Abstract
Details are presented on the planning, design and installation of corrosion protection facilities to provide 100-year design life for a 7-mile, 22-inch steel pipe sewer outfall, the outer end of which is in ocean water 340 feet deep. The outfall serves the sewerage systems of Los Angeles and 16 other adjacent municipalities.
An impressed current cathodic protection system is used to protect the exterior of the pipe which is wrapped with a multiple-layer coal tar coating reinforced with glass fiber with bonded impregnated asbestos felt shield. A reinforced pneumatically applied cement mortar jacket provides negative buoyancy. Interior is protected by centrifugally-spun mortar lining with epoxy sleeves at welded tie-in joints.
Because of the depth of water in which the pipe was to be placed several novel features were necessary. Cathodic protection was applied continuously during installation by the use of zinc anodes. This system was monitored to detect any serious coating holiday before the pipe was laid in deep water. Permanent test leads also were attached to the pipe so performance of the impressed current system could be checked, continuously.
After 1½ years' operation there has been very little change in effective coating resistance, a pipe potential of —1.05 volts versus a copper/copper sulfate electrode being maintained with consumption of about 150 ma. 5.2.3
Influence of Anodic Current on Corrosion Protection of Buried Steel Pipeline under Cathodic Protection