Stress corrosion cracking of carbon steel in amine service

Background and project purpose?
For amine-based gas treatment plants in the oil and gas industry observations and operational experience has revealed stress corrosion of carbon steel for some amine-based solutions as for instance MEA and DEA at certain specific process conditions as a problem. Stress corrosion leads to fractures in materials and happens were the stress is high in the material, typically in welds. -hence standards are developed (i.e API-RP-945) recommending post weld heat treatment (PWHT) of all welds were process conditions so demands. PWHT is a cost increasing process for construction of CO₂ capture plants. If this project reveals stress corrosion as a non-problem at the process conditions relevant for a CO₂ capture plant and for the solvents in mind for these plants, a cost reduction for full scale plants by avoiding PWHT can be achieved.

What was the project objective?
Proving to what extent alkaline stress corrosion is relevant for Aker Carbon Capture’s proprietary amine.
What has the project done in terms of activities?
Literary study related to alkaline stress corrosion.
Expose welded carbon steel to amine based solvent in an environment simulating the process conditions in a CO₂ capture plant.

What has the project achieved? Did the project achieve its objective?
The performed experiments did not reveal stress corrosion when simulating CO₂ capture process environments with standard methods for testing materials for stress corrosion. Aker Carbon Capture’s proprietary solvent and MEA based solvent yielded identical results.
Accordingly, the conclusion became not to specify PWHT of carbon steel exposed to our proprietary solvent in the future. Hence, the objective of the project was achieved.

Future plans?
Remove requirements of PWHT for carbon steel exposed to amine based solvent for future CO₂ capture plants based on Aker Carbon Capture present technology and solvent.

Presently there are no planned activities. However, monitoring of new CO₂ capture plants with respect to alkaline stress corrosion cracking is seen as a natural task in the future.