Intergranular wet hydrogen sulfide cracking

Journal Article · Mon Nov 01 00:00:00 EST 1993 · Materials Performance; (United States)

OSTI ID:5432119

Schutt, H U ^[1]

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1. Shell Development Co., Houston, TX (United States)

Wet hydrogen sulfide cracking is a term used for a variety of stress corrosion cracking (SCC) failure modes of carbon steel exposed to aqueous sour refinery environments. More extensive use of the wet fluorescent magnetic particle technique in recent years as a refinery equipment inspection tool has highlighted the extent and magnitude of the wet hydrogen sulfide cracking problem. Environmental analyses and metallographic examinations indicate that the failure modes include corrosion mechanisms involving hydrogen entry into the steel, as well as a SCC mechanism that produces an intergranular crack pattern. The latter failure mode is expected to be relevant when steel surfaces are more positively polarized through the formation of a properly adhering corrosion product film than in the hydrogen-induced cracking cases. The intragranular SCC (IGSCC) mechanism can depend on a specific solution chemistry and residual tensile stresses in the exposed steel. The prevalence of the intergranular failure mode in aqueous sour refinery environments of catalytic cracking units is estimated to be 30 to 40% of all equipment with crack indications detected. The high rate makes clarification of the intergranular-type wet hydrogen sulfide cracking mechanism highly desirable. The slow strain rate technique seemed the most appropriate investigative tool. Slow strain rate testing used strain rates of around 10[sup [minus]6] s[sup [minus]1] and imposed predetermined potentials on tensile specimens that were strained, when necessary, to more adequately provide relevant steel surface conditions. In addition, potentiodynamic polarization curves were recorded for the study of film-forming processes and for guidance in determining the control potentials which might be applied in subsequent straining experiments. Synthetic solutions, made with the sodium salts of the anionic species of interest, were used throughout the study.

• OSTI ID: 5432119
• Journal Information: Materials Performance; (United States), Vol. 32:11; ISSN 0094-1492
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CARBON STEELS
FRACTURE MECHANICS
CRACKS
FAILURE MODE ANALYSIS
HYDROGEN SULFIDES
STRESS CORROSION
ALLOYS
CHALCOGENIDES
CHEMICAL REACTIONS
CORROSION
HYDROGEN COMPOUNDS
IRON ALLOYS
IRON BASE ALLOYS
MECHANICS
STEELS
SULFIDES
SULFUR COMPOUNDS
SYSTEM FAILURE ANALYSIS
SYSTEMS ANALYSIS
360105* - Metals & Alloys- Corrosion & Erosion