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The atomic force microscope (AFM) was used to examine the influence of an applied electrochemical potential on the interfacial properties of the electrode/electrolyte interface. Measurements of electrostatic force, adhesion, and friction coefficient were performed at two different electrode surfaces: glassy carbon and a thin film of sulfonate-derivatized poly(aniline) (SPANi). At the carbon electrode, changes in electrostatic force between probe and substrate exhibited a potential-dependent transition from repulsive to attractive values at potentials negative and positive of the potential of zero charge (Epzc). Simultaneous measurements of tip−substrate adhesion and friction coefficient showed a change from low to high values over the same potential range, suggesting a common mechanism dominated by the electrostatic force. Measurement of these same properties at a SPANi-coated electrode also displayed a potential-dependent response. The electrostatic force and the adhesion tracked with the oxidation stat...