Abstract
Concrete coatings are applied on top of anti-corrosion coatings as weight coating. Concrete coatings are used in off-shore pipelines for buoyancy protection and in on-shore pipelines as backfill protection. Backfill protection with concrete is used in rocky locations and at river crossings. Application of concrete coatings on oil and gas pipelines is relatively new, but steel-polymeric coatings-concrete system is extensively used in many structures including bridges and buildings. In those industries, the use of epoxy anti corrosion coating beneath the concrete coating has been much debated. Some regulations in those industries require application of epoxy coating while others prohibit the use of epoxy coating beneath concrete coating, i.e., in the infrastructure industry the use of concrete is mandatory while that of epoxy coating is optional, whereas in the oil and gas industry the use of anti-corrosion coating is mandatory while concrete coating is used in special circumstances.
In this paper, long-term cathodic disbondment test was carried out using a pipe sample protected with both epoxy anticorrosion coating and concrete coating. During the investigation the corrosion potential and pH were recorded. After the test the disbonded area of the anticorrosion coating was measured. From the online and postmortem results, the compatibility between concrete coating, mainline coating, and cathodic protection was investigated. There was no cathodic disbondment of anticorrosion coating after 120-day test indicating that the application of outer concrete coating does not physically damage the anticorrosion coating.
