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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The electron equivalent for 1 g of an alloy, Q is then: This practice is intended to provide guidance in calculating mass loss and penetration rates for such alloys. 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. Users of this standard are expressly advised astk determination of the validity of any such patent rights, and the risk of infringement of such rights, are entirely their own responsibility.
In addition, some guidelines for converting polarization resistance values to corrosion rates are provided. No other units of measurement are included in this standard. Historical Version s – view previous versions of standard. It is best if asmt independent technique can be used to establish the proper valence for each alloying element.
NOTE 2—Mid-range values were assumed for concentrations of alloying elements. A, and A 5 exposed specimen area, cm2. Other redox couples that do not necessarily participate in the corrosion aztm may have similar effects. For pure elements, the equivalent weight is given by: Values of 65 and mV are also commonly used. Several approaches have been proposed based on analyses of electrode kinetic models.
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. Wi 4 unless a better basis is available.
A sample calculation is given in Appendix X6. If this is g10 true, then the calculation approach will need to be adjusted to re? In some computerized polarization equipment, this calculation is made automatically after the specimen area is programmed into the computer. Consequently, the Stern-Geary constant B will be in? Your comments will receive careful consideration at a meeting of the responsible technical committee, which you may attend.
In general, Eq 7 and Eq 8 may be used, and the corrosion rate calculated by these two approximations may be used as lower and upper limits of the true rate. For simple one electron reactions, K is usually found to be 2. In cases where the actual analysis of an alloy is not available, it is conventional to use the mid-range of the composition speci?
ASTM G102 Standard Practice
The error is illustrated by Eq Some approaches for estimating this information are given. Corrosion Current Density 4. Therefore, the gram equivalents of the dissolved components are given by Eq 3. B5 ba bc 2.
W 5 the atomic weight of the element, and n 5 the number of electrons required to oxidize an atom of the element in the corrosion process, that is, the valence of the element. This will cause either the anodic or cathodic b value to appear smaller than the corrosion reaction above.
Generally, this error is small with modest scan rates Individual reprints single or multiple copies of this standard may be obtained by contacting ASTM at the above address or at phonefaxor service astm. 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. B icor 5 R 10 p where: A sample calculation is given in Appendix X4.
ASTM G Standard Practice – Free Download PDF
Icor icor 5 A 1 where: This is especially true for metals exhibiting passive behavior. Consider a unit mass of alloy oxidized. The conversion of these results to either mass loss or penetration rates requires additional electrochemical information. Referenced Xstm purchase separately The documents listed below are referenced within the subject standard but are not provided as part of the standard.
Originally published as G — Your comments are invited either for revision of this standard or for additional standards and should be addressed to ASTM Headquarters.