Time-dependent polarization behaviour of pipeline grade steel in low ionic strength environments

A bench-top experimental approach is described for estimation of the polarization behaviour of pipeline steel as a function of the time-dependent formation of scale and calcareous deposits in simulated soil leachates. A three-time constant process model provided a common set of parameters for a given soil environment and level of aeration. The parameters estimated could be applied to a broad range of current values and were independent of time, potential and applied current. The experimental approach, model and regression procedure are general and could be used to determine the physical parameters associated with the seasonal variations (wet–dry cycles) in the soils surrounding pipelines or with other factors that influence general corrosion. The polarization model could provide a boundary condition for mathematical models for cathodic protection of pipelines or other buried structures. The separation of current contributions implicit in the model can be used to assess the reduction of corrosion current associated with specific CP criteria.