A numerical model is described for electrohydrodynamic impedance spectroscopy (EHDIS) in the presence of viscosity and diffusivity gradients near the electrode. The viscosity is assumed to depend on the concentration of a diffusion-limited reaction product raised to a power. An effective diffusion coefficient measured from a Levich analysis is shown to approach the near-surface value of the diffusion coefficient when the near-surface kinematic viscosity is greater than in the bulk. Similarly, EHDIS measurements can lead to quick estimates of near-surface viscosity. The model is applied to interpret experimental data for the steady-state limiting current and electrohydrodynamic impedance of the zinc-KOH system.