Intergranular stress corrosion cracking (IGSCC) of carbon steel pipelines can occur in a highly concentrated bicarbonate-carbonate solution with high pH ( 9 to 11). This type of SCC occurs in a very restricted range of electrochemical potentials (-550 mV/-650mV versus a saturated calomel electrode). Dominated by film rupture and dissolution, this is the so-called classical SCC. However, several instances of transgranular stress corrosion cracking (TGSCC) were detected recently at coating disbondment areas of Canadian pipelines. Slow strain rate tests (SSRT) and fractographic examination of X-80 and X-52 pipeline steels showed transgranular stress corrosion cracking (TGSCC) could occur in a dilute aqueous solution with near-neutral pH. SCC intensity increased as the applied electrochemical potential and strain rates decreased. Bubbling of CO, through the test solutions played important role in the process of TGSCC. Remarkable reductions were obtained in the ductility to fracture, especially at the lower strain rate. Hydrogen precharging or addition of carbon dioxide (CO2) facilitated the process of SCC, suggesting that dissolution and hydrogen ingress were involved in the cracking process. The mechanism of SCC in pipeline steels for low pH solution, near Ecorr was dominated possibly by anodic dissolution. Local acidification resulting from dissolution or pitting facilitated some reactions involved in the crack growth process. At cathodic potentials, cracking was controlled by hydrogen induced cracking.
Transgranular stress corrosion cracking of X-80 and X-52 pipeline steels in dilute aqueous solution with near-neutral pH
Transkristalline Spannungsrißkorrosion der Röhrenstähle X-80 und X-52 in verdünnter wässriger nahezu neutraler Lösung
Corrosion, Houston ; 55 , 3 ; 312-318
1999
7 Seiten, 11 Bilder, 3 Tabellen, 19 Quellen
Aufsatz (Zeitschrift)
Englisch