Reaction Dependent on Potential and Mass Transfer

From this last equation, icon can be obtained if the Tafel slopes and the overall charge-transfer resistance are measured. This relation was first developed by Stem and Geary and is applied by some industrial instrumentation to determine the corrosion rate. 

Many electrochemical reactions are influenced by the rate of transport of reactants to the electrode surface. Formal treatment of the impedance response for such a system requires both the kinetic analysis presented in this chapter and consideration of mass transfer as presented in Chapter 11. 

A second equation is needed in order to evaluate the oscillating component of the current density with respect to the oscillating component of the interfacial potential, i.e., 

The approximation of a linear concentration gradient used in equation (5.25) can apply only for the steady-state condition, and cannot be employed for equation (10.44). It can be convenient to write equation (10.44) in terms of dimensionless position = y/ A and dimensionless concentration 0a = ca/ca,o as 

The relationships presented in Table 10.1 (equations (10.22)-(10.24)) can be introduced to obtain a relationship for impedance in terms of capacitance and electrolyte resistance as 

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