ASTM G5-14(2021)

Standard Reference Test Method for Making Potentiodynamic Anodic Polarization Measurements

SIGNIFICANCE AND USE
3.1 The availability of a standard procedure, standard material, and a standard plot should make it easy for an investigator to check his techniques. This should lead to polarization curves in the literature which can be compared with confidence.  
3.2 Samples of a standard ferritic Type 430 stainless steel (UNS S43000) used in obtaining standard reference plot are available for those who wish to check their own test procedure and equipment.3  
3.3 Standard potentiodynamic polarization plots are shown for a lot of material originally purchased in 1992. This reference test method is not applicable for standard material purchased before 1992. These reference data are based on the results from different laboratories that followed the standard procedure, using that material in 1.0 N H2SO4. The four sigma probability bands for current density values are shown at each potential to indicate the acceptable range of values.  
3.4 This reference test method may not be appropriate for polarization testing of all materials or in all environments.  
3.5 This reference test method is intended for use in evaluating the accuracy of a given electrochemical test apparatus, not for use in evaluating materials performance. Therefore, the use of the plots in Fig. 1 is not recommended to evaluate alloys other than Type 430, or lots of Type 430 other than those available through Metal Samples. The use of the data in this reference test method in this manner is beyond the scope and intended use of this reference test method. Users of this reference test method are advised to evaluate test results relative to the scatter bands corresponding to the particular lot of Type 430 stainless steel that was tested.
FIG. 1 Typical Standard Potentiodynamic Anodic Polarization Plot
CURRENT DENSITY (μA/cm2)
SCOPE
1.1 This reference test method covers an experimental procedure for checking experimental technique and instrumentation. If followed, this reference test method will provide repeatable potentiodynamic anodic polarization measurements that will reproduce data determined by others at other times and in other laboratories provided all laboratories are testing reference samples from the same lot of Type 430 stainless steel.  
1.2 Units—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.  
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

• Status: Published
• Publication Date: 31-Jul-2021
• ICS: 71.040.50 - Physicochemical methods of analysis
• Technical Committee: G01 - Corrosion of Metals
• Drafting Committee: G01.11 - Electrochemical Measurements in Corrosion Testing

Relations

• Refers: ASTM G3-14(2019) - Standard Practice for Conventions Applicable to Electrochemical Measurements in Corrosion Testing
• Effective Date: 01-May-2019
• Refers: ASTM G3-14 - Standard Practice for Conventions Applicable to Electrochemical Measurements in Corrosion Testing
• Effective Date: 15-Dec-2014
• Refers: ASTM G3-13 - Standard Practice for Conventions Applicable to Electrochemical Measurements in Corrosion Testing
• Effective Date: 01-Dec-2013
• Refers: ASTM E691-13 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-May-2013
• Refers: ASTM E691-11 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-Nov-2011
• Refers: ASTM G3-89(2010) - Standard Practice for Conventions Applicable to Electrochemical Measurements in Corrosion Testing
• Effective Date: 01-May-2010
• Refers: ASTM E1338-09 - Guide for Identification of Metals and Alloys in Computerized Material Property Databases
• Effective Date: 01-Sep-2009
• Refers: ASTM E691-08 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-Oct-2008
• Refers: ASTM G107-95(2008) - Standard Guide for Formats for Collection and Compilation of Corrosion Data for Metals for Computerized Database Input
• Effective Date: 01-May-2008
• Refers: ASTM E691-05 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-Nov-2005
• Refers: ASTM G3-89(2004) - Standard Practice for Conventions Applicable to Electrochemical Measurements in Corrosion Testing
• Effective Date: 01-Nov-2004
• Refers: ASTM E1338-97(2003) - Guide for Identification of Metals and Alloys in Computerized Material Property Databases
• Effective Date: 10-Sep-2003
• Refers: ASTM G3-89(1999) - Standard Practice for Conventions Applicable to Electrochemical Measurements in Corrosion Testing
• Effective Date: 10-Aug-1999
• Refers: ASTM E691-99 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 10-May-1999
• Refers: ASTM G107-95(2002) - Standard Guide for Formats for Collection and Compilation of Corrosion Data for Metals for Computerized Database Input
• Effective Date: 10-Dec-1995

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: G5 − 14 (Reapproved 2021)
Standard Reference Test Method for
Making Potentiodynamic Anodic Polarization
Measurements
This standard is issued under the fixed designation G5; 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 Measurements in Corrosion Testing
G107Guide for Formats for Collection and Compilation of
1.1 This reference test method covers an experimental
Corrosion Data for Metals for Computerized Database
procedureforcheckingexperimentaltechniqueandinstrumen-
Input
tation. If followed, this reference test method will provide
repeatable potentiodynamic anodic polarization measurements
3. Significance and Use
that will reproduce data determined by others at other times
3.1 The availability of a standard procedure, standard
and in other laboratories provided all laboratories are testing
material, and a standard plot should make it easy for an
referencesamplesfromthesamelotofType430stainlesssteel.
