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Dealing with Pipelines Positive Potential a Case of Study

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The pipeline is the Gibraltar-Bucaramanga Gas Pipeline which is divided in two electrically isolated sections by the use of a monolithic joint. The study concluded that it was necessary to complete additional actions to guarantee pipeline integrity, and to assure low corrosion rates.

Product Number: 51317--9202-SG
ISBN: 9202 2017 CP
Author: Javier Montanez Villamizar
Publication Date: 2017
Industry: Gas/Liquid Pipelines
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Structure to electrolyte potential survey is a useful and important test to evaluate cathodic protection systems.The structure to electrolyte potential values on carbon steel pipelines should be negatives when the voltmeter positive terminal is connected to the structure and the negative terminal is connected to the copper sulfate reference electrode however in this case of study those values were electropositive.Ones no operational mistakes in measures were verified discarding causes like rectifier incorrect connections or interferences from others systems additional measures were performed to find possible causes. At locations with positive potentials the measures showed severe corrosion on coupon test stations when coupons were connected to the pipeline and showed moderate corrosion on coupons expose to soil with no connection to the pipeline. These results were confirmed by current direction from the coupons to the electrolyte evidence of an anodic comportment.A minimum of 100 mV of cathodic polarization criteria does not guarantee pipeline protection because of positives potentials and it was determinate the possible existence of a corrosion macro cell in the pipeline with unknown cause.It concludes that it´s necessary additionally actions to guarantee pipeline integrity and to assure low corrosion rates.Keywords: Pipelines Corrosion cathodic protection positive potentials coupons telluric current criteria.

Key words: Pipelines, Corrosion, cathodic protection, positive potentials, coupons, telluric current, criteria.

Structure to electrolyte potential survey is a useful and important test to evaluate cathodic protection systems.The structure to electrolyte potential values on carbon steel pipelines should be negatives when the voltmeter positive terminal is connected to the structure and the negative terminal is connected to the copper sulfate reference electrode however in this case of study those values were electropositive.Ones no operational mistakes in measures were verified discarding causes like rectifier incorrect connections or interferences from others systems additional measures were performed to find possible causes. At locations with positive potentials the measures showed severe corrosion on coupon test stations when coupons were connected to the pipeline and showed moderate corrosion on coupons expose to soil with no connection to the pipeline. These results were confirmed by current direction from the coupons to the electrolyte evidence of an anodic comportment.A minimum of 100 mV of cathodic polarization criteria does not guarantee pipeline protection because of positives potentials and it was determinate the possible existence of a corrosion macro cell in the pipeline with unknown cause.It concludes that it´s necessary additionally actions to guarantee pipeline integrity and to assure low corrosion rates.Keywords: Pipelines Corrosion cathodic protection positive potentials coupons telluric current criteria.

Key words: Pipelines, Corrosion, cathodic protection, positive potentials, coupons, telluric current, criteria.

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ISBN: 9049 2017 CP
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00741 PRACTICAL TELLURIC COMPENSATION FOR PIPELINE CLOSE INTERVAL SURVEY

Product Number: 51300-00741-SG
ISBN: 00741 2000 CP
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04050 Telluric Currents and Their Effect on Cathodic Protection of Pipelines

Product Number: 51300-04050-SG
ISBN: 04050 2004 CP
Author: David Boteler, Geological Survey of Canada
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Telluric currents cause variations in pipe-to-soil potentials that take the potentials outside the desired range for cathodic protection. This paper reviews the causes of telluric currents, such as geomagnetic storms and tidal water movements, and shows how knowledge of these phenomena can be used to determine the occurrence of telluric current in pipelines.
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