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PRCI PR-208-631
- Shielding Effects of Concrete and Foam External Pipeline Coatings
- Report / Survey by Pipeline Research Council International, 01/01/1992
- Publisher: PRCI
$225.00$449.00
L51656e
Northwestern University Industrial Research Lab(BIRL)
Need: Protection of gas-transmission pipelines from external corrosion is achieved by the application of a good anticorrosion coating and cathodic protection. In very rocky areas, pipeline-construction operations sometimes dictate that an external impact-resistant or barrier material be applied over the pipe to protect the anticorrosion coating from damage during backfilling. The use of a select backfill, such as compacted sand, is often specified, but transportation of the backfill and access to sufficient right-of-way to truck the sand into more remote areas becomes costly. As an alternative, recent practice has been to specify that a barrier coating of concrete or urethane foam be applied over the anticorrosion coating. However, concern has been raised regarding possible shielding of cathodic-protection currents by these external barrier materials.
Benefit: Basic Industry Research Laboratory (BIRL) Describes the investigation of shielding effects of barrier coatings on attempts to maintain CP levels on natural gas pipelines. Investigation included lab experiments with five representative barrier coatings materials carried out to determine the degree to which shielding occurred and the levels of CP needed to overcome this effect when occurring.
Result: The conclusions that follow are based upon the specific barrier and anticorrosion coatings, and the conditions studied: Although there are trade offs in their physical and electrochemical properties, none of the concrete, urethane foam, or sand barrier coatings studied shielded the steel from cathodic-protection currents under the conditions tested; All of the barrier coatings studied effectively reduce the corrosion rate of the underlying steel and the current required to protect it, with the urethane foams showing the greatest reductions, followed by the concrete materials, and then sand; Normal levels of cathodic protection based upon presently accepted criteria and system operation in the field should be adequate to control corrosion with barrier coatings and a good anticorrosion coating on a pipeline; Sand, concrete, and urethane foam are all compatible with obtaining adequate levels of cathodic protection to provide corrosion control.
Northwestern University Industrial Research Lab(BIRL)
Need: Protection of gas-transmission pipelines from external corrosion is achieved by the application of a good anticorrosion coating and cathodic protection. In very rocky areas, pipeline-construction operations sometimes dictate that an external impact-resistant or barrier material be applied over the pipe to protect the anticorrosion coating from damage during backfilling. The use of a select backfill, such as compacted sand, is often specified, but transportation of the backfill and access to sufficient right-of-way to truck the sand into more remote areas becomes costly. As an alternative, recent practice has been to specify that a barrier coating of concrete or urethane foam be applied over the anticorrosion coating. However, concern has been raised regarding possible shielding of cathodic-protection currents by these external barrier materials.
Benefit: Basic Industry Research Laboratory (BIRL) Describes the investigation of shielding effects of barrier coatings on attempts to maintain CP levels on natural gas pipelines. Investigation included lab experiments with five representative barrier coatings materials carried out to determine the degree to which shielding occurred and the levels of CP needed to overcome this effect when occurring.
Result: The conclusions that follow are based upon the specific barrier and anticorrosion coatings, and the conditions studied: Although there are trade offs in their physical and electrochemical properties, none of the concrete, urethane foam, or sand barrier coatings studied shielded the steel from cathodic-protection currents under the conditions tested; All of the barrier coatings studied effectively reduce the corrosion rate of the underlying steel and the current required to protect it, with the urethane foams showing the greatest reductions, followed by the concrete materials, and then sand; Normal levels of cathodic protection based upon presently accepted criteria and system operation in the field should be adequate to control corrosion with barrier coatings and a good anticorrosion coating on a pipeline; Sand, concrete, and urethane foam are all compatible with obtaining adequate levels of cathodic protection to provide corrosion control.
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