investigator to check his techniques. This should lead to
1.2 Units—The values stated in SI units are to be regarded
polarization curves in the literature which can be compared
asstandard.Nootherunitsofmeasurementareincludedinthis
with confidence.
standard.
3.2 Samples of a standard ferritic Type 430 stainless steel
1.3 This standard does not purport to address all of the
(UNS S43000) used in obtaining standard reference plot are
safety concerns, if any, associated with its use. It is the
available for those who wish to check their own test procedure
responsibility of the user of this standard to establish appro-
and equipment.
priate safety, health, and environmental practices and deter-
3.3 Standard potentiodynamic polarization plots are shown
mine the applicability of regulatory limitations prior to use.
for a lot of material originally purchased in 1992. This
1.4 This international standard was developed in accor-
reference test method is not applicable for standard material
dance with internationally recognized principles on standard-
purchased before 1992. These reference data are based on the
ization established in the Decision on Principles for the
results from different laboratories that followed the standard
Development of International Standards, Guides and Recom-
procedure, using that material in 1.0 N H SO .The four sigma
2 4
mendations issued by the World Trade Organization Technical
probability bands for current density values are shown at each
Barriers to Trade (TBT) Committee.
potential to indicate the acceptable range of values.
2. Referenced Documents
3.4 This reference test method may not be appropriate for
polarization testing of all materials or in all environments.
2.1 ASTM Standards:
E691Practice for Conducting an Interlaboratory Study to
3.5 This reference test method is intended for use in
Determine the Precision of a Test Method
evaluating the accuracy of a given electrochemical test
E1338Guide for Identification of Metals and Alloys in
apparatus, not for use in evaluating materials performance.
Computerized Material Property Databases
Therefore, the use of the plots in Fig. 1 is not recommended to
G3Practice for Conventions Applicable to Electrochemical
evaluate alloys other than Type 430, or lots of Type 430 other
than those available through Metal Samples. The use of the
data in this reference test method in this manner is beyond the
This reference test method is under the jurisdiction ofASTM Committee G01
scope and intended use of this reference test method. Users of
onCorrosionofMetalsandisthedirectresponsibilityofG01.11onElectrochemical
this reference test method are advised to evaluate test results
Measurements in Corrosion Testing.
Current edition approved Aug. 1, 2021. Published August 2021. Originally
relative to the scatter bands corresponding to the particular lot
ε1
approved in 1969. Last previous edition approved in 2014 as G5–14 . DOI:
of Type 430 stainless steel that was tested.
10.1520/G0005-14R21.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
These standard samples are available from Metal Samples, 152 Metal Samples
Standards volume information, refer to the standard’s Document Summary page on
Rd., Mumford,AL 36268. Generally, one sample can be repolished and reused for
the ASTM website. many runs. This procedure is suggested to conserve the available material.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
G5 − 14 (2021)
CURRENT DENSITY (µA/cm )
FIG. 1 Typical Standard Potentiodynamic Anodic Polarization Plot
4. Apparatus
4.1 The test cell should be constructed to allow the follow-
ing items to be inserted into the solution chamber: the test
electrode, two auxiliary electrodes, a Luggin capillary with
salt-bridge connection to the reference electrode, inlet and
outletforaninertgas,andathermometer.Thetestcellshallbe
constructed of materials that will not corrode, deteriorate, or
otherwise contaminate the test solution.
NOTE 1—Borosilicate glass and TFE-fluorocarbon have been found
suitable.
4.1.1 A suitable cell is shown in Fig. 2 (1). A 1L, round-
bottom flask has been modified by the addition of various
necks to permit the introduction of electrodes, gas inlet and
outlet tubes, and a thermometer. The Luggin probe-salt bridge
separates the bulk solution from the saturated calomel refer-
FIG. 2 Schematic Diagram of Polarization Cell (1)
enceelectrode,andtheprobetipcanbeeasilyadjustedtobring
it in close proximity with the working electrode.
