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

A bench-top experimental approach is described for estimation of the polari zation behaviour of pipeline steel as a function of the time-dependent form ation of scale and calcareous deposits in simulated soil leachates. A three -time constant process model provided a common set of parameters for a give n soil environment and level of aeration. The parameters estimated could be applied to a broad range of current values and were independent of time, p otential and applied current. The experimental approach, model and regressi on procedure are general and could be used to determine the physical parame ters associated with the seasonal variations (wet-dry cycles) in the soils surrounding pipelines or with other factors that influence general corrosio n. The polarization model could provide a boundary condition for mathematic al models for cathodic protection of pipelines or other buried structures. The separation of current contributions implicit in the model can be used t o assess the reduction of corrosion current associated with specific CP cri teria.