Steel pipelines externally exposed to seawater pit more severely in heat-affected weld zones but longer-term quantitative data are scarce. Maximum pit depths and variability are reported for the longitudinal weld in API X56 Spec 5 L grade steel pipeline samples exposed continuously to natural Pacific Ocean seawater for 3.5 years. For the first year maximum pit depths and pit depth variability for the different weld zones were very similar. Both became much greater subsequently, with the greatest increases for the heat affected zone. Pit extreme value trends are not consistent with the conventional Gumbel distribution. Numerous maximum pit depth for the HAZ results from localized anoxic corrosion niches. This is compared with steel composition and grain size and potential reasons for the observations discussed.
Pitting corrosion in pipeline steel weld zones
Lochfraßkorrosion an Schweißzonen von Rohrleitungen
Corrosion Science ; 53 , 11 ; 4026-4032
2011
7 Seiten, 12 Bilder, 1 Tabelle, 35 Quellen
Article (Journal)
English
Rohrstahl , Rohrleitungskorrosion , Meerwasser , Schweißverbindung , Gewichtsverlust , Lochfraßkorrosion , Modelluntersuchung , Längsnaht , Mikrostruktur , Wärmeeinflusszone , Grundmaterial , Korrosionstiefe , statistische Verteilung , Korrosionseinleitung , Langzeitversuch , Feldversuch , Zeitfaktor , Pazifischer Ozean
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