A new equation for potential attenuation and anode current output projection for cathodically polarized marine pipelines and risers
A first principles based equation for potential attenuation along a marine pipeline or riser that was cathodically polarized by multiple, equally spaced, identical galvanic anodes and that incorporated the electrolyte (anode), coating, and metallic path resistances, as well as the pipe polarization resistance, was derived. Finite different method (FDM) solutions for this equation showed that the potential profile consisted of a relatively abrupt polarization decay within the first several meters of an anode and an essentially constant potential beyond this for cases where anode spacing was {approximately}< 1 km (this distance varied with pipe and anode dimensions, properties, and exposure conditions). For anode spacings greater than this, metallic path resistance became important such that a potential gradient resulted along the entire pipe length. Comparison of the RDM solutions for the case of a pipeline of typical dimensions and marine exposure conditions with results from boundary element modeling (BEM) indicated excellent agreement between the two for situations where the metallic resistance was negligible. For cases where this term was not negligible (relatively large anode spacings), the FDM solutions were more accurate since BEM did not incorporate metallic path resistance. It was concluded that the derived equation has utility for design of pipeline cathodic protection systems and for analysis of data there from, particularly in cases where anode spacing is sufficiently large that metallic path resistance is non-negligible.
- Research Organization:
- Florida Atlantic Univ., Dania Beach, FL (US)
- OSTI ID:
- 20050515
- Journal Information:
- Corrosion (Houston), Vol. 56, Issue 4; Other Information: PBD: Apr 2000; ISSN 0010-9312
- Country of Publication:
- United States
- Language:
- English
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