4.3.1 The potential-measuring circuit should have high
4.2 Potentiostat (Note 2):
11 14
input impedance on the order of 10 Ω to 10 Ω to minimize
4.2.1 Apotentiostatthatwillmaintainanelectrodepotential
current drawn from the system during measurements. Such
within 1 mV of a preset value over a wide range of applied
circuits are provided with most potentiostats. Instruments
currents should be used. For the type and size of standard
should have sufficient sensitivity and accuracy to detect a
specimen supplied, the potentiostat should have a potential
change of 1.0 mV over a potential range between −0.6V and
range from −0.6Vto 1.6Vand an anodic current output range
1.6 V. Potentiostats that scan potential by making frequent
from 1.0µA to 10 µA.
potential steps of less than 1.0 mV and those that make
4.3 Potential-Measuring Instruments (Note 2):
continuous analog potential sweeps are both suitable for this
reference test method, providing that they can achieve the
required potential scan rate.
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
this test method. 4.4 Current-Measuring Instruments (Note 2):
G5 − 14 (2021)
4.4.1 An instrument that is capable of measuring a current
accurately to within1%ofthe absolute value over a current
rangebetween1.0µAand10 µAforaType430stainlesssteel
(UNS S43000) specimen with a surface area of approximately
5cm .
4.5 Anodic Polarization Circuit:
4.5.1 Aschematicwiringdiagram (2)isillustratedinFig.3.
4.5.2 A scanning potentiostat is used for potentiodynamic
measurements.Forsuchmeasurementsthepotentiostatshallbe
capableofautomaticallyvaryingthepotentialataconstantrate
between two preset potentials. A record of the potential and
current is plotted continuously using such instruments as an
X-Y recorder and a logarithmic converter incorporated into the
circuit shown in Fig. 3. Some potentiostats have an output of
the logarithm of the current as a voltage, which allows direct
plotting of the potential log current curve using an X-Y
recorder.
NOTE 2—The instrumental requirements are based upon values typical
of the instruments in the laboratories that participated in the round robin.
4.6 Electrode Holder (1):
4.6.1 The auxiliary and working electrodes are mounted in
the type of holder shown in Fig. 4.Alonger holder is required
for the working electrode than for the auxiliary electrode. A
leakproof assembly is obtained by the proper compression fit
between the electrode and a TFE-fluorocarbon gasket. (Too FIG. 4 Specimen Mounted on Electrode Holder
much pressure may cause shielding of the electrode or break-
age of the glass holder, and too little pressure may cause
leakage and subsequently crevice corrosion which may affect 4.7.1.1 The standard AISI Type 430 stainless steel (UNS
S43000) should be used if one wishes to reproduce a standard
the test results.)
reference plot. This material is prepared from a single heat of
4.7 Electrodes:
metal that is mill-annealed for ⁄2 h at 815°C and air cooled.
4.7.1 Working Electrode, prepared from a 12.7mm length
The chemical composition of the standard stainless steel is
of9.5mmdiameterrodstock.Eachelectrodeisdrilled,tapped,
supplied with the purchase of reference material.
and mounted in the manner discussed in 4.6.1.
4.7.2 Auxiliary Electrodes:
NOTE 3—If specimen forms are used other than those called for by this
4.7.2.1 Twoplatinumauxiliaryelectrodesarepreparedfrom
reference test method, for example, flat sheet specimen, care should be
high-purity rod stock. Each electrode is drilled, tapped, and
taken since it was shown that crevices may be introduced which can lead
mounted with a TFE-fluorocarbon gasket in the same manner
to erroneous results (see Fig. X1.1).
as the working electrode. A large platinum sheet sealed into a
glass holder is also acceptable.
4.7.2.2 A platinized surface may be utilized because of the
increased surface area. This may be accomplished by cleaning
the surface in hot aqua regia (3 parts concentrated HCl and
1part concentrated HNO ), washing, and then drying. Both
electrodes are platinized by immersing them in a solution of
3%platinicchlorideand0.02%leadacetateandelectrolyzing
2 2
at a current density of 40mA⁄cm to 50 mA/cm for 4min or
5 min (1, 3). The polarity is reversed every minute. Occluded
chlorideisremovedbyelectrolyzinginadilute(10%)sulfuric
acid solution for several minutes with a reversal in polarity
every minute. Electrodes are rinsed thoroughly and stored in
distilledwateruntilreadyforuse.Sincecertainionscanpoison
these electrodes, periodic checks of platinized platinum poten-
tials against a known reference electrode should be made.
