Here, we consider a description of the time constant for interfacial charging analogous to the RC-time to predict the spatial extend of an electrical pulse applied to a scanning electrode. The charging time τC has been identified as the RC time for a simple electrochemical system of two parallel plate, blocking electrodes (i.e. without Faradaic current), with a z:z electrolyte (i.e. each ion has equal charge), and an applied step potential, and is given by ; with λD the Debye screening length, L the electrode separation, D the diffusion coefficient, ε(0) the (vacuum) permittivity, kB the Boltzmann constant, T the temperature, z the charge number, e the elementary charge, Na the Avogadro constant, and C the concentration of the electrolyte. It is important to note that τC is essentially the same as the RC-time, but is defined only in terms of constants of the electrolyte, rather than requiring additional measurement or computation of the solution resistance and interface capacitance .