Steady‐state electrolytic mass transfer to a rotating disk has been characterized in dilute solutions, with an excess of supporting electrolyte, for systems where the major ions of the supporting electrolyte participate in the electrochemical reaction. Although it is difficult a priori to predict accurately concentration variations of the electrolyte, the analytic model that has been developed can be used to calculate concentration‐difference ratios enabling the concentration profiles next to the disk to be sketched qualitatively. In three of the four electrochemical systems investigated, the model predicts unexpected maxima in the counterion concentration profile. An explanation for this interesting behavior is presented in terms of the speed at which the species move, according to the magnitude of their diffusion coefficients. Alternatively, examination of the diffusion potential yields insight into this occurrence and the corresponding minima in the potential.