2012 Frank Newman Speller Award: Cathodic Protection of Offshore Structures-History and Current Status

Categories of marine structures that use cathodic protection (CP) include port and harbor facilities, ships, coastal reinforced concrete bridges, pipelines, and those used for petroleum production. Primary focus of the present paper was on the last of these (offshore petroleum production structures) and CP theory and practice advances that have been made during the past several decades. Because of structure size, carbon or high-strength steel is the most common material of construction. The inception studies by Davy almost 200 years ago are reviewed briefly, followed by a review of subsequent CP evolvement and application. CP has been the primary corrosion control methodology for the submerged portion of offshore structures and pipelines for the past 60-plus years. Until the last several decades, however, improvements in marine CP design were incremental and based largely upon trial and error and empirical algorithms. These include the earlier single and subsequent triplicate design current density methods, which are reviewed. Also addressed are the recently developed first-principles-based slope parameter and unified design equation concepts, which require but a single design current density. Importance of the specified design current density, as affected by environmental conditions and calcareous deposits, is emphasized. Special topics, including deep water applications and design of retrofit systems, are discussed.