Deep water cathodic protection: Part 2 - Field deployment results

Instrumented. steel plate specimens with various levels of galvanic anode cathodic protection were deployed at a 899-m (2.950-ft) Gulf of Mexico site for 405 days. Subsequent to recovery. potential and current records were analyzed; and the long-term. steady-state current density demand determined. This parameter (current density demand) was greater for specimens with a polished surface finish compared to ones that were atmospherically pre-rusted. Also, steady-state current density for the former was more sensitive to water velocity than were the latter. Current densities, particularly for the pre-rusted specimens, were relatively independent of the slope parameter (alternatively, initial current density) within the range of this parameter that was investigated, suggesting that rapid polarization afforded little or no advantage. The calcareous deposits were characterized using scanning electron microscopy and x-ray diffraction, and the data and nature of the deposits are compared with results from companion laboratory experiments in which deep water exposure conditions were simulated.