ASTM G102 PDF
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 X1. Link to Active This link will always route to the current Active version of the standard. Generally, this error is small with modest scan rates It is best if an independent technique can be used to establish the proper valence for each alloying element.
Current edition approved Feb. 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 g02 the electrode.
The estimation of a B value for situations involving mixed control requires more information in general and is beyond the scope of this astmm. Consequently, the Stern-Geary constant B will be in? Values of 65 and mV are also commonly used.
ASTM G Standard Practice – Free Download PDF
For pure elements, the equivalent weight is given by: Therefore, the gram equivalents of the dissolved components are given by Eq 3. For simple one electron reactions, K is usually found to be 2. This is accomplished by dividing the total current by the geometric area of the electrode exposed to the solution.
Several approaches have been proposed based on analyses of electrode kinetic models. B icor 5 R 10 p where: The capacitance charging effect will cause the calculated polarization resistance g10 be in error. Your comments are invited either for revision of this standard or for additional standards and should be addressed to Aatm Headquarters. Therefore, the alloy equivalent weight, EW, is the reciprocal of this quantity: Calculation methods for awtm corrosion current density values to either mass loss rates 1g02 average penetration rates are given for most engineering alloys.
Your comments will g02 careful consideration at a meeting ast, the responsible technical committee, which you may attend. 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. Some typical values of equivalent weights for a variety of metals and alloys are provided. Q 5 Wi 3 where: This is equivalent to the calculation shown in ast.
In most programmable potentiodynamic polarization equipment, the current is converted to current density automatically and the resulting plot is of i versus E. These diagrams are known as Potential-pH Pourbaix diagrams and have been published by several authors 2, 3.
Individual reprints single or multiple copies of this standard may be obtained by contacting ASTM at the above address or at phonefaxor service astm. 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.
In cases where the actual analysis of an alloy is not available, it is conventional to use the mid-range of the composition speci?
This standard is subject to revision at any f102 by the responsible technical committee and must be reviewed every? 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.
B5 ba bc 2. Calculation methods for converting corrosion current density values v102 either mass loss rates or average penetration rates are given for most engineering alloys. Wi 4 unless a better basis is available.
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. The effect of solution resistance is a function of the cell geometry, but the following expression may be used to approximate its magnitude.
W 5 the atomic weight of the element, and y102 5 the number of electrons required to oxidize an atom of the element in the corrosion process, that is, the valence of the element. See Refs for more information.
ASTM G102 Standard Practice
Rp 5 Ra 2 ashm 11 where: Some sstm values of equivalent weights for a variety of metals and alloys are provided. Last previous edition G — 89 e1. Consider a unit mass of alloy oxidized.
The reaction under mixed control will have an apparently larger b value than predicted for an activation control, and a plot of E versus log I will tend to curve to an asymptote parallel to the potential axis. KRT b 5 nF 9 where: Equilibrium diagrams showing regions of stability astk various phases as a function of potential and pH may be created from thermodynamic data.
It is usually assumed that the process of oxidation is uniform and Copyright? The conversion of these results to either mass loss or penetration rates requires additional electrochemical information.
Some approaches for estimating this information are given.