Galvanic currents and potentials have been calculated on heterogeneous electrode surfaces comprised of random configurations of coplanar anodes and cathodes, for the purpose of investigating system behavior on different electrode geometries. The electrode surface was simulated by generation and subsequent patterning of a Voronoi tessellation. The electrochemical transport equations were solved in the absence of mass-transfer effects with a three-dimensional application of the finite element method. The galvanic currents and potentials so calculated were investigated for similarities linking behavior on different electrode geometries. It has been found that for a wide range of system parameters galvanic currents scale with the active perimeter separating anodic and cathodic regions on the electrode surface. Moreover, this effect enables the accurate prediction of galvanic current for an arbitrarily complex electrode surface geometry.