ASTM G82-98(2009)
(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
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.
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.
Types of Galvanic Series:
Oe 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.
The second type of galvanic series is similar to the first in that it lists the metals of interest in order of their corrosion potentials. The actual potentials themselves are not specified, however. Thus, only the relative position of materials in the series is known and not the magnitude of their potential difference. Such a series is shown in Fig. 2.
Use of a Galvanic Series:
Generally, upon coupling two metals in the Galvanic Series, the more active (electro...
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 and health practices and determine the applicability of regulatory limitations prior to use. Specific precautionary statements are given in Section 5.
General Information
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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: G82 − 98(Reapproved 2009)
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.
1. Scope 3.2 active—the negative (decreasingly oxidizing) direction
of electrode potential.
1.1 This guide covers the development of a galvanic series
3.3 corrosionpotential—thepotentialofacorrodingsurface
and its subsequent use as a method of predicting the effect that
one metal can have upon another metal can when they are in in an electrolyte relative to a reference electrode measured
under open-circuit conditions.
electrical contact while immersed in an electrolyte. Sugges-
tions for avoiding known pitfalls are included.
3.4 galvanic corrosion—accelerated corrosion of a metal
because of an electrical contact with a more noble metal or
1.2 The values stated in SI units are to be regarded as
nonmetallic conductor in a corrosive electrolyte.
standard. No other units of measurement are included in this
standard.
3.5 galvanic series—a list of metals and alloys arranged
according to their relative corrosion potentials in a given
1.3 This standard does not purport to address all of the
environment.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
3.6 noble—thepositive(increasinglyoxidizing)directionof
priate safety and health practices and determine the applica-
electrode potential.
bility of regulatory limitations prior to use. Specific precau-
3.7 passive—the state of the metal surface characterized by
tionary statements are given in Section 5.
low corrosion rates in a potential region that is strongly
oxidizing for the metal.
2. Referenced Documents
3.8 polarization—the change from the open-circuit elec-
2.1 ASTM Standards:
trode potential as the result of the passage of current.
G3Practice for Conventions Applicable to Electrochemical
Measurements in Corrosion Testing
4. Significance and Use
G15TerminologyRelatingtoCorrosionandCorrosionTest-
4.1 When two dissimilar metals in electrical contact are
ing (Withdrawn 2010)
exposed to a common electrolyte, one of the metals can
G16Guide for Applying Statistics to Analysis of Corrosion
Data undergo increased corrosion while the other can show de-
creasedcorrosion.Thistypeofacceleratedcorrosionisreferred
G71Guide for Conducting and Evaluating Galvanic Corro-
sion Tests in Electrolytes toasgalvaniccorrosion.Becausegalvaniccorrosioncanoccur
at a high rate, it is important that a means be available to alert
3. Terminology
the user of products or equipment that involve the use of
dissimilar metal combinations in an electrolyte of the possible
3.1 Definitions of terms used in this guide are from Termi-
effects of galvanic corrosion.
nology G15.
4.2 Onemethodthatisusedtopredicttheeffectsofgalvanic
corrosion is to develop a galvanic series by arranging a list of
This guide is under the jurisdiction ofASTM Committee G01 on Corrosion of
the materials of interest in order of observed corrosion poten-
Metalsand is the direct responsibility of Subcommittee G01.11 on Electrochemical
tials in the environment and conditions of interest. The metal
Measurements in Corrosion Testing.
that will suffer increased corrosion in a galvanic couple in that
Current edition approved May 1, 2009. Published May 2009. Originally
approved in 1983. Last previous edition approved in 2003 as G82–98(2003). DOI:
environmentcanthenbepredictedfromtherelativepositionof
10.1520/G0082-98R09.
the two metals in the series.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
4.3 Types of Galvanic Series:
Standards volume information, refer to the standard’s Document Summary page on
4.3.1 OnetypeofGalvanicSeriesliststhemetalsofinterest
the ASTM website.
in order of their corrosion potentials, starting with the most
The last approved version of this historical standard is referenced on
www.astm.org. active (electronegative) and proceeding in order to the most
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
G82 − 98 (2009)
noble (electropositive). The potentials themselves (versus an series of bars displaying the range of potentials exhibited by
appropriate reference half-cell) are listed so that the potential themetallistedoppositeeachbar.Suchaseriesisillustratedin
differencebetweenmetalsintheseriescanbedetermined.This
Fig. 1.
type of Galvanic Series has been put in graphical form as a
NOTE 1—Dark boxes indicate active behavior of active-passive alloys.
FIG. 1 Galvanic Series of Various Metals in Flowing Seawater at 2.4 to 4.0 m/s for 5 to 15 Days at 5 to 30°C (Redrawn from Original)
(see Footnote 5)
G82 − 98 (2009)
4.3.2 Thesecondtypeofgalvanicseriesissimilartothefirst factorsbeingequal,andsubjecttotheprecautionsinSection5,
in that it lists the metals of interest in order of their corrosion this increased driving force frequently, although not always,
potentials. The actual potentials themselves are not specified, results in a greater degree of galvanic corrosion.
however. Thus, only the relative position of materials in the
5. Precautions in the Use of a Galvanic Series
series is known and not the magnitude of their potential
5.1 The galvanic series should not be confused with the
difference. Such a series is shown in Fig. 2.
electromotiveforceseries,which,althoughofasimilarappear-
4.4 Use of a Galvanic Series:
ance to the galvanic series, is based on standard electrodepo-
4.4.1 Generally, upon coupling two metals in the Galvanic
tentials of elements and not on corrosion potentials of metals.
