Computer Modeling of a Sacrificial Anode Cathodic Protection Design for Marine Steel Pipe Piling

This article focuses on sacrificial anode cathodic protection design and analysis for near shore steel-fixed piling structures.

The electrolyte resistivities along the immersed and buried portions of a marine pile can vary by several orders of magnitude.  A single pile can be exposed to extreme resistivity differences, and the higher resistivities in the mud zone make it less attractive to receive cathodic protection current from an anode in the immersion zone, especially with increasing depth below the mud line.  Additionally, steel piling are often not coated from 3 m below the mud line to the bottom.

The industry accepted design methodology is satisfactory to determine the anode requirements for marine structures, including the necessary protective current, initial and final current output, A.hr and kg requirements, type, dimensions, and quantity.  However, for piling, the actual levels and spread of protection throughout the immersed and buried length of the pile can significantly vary.

Specialized computer software was used to model the cathodic protection design as determined by conventional methods to closely examine and predict the adequacy of the design.  The predicted pipe to electrolyte potentials and protective current density were computed along the pile length versus depth.  Interesting results were observed.