Induced polarization and surface electrochemistry

Induced-polarization (IP) responses arising from activation overvoltage are investigated, with the goal of relating established electrochemical properties and processes to IP time constants. In activation overvoltage, an electrical double layer with a well-defined areal capacitance forms at the mineral-electrolyte interface. This study shows that the known capacitance of the interface is compatible with observed initial time constants for the decay of electrode polarization. Furthermore, because the electrical double-layer capacitance is determined largely by the electrolyte and not the mineral, the conclusion is that, although the polarization is caused by the presence of the mineral, the time constants of the decay are determined primarily by the electrolyte and not the mineral. The dependence of the capacitance on the sign and magnitude of the potential implies that the effective decay time constant will be small at the start of depolarization and will progress to larger values as the decay proceeds.