ASTM G106-89(2023)
(Practice)Standard Practice for Verification of Algorithm and Equipment for Electrochemical Impedance Measurements
Standard Practice for Verification of Algorithm and Equipment for Electrochemical Impedance Measurements
SIGNIFICANCE AND USE
5.1 The availability of a standard procedure, standard material, and standard plots should allow the investigator to check his laboratory technique. This practice should lead to electrochemical impedance curves in the literature which can be compared easily and with confidence.
5.2 Samples of a standard ferritic type 430 stainless steel (UNS 430000) used to obtain the reference plots are available for those who wish to check their equipment. Suitable resistors and capacitors can be obtained from electronics supply houses.
5.3 This test method may not be appropriate for electrochemical impedance measurements of all materials or in all environments.
SCOPE
1.1 This practice covers an experimental procedure which can be used to check one's instrumentation and technique for collecting and presenting electrochemical impedance data. If followed, this practice provides a standard material, electrolyte, and procedure for collecting electrochemical impedance data at the open circuit or corrosion potential that should reproduce data determined by others at different times and in different laboratories. This practice may not be appropriate for collecting impedance information for all materials or in all environments.
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.
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.
Designation: G106 − 89 (Reapproved 2023)
Standard Practice for
Verification of Algorithm and Equipment for Electrochemical
Impedance Measurements
This standard is issued under the fixed designation G106; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope G5 Reference Test Method for Making Potentiodynamic
Anodic Polarization Measurements
1.1 This practice covers an experimental procedure which
G15 Terminology Relating to Corrosion and Corrosion Test-
can be used to check one’s instrumentation and technique for
ing (Withdrawn 2010)
collecting and presenting electrochemical impedance data. If
G59 Test Method for Conducting Potentiodynamic Polariza-
followed, this practice provides a standard material,
tion Resistance Measurements
electrolyte, and procedure for collecting electrochemical im-
pedance data at the open circuit or corrosion potential that
3. Terminology
should reproduce data determined by others at different times
3.1 Definitions—For definitions of corrosion related terms,
and in different laboratories. This practice may not be appro-
see Terminology G15.
priate for collecting impedance information for all materials or
in all environments. 3.2 Symbols:
1.2 The values stated in SI units are to be regarded as
standard. No other units of measurement are included in this −2
C = capacitance (farad-cm )
standard.
Eʹ = real component of voltage (volts)
1.3 This standard does not purport to address all of the E" = imaginary component of voltage (volts)
E = complex voltage (volts)
safety concerns, if any, associated with its use. It is the
−1
f = frequency (s )
responsibility of the user of this standard to establish appro-
−2
Iʹ = real component of current (amp-cm )
priate safety, health, and environmental practices and deter-
−2
I" = imaginary component of current (amp-cm )
mine the applicability of regulatory limitations prior to use.
−2
I = complex current (amp-cm )
1.4 This international standard was developed in accor-
j =
=21
dance with internationally recognized principles on standard-
L = inductance (henry − cm )
ization established in the Decision on Principles for the
R = solution resistance (ohm-cm )
s
Development of International Standards, Guides and Recom-
R = polarization resistance (ohm-cm )
p
mendations issued by the World Trade Organization Technical
R = charge transfer resistance (ohm-cm )
t
Barriers to Trade (TBT) Committee.
Zʹ = real component of impedance (ohm-cm )
Z" = imaginary component of impedance (ohm-cm )
2. Referenced Documents
Z = complex impedance (ohm-cm )
2.1 ASTM Standards:
α = phenomenological coefficients caused by depression
D1193 Specification for Reagent Water
of the Nyquist plot below the real axis, α is the
G3 Practice for Conventions Applicable to Electrochemical
exponent and τ is the time constant(s).
Measurements in Corrosion Testing
θ = phase angle (deg)
−1
ω = frequency (radians-s )
3.3 Subscripts:
This practice is under the jurisdiction of ASTM Committee G01 on Corrosion
of Metals and is the direct responsibility of Subcommittee G01.11 on Electrochemi-
cal Measurements in Corrosion Testing.
Current edition approved June 1, 2023. Published June 2023. Originally
x = in-phase component
approved in 1989. Last previous edition approved in 2015 as G106 – 89 (2015).
y = out-of-phase component
DOI: 10.1520/G0106-89R23.
