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Standard Test Method for Conducting Potentiodynamic Polarization Resistance Measurements
Automaticky přeložený název:
Standardní zkušební metoda pro dirigování potenciodynamické polarizační Měření odporu
NORMA vydána dne 1.5.2009
Označení normy: ASTM G59-97(2009)
Poznámka: NEPLATNÁ
Datum vydání normy: 1.5.2009
Kód zboží: NS-57743
Počet stran: 4
Přibližná hmotnost: 12 g (0.03 liber)
Země: Americká technická norma
Kategorie: Technické normy ASTM
Keywords:
anodic polarization, auxiliary electrode, cathodic polarization, corrosion, corrosion potential, corrosion rate, current density, electrochemical cell, electrochemical potential, Luggin probe, mixed potential, open-circuit potential, overvoltage, polarization resistance, potentiodynamic, reference electrode, solution resistance, Stern-Geary coefficient, Tafel slope, working electrode, Anodic polarization measurement, Cathodic polarization, Corrosion--metals/alloys
Significance and Use | ||||||
This test method can be utilized to verify the performance of polarization resistance measurement equipment including reference electrodes, electrochemical cells, potentiostats, scan generators, measuring and recording devices. The test method is also useful for training operators in sample preparation and experimental techniques for polarization resistance measurements. Polarization resistance can be related to the rate of general corrosion for metals at or near their corrosion potential, Ecorr. Polarization resistance measurements are an accurate and rapid way to measure the general corrosion rate. Real time corrosion monitoring is a common application. The technique can also be used as a way to rank alloys, inhibitors, and so forth in order of resistance to general corrosion. In this test method, a small potential
scan, ΔE(t), defined with respect to the corrosion
potential (ΔE = E
– Ecorr), is applied
to a metal sample. The resultant currents are recorded. The
polarization resistance, RP,
of a corroding electrode is defined from Eq 1 as the slope of a
potential versus current density plot at i = 0 (1-4): The current density is given by
i. The corrosion current density,
icorr, is related to the
polarization resistance by the Stern-Geary coefficient,
B. (3), The dimension of Rp is ohm-cm 2, icorr is muA/cm2, and
B is in V. The Stern-Geary coefficient
is related to the anodic, ba, and cathodic, bc, Tafel slopes as per Eq 3. 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
the equivalent weight of the corroding species in grams and
ρ is the density of the corroding
material in g/cm3. Refer to Practice G 102 for derivations of the above equations and methods for estimating Tafel slopes. The test method may not be appropriate to measure polarization resistance on all materials or in all environments. See 9.2 for a discussion of method biases arising from solution resistance and electrode capacitance. |
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1. Scope | ||||||
1.1 This test method covers 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 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 and health practices and determine the applicability of regulatory limitations prior to use. |
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2. Referenced Documents | ||||||
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