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  • Mechanisms of degradation by sulphide stress corrosion cracking in humid and acid environments: Advanced implementation in high grade gas pipelines


The aim of this study is to define the reaction of steels in stress corrosion in a humid, acid sulphur environment, in tubes of type API 5L, grade X60, with a high level of carbon, allied with manganese, and micro-allied with niobium and with vanadium. In order to do this, we have worked in four different environments, for which we have speeded up slow cooling, with a view to obtain different structures. We also wanted to define their influence on the sulphide stress corrosion cracking (SSCC). Then, we looked for the sites of crack initiation, for a better understanding of the SSCC, linked to microstructure (nature and volume fraction of the components).

In all the cases, whatever the environment was, we had very good results on the SSCC. The limit of non-rupture was largely above 80% of the limit of elasticity, corresponding to the grade API X60. We have shown that the micro-segregation does not have any influence on the threshold of cracking by SSCC. It seems that it is the extreme cleanliness of the inclusion that explains the excellent holding of the SSCC. The metallographic characterisations show that a martensitic structure will give mainly a type stress-oriented hydrogen-induced cracking (SOHIC) cracking. During the experiments, we noticed some micro-cavities in all cases, which are sometimes related to some inclusions. We must note that a high quantity of cracking of SSCC types and of micro-cavities does not lead automatically to a weak resistance to stress corrosion. Type SOHIC cracking has the worst influence on the SSCC.

Additional information

Authors: GINGELL A, IRSID, Maizières-lès-Metz (FR);RENAUD J J, IRSID, Maizières-lès-Metz (FR);GARAT X, IRSID, Maizières-lès-Metz (FR);JANKOWSKI I, IRSID, Maizières-lès-Metz (FR);MEDARD J, IRSID, Maizières-lès-Metz (FR)
Bibliographic Reference: EUR 18440 FR (1998) 116pp., ECU 20
Availability: Available from the (2)
ISBN: ISBN 92-828-4601-6
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