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 last approved version of this historical standard is referenced on
the ASTM website. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
G106 − 89 (2023)
FIG. 1 Circuit Diagram for Dummy Cell Showing Positions for Hook-Up to Potentiostat
4. Summary of Practice have a stated precision of 60.1 %. The capacitor can have a
precision of 620 %. The cell can be constructed from readily
4.1 Reference impedance plots in both Nyquist and Bode
available circuit elements by following the circuit diagram
format are included. These reference plots are derived from the
shown in Fig. 1.
results from nine different laboratories that used a standard
dummy cell and followed the standard procedure using a
6.2 Test Cell—The test cell should be constructed to allow
specific ferritic type alloy UNS-S43000 in 0.005 M H SO
2 4 the following items to be inserted into the solution chamber:
and 0.495 M Na SO . The plots for the reference material are
2 4
the test electrode, two counter electrodes or a symmetrically
presented as an envelope that surrounds all of the data with and
arranged counter electrode around the working electrode, a
without inclusion of the uncompensated resistance. Plots for
Luggin-Haber capillary with salt bridge connection to the
one data set from one laboratory are presented as well. Since
reference electrode, an inlet and an outlet for an inert gas, and
the results from the dummy cell are independent of laboratory,
a thermometer or thermocouple holder. The test cell must be
only one set of results is presented.
constructed of materials that will not corrode, deteriorate, or
4.2 A discussion of the electrochemical impedance otherwise contaminate the solution.
technique, the physics that underlies it, and some methods of
6.2.1 One type of suitable cell is described in Reference Test
interpreting the data are given in the Appendix X1 – Appendix
Method G5. Cells are not limited to that design. For example,
X6. These sections are included to aid the individual in
a 1 L round-bottom flask can be modified for the addition of
understanding the electrochemical impedance technique and
various necks to permit the introduction of electrodes, gas inlet
some of its capabilities. The information is not intended to be
and outlet tubes, and the thermometer holder. A Luggin-Haber
all inclusive.
capillary probe could be used to separate the bulk solution from
the saturated calomel electrode. The capillary tip can be easily
5. Significance and Use
adjusted to bring it into close proximity to the working
5.1 The availability of a standard procedure, standard
electrode. The minimum distance should be no less than two
material, and standard plots should allow the investigator to
capillary diameters from the working electrode.
check his laboratory technique. This practice should lead to
6.3 Electrode Holder—The auxiliary and working elec-
electrochemical impedance curves in the literature which can
trodes can be mounted in the manner shown in Reference Test
be compared easily and with confidence.
Method G5. Precautions described in Reference Test Method
5.2 Samples of a standard ferritic type 430 stainless steel
G5 about assembly should be followed.
(UNS 430000) used to obtain the reference plots are available
for those who wish to check their equipment. Suitable resistors 6.4 Potentiostat—The potentiostat must be of the kind that
allows for the application of a potential sweep as described in
and capacitors can be obtained from electronics supply houses.
Reference Test Method G5 and Reference Practice G59. The
5.3 This test method may not be appropriate for electro-
potentiostat must have outputs in the form of voltage versus
chemical impedance measurements of all materials or in all
ground for both potential and current. The potentiostat must
environments.
have sufficient bandwidth for minimal phase shift up to at least
1000 Hz and preferably to 10 000 Hz. The potentiostat must be
6. Apparatus
capable of accepting an external excitation signal. Many
6.1 Dummy Cell—The dummy cell used to check the
commercial potentiostats meet the specification requirements
equipment and method for generating electrochemical imped-
for these types of measurements.
ance data is composed of a 10 Ω precision resistor placed in
series with a circuit element composed of a 100 Ω precision
6.5 Collection and Analysis of Current-Voltage Response—
resistor in parallel with a 100 μF capacitor. The resistors should
The potential and current measuring circuits must have the
characteristics described in Reference Test Method G5 along
with sufficient band-width as described above. The impedance
These standard samples are available from ASTM Headquarters. Generally, one
can be calculated in several ways, for example, by means of a
sample can be repolished and reused for many runs. This procedure is suggested to
conserve the available material. transfer function analyzer, Lissajous figures on an oscilloscope,
G106 − 89 (2023)
FIG. 2 Nyquist Plot of Electrochemical Impedance Response for
FIG. 3 Bode Plot, Impedance Magnitude Versus Frequency, of
Dummy Cell
Electrochemical Impedance Response for Dummy Cell
or transient analysis of a white noise input using a Fast Fourier
Transform algorithm. Other methods of analysis exist.
6.6 Electrodes:
6.6.1 Working electrode preparation should follow Refer-
ence Test Method G5, which involves drilling and tapping the
specimen and mounting it on the electrode holder.
6.6.2 Auxillary electrode preparation should follow Refer-
ence Test Method G5. The auxillary electrode arrangement
should be symmetrical around the working electrode.
6.6.3 Reference electrode type and usage should follow
Reference Test Method G5. The reference electrode is to be a
saturated calomel electrode.
