Threshold hydrogen concentration (CthH) and threshold pH (pHth) for hydrogen-induced cracking (HIC) were determined for commercial sour service linepipe steels exposed to H2S-saturated buffer solutions. Metallographic examination of the steel samples by optical and electron microscopy showed that ultrasonic C-scan is an effective method for detecting HIC and for locating cracks in exposed steel coupons. A banded microstructure was found to be detrimental to the HIC resistance of clean steels. The obtained pHth values can be used to rank the steels with respect to HIC resistance.

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NACE International
1993
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