ASTM G192-08(2020)e1
(Test Method)Standard Test Method for Determining the Crevice Repassivation Potential of Corrosion-Resistant Alloys Using a Potentiodynamic-Galvanostatic-Potentiostatic Technique
Standard Test Method for Determining the Crevice Repassivation Potential of Corrosion-Resistant Alloys Using a Potentiodynamic-Galvanostatic-Potentiostatic Technique
SIGNIFICANCE AND USE
5.1 The THE test method is designed to provide highly reproducible crevice repassivation potentials for corrosion–resistant alloys (for example, Alloy 22) in a wide range of environments from non-aggressive to highly aggressive. In conditions of low environmental aggressiveness (such as low temperature or low chloride concentration), corrosion–resistant alloys such as Alloy 22 will resist crevice corrosion initiation and the cyclic potentiodynamic polarization test (Test Method G61) may fail to promote crevice corrosion mainly because it drives the alloy into transpassive dissolution instead of nucleating crevice corrosion. The THE test method provides a more controlled way of applying the electrical charge to the test electrode, which may induce crevice corrosion without moving it into transpassive potentials.
5.2 The more noble this crevice corrosion repassivation potential (ER,CREV) value, the more resistant the alloy is to crevice corrosion in the tested electrolyte. This is similar to other test methods to measure localized corrosion resistance such as Test Method G61 and Test Methods G48. The results from this test method are not intended to correlate in a quantitative manner with the rate of propagation that one might observe in service when localized corrosion occurs.
5.3 This test method may be used to rank several alloys by using the same testing electrolyte and temperature. It can also be used to determine the response of a given alloy when the environmental conditions (such as electrolyte composition and temperature) change.
SCOPE
1.1 This test method covers a procedure for conducting anodic polarization studies to determine the crevice repassivation potential for corrosion–resistant alloys. The concept of the repassivation potential is similar to that of the protection potential given in Reference Test Method G5.
1.2 The test method consists in applying successively potentiodynamic, galvanostatic, and potentiostatic treatments for the initial formation and afterward repassivation of crevice corrosion.
1.3 This test method is a complement to Test Method G61.
1.4 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.5 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.
1.6 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
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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: G192 − 08 (Reapproved 2020)
Standard Test Method for
Determining the Crevice Repassivation Potential of
Corrosion-Resistant Alloys Using a Potentiodynamic-
Galvanostatic-Potentiostatic Technique
This standard is issued under the fixed designation G192; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
ε NOTE—Ref (1) was completed editorially, and other editorial changes were made throughout in December 2020.
1. Scope B575 Specification for Low-Carbon Nickel-Chromium-
Molybdenum, Low-Carbon Nickel-Chromium-
1.1 This test method covers a procedure for conducting
Molybdenum-Copper, Low-Carbon Nickel-Chromium-
anodic polarization studies to determine the crevice repassiva-
Molybdenum-Tantalum, Low-Carbon Nickel-Chromium-
tionpotentialforcorrosion–resistantalloys.Theconceptofthe
Molybdenum-Tungsten, and Low-Carbon Nickel-
repassivation potential is similar to that of the protection
Molybdenum-Chromium Alloy Plate, Sheet, and Strip
potential given in Reference Test Method G5.
D1193Specification for Reagent Water
1.2 The test method consists in applying successively
E691Practice for Conducting an Interlaboratory Study to
potentiodynamic, galvanostatic, and potentiostatic treatments
Determine the Precision of a Test Method
for the initial formation and afterward repassivation of crevice
G1Practice for Preparing, Cleaning, and Evaluating Corro-
corrosion.
sion Test Specimens
G5Reference Test Method for Making Potentiodynamic
1.3 This test method is a complement to Test Method G61.
Anodic Polarization Measurements
1.4 The values stated in SI units are to be regarded as the
G48Test Methods for Pitting and Crevice Corrosion Resis-
standard. The values given in parentheses are for information
tance of Stainless Steels and Related Alloys by Use of
only.
