Composite repairs have been extensively used over the past twenty-plus years as a high-integrity repair technology for high pressure transmissions pipelines. Numerous industry test programs have increased the knowledge related to repair techniques, repair design, and quality control of installations. However, little work has been performed related to the interactions of cathodic protection and composite repairs. This paper reviews several approaches for determining if cathodic shielding may occur under a composite repair.
Preventing cathodic shielding can be considered in two different phases. First, the coating (or composite repair) must disbond or fail creating a local environment below the coating. Secondly, the coating (or composite repair) must allow for the permeation of cathodic current to the pipe surface providing the corrosion protection. Current industry standards, such as ASME PCC-2, can address the first aspect by examining the results of the cathodic disbondment tests and quantifying the level of disbondment. The second aspect can be addressed through an innovative and comprehensive test program that investigates several commercially available composite repair systems and their interactions with cathodic protection. Multiple test methods were utilized to prove there remains a low probability of shielding for composites of typical thickness and operating environment.
The motivation for this work was to perform a comprehensive test program to investigate several commercially available composite repair systems and their interactions with cathodic protection. Multiple test methods were utilized to prove there remains a low probability of shielding for composites of typical thickness and in a typical environment. This work will also discuss how results from current industry qualification tests (such as those specified in ASME PCC-2) can be considered when making long-term decisions regarding the effects of cathodic protection on composite repairs and the pipelines on which they are installed. This paper provides an innovative approach to test and validate the interactions of cathodic protection with several commercially available composite repair systems. There is no current testing approach available within industry standards, so these results address much needed questions and provide a consistent approach to evaluate other composite repair systems.