ASTM G59-97(2014)
实施动电势极化电阻测量的标准试验方法

Standard Test Method for Conducting Potentiodynamic Polarization Resistance Measurements

被代替

标准号

ASTM G59-97(2014)

发布

1997年

发布单位

美国材料与试验协会

替代标准

ASTM G59-97(2020)

当前最新

ASTM G59-23

 

 

引用标准

ASTM G102 ASTM G3 ASTM G5

适用范围

3.1 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.

3.2 Polarization resistance can be related to the rate of general corrosion for metals at or near their corrosion potential, E_corr. 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.

3.3 In this test method, a small potential scan, ΔE(t), defined with respect to the corrosion potential (ΔE = E – E_corr), is applied to a metal sample. The resultant currents are recorded. The polarization resistance, R_P, of a corroding electrode is defined from Eq 1 as the slope of a potential versus current density plot at i = 0 (1-4):³

The current density is given by i. The corrosion current density, i_corr, is related to the polarization resistance by the Stern-Geary coefficient, B. (3),

The dimension of R_p is ohm-cm ², i_corr is muA/cm², and B is in V. The Stern-Geary coefficient is related to the anodic, b_a, and cathodic, b_c, 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/cm ³.

Refer to Practice G102 for derivations of the above equations and methods for estimating Tafel slopes.

3.4 The test method may not be appropriate to measure polarization resistance on all materials or in all environ......

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