ASTM G82-98(2003)
(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
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 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.
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Designation:G82–98 (Reapproved 2003)
Standard Guide for
Development and Use of a Galvanic Series for Predicting
Galvanic Corrosion Performance
ThisstandardisissuedunderthefixeddesignationG82;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginal
adoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscript
epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 3.5 galvanic series—a list of metals and alloys arranged
according to their relative corrosion potentials in a given
1.1 This guide covers the development of a galvanic series
environment.
and its subsequent use as a method of predicting the effect that
3.6 noble—thepositive(increasinglyoxidizing)directionof
one metal can have upon another metal can when they are in
electrode potential.
electrical contact while immersed in an electrolyte. Sugges-
3.7 passive—the state of the metal surface characterized by
tions for avoiding known pitfalls are included.
low corrosion rates in a potential region that is strongly
1.2 This standard does not purport to address all of the
oxidizing for the metal.
safety concerns, if any, associated with its use. It is the
3.8 polarization—the change from the open-circuit elec-
responsibility of the user of this standard to establish appro-
trode potential as the result of the passage of current.
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use. Specific precau-
4. Significance and Use
tionary statements are given in Section 5.
4.1 When two dissimilar metals in electrical contact are
2. Referenced Documents exposed to a common electrolyte, one of the metals can
undergo increased corrosion while the other can show de-
2.1 ASTM Standards:
creasedcorrosion.Thistypeofacceleratedcorrosionisreferred
G3 PracticeforConventionsApplicabletoElectrochemical
toasgalvaniccorrosion.Becausegalvaniccorrosioncanoccur
Measurements in Corrosion Testing
at a high rate, it is important that a means be available to alert
G15 Terminology Relating to Corrosion and Corrosion
the user of products or equipment that involve the use of
Testing
dissimilar metal combinations in an electrolyte of the possible
G16 GuideforApplyingStatisticstoAnalysisofCorrosion
effects of galvanic corrosion.
Data
4.2 Onemethodthatisusedtopredicttheeffectsofgalvanic
G71 Guide for Conducting and Evaluating Galvanic Cor-
corrosion is to develop a galvanic series by arranging a list of
rosion Tests in Electrolytes
the materials of interest in order of observed corrosion poten-
3. Terminology
tials in the environment and conditions of interest. The metal
that will suffer increased corrosion in a galvanic couple in that
3.1 Definitions of terms used in this guide are from Termi-
environmentcanthenbepredictedfromtherelativepositionof
nologyG15.
the two metals in the series.
3.2 active—the negative (decreasingly oxidizing) direction
4.3 Types of Galvanic Series:
of electrode potential.
4.3.1 OnetypeofGalvanicSeriesliststhemetalsofinterest
3.3 corrosionpotential—thepotentialofacorrodingsurface
in order of their corrosion potentials, starting with the most
in an electrolyte relative to a reference electrode measured
active (electronegative) and proceeding in order to the most
under open-circuit conditions.
noble (electropositive). The potentials themselves (versus an
3.4 galvanic corrosion—accelerated corrosion of a metal
appropriate reference half-cell) are listed so that the potential
because of an electrical contact with a more noble metal or
differencebetweenmetalsintheseriescanbedetermined.This
nonmetallic conductor in a corrosive electrolyte.
type of Galvanic Series has been put in graphical form as a
series of bars displaying the range of potentials exhibited by
themetallistedoppositeeachbar.Suchaseriesisillustratedin
This guide is under the jurisdiction ofASTM Committee G01 on Corrosion of
Metals and is the direct responsibility of Subcommittee G01.11 on Electrochemical
Fig. 1.
Measurements in Corrosion Testing.
4.3.2 Thesecondtypeofgalvanicseriesissimilartothefirst
Current edition approved October 1, 2003. Published October 2003. Originally
in that it lists the metals of interest in order of their corrosion
approved in 1983. Last previous edition approved in 1998 as G 82–98.
Annual Book of ASTM Standards, Vol 03.02. potentials. The actual potentials themselves are not specified,
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
G82–98 (2003)
NOTE—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)
however. Thus, only the relative position of materials in the tendency to undergo increased corrosion while the more noble
series is known and not the magnitude of their potential (electropositive) metal will have a tendency to undergo re-
difference. Such a series is shown in Fig. 2. duced corrosion.
