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J. Peter Nicholson, World Pipelines, March 2003

Cathodic protection is an electrical method of reducing the corrosion rate of buried or submerged metallic structures, such as a pipeline.  Since cathodic protection requires the flow of electrical current through the soil and onto the pipeline, chemical changes occur at the pipeline soil interface.  Current flowing onto a metallic pipeline results in the formation of calcareous deposit, which consists principally of calcium hydroxide and magnesium hydroxides.  The result is an increase in the pH at the soil pipeline interface, and the formation of hydrogen on the surface of the pipeline; a situation commonly referred to as  polarisation.

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