Ferric Chloride Solution
1.5 This standard does not purport to address all of the
G61Test Method for Conducting Cyclic Potentiodynamic
safety concerns, if any, associated with its use. It is the
Polarization Measurements for Localized Corrosion Sus-
responsibility of the user of this standard to establish appro-
ceptibility of Iron-, Nickel-, or Cobalt-Based Alloys
priate safety, health, and environmental practices and deter-
G78Guide for Crevice Corrosion Testing of Iron-Base and
mine the applicability of regulatory limitations prior to use.
Nickel-Base Stainless Alloys in Seawater and Other
1.6 This international standard was developed in accor-
Chloride-Containing Aqueous Environments
dance with internationally recognized principles on standard-
G193Terminology and Acronyms Relating to Corrosion
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
3. Terminology
mendations issued by the World Trade Organization Technical
3.1 Definitions—For definitions of corrosion-related terms
Barriers to Trade (TBT) Committee.
used in this test method, see Terminology G193.
2. Referenced Documents
4. Summary of Test Method
2.1 ASTM Standards:
4.1 This anodic polarization test method combines tech-
niques such as potentiodynamic, galvanostatic, and potentio-
static polarization methods. This test method is called the
This test method is under the jurisdiction of ASTM Committee G01 on
Tsujikawa-Hisamatsu Electrochemical (THE) test method to
Corrosion of Metals and is the direct responsibility of Subcommittee G01.11 on
Electrochemical Measurements in Corrosion Testing. honorthetwoprecursorsofthistechnique(seeRefs 1 and 2).
Current edition approved Nov. 1, 2020. Published December 2020. Originally
The new technique will be called the THE test method. This
approvedin2008.Lastpreviouseditionapprovedin2014asG192–08(2014).DOI:
newTHEtestmethodismoretime-consumingthanthealready
10.1520/G0192-08R20E01.
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
Standards volume information, refer to the standard’s Document Summary page on The boldface numbers in parentheses refer to a list of references at the end of
the ASTM website. this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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G192 − 08 (2020)
well-established cyclic potentiodynamic polarization (CPP) ating crevice corrosion. The THE test method provides a more
described in Test Method G61. controlled way of applying the electrical charge to the test
electrode,whichmayinducecrevicecorrosionwithoutmoving
4.2 The THE test method can be used with any corrosion-
it into transpassive potentials.
resistant alloy, but it was developed by studying Alloy 22
(UNSN06022).ThecompositionandotherpropertiesofAlloy
5.2 The more noble this crevice corrosion repassivation
22 are given in Specification B575.Alloy 22 is a nickel-based potential (ER,CREV) value, the more resistant the alloy is to
alloy containing approximately 22wt% Cr, 13wt% Mo, 3wt%
crevice corrosion in the tested electrolyte. This is similar to
W and 3wt% Fe. The THE test method is a complement to the other test methods to measure localized corrosion resistance
cyclic potentiodynamic polarization (CPP) described in Test
such as Test Method G61 and Test Methods G48. The results
MethodG61.CPPmaybeusedasafirstfastscreeningmethod from this test method are not intended to correlate in a
andTHEtestmethodforfine-tuningtherepassivationpotential
quantitativemannerwiththerateofpropagationthatonemight
for crevice corrosion when the environment is not highly observe in service when localized corrosion occurs.
aggressive(3-6).TheTHEtestmethodhasalsobeenappliedto
5.3 This test method may be used to rank several alloys by
other highly corrosion-resistant alloys, such as Titanium grade
using the same testing electrolyte and temperature. It can also
7 (Ref 7).
be used to determine the response of a given alloy when the
4.3 The THE test method can be used with any electrolyte
environmental conditions (such as electrolyte composition and
solution. A standard 1 M NaCl solution at 90°C or lower
temperature) change.
temperature may be used to compare alloys of interest. The
round robin described in Section 15 was carried out in 1 M
6. Apparatus
NaCl solution at 90°C.
