Laboratory and Field Characterization of a New Sacrificial Anode for Cathodic Protection of Offshore Structures

Abstract

A new type of sacrificial anode for cathodic protection (CP) of structures immersed in seawater, such as the steel jackets of offshore platforms, was developed. The anode is constructed of two diverse anodic materials (aluminum alloy on the inside and magnesium in the surface layers) and offers significant reductions in weight and cost of the anodic material. These reductions result from the effect of a highly protective calcareous deposit that forms on the structures. Laboratory scale tests were carried out to simulate and characterize the behavior of anodes in use and to optimize their application. Protective characteristics of the calcareous deposits also were evaluated. Deposits taken from AGIP platforms in the Adriatic sea were analyzed. Traditional aluminum anodes protected the Garibaldi D, which carried two new anodes, and the Daria A was protected entirely with the new type. Such positive experimental results in the field, on platforms in the Adriatic sea, and in laboratory tests enabled this system to be adopted on structures currently under continuous observation.