Series, the more active (electronegative) metal will have a
The electromotive force series should not be used for galvanic
tendency to undergo increased corrosion while the more noble
corrosion prediction.
(electropositive) metal will have a tendency to undergo re-
5.2 Each series is specific to the environment for which it
duced corrosion.
was compiled. For example, a series developed in a flowing
4.4.2 Usually, the further apart two metals are in the series,
ambienttemperatureseawatershouldnotbeusedtopredictthe
and thus the greater the potential difference between them, the
performance of galvanic couples in fresh water or in heated
greater is the driving force for galvanic corrosion. All other
seawater.
5.3 Corrosion potentials can change with time and the
ACTIVE END Magnesium
environment. These changes can affect the potential difference
(−) Magnesium Alloys
between the metals of interest and, in some cases, can reverse
↑ Zinc
| Galvanized Steel
relative positions. It is thus imperative that the series used for
| Aluminum 1100
thepredictionbeobtainedundersimilarconditionsofexposure
| Aluminum 6053
duration and electrolyte composition as the situation being
| Alclad
| Cadmium
predicted.
| Aluminum 2024 (4.5 Cu, 1.5 Mg, 0.6 Mn)
| Mild Steel 5.4 Galvanic corrosion can occur between two identical
| Wrought Iron
materials in different environments. The galvanic series gen-
| Cast Iron
erated herein cannot be applied to this situation.
| 13 % Chromium Stainless Steel
| Type 410 (Active)
5.5 Use of a galvanic series provides qualitative prediction
| 18-8 Stainless Steel
of galvanic corrosion. It should not be used for quantitative
| Type 304 (Active)
| 18-12-3 Stainless Steel
predictions of galvanic corrosion rate. A more precise deter-
| Type 316 (Active)
mination of the effect of galvanic coupling can be obtained by
| Lead-Tin Solders
themeasurementofthecorrosioncurrentsinvolvedasoutlined
| Lead
4,5
|Tin
in Guide G71.
| Muntz Metal
| Manganese Bronze 5.6 SomepublishedGalvanicSeries,suchasthoseinFig.1
| Naval Brass
and Fig. 2, consider the possibility of there being more than
| Nickel (Active)
one potential range for the same material, depending on
| 76 Ni-16 Cr-7 Fe alloy (Active)
whether the material is in the active or the passive state.
| 60 Ni-30 Mo-6 Fe-1 Mn
| Yellow Brass
Knowledge of conditions affecting passivity of these materials
| Admirality Brass
is necessary to determine which potential range to use in a
| Aluminum Brass
| Red Brass particular application.
| Copper
5.7 Galvanic corrosion behavior is affected by many factors
| Silicon Bronze
| 70:30 Cupro Nickel
besides corrosion potentials. These factors must also be con-
| G-Bronze
sidered in judging the performance of a galvanic couple. They
| M-Bronze
include, but are not limited to, the following:
| Silver Solder
| Nickel (Passive)
5.7.1 Anode-to-cathode area ratio,
| 76 Ni-16 Cr-7 Fe
5.7.2 Electrolyte conductivity,
| Alloy (Passive)
5.7.3 Distance between coupled metals,
| 67 Ni-33 Cu Alloy (Monel)
| 13 % Chromium Stainless Steel
5.7.4 Shielding of metal surfaces by marine growth, sedi-
| Type 410 (Passive)
ments, and so forth,
| Titanium
5.7.5 Localized electrolyte concentration changes in
| 18-8 Stainless Steel
| Type 304 (Passive)
shielded areas, and
| 18-12-3 Stainless Steel
↓ Type 316 (Passive)
(+) Silver Brasunas, A., Editor, NACE Basic Corrosion Course, Chapter 3, NACE,
NOBLE or Graphite Houston, TX, 1970.
PASSIVE END Gold
Baboian, R., “ElectrochemicalTechniques for Predicting Galvanic Corrosion,”
Platinum
Galvanic and Pitting Corrosion-Field and Laboratory Studies, ASTM STP 576,Am.
Soc. Testing Mats., 1976, pp. 5–19.
FIG. 2 Galvanic Series of Various Metals Exposed to Seawater LaQue, F. L., Marine Corrosion, Causes and Prevention, JohnWiley and Sons,
(see Footnote 3) New York, NY, 1975.
G82 − 98 (2009)
5.7.6 Polarization characteristics of the metals involved. anticipated duration of exposure, should be selected. During
exposure of the panels, their corrosion potential relative to the
5.8 Some materials that are subject to chemical attack in
reference half-cell will be measured periodically, using a
alkaline solutions may suffer increased attack when made the
voltmeter.
cathodeinagalvaniccoupledueto
...
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