Description. ASTM G Standard Practice for Calculation of Corrosion Rates and Related Information from Electrochemical Measurements. View more. ASTM G()e1. Standard Practice for Calculation of Corrosion Rates and Related Information from Electrochemical Measurements. ASTM-G Standard Practice for Calculation of Corrosion Rates and Related Information from Electrochemical Measurements – corrosion.
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NOTE 2—Mid-range values were assumed for concentrations of alloying elements. The American Society for Testing and Materials takes no position respecting the validity of any patent rights asserted in connection with any item mentioned in this standard. A sample calculation is given in Appendix X2 1.
It is assumed that the current distributes uniformly across the area used in this calculation. In cases where the actual analysis of an alloy is not available, it is conventional to use the mid-range of the composition speci?
Other redox couples that do not necessarily participate in the corrosion reaction may have similar effects. A sample calculation is given in Appendix X1. Some typical values of equivalent weights for a variety of metals and alloys are provided.
NOTE 2—Some of the older publications used inaccurate thermodynamic data to construct the diagrams and consequently they are in error. A sample calculation is given in Appendix X6. In addition, some guidelines for converting polarization resistance values to corrosion rates are provided.
It is usually assumed that the process of oxidation is uniform and Copyright? In most programmable potentiodynamic polarization equipment, the current is converted to current density automatically and the resulting plot is of i versus E.
Some typical values of equivalent weights for a variety of metals and alloys are provided.
ASTM G Standard Practice – Free Download PDF
See Refs for more information. This standard is subject to revision at any time by the responsible technical committee and must be reviewed every? KRT b 5 nF 9 where: Some approaches for estimating this information are given. This g1002 cause either the anodic or cathodic b value to appear smaller than the corrosion reaction above.
A sample calculation is given in Appendix X5. This is equivalent to the calculation shown in 4. This will make results from different studies more comparable and minimize calculation errors that may occur in transforming electrochemical results to corrosion rate values. Sometimes it is possible to analyze the corrosion products and use those results to establish the proper valence. Link to Active This link will always route to the current Active version of the standard.
Ra 5 the apparent b102 resistance, ohm cm2, r 5 the electrolyte resistivity in ohm cm, l 5 the distance between the specimen electrode and the Luggin probe tip, or the reference electrode in cm, and Rp 5 the true polarization resistance in ohm cm2. Therefore, the gram equivalents of the dissolved components are given by Wstm 3.
In adtm computerized polarization equipment, this calculation is made automatically after the specimen area is programmed into the computer. Wi 4 unless a better basis is available. NOTE 3—Only consistent valence groupings were used.
Normally only elements above 1 mass percent in the alloy are included in the calculation. Some approaches for estimating this information are given.
Therefore, the alloy equivalent weight, EW, is the reciprocal of this quantity: Referenced Documents purchase separately The documents listed below are referenced within the subject standard but are not provided as part of the standard.
Another approach is to measure or estimate the electrode potential of the corroding surface. The capacitance charging effect will cause the calculated polarization resistance to be in error.
Current edition approved Feb. In this case, the magnitude of the error is proportional to scan rate. A, and A 5 exposed specimen area, cm2. Other units may be used in this calculation. B Registered trademark Haynes International. This is especially true for metals exhibiting passive behavior. Your comments are invited either for revision of this standard or for additional standards and should be addressed to ASTM Headquarters.
This practice is intended to provide guidance in calculating mass loss and penetration rates for such alloys.
ASTM G102 Standard Practice
Originally published as G — In addition, some rationale must be adopted for assigning values of n to the elements in the alloy because many elements exhibit more than one valence value. In addition, some guidelines for converting polarization resistance values to corrosion rates are provided. No other units of measurement are included in this standard. Several approaches have been proposed based on analyses of electrode kinetic models.
It is best if an independent technique can be used to asym the proper valence for each alloying element. These diagrams are known as Potential-pH Pourbaix diagrams and have been published by several authors 2, 3.