Unique Methods for Applying and Monitoring Platform Cathodic Protection in Cook Inlet

Platform cathodic protection in Cook Inlet is unique from that in other offshore areas, such as the Gulf of Mexico, North Sea, Java Sea, and others. The Cook Inlet environment is extremely harsh and hostile. Tides of 30 feet are common and slack periods occur approximately four times each day. Ice covers the Inlet from mid-November to mid-April and ice floes up to 6 feet thick are not uncommon. Water temperatures range from 30°F in winter to 42°F in summer. Because of these low temperatures, the water contains a higher concentration of dissolved oxygen than is normally encountered in other areas. Water flows past the platforms at velocities of 6 to 8 knots and is constantly moving even at so called slack tide periods. In addition, the inlet water contains a high concentration of glacial silt ranging from 1 to 5 microns in size, which causes a scouring effect on the steel platform members. The Cook Inlet water is extremely turbid and visibility is practically non-existent. These conditions not only make the area unique, but have contributed greatly to making the application of cathodic protection to offshore platforms in Cook Inlet extremely difficult and costly.