A recently proposed potential attenuation equation for pipelines and risers with multiple, equally spaced, identical superimposed (bracelet) galvanic anodes that incorporates all relevant resistance terms (anode, coating, polarization, and metallic return path) has been modified for situations where anodes are displaced. The equation is solved numerically using the coordinate mapping based finite difference method, and potential vs distance plots are provided for several examples with accuracy being proven by independent calculations. The solutions are compared with those of the classical equation of Uhlig, and it is concluded that the latter is overly conservative in situations where the pipeline or a portion thereof lies in the potential field of the anode. It is demonstrated further how the equation can be used for pipelines polarized by impressed current anodes.

Subject
Piping, Anode potential, Pipelines, Electrolyte resistance, Anode resistance, Bracelet anodes, Maritime, Attenuation, Polarization, Polarization resistance, Corrosion potential, Electrolytes, Anodes
Keywords:
attenuation, cathodic protection, inclusive equation, offset anodes, pipelines
NACE International
2004
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