Currently the use of sour service metallic materials is guided by ISO 15156/NACE MR0175
standard and guideline documents such EFC N°16 and 17. Carbon and low alloy steels are
used according to the sulfide stress cracking (SSC) severity diagram in ISO 15156-2. However,
there is a zone in the lower left hand corner which is undefined so far. Hence, the severity is
unknown and qualification may need to be specifically carried out for using steels under these
conditions. Work has been undertaken to test several steels of known sour service resistance
to better assess the severity in this area of the diagram.
For corrosion resistant alloys such as stainless steels the limits of use are still under
investigation and so far only limited data is available in the open literature. The work reported
here has been carried out to test the resistance of UNS S31603 (AISI 316L) stainless steel in a
number of sour service media. The data obtained has been compared with published data to
better assess the limits of use of this alloy and extend its use in upstream sour service.
The first part of the paper deals with the resistance of carbon and low alloy steels and the limits
of use of UNS S31603 stainless steel are addressed in the second part. Both topics are
important to optimise the use of these steels in sour service conditions.
Keywords: Low alloy steels, stainless steels, H2S, sulphide stress cracking, stress corrosion
cracking, ISO 15156