The stability of an electrodeposited collection of metal particles under open-cell conditions is investigated, using mercury on platinum as a model. The agglomeration process is analysed for the case of two mercury droplets which constitute a local cell. It is shown that, making some reasonable simplifying assumptions, the model allows the formulation of an analytical solution for the volume ratio of the droplets as a function of time, which can be cast in dimensionless form. Some typical values for agglomeration times are given.