Carbon steel coupons were permanently exposed to seawater in the low water zone of two French harbors for 5 years before to be subjected to cathodic protection (CP) (potential about -0.95 V vs. Ag/AgCl/seawater) for 1 year. Cathodic polarization of corroded carbon steel induces changes in the rust layers. The application of cathodic polarization to the previously unprotected coupons induced the transforms sulfated green rust into carbonated green rust. Other coupons were permanently protected by cathodic protection during the 6 years immersion. Green rust and FeS are formed on steel under cathodic protection in natural seawater. A thin film of green rust and mackinawite was observed on the steel surface. This film was covered by a thicker layer of calcareous deposits. CP decreases the corrosion rate but the resulting products are basically unchanged. The study of this ''residual corrosion'' process may provide information allowing quantifying the effectiveness of CP.
Electrochemical formation and transformation of corrosion products on carbon steel under cathodic protection in seawater
Elektrochemische Bildung und Umwandlung von Korrosionsprodukten auf Kohlenstoffstahl unter kathodischem Schutz in Meerwasser
Corrosion Science ; 71 ; 32-36
2013
5 Seiten, 5 Bilder, 1 Tabelle, 32 Quellen
Article (Journal)
English
kohlenstoffreicher Stahl , Meerwasser , Hafenbecken , kathodischer Korrosionsschutz , Korrosionsprodukt , elektrochemische Umwandlung , Oberflächenschicht , Inkrustierung , Langzeitversuch , Tauchprüfung , Sulfat , Carbonat , Raman-Spektroskopie , mineralogische Zusammensetzung , chemische Zusammensetzung , Frankreich
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