Tafel extrapolation is a mathematical technique used to estimate either the corrosion current (Icorr) or the corrosion potential (Ecorr) in an electrochemical cell, and by extension, the corrosion rate. Extrapolation involves extending a known sequence of linear values within a Tafel plot to determine these parameters. Tafel extrapolations can be performed either manually or by specialized computer software.
Graphical extrapolation is one of the essential techniques in classic Tafel analysis. A Tafel plot, which is a graphical relationship between the current generated in an electrochemical cell and the electrode potential, usually consists of two diverging logarithmic plot lines representing the anodic and cathodic currents.
Extrapolation is performed by extending the linear portions of the anodic and cathodic plots back to their intersection. These two lines eventually meet at a point where the corrosion current, Icorr, is obtained. The value of Icorr can then be input into specific mathematical equations to calculate parameters such as corrosion rate.