The Levich Equation models the diffusion and solution flow conditions around a Rotating disk electrode

Rotating disk electrode

A rotating disk electrode is a hydrodynamic working electrode used in a three electrode system. The electrode rotates during experiments inducing a flux of analyte to the electrode. These working electrodes are used in electrochemical studies when investigating reaction mechanisms related to...

 (RDE). It is named after Veniamin Grigorievich Levich who first developed an RDE as a tool for electrochemical research. It can be used to predict the current observed at an RDE, in particular, the Levich equation gives the height of the sigmoidal

Sigmoidal

Sigmoidal or sigmoid, literally means S-shaped and can refer to:* Sigmoid function* Sigmoidal artery* Sigmoid colon...

 wave observed in rotating disk voltammetry. The sigmoidal wave height is often called the Levich current.

The Levich Equation is written as:



where

• i_L is the Levich current
• n is the number of electrons transferred in the half reaction
• F is the Faraday constant
• A is the electrode area
• D is the diffusion coefficient (see Fick's law of diffusion
  Fick's law of diffusion
  Fick's laws of diffusion describe diffusion and can be used to solve for the diffusion coefficient, D. They were derived by Adolf Fick in the year 1855.- Fick's first law :...
  
  )
• w is the angular rotation rate of the electrode
• v is the kinematic viscosity
• C is the analyte
  Analyte
  An analyte, or component , is a substance or chemical constituent that is of interest in an analytical procedure. Grammatically, it is important to note that experiments always seek to measure properties of analytes—and that analytes themselves can never be measured. For instance, one cannot...
  
  concentration

While the Levich equation suffices for many purposes, improved forms based on derivations utilising more terms in the velocity expression are available.