This study investigates the role of CO2 and cyclic stress R-ratio (R = minimum stress/maximum stress) on near-neutral pH SCC initiation mechanism(s) under a disbonded coating of pipeline steel protected by cathodic protection (CP). It was found that depending on CO2 concentration and level of CP, different localized environments with various pH could be formed under the disbonded coating. Cracks are mainly initiated at regions with limited CP, not completely free from CP. When cyclic loading was applied, different SCC initiation mechanisms were involved depending on the pH of the localized environments. Reducing the R-ratio had different effects on the initiation mechanisms, R-ratio may promote or not affect the SCC initiation depending on the level of CO2.
Effect of CO2 and R-ratio on near-neutral pH stress corrosion cracking initiation under a disbonded coating of pipeline steel
Einfluss von CO2 und vom R-Verhältnis bei fast neutralem pH-Wert auf die Einleitung der Spannungsrisskorrosion von Rohrstahl unter einer abgelösten Beschichtung
Corrosion Science ; 53 , 6 ; 2318-2327
2011
10 Seiten, 15 Bilder, 5 Tabellen, 26 Quellen
Article (Journal)
English
Rohrstahl , organischer Überzug , Schichtablösung , angerissene Oberflächenschicht , kathodischer Korrosionsschutz , Lochfraßkorrosion , Spannungsrisskorrosion , neutrales Medium , mechanische Spannungsverteilung , mechanischer Spannungsverlauf , zyklische Belastung , Salzlösung , Konzentrationseinfluss , Risseinleitung , Potenzialverteilung , Korrosionspotenzial , Korrosionsgeschwindigkeit , Lochfraßtiefe
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