials. These factors must also be con-
4.3.2 Thesecondtypeofgalvanicseriesissimilartothefirst
sidered in judging the performance of a galvanic couple. They
in that it lists the metals of interest in order of their corrosion
include, but are not limited to, the following:
potentials. The actual potentials themselves are not specified,
5.7.1 Anode-to-cathode area ratio,
however. Thus, only the relative position of materials in the
5.7.2 Electrolyte conductivity,
series is known and not the magnitude of their potential
5.7.3 Distance between coupled metals,
difference. Such a series is shown in Fig. 2.
5.7.4 Shielding of metal surfaces by marine growth,
sediments, and so forth,
4.4 Use of a Galvanic Series:
5.7.5 Localized electrolyte concentration changes in
4.4.1 Generally, upon coupling two metals in the Galvanic
shielded areas, and
Series, the more active (electronegative) metal will have a
5.7.6 Polarization characteristics of the metals involved.
tendency to undergo increased corrosion while the more noble
(electropositive) metal will have a tendency to undergo re-
5.8 Some materials that are subject to chemical attack in
duced corrosion.
alkaline solutions may suffer increased attack when made the
4.4.2 Usually, the further apart two metals are in the series,
cathodeinagalvaniccoupleduetogenerationofhydroxylions
and thus the greater the potential difference between them, the
by the cathodic reaction. Use of a galvanic series will not
greater is the driving force for galvanic corrosion. All other
predict this behavior.
factorsbeingequal,andsubjecttotheprecautionsinSection5,
5.9 A more detailed discussion of the theory of galvanic
this increased driving force frequently, although not always,
corrosionpredictionispresentedinAppendixX1andinASTM
results in a greater degree of galvanic corrosion.
STP 576.
5. Precautions in the Use of a Galvanic Series
6. Development of a Galvanic Series
5.1 The galvanic series should not be confused with the
6.1 The development of a Galvanic Series may be divided
electromotiveforceseries,which,althoughofasimilarappear-
into several steps. First is the selection of the environment and
ance to the galvanic series, is based on standard electrode
conditions of interest. During the exposures, the environment
potentials of elements and not on corrosion potentials of
and conditions should be as close as possible to service
metals. The electromotive force series should not be used for
conditions.Alist of environmental factors and conditions that
galvanic corrosion prediction.
could affect open-circuit potentials follows. This is not in-
tended to be a complete listing, but it should serve as a guide
5.2 Each series is specific to the environment for which it
to the types of factors that require consideration:
was compiled. For example, a series developed in a flowing
6.1.1 Temperature,
ambienttemperatureseawatershouldnotbeusedtopredictthe
6.1.2 Flow velocity, and
performance of galvanic couples in fresh water or in heated
6.1.3 Electrolyte composition:
seawater.
6.1.3.1 Dissolved oxygen;
5.3 Corrosion potentials can change with time and the
6.1.3.2 Salinity;
environment. These changes can affect the potential difference
6.1.3.3 Heavy-metal ions;
between the metals of interest and, in some cases, can reverse
6.1.3.4 Organic matter, including bacteria and marine
relative positions. It is thus imperative that the series used for
growth;
thepredictionbeobtainedundersimilarconditionsofexposure
6.1.3.5 Soluble corrosion products;
duration and electrolyte composition as the situation being
predicted.
Brasunas, A., Editor, NACE Basic Corrosion Course, Chapter 3, NACE,
5.4 Galvanic corrosion can occur between two identical
Houston, TX, 1970.
materials in different environments. The galvanic series gen- 4
Baboian, R., “ElectrochemicalTechniques for Predicting Galvanic Corrosion,”
erated herein cannot be applied to this situation. GalvanicandPittingCorrosion-FieldandLaboratoryStudies,ASTMSTP576,Am.
Soc. Testing Mats., 1976, pp. 5–19.
5.5 Use of a galvanic series provides qualitative prediction
LaQue,F.L.,MarineCorrosion,CausesandPrevention,JohnWileyandSons,
of galvanic corrosion. It should not be used for quantitative New York, NY, 1975.
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G82 − 98 (2021)
NOTE 1—Dark boxes indicate active behavior of active-passive alloys.
FIG. 1 Galvanic Series of Various Metals in Flowing Seawater at 2.4 m/s to 4.0 m/s for 5 to 15 Days at 5 ° C to 30 ° C (Redrawn from
Original) (see Footnote 5)
6.1.3.6 pH; 6.1.3.9 Waterline effects.
6.1.3.7 Conductivity;
6.2 The metals of
...
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