A 515-km pipeline in northeastern Australia exhibited 5 V telluric potential fluctuations in the 130 km of its length adjacent to the coast. The rest of the pipeline was relatively unaffected. The potential fluctuations were constrained using a combination of potentiostatic cathodic protection (CP) units, diodes connecting the pipeline to Earths, and insulating joints. There remained a significant rate of corrosion in the telluric-affected area. The CP criterion is to be modified and based on potentials that have been correlated with electrical-resistance probe data. This minimizes the effect of the variable soil voltage gradient errors in potential measurement resulting from the telluric effects and also the unknown effects of short duration positive transients. Additional work is required to determine acceptable transient potential frequencies, amplitudes and durations.

Subject
Electric current, Materials, Corrosion rate, Cathodic potential, Pipeline sections, Probes, Pipelines, Silicon carbide, Joints, Constants, Current densities, Electric potential, Corrosion probes
Keywords:
cathodic protection, pipeline corrosion, solar-induced currents, stray current, telluric effects
NACE International
1993
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