4.7.2.3 Alternatively, graphite auxiliary electrodes can be
used, but material retained by the graphite may contaminate
subsequentexperiments.Thiscontaminationcanbeminimized
by using high-density graphite or avoided by routinely replac-
FIG. 3 Schematic Wiring Diagram (2) ing the graphite electrode.
G5 − 14 (2021)
TABLE 1 Compliance Limits for Current Densities (µA/cm )at
4.7.3 Reference Electrode (4):
Cited Potentials for Type 430 Stainless Steel in G5 Polarization
4.7.3.1 Asaturated calomel electrode with a controlled rate
Tests
of leakage (about 3 µL/h) is recommended. This type of
Potential Volts (versus Min Max
electrode is durable, reliable, and commercially available.
SCE)
Precautions shall be taken to ensure that it is maintained in the
–0.450 5160 13,860
–0.100 2.16 15.60
propercondition.Thepotentialofthecalomelelectrodeshould
0.000 25.8a 134.8
be checked at periodic intervals to ensure the accuracy of the
+0.400 0.883 1.669
electrode. For other alloy-electrolyte combinations a different
reference electrode may be preferred in order to avoid con-
tamination of the reference electrode or the electrolyte.
counter electrodes and hydrogen gas are used, record the
4.7.3.2 Alternatively, a saturated calomel electrode utilizing
platinum potential 50 min after immersion of the specimen.
a semipermeable membrane or porous plug tip may be used.
5.11 Potential Scan:
These may require special care.
5.11.1 Startthepotentialscan1hafterspecimenimmersion,
beginning at the corrosion potential (E ). Proceed through
5. Experimental Procedure corr
+1.60 V versus saturated calomel electrode (SCE) (active to
5.1 Prepare 1 L of 1.0 N H SO fromA.C.S. reagent grade
2 4
noble).
acidanddistilledwater,forexample,byusing27.8mLof98%
5.11.2 Use a potentiodynamic potential sweep rate of
H SO /Lof solution.Transfer 900 mLof solution to the clean
2 4
0.6V⁄h (65 %) recording the current continuously with
polarization cell.
changeinpotentialfromthecorrosionpotentialto+1.6VSCE.
5.2 Place the platinized auxiliary electrodes, salt-bridge
5.12 Plot anodic polarization data semilogarithmically in
probe, and other components in the test cell and temporarily
accordance with Practice G3, (potential-ordinate, current
close the center opening with a glass stopper. Fill the salt
density-abscissa).
bridge with test solution.
6. Standard Reference Plots and Compliance Limits
NOTE 4—When using a controlled leakage salt bridge, the levels of the
solutioninthereferenceandpolarizationcellsshouldbethesametoavoid
6.1 Astandardpolarizationplotpreparedfromtheinterlabo-
siphoning. If this is impossible, a closed solution-wet (not greased)
ratorytestingprogramisshowninFig.1.SeeResearchReport
stopcock can be used in the salt bridge to eliminate siphoning, or a
RR:G01-1026. The confidence bands were calculated by
semipermeable membrane or porous plug tip may be used on the salt
bridge. determining logarithmic average of the current densities at
each potential and plotting the current density limits at four
5.3 Bringthetemperatureofthesolutionto30°C 61°Cby
logarithmic standard deviations on either side of the logarith-
immersing the test cell in a controlled-temperature water bath
mic average.The average corrosion potential was –0.52V, and
or by other convenient means.
the average platinized platinum/hydrogen potential was
5.4 Reduce oxygen levels in solution prior to immersion of
–0.26V versus SCE reference electrode.
the test specimen. This may be accomplished by bubbling an
6.2 Tojudgecompliancewiththisreferencetestmethod,the
oxygen-free gas such as hydrogen, argon, or nitrogen at a rate
current density at four potentials shall be measured and
of 150 cm /min for a minimum of ⁄2 h.
compared to the limits shown in Table 1. The probability that
5.5 Prepare the working electrode surface within1hofthe
testresultswouldfalloutsideoftheselimitswhilestillbeingin
experiment.Wetgrindwith240gritSiCpaper,wetpolishwith
compliance with this method is less than 0.001.
600gritSiCpaperuntilpreviouscoarsescratchesareremoved,
...