6.1 Cell—The polarization cell should be similar to the one
4.4 Thetestinvolvesinpolarizingthetestelectrodeinthree
described in ReferenceTest Method G5 andTest Method G61.
steps:
Other polarization cells may be equally suitable. The cell
4.4.1 Step 1—The test electrode is polarized potentiody-
should have a capacity of about 1 L and should have suitable
namically at a rate of 0.168 mV/s (as in Test Method G61)
necksorsealstopermittheintroductionofelectrodes,gasinlet
starting at or slightly below the corrosion potential until a
and outlet tubes, and a thermometer or thermocouple. The
preset current (or current density) is reached (for example,
Luggin probe-salt bridge separates the bulk solution from the
2µA⁄cm ). After this initial potentiodynamic polarization, the
saturated calomel or saturated silver chloride reference elec-
polarization control is changed to galvanostatic mode (Step 2).
trode.
4.4.2 Step 2—The preset current of 2 µA/cm is kept
6.2 Test Electrode (Specimen) Holder—The test electrode
constant for a 2h period to develop and grow a crevice
holder and the mounting rod should be similar to the one
corroded area (if any develops). During the galvanostatic Step
described in Figure 5 in Reference Test Method G5 (repro-
2, the potential output is monitored.
duced in Fig. 1). A leakproof PTFE compression gasket, as
4.4.3 Step 3—The polarization control is shifted to the
described in subsection 4.6.1 in Reference Test Method G5,is
potentiostatic mode. The potential at the end of the galvanos-
also necessary.
tatic hold (Step 2) is read, and then 10 mV are subtracted. The
resultingvalueofpotentialisappliedfora2hperiodwhilethe 6.3 Potentiostat and Output Potential and Current Measur-
ing Instruments—The potentiostat and other instruments
current output is monitored. Then successive potentiostatic
treatments are applied, each time at 10 mV lower than the should be similar to the ones specified in Test Method G61.
Mostcommercialpotentiostatandrelatedinstrumentsmeetthe
previoustreatment.Atotalof10to15potentiostatictreatments
are usually required to finish Step 3. specific requirements for these types of measurements.
4.5 The crevice repassivation potential (ER,CREV) is the 6.4 Electrodes—The standard recommended working or
highest potential in Step 3 for which current density does not testing electrode is shown in Fig. 1, which is a prismatic
increase as a function of time. It is understood that at a measuring 0.75in. by 0.75in. by 0.375in. thick (approxi-
potential below ER,CREV the alloy will not develop crevice mately 20mm by 20mm by 10 mm). It has a drilled and
corrosion under the tested conditions. tappedholeontopfortheconnectingrod(asinReferenceTest
MethodG5).Theelectrodesalsohavea7mmdiameterholein
5. Significance and Use the center for mounting two crevice formers, one at each side
using a bolt. The test electrode could be cut from any plate or
5.1 The THE test method is designed to provide highly
extruded bar. It is recommended that the creviced faces of the
reproducible crevice repassivation potentials for corrosion–re-
testelectrodecorrespondtotherollingorextrudeddirection.In
sistant alloys (for example, Alloy 22) in a wide range of
certain tested conditions the test electrode may show end grain
environments from non-aggressive to highly aggressive. In
attack in the short transverse direction, but generally the
conditions of low environmental aggressiveness (such as low
crevice former provides a more active path for corrosion than
temperatureorlowchlorideconcentration),corrosion–resistant
the freely exposed surfaces.
alloys such as Alloy 22 will resist crevice corrosion initiation
and the cyclic potentiodynamic polarization test (Test Method 6.5 Crevice Former or Crevice Washer—Thecreviceformer
G61) may fail to promote crevice corrosion mainly because it is a multiple crevice assembly (MCA), and it is described in
drives the alloy into transpassive dissolution instead of nucle- subsection 5.4 of Test Methods G48, in subsection 9.2.2 in
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G192 − 08 (2020)
FIG. 1 Prismatic Test Electrode (0.75 in. by 0.75 in. by 0.375 in. or approximately 20 mm by 20 mm by 10 mm)
GuideG78,andinRef(8).ThisMCAcreviceformershouldbe be avoided. Effective insulation may be provided by the use of
fabricated using a hard non-conductive ceramic material such nonmetallic sleeves or by wrapping the assembly bolt with
as alumina or mullite (Fig. 2). Before mounting on the test PTFE tape.
