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.
|Published (Last):||21 February 2015|
|PDF File Size:||7.90 Mb|
|ePub File Size:||7.4 Mb|
|Price:||Free* [*Free Regsitration Required]|
In some computerized polarization equipment, this calculation is made automatically after the specimen area is programmed into the computer. Equilibrium diagrams showing regions of stability of various phases as a function of potential and pH may be created from thermodynamic data.
Consider a unit mass of alloy oxidized. Values ashm 65 and mV are also commonly used. NOTE 4— Eq 4 was used to make these calculations. Referenced Documents purchase satm The documents listed below are referenced within the subject standard but are not provided as part of the standard.
Link to Active This link will always route to the current Active version of the standard. In addition, some guidelines for converting polarization resistance values to corrosion rates are provided. B icor 5 R 10 p where: NOTE 2—Mid-range values were assumed for concentrations of alloying elements. A number in parentheses indicates the year of last reapproval. If this is not true, then the calculation approach will need to be adjusted to re? Sometimes it is possible to analyze the corrosion products and use those results to establish the proper valence.
In addition, some guidelines for converting polarization resistance values to corrosion rates are provided. A sample calculation is given in Appendix X4.
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. Another approach is to measure or estimate the electrode potential of the corroding surface.
This is equivalent to the calculation shown in 4. It is assumed that the current distributes uniformly across the area used in this calculation. Therefore, the gram equivalents of the dissolved components are given by Eq 3. Q 5 Wi 3 where: This calculation may be expressed as follows: 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.
ASTM G102 Standard Practice
Last previous edition G — 89 e1. 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 will cause either the anodic or cathodic b value to appear smaller than the corrosion reaction above. This is especially true for metals exhibiting passive behavior. Other units may be used in this calculation.
No other units of measurement are included in this standard. Icor icor g12 A 1 where: A superscript epsilon e indicates ast editorial change since the last revision or reapproval. In the case of galvanic couples, the exposed area of the anodic specimen should be used. The error is illustrated by Eq Consequently, the Stern-Geary constant B will be in? Users of this standard are expressly advised that determination of the validity of any such patent rights, and the risk of infringement of such rights, are entirely their own responsibility.
The effect of solution resistance is a function of the cell geometry, but the following expression may be used to approximate its magnitude. Wi 4 unless a better basis is available.
B Registered trademark Haynes International. 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.
ASTM G Standard Practice – Free Download PDF
Generally, this error is small with modest scan rates Other redox couples that do not necessarily participate in the corrosion reaction may have similar effects.
NOTE 4—Electrodes exhibiting stable passivity will behave as if the anodic reaction were diffusion limited, except that the passive current density is not affected by agitation. Ra 5 the g1002 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.