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. Calculation methods for converting corrosion current density values to either mass loss rates or average penetration rates are given g1022 most engineering alloys.
A sample calculation is given in Appendix X2 1. In some computerized polarization equipment, this calculation is made automatically after the specimen area is programmed into the computer. The error is illustrated by Eq The electron equivalent for 1 g of an alloy, Q is then: Calculation methods for converting corrosion current density values to either mass loss rates or average penetration rates are given for most engineering alloys.
KRT b 5 nF 9 where: A superscript epsilon e indicates an editorial change since the last revision or reapproval.
These diagrams are known as Potential-pH Pourbaix diagrams and have been published by several authors 2, 3. 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. A sample calculation is given in Appendix X5.
This is especially true for metals exhibiting passive behavior. Other redox couples that do not necessarily participate in the corrosion reaction may have similar effects. In the case of galvanic couples, the exposed area of the anodic specimen should be used.
ASTM G Standard Practice – Free Download PDF
If this is not true, then the calculation approach will need to be adjusted to re? This will cause either the anodic or cathodic b value to appear smaller than the corrosion reaction above.
In general, Tafel slopes are given by Historical Version s – view previous versions of standard. No other units of measurement are included in this standard.
The conversion of these results to either mass loss or penetration rates requires additional electrochemical information. NOTE 2—Some of the older publications used inaccurate thermodynamic data to construct the diagrams and consequently they are in error.
Ra 5 the apparent polarization 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.
This practice is intended to provide guidance in calculating mass loss and penetration rates for such alloys. Another approach is to measure or estimate the electrode potential of the corroding surface. 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.
Therefore, the alloy equivalent weight, EW, is the reciprocal of this quantity: Icor icor 5 A 1 where: Asstm 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. This is equivalent to the calculation shown in 4. In general, Eq 7 and Eq 8 may be used, g120 the corrosion rate calculated by these two approximations may be used as lower and upper limits of the true rate.
It is usually assumed that the process of oxidation is uniform and Copyright?
ASTM G102 Standard Practice
Individual reprints single or multiple copies of this standard may be obtained by contacting ASTM at the above address or at phonefaxor atm astm. Consequently, the Stern-Geary constant B will be in?
Some typical values of equivalent weights for a variety of metals and alloys are provided. Rp 5 Ra 2 rl 11 where: