Field Testing of Deep Water Cathodic Protection on the Norwegian Continental Shelf

Abstract

Abstract Field testing has been carried out on the Norwegian Continental Shelf (Tromsøflaket and Troll field) at depths down to 500 meters, utilizing automatic logging units for in-situ monitoring of cathodic protection and environmental data. The main objective was to establish design data for cathodic protection of future installations in these areas and at large water depths. Very high design current densities were necessary to achieve rapid and efficient cathodic polarization at Tromsøflaket and Troll. The polarization behaviour of steel cathodes and galvanic anodes has been related to sea water environmental parameters, CP design and the characteristics of the calcareous layers formed. The results illustrate that a high design initial current density promotes the formation of dense calcareous layers, thereby reducing the long-term current consumption for maintenance of cathodic protection. Once such layers have formed, variations in sea water flow had very little effect on the cathodic current density. No incidences of cathodic depolarization related to erosion or spalling of calcareous layers were registered.