The Tafel curve is widely used in electrochemistry, especially in the study of corrosion. Using the Tafel curve one can determine the corrosion potential or open circuit potential. The coefficient of charge transfer can also be determined as the slope of the Tafel curve. This Demonstration shows the current-potential curve on the left and the Tafel curve, on the right.
The current-potential curve on the left obeys the Butler–Volmer equation for a kinetic-controlled reaction,
where is the charge transfer coefficient, is the number of electrons transferred, is Faraday's constant, is temperature, is the gas constant, and are the concentrations of oxidant and reductant, is the standard rate constant, and is the standard potential or corrosion potential .
The potential curve on the right is the Tafel curve.
For high overpotential ,
So the anodic slope is ; as increases, this slope decreases.
For large negative potential ,
Thus the absolute value of cathodic slope is ; as increases, the slope increases.
The Tafel slope can be used to calculate the charge transfer coefficient and the corrosion potential .