electrode (specimen), the crevice washers should be covered
6.6 Counter Electrode—The counter electrodes may be
with a PTFE tape. This tape is 1.5in. wide and 0.003in. thick
prepared as in Reference Test Method G5 or may be prepared
(standard military grade MIL-T-27730A). A corrosion–resis-
from high-purity platinum flat stock and wire. Counter elec-
tant fastener is used to secure the two MCA washers, one on
trodescouldbeeasilyfabricatedbyspotweldingplatinumwire
each side of the test electrode. Crevice formers made of solid
to a platinum foil, which could be curved to adapt to the cell
PTFE such as in Test Methods G48 or Guide G78 are not as
geometry. It is recommended that the area of the platinum
effective,sincetheydonotformacrevicegaptightenoughfor
counter electrode be twice as large as the one of the working
certain high end corrosion–resistant materials. This may result
electrode (test electrode or specimen).
in higher and poorly reproducible repassivation potential
values. Two standard metal washers are used as well (Figs. 1 6.7 Reference Electrode—Reference electrodes could be
and2).ThestandardpressureontheMCAcreviceformersmay commercially available saturated calomel or silver-silver chlo-
vary (depending of the study underway) but a minimum of ride. These electrodes are durable and reliable; however, they
30in.·lb (3.4N·m) torque may be needed to form a tight shouldbemaintainedintheproperconditions.Thepotentialof
crevice. Use a calibrated torque wrench to apply the torque. thereferenceelectrodesshouldbecheckedatperiodicintervals
Electricalcontactbetweentheboltandthetestelectrodeshould to ensure their accuracy.
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G192 − 08 (2020)
FIG. 1 Prismatic Test Electrode (0.75 in. by 0.75 in. by 0.375 in. or approximately 20 mm by 20 mm by 10 mm) (continued)
7. Reagents and Materials enough to handle the mounting rod mechanism. Thicker
materials are easier to prepare (polish).Afresh (or 1 h prior to
7.1 Purity of Reagents—Reagent grade chemicals should be
testing) finish wet grinding of 600 grit silicon carbine paper is
used in all tests.
recommended. If surface effects are being studied, other
7.2 Purity of Water—The water should be distilled or
surface finishing may be considered.
deionized conforming to the requirements of Specification
9.2 If other than mill finishes are investigated, the test
D1193, Type IV reagent water.
electrodes may be reused after remachining or grinding to
7.3 Sodium Chloride (NaCl)—To prepare 1 L of 1 M NaCl
removealltracesofpreviouslyincurredattack.Theimportance
solution, dissolve 58.45 g of NaCl in purified water to obtain a
of maintaining parallel/prismatic surfaces cannot be overstated
total volume of solution of 1 L.
with regard to reproducing crevice conditions and the preven-
7.4 Purging Gas—Ifdeaerationisnecessary,nitrogengasof
tion of possible fracture of the ceramic devices.
a minimum 99.99 purity should be used. Tests could also be
9.3 The test electrodes could be prepared using wrought or
run under normal aeration conditions or under any other
cast material, or machined weld metal.
atmosphere.
9.4 The bolt, nut, and flat washer must be made of a
7.5 Prismatic-Shaped Test Electrodes of the Corrosion–Re-
corrosion–resistant material. It is recommended to use Ti Gr 2
sistant Alloy—Other type of creviced test electrodes may also
(UNS R52400). Fastening devices can also be fabricated using
be used, depending on the specific study being performed.
other readily available materials such asAlloys C-276 and 625
8. Hazards
(UNS N10276 and N06625, respectively). The crevice
...
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