To accurately assess galvanic performance of dissimilar metal components under atmospheric corrosion we need to predict corrosion rates for galvanic couples covered by thin layer electrolytes that commonly occur in the natural environment. In this study we used finite element models of interdigitated electrode (IDE) sensors to help characterize the changing electrolyte properties on a sensor surface during a salt aerosol spray dosing experiment. Different volumes of a sodium chloride solution were sprayed on electrode grids capable of measuring either solution conductance or galvanic current. Computer models of these electrode grids were developed to predict the relative changes in electrolyte properties occurring as applied salt loading was increased; experimental measurements were used to guide model assumptions. The goal of this approach is to characterize electrolyte properties representative of thin film environments in a laboratory controlled environment. Results from this work provide new insight into the spatial extent of electrolyte films developing under different salt loads during simple relative humidity cycle testing. This work supports advancement in understanding the nature of electrolyte films that may occur in the natural environment and provides further guidance on appropriate domain and boundary conditions to consider in finite-element based atmospheric corrosion models.