7. Experimental Procedure
7.1 Test of Algorithm and Electronic Equipment (Dummy
Cell):
7.1.1 Measure the impedance of a dummy cell consisting of
a 10 Ω resistor in series with a parallel combination of a 100 Ω
resistor and a 100 μF capacitor. The circuit diagram is shown
in Fig. 1.
FIG. 4 Bode Plot, Phase Angle Versus Frequency, of Electro-
7.1.2 Typical connections from the potentiostat are shown in
chemical Impedance Response for Dummy Cell
Fig. 1. Connect the auxiliary electrode and reference electrode
leads to the series resistor side of the circuit. Connect the
attempted until that agreement is established. Results using the
working electrode lead to the opposite side of the circuit
dummy circuit were found to be independent of laboratory.
beyond the resistor-capacitor parallel combination.
7.1.3 Set the potential at 0.0 V. Collect the electrochemical 7.2 Test of Electrochemical Cell:
impedance data between 10 000 Hz (10 kHz) and 0.1 Hz 7.2.1 Test specimens of the reference material should be
(100 mHz) at 8 to 10 steps per frequency decade. The ampli- prepared following the procedure described in Reference Test
tude must be the same as that used to check the electrochemical Method G5. This procedure involves polishing the specimen
cell, 10 mV. The resulting frequency response when plotted in with wet SiC paper with a final wet polish using 600 grit SiC
Nyquist format (the negative of the imaginary impedance paper prior to the experiment. There should be a maximum
versus the real impedance) must agree with that shown in Figs. delay of 1 h between final polishing and immersion in the test
2-4. Testing with the electrochemical cell should not be solution.
G106 − 89 (2023)
7.2.2 Prepare a 0.495 M Na SO solution containing
2 4
0.005 M H SO from reagent grade sulfuric acid and sodium
2 4
sulfate and Type IV reagent water described in Specification
D1193. The test is to be carried out at 30 °C 6 1 °C.
7.2.3 At least 1 h before specimen immersion, start purging
the solution with oxygen-free argon, hydrogen, or nitrogen gas
3 3
at a flow rate of about 100 cm /min to 150 cm /min. Continue
the purge throughout the test.
7.2.4 Transfer the specimen to the test cell. Adjust the
Luggin-Haber probe tip so that it is no less than two capillary
diameters from the sample. However, since this distance will
affect the uncompensated solution resistance, the greater the
distance, the larger the resistance. Therefore, close placement
is important.
7.2.5 Connect the potentiostat leads to the appropriate
electrodes, for example, working electrode lead to working
electrode, counter electrode lead to counter electrode, and
reference electrode lead to reference electrode. Hook-up in-
FIG. 5 Nyquist Plot of Typical Frequency Response for UNS-
structions provided with the potentiostat must be followed.
S43000 From One Laboratory
7.2.6 Record the open circuit potential, that is, the corrosion
potential, for 1 h. The potential should be about −645 mV 6
10 mV relative to the saturated calomel electrode. If the
potential is more positive than −600 mV (SCE) then the
specimen may have passivated. If so, remove the specimen and
repolish with 600 grit wet silicon carbide paper. Then reim-
merse the sample and monitor the corrosion potential for 1 h.
If the potential again becomes more positive than −600 mV
(SCE) check for oxygen contamination of the solution.
7.2.7 Record the frequency response between 10 000 Hz
(10 kHz) and 0.1 Hz (100 mHz) at the corrosion potential
recorded after 1 h of exposure using 8 to 10 steps per frequency
decade. The amplitude must be the same as that used in 7.1.3,
10 mV.
7.2.8 Plot the frequency response in both Nyquist format
(real response versus the negative of the imaginary response)
and Bode format (impedance modulus and phase angle versus
frequency). Frequency can be reported in units of radians/
second or hertz (cycles/s).
7.2.9 There was no attempt to estimate circuit analogues for
the electrochemical impedance curves since there is no univer-
FIG. 6 Bode Plot, Impedance Magnitude Versus Frequency, for
sally recognized, standard method for making such estimates.
UNS-S43000 From One Laboratory
8. Standard Reference Results and Plots
from the nine laboratories. The solution resistance from each
8.1 Dummy Cell:
laboratory was not subtracted out prior to making this plot.
8.1.1 The results from nine different laboratories were
8.2.2 The average solution resistance from the nine labora-
2 2
virtually identical and overlaid each other almost perfectly.
tories in 3.3 Ω-cm 6 1.8 Ω-cm (one standard deviation). The
Typical plots of the raw data are shown in Figs. 2-4. No attempt
solution resistance of the user’s test cell as measured by the
has been made to estimate the variance and standard deviation
high frequency intercept on the Nyquist plot must
...
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