4.4 Use of a Galvanic Series: 4.4.2 Usually, the further apart two metals are in the series,
4.4.1 Generally, upon coupling two metals in the Galvanic and thus the greater the potential difference between them, the
Series, the more active (electronegative) metal will have a greater is the driving force for galvanic corrosion. All other
G82–98 (2003)
5.3 Corrosion potentials can change with time and the
ACTIVE END Magnesium
(−) Magnesium Alloys
environment. These changes can affect the potential difference
↑ Zinc
between the metals of interest and, in some cases, can reverse
| Galvanized Steel
relative positions. It is thus imperative that the series used for
| Aluminum 1100
| Aluminum 6053
thepredictionbeobtainedundersimilarconditionsofexposure
| Alclad
duration and electrolyte composition as the situation being
| 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)
predictions of galvanic corrosion rate.Amore precise determi-
| 18-12-3 Stainless Steel
| Type 316 (Active)
nationoftheeffectofgalvaniccouplingcanbeobtainedbythe
| Lead-Tin Solders
measurement of the corrosion currents involved as outlined in
| Lead
,
Guide G 71.
|Tin
| Muntz Metal
5.6 SomepublishedGalvanicSeries,suchasthoseinFig.1
| Manganese Bronze
and 2, consider the possibility of there being more than one
| Naval Brass
potential range for the same material, depending on whether
| Nickel (Active)
| 76 Ni-16 Cr-7 Fe alloy (Active)
the material is in the active or the passive state. Knowledge of
| 60 Ni-30 Mo-6 Fe-1 Mn
conditions affecting passivity of these materials is necessary to
| Yellow Brass
| Admirality Brass determine which potential range to use in a particular applica-
| Aluminum Brass
tion.
| Red Brass
5.7 Galvanic corrosion behavior is affected by many factors
| Copper
| Silicon Bronze besides corrosion potentials. These factors must also be con-
| 70:30 Cupro Nickel
sidered in judging the performance of a galvanic couple. They
| G-Bronze
include, but are not limited to, the following:
| M-Bronze
| Silver Solder 5.7.1 Anode-to-cathode area ratio,
| Nickel (Passive)
5.7.2 Electrolyte conductivity,
| 76 Ni-16 Cr-7 Fe
5.7.3 Distance between coupled metals,
| Alloy (Passive)
| 67 Ni-33 Cu Alloy (Monel) 5.7.4 Shielding of metal surfaces by marine growth, sedi-
| 13 % Chromium Stainless Steel
ments, and so forth,
| Type 410 (Passive)
5.7.5 Localized electrolyte concentration changes in
| Titanium
| 18-8 Stainless Steel
shielded areas, and
| Type 304 (Passive)
5.7.6 Polarization characteristics of the metals involved.
| 18-12-3 Stainless Steel
5.8 Some materials that are subject to chemical attack in
↓ Type 316 (Passive)
(+) Silver
alkaline solutions may suffer increased attack when made the
NOBLE or Graphite
cathodeinagalvaniccoupleduetogenerationofhydroxylions
PASSIVE END Gold
by the cathodic reaction. Use of a galvanic series will not
Platinum
predict this behavior.
FIG. 2 Galvanic Series of Various Metals Exposed to Sea Water
5.9 A more detailed discussion of the theory of galvanic
corrosionpredictionispresentedinAppendixX1andinASTM
STP 576.
factorsbeingequal,andsubjecttotheprecautionsinSection5,
this increased driving force frequently, although not always,
6. Development of a Galvanic Series
results in a greater degree of galvanic corrosion.
6.1 The development of a Galvanic Series may be divided
into several steps. First is the selection of the environment and
5. Precautions in the Use of a Galvanic Series
conditions of interest. During the exposures, the environment
5.1 The galvanic series should not be confused with the
and conditions should be as close as possible to service
electromotiveforceseries,which,althoughofasimilarappear-
conditions.Alist of environmental factors and conditions that
ance to the galvanic series, is based on standard electrodepo-
tentials of elements and not on corrosion potentials of metals.
The electromotive force series should not be used for galvanic
corrosion prediction. 3
Brasunas, A., Editor, NACE Basic Corrosion Course, Chapter 3, NACE,
5.2 Each series is specific to the environment for which it
Houston, TX, 1970.
Baboian, R., “ElectrochemicalTechniques for Predicting Galvanic Corrosion,”
was compiled. For example, a series developed in a flowing
GalvanicandPittingCorrosion-FieldandLaboratoryStudies,ASTMSTP576,Am.
ambienttemperatureseawatershouldnotbeusedtopredictthe
Soc. Testing Mats., 1976, pp. 5–19.
performance of galvanic couples in fresh wat
...
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