The risks of alternating current (AC) corrosion, overprotection, and stray direct current (DC) corrosion are increasing on cathodically protected buried steel pipelines due to the recent changes in factors such as burial conditions, the characteristics of coatings, and pipe material. In the present study, field tests as well as a review of the literature on these risks were conducted. As a result, it has been revealed that there is a certain limitation to assess these risks with respect to conventional cathodic protection (CP) criteria based on pipe-to-soil potential. Therefore, new CP criteria for the elimination of these risks have been developed based on DC and AC current density measurements on coupons. The effectiveness of the new CP criteria was evaluated through the design of CP systems on newly constructed pipelines subject to the risks of AC corrosion, overprotection, and stray DC corrosion. Using these new CP criteria, the design and installation of CP systems as well as the elimination of these risks were completed successfully. The risks of overprotection as well as stray DC corrosion were eliminated by providing an appropriate level of DC current from CP rectifiers. The elimination of the AC corrosion risk was accomplished using distributed magnesium anodes and solid-state DC decoupling devices. Finally, the new CP criteria were proven to be effective in eliminating the risks of AC corrosion, overprotection, and stray DC corrosion on buried steel pipelines.
New cathodic protection criteria based on direct and alternating current densities measured using coupons and their application to modern steel pipelines
Neue Kriterien des Kathodenschutzes auf Basis von Gleich- und Wechselstromdichtemessungen an Coupons und deren Anwendung bei modernen Stahlrohrleitungen
Corrosion, Houston ; 60 , 3 ; 304-312
2004
9 Seiten, 10 Bilder, 2 Tabellen, 17 Quellen
Aufsatz (Zeitschrift)
Englisch
Effect of alternating current on cathodic protection on pipelines
Tema Archiv | 2012
|Effects from alternating current on cathodic protection of submarine pipelines
Tema Archiv | 2011
|Design criteria examined for cathodic protection of hot submarine pipelines
Tema Archiv | 1984
|Current densities for cathodic protection of steel in tropical sea water
Tema Archiv | 1998
|