Stress corrosion cracking and hydrogen cracking: differences similarities and confusion

摘要

Stress corrosion cracking and hydrogen cracking are two important forms of environmental cracking which can cause serious failures in the oil and gas, pipeline, process and many other industries. Both forms of cracking result in normally ductile metals failing in a brittle manner. In many if not most cases, analysis clearly shows which of these failure modes has occurred. However, there can be situations where the two can be confused. This paper reviews the differences and similarities between the two modes, concentrating on the metals and environments, especially steels in sulphide environments, where confusion can arise. It looks at the various forms of cracking, the nature of cracking, its causes and how it is prevented. Sulphide stress cracking can be especially troublesome as, unlike other forms of hydrogen damage, the cracking initiates at the surface. A review of the mechanism of sulphide stress cracking is given, along with its relationship to stepwise cracking. There can also be confusion between these two forms of damage, as a case study from the literature shows.