Polarization resistance deviations from linearity

J. Diard, B. LeGorrec, and C. Montella, "Deviation from the Polarization Resistance Due to Non-Linearity 3. Polarization Resistance Determination from Non-Linear Impedance Measurements," Journal of Electroanalytical Chemistry, 432 (1997)53-62. 

The calculation becomes more difficult when the polarization resistance RP is relatively small so that diffusion of the oxidized and reduced forms to and from the electrode becomes important. Solution of the partial differential equation for linear diffusion (2.5.3) with the boundary condition D(dcReJdx) = —D(d0x/dx) = A/sin cot for a steady-state periodic process and a small deviation of the potential from equilibrium is... 

---