Warm pipelines may be elevated above ice-rich permafrost, but buried in unfrozen ground or in ice-containing permafrost which is regarded as mechanically thaw-stable. In northern regions, the concentration of ionospheric electrical currents causes not only aurora borealis but also a time-variable magnetic field at the earth's surface, and the induction of electrical currents in the soil and in pipelines. A model is presented for electrical current flow in a typical warm pipeline segment, including both buried and elevated sections, soil resistances, corrosion protection sacrificial anodes, and regions of damaged pipeline coatings. The circuit is analyzed, and specific conditions under which corrosion currents may leave the pipeline at locations of coating damage, thus causing corrosion, are identified. The flow of telluric currents both into and out of the sacrificial anodes which may be connected to the pipeline is described, and the conditions for this are discussed. Certain conditions are described under which sacrificial anodes may become disconnected from the pipeline. Possible methods for alleviating corrosion related to telluric currents are presented, including the choice of grounding locations, insulating flanges, and adaptive impressed-current sources.

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