High CP Potential Effects on Pipelines

Main Objective

The objective of the proposed research is to develop a set of guidelines for operators, which would enable the users to determine the limiting cathodic protection potentials for a given steel metallurgy and coating type and thickness to mitigate possible hydrogen-induced damage and coating disbondment and/or blistering.

Public Abstract

Concern over the effects of high cathodic protection potentials ("overprotection") on pipelines has been discussed for many years. The concern focuses in two areas: (1) high potentials increasing the disbondment of pipeline coatings and (2) high potentials resulting in the production of hydrogen as a reduction reaction product at the steel surface resulting in hydrogen damage of the steel. There exists a need for specific data linking the cathodic protection potentials and hydrogen-induced damage on higher strength pipeline steels (X-60 and above) and external coating disbondment.

The objective of the proposed research is to develop a set of guidelines for the pipeline operators, which would enable the users to determine the limiting cathodic protection potentials for a given steel metallurgy and coating type and thickness to mitigate possible hydrogen-induced damage and coating disbondment and/or blistering.

The proposed one year-long project will run concurrently with the existing Pipeline Research Council International (PRCI)-funded effort to evaluate the effects of high CP potentials on cathodic disbondment and hydrogen-induced corrosion susceptibility of different pipeline steel grades (of varying inclusion content and including local ‘hard spots'.) This PRCI project is limited in scope; the proposed effort considerably expands the number of tested CP potentials/steel metallurgy/soil environment conditions to allow for greater control of the consistency of the experimental data and reliability of the conclusions.

Final Report

Final Report. November 2004.

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