ASTM G59-97

Standard Test Method for Conducting Potentiodynamic Polarization Resistance Measurements

SCOPE
1.1 This test method describes an experimental procedure for polarization resistance measurements which can be used for the calibration of equipment and verification of experimental technique. The test method can provide reproducible corrosion potentials and potentiodynamic polarization resistance measurements.
1.2 This standard does not purport to address all of the safety problems, 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.

General Information

• Status: Historical
• Publication Date: 31-Dec-1990
• Technical Committee: G01 - Corrosion of Metals
• Drafting Committee: G01.11 - Electrochemical Measurements in Corrosion Testing

Standards Content (Sample)

Designation: G 59 – 97
AMERICAN SOCIETY FOR TESTING AND MATERIALS
100 Barr Harbor Dr., West Conshohocken, PA 19428
Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
Standard Test Method for
Conducting Potentiodynamic Polarization Resistance
1
Measurements
This standard is issued under the fixed designation G 59; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope corrosion monitoring is a common application. The technique
can also be used as a way to rank alloys, inhibitors, and so forth
1.1 This test method describes an experimental procedure
in order of resistance to general corrosion.
for polarization resistance measurements which can be used for
3.3 In this test method, a small potential scan, DE(t), defined
the calibration of equipment and verification of experimental
with respect to the corrosion potential (DE 5 E–E ), is
corr
technique. The test method can provide reproducible corrosion
applied to a metal sample. The resultant currents are recorded.
potentials and potentiodynamic polarization resistance mea-
The polarization resistance, R , of a corroding electrode is
P
surements.
defined from Eq 1 as the slope of a potential versus current
1.2 This test method does not purport to address all of the
4
density plot at i 5 0 (1-4):
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro- ]DE
R 5 (1)
S D
p
] i
priate safety and health practices and determine the applica-
i50, dE/dt→0
bility of regulatory limitations prior to use.
The current density is given by i. The corrosion current
density, i , is related to the polarization resistance by the
corr
2. Referenced Documents
Stern-Geary coefficient, B. (3),
2.1 ASTM Standards:
B
6
G 3 Practice for Conventions Applicable to Electrochemical
i 5 10 (2)
corr
R
p
2
Measurements in Corrosion Testing
2 2
The dimension of R is ohm-cm , i is muA/cm , and B is
G 5 Test Method for Making Potentiostatic and Potentiody- p corr
2
in V. The Stern-Geary coefficient is related to the anodic, b ,
namic Anodic Polarization Measurements a
and cathodic, b , Tafel slopes as per Eq 3.
G 102 Practice for Calculation of Corrosion Rates and c
2
Related Information from Electrochemical Measurements
b b
a c
B 5 (3)
2.2 Adjunct: 2.303~b 1 b !
a c
Samples of the Standard AISI Type 430 Stainless Steel (UNS
The units of the Tafel slopes are V. The corrosion rate, CR,
3
S43000)
in mm per year can be determined from Eq 4 in which EW is
the equivalent weight of the corroding species in grams and r
3. Significance and Use
3
is the density of the corroding material in g/cm .
3.1 This test method can be utilized to verify the perfor-
i EW
–3 corr
mance of polarization resistance measurement equipment in-
CR 5 3.27 3 10 (4)
r
cluding reference electrodes, electrochemical cells, poten-
Refer to Practice G 102 for derivations of the above
tiostats, scan generators, measuring and recording devices. The
equations and methods for estimating Tafel slopes.
test method is also useful for training operators in sample
3.4 The test method may not be appropriate to measure
preparation and experimental techniques for polarization resis-
polarization resistance on all materials or in all environments.
tance measurements.
See 8.2 for a discussion of method biases arising from solution
3.2 Polarization resistance can be related to the rate of
resistance and electrode capacitance.
general corrosion for metals at or near their corrosion potential,
E . Polarization resistance measurements are an accurate and
corr
4. Apparatus
rapid way to measure the general corrosion rate. Real time
4.1 The apparatus is described in Test Method G 5. It
includesa1L round bottom flask modified to permit the
1
This practice is under the jurisdiction of ASTM Committee G–1 on Corrosion
addition of inert gas, thermometer, and electrodes. This
of Metals, and is the direct responsibility of Subcommittee G 01.11 on Electro-
standard cell or an equivalent cell can be used. An equivalent
chemical Measurements in Corrosion Testing.
Current edition approved Dec. 10, 1997. Published February 1998. Originally
published as G 59 – 78. Last previous edition G 59 – 91.
2 4
Annual Book of ASTM Standards, Vol 03.02. The boldface numbers in parentheses refer to the list of references at the end of
3
Available from ASTM Headquarters. Order PCN 12-700050-00. this standard.
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G59
cell must be constructed of inert materials and be able to 6.4 Immediately prior to immersion the specimen is
reproduce the standard curve in Test Method G 5. degreased with a solvent such as acetone and rinsed with
4.2 A potentiostat capable of varying potential at a constant distilled w
...