An increasing number of wells contain considerable amounts of hydrogen sulphide H2S. This requires the use of sour resistant steel, to avoid phenomena such as hydrogen-induced cracking (HIC) and sulphide-stress cracking (SSC).
Although both HIC and SSC are hydrogen cracking phenomena in steel, the microstructural parameters that control HIC are different from those that control SSC due to the superimposed stress.
Some metallurgical features are known to contribute to sour resistance, but a comprehensive understanding of the mechanism is still missing. OCAS therefore launched a project to review the main specificities of SSC testing linked to hydrogen embrittlement. To acquire in-depth understanding of this behaviour, OCAS is investigating the amount of hydrogen entering into the steel for different conditions of time, material and environment. For this purpose, a specific test set-up able to extract specimens from a sour solution has been developed. Care is particularly taken to avoid release of hydrogen before the hydrogen behaviour is being measured, once the sample is no longer in contact with the solution.
Recently, the possibility to measure the permeation of hydrogen through the sample under sour conditions, has been added to the capabilities of the lab. These measurements provide better insight for modelling the behaviour of materials in sour conditions.
Watch the video on the OCAS offer in the field of sour corrosion.
OCAS has a fully equipped sour corrosion lab:
- Standard HIC and SSC tests, including double cantilever beam test (SSC Method D)
- NACE TM0284
- NACE TM0177
- EFC 16
- Mild and severe sour test capability (both HIC and SSC) to simulate virtually any service condition
- Slow Strain Rate test (NACE TM0198) to rank materials for sour service
- Four-point bending test
- C-ring test
- Rigorous methodologies to ensure the integrity of the tests e.g. H2S saturation, temperature, pH, etc.
- Fast extraction
- Post-test analysis techniques: ultrasound, magnetic particle inspection, electron microscopy, XRD analysis of corrosion products
- Advanced non-standard testing set-ups for fast extraction of specimen immersed in H2S-containing environments, permeation tests in H2S environment
The skilled OCAS team not only performs tests in its in-house state-of-the-art sour corrosion lab, they also provide advanced result-driven technical support in the fields of structural integrity & fit-for service, welding recommendations, combined durability conditions, etc.
“OCAS’s new non-standard test set-ups and the H2S permeation test will allow for more precise measurement and analysis.”
