ASTM G59-97(2003)

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 test method 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.

General Information

• Status: Historical
• Publication Date: 09-Dec-1997
• ICS: 17.220.20 - Measurement of electrical and magnetic quantities
• Technical Committee: G01 - Corrosion of Metals
• Drafting Committee: G01.11 - Electrochemical Measurements in Corrosion Testing

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:G59–97 (Reapproved 2003)
Standard Test Method for
Conducting Potentiodynamic Polarization Resistance
1
Measurements
ThisstandardisissuedunderthefixeddesignationG 59;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginal
adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.Asuperscript
epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope rapid way to measure the general corrosion rate. Real time
corrosion monitoring is a common application. The technique
1.1 This test method describes an experimental procedure
canalsobeusedasawaytorankalloys,inhibitors,andsoforth
forpolarizationresistancemeasurementswhichcanbeusedfor
in order of resistance to general corrosion.
the calibration of equipment and verification of experimental
3.3 Inthistestmethod,asmallpotentialscan, DE(t),defined
technique. The test method can provide reproducible corrosion
with respect to the corrosion potential (DE=E–E ), is
potentials and potentiodynamic polarization resistance mea- corr
applied to a metal sample. The resultant currents are recorded.
surements.
The polarization resistance, R , of a corroding electrode is
1.2 This test method does not purport to address all of the P
defined from Eq 1 as the slope of a potential versus current
safety concerns, if any, associated with its use. It is the
4
density plot at i=0 (1-4):
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica- ]DE
R 5 (1)
S D
p
] i
bility of regulatory limitations prior to use.
i50, dE/dt→0
The current density is given by i. The corrosion current
2. Referenced Documents
density, i , is related to the polarization resistance by the
corr
2.1 ASTM Standards:
Stern-Geary coefficient, B. (3),
G 3 PracticeforConventionsApplicabletoElectrochemical
B
2
6
Measurements in Corrosion Testing
i 5 10 (2)
corr
R
p
G 5 Test Method for Making Potentiostatic and Potentiody-
2 2
2
The dimension of R is ohm-cm , i is muA/cm , and B is
namic Anodic Polarization Measurements p corr
in V. The Stern-Geary coefficient is related to the anodic, b ,
a
G 102 Practice for Calculation of Corrosion Rates and
2
and cathodic, b , Tafel slopes as per Eq 3.
Related Information from Electrochemical Measurements c
2.2 Adjunct:
b b
a c
B 5 (3)
SamplesoftheStandardAISIType430StainlessSteel(UNS 2.303~b 1 b !
a c
3
S43000)
The units of the Tafel slopes are V. The corrosion rate, CR,
in mm per year can be determined from Eq 4 in which EW is
3. Significance and Use
the equivalent weight of the corroding species in grams and r
3.1 This test method can be utilized to verify the perfor- 3
is the density of the corroding material in g/cm .
mance of polarization resistance measurement equipment in-
i EW
corr
–3
cluding reference electrodes, electrochemical cells, poten-
CR 5 3.27 3 10 (4)
r
tiostats, scan generators, measuring and recording devices.The
Refer to Practice G 102 for derivations of the above equa-
test method is also useful for training operators in sample
tions and methods for estimating Tafel slopes.
preparation and experimental techniques for polarization resis-
3.4 The test method may not be appropriate to measure
tance measurements.
polarization resistance on all materials or in all environments.
3.2 Polarization resistance can be related to the rate of
See 8.2 for a discussion of method biases arising from solution
generalcorrosionformetalsatorneartheircorrosionpotential,
resistance and electrode capacitance.
E .Polarizationresistancemeasurementsareanaccurateand
corr
4. Apparatus
1
This practice is under the jurisdiction of ASTM Committee G01 on Corrosion
4.1 The apparatus is described in Test Method G 5. It
of Metals, and is the direct responsibility of Subcommittee G 01.11 on Electro-
includesa1L round bottom flask modified to permit the
chemical Measurements in Corrosion Testing.
Current edition approved Dec. 10, 1997. Published February 1998. Originally
approved in 1978. Last previous edition approved in 1991 as 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.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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G59–97 (2003)
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addition of inert gas, thermometer, and electrodes. This stan- surface area of the specimen to the nearest 0.01 cm and
dard cell or an equivalent cell can be used. An equivalent cell subtract for the area under the gasket (typically 0.20 to 0.25
2
must be constructed of inert materials and be able to reproduce cm ).
the standard c
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