In the first scenario (Fig. ) the coverage of intermediates/free sites that act as reactants is "well-behaved", i. In the third scenario (Fig. ) the src step transfers two electrons rather than one, causing its exponential term to overtake that of the hrc step at high overpotentials, with the hrc step becoming the rds. A similar behavior would also result from substantially different symmetry coefficients, 𝛼 𝑘 , for the src and hrc steps, a situation more likely than the transfer of two electrons in a single step. All scenarios have in common that the i-V curves follow the Tafel relationship with constant kinetic parameters only when the reactant activities of the rds become constant at a logarithmic scale. We call the potential region where this condition is not met the varying-coverage Tafel region. In the varying-coverage Tafel region a Tafel analysis may be performed, but its results may lead to false conclusions on the reaction mechanism if the varying coverage is not taken into consideration. At sufficiently large overpotentials, the constant-coverage Tafel region is generally approached, and one can perform a consistent Tafel analysis. In the following we examine the Tafel exchange current density in the constant-coverage-Tafel region and the Tafel-slope in the general case of constant or varying coverage.