Metals may be protected with highly resistive but electroactive overlayers. Through holes and defects on such surfaces, the exposed substrate may corrode, and the corrosion may be exacerbated by galvanic coupling with the surrounding (cathodic) overlayer. The modeling of a system with an overlayer of finite conductivity has not been attempted before, and we report here our results of current and potential distribution modeling as a function of the characteristic parameters of the system. The finite element method was used for the analysis. The cathodic galvanic current was found to flow mainly to areas at the periphery of holes and defects; total cathodic area was not important in determining galvanic current.