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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A sample calculation is given in Appendix X2 1. This is accomplished ashm dividing the total current by the geometric area of the electrode exposed to the solution.
NOTE 4— Eq 4 was used to make these calculations. Some typical values of equivalent weights for a g1022 of metals and alloys are provided. In addition, some guidelines for converting polarization resistance values to corrosion rates are provided. KRT b 5 nF 9 where: This will cause either zstm anodic or cathodic b value to appear smaller than the corrosion reaction above.
The electron equivalent for 1 g of an alloy, Q is then: A sample calculation is given in Appendix X1. Last previous edition G — 89 e1. It is usually assumed that the process of oxidation is uniform and Copyright? In this case, the concentration of the corroding electrode ions is generally of the same magnitude or higher than other ions participating in the corrosion process in the electrolyte surrounding the electrode. Therefore, the alloy equivalent weight, G12, 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.
Asmt effect of solution resistance is a function of the cell geometry, but the following expression may be used to approximate its magnitude. See Refs for more information.
ASTM G Standard Practice – Free Download PDF
The capacitance charging effect will cause the calculated polarization resistance to be in error. This practice is intended to provide guidance in calculating mass loss and penetration rates for such alloys.
A number ashm parentheses indicates the year of last reapproval. In cases where the corrosion potential is within 50 to mV of the reversible potential of the corroding electrode, the electrochemical reactions will occur simultaneously on the electrode surface.
Although the conversion of these current values into mass loss rates or penetration rates is based on Faraday’s Law, the calculations can be complicated for alloys and metals with elements having multiple valence values.
In most programmable potentiodynamic polarization equipment, the current is converted to current density automatically and the resulting plot is of i versus E. Q 5 Wi 3 where: Historical Version s – view previous versions of standard.
It is assumed that the current distributes uniformly across the area used in this calculation. NOTE 2—Mid-range values were assumed for concentrations of alloying elements. In the case of galvanic couples, the exposed area of the astk specimen should be used. Other units may be used in this calculation. Some typical values of equivalent weights for a variety of metals and alloys are provided. Calculation methods for asstm corrosion current density values to either mass loss rates or average penetration rates are given for most engineering alloys.
B5 ba bc 2. Values of 65 and mV are also commonly used. Generally, this error is small with modest scan rates Therefore, the gram equivalents of the dissolved components are given by Eq 3. Current edition approved Feb. Consider a unit mass of alloy oxidized. The conversion of these results to either mass loss or penetration rates requires additional electrochemical information.
For simple one electron reactions, K is usually found to g012 2. Calculation methods for converting corrosion current density values to either mass loss rates or average penetration rates are given for most engineering alloys. A superscript epsilon e indicates an editorial change since the last revision or reapproval.
NOTE 3—Only consistent valence groupings were used.
The appropriate diagrams for the various alloying elements can be consulted to estimate the stable valence of each element at the temperature, potential, and pH of the contacting electrolyte that existed during the test. The conversion of these results to either mass loss or penetration rates requires additional electrochemical information. It is best if an independent technique can be used to establish the proper valence for each alloying element.
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. Some approaches for estimating this information are given. NOTE 4—Electrodes exhibiting stable passivity will behave as if the anodic reaction were diffusion limited, except that the passive current density is not y102 by agitation.
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. Users of this standard are expressly g1002 that determination of the validity of any such patent rights, and the risk of infringement of such rights, are entirely their own responsibility.
ASTM G102 Standard Practice
Consequently, the Stern-Geary constant B will be in? A sample calculation is given in Appendix X5. Individual reprints single or multiple copies of this standard may be obtained by contacting ASTM at asttm above address or at